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1.  A Co-blended Locust Bean Gum and Polymethacrylate-NaCMC Matrix to Achieve Zero-Order Release via Hydro-Erosive Modulation 
AAPS PharmSciTech  2015;16(6):1377-1389.
Locust bean gum (LBG) was blended with a cellulose/methacrylate-based interpolyelectrolyte complex (IPEC) to assess the hydro-erosive influence of addition of a polysaccharide on the disposition and drug delivery properties inherent to IPEC matrix. The addition of LBG modulated the drug (levodopa) release characteristics of the IPEC by reducing excessive swelling and preventing bulk erosion. After 8 h in pH 4.5 dissolution medium, gravimetric analysis established that IPEC tablet matrix eroded by 30% of the initial weight due to bulk erosion while LBG-blended IPEC (LBG-b-IPEC) demonstrated surface erosion accounting to 62% of initial weight (596→226.8 mg). Mathematical modeling of the drug release data depicted a transformation from non-Fickian mechanism (IPEC matrices) to zero-order drug release pattern (LBG-b-IPEC matrices) with the linearity of release profile being close to 1 (R2 = 0.99). Physicochemical characterizations employing Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) explicated that LBG interacted with IPEC by its hydrophilic groups associating with the existing water-holding bodies of IPEC to produce compact matrices. The lattice atomistic modeling elucidated that LBG acted as a linker with the formation of intra- and intermolecular hydrogen bonds generating a highly stabilized polysaccharide-polyelectrolytic structure which influenced the improved properties observed.
doi:10.1208/s12249-015-0326-9
PMCID: PMC4666261  PMID: 25956484
controlled release; interpolyelectrolyte complex; levodopa; locust bean gum; oral drug delivery; swelling and erosion
2.  A Menthol-Based Solid Dispersion Technique for Enhanced Solubility and Dissolution of Sulfamethoxazole from an Oral Tablet Matrix 
AAPS PharmSciTech  2014;16(4):771-786.
A menthol-based solid dispersion was designed to improve the intrinsic solubility of the poorly soluble sulfamethoxazole- a class II drug molecule of Biopharmaceutics Classification System (BCS) displaying widespread antibacterial activity. Solid dispersions of menthol and sulfamethoxazole were compressed with hydroxypropyl methylcellulose (HPMC) into suitable sulfamethoxazole-loaded matrix tablets for oral drug delivery. The sulfamethoxazole-loaded solid dispersions and compressed tablets were characterized for their physicochemical and physicomechanical properties such as changes in crystallinity, melting point, molecular transitions, and textural analysis for critical analysis of their effects on the solubility and dissolution of sulfamethoxazole. The formulations were further evaluated for swelling, degradation, solubility, and in vitro drug release behavior. In vitro drug release from the sulfamethoxazole-loaded matrix tablets displayed a minimum and maximum fractional release of 0.714 and 0.970, respectively. The tablets further displayed different release rate profiles over the study periods of 12, 16, 48, and 56 h which were attributed to the varying concentrations of menthol within each formulation. Menthol was determined as a suitable hydrophilic carrier for sulfamethoxazole since it functioned as a solubilizing and release-retarding agent for improving the solubility and dissolution of sulfamethoxazole as well as controlling the rate at which it was released.
doi:10.1208/s12249-014-0271-z
PMCID: PMC4508297  PMID: 25549792
crystallinity; menthol; oral solubility and dissolution; solid dispersion; sulfamethoxazole
3.  Bypassing P-Glycoprotein Drug Efflux Mechanisms: Possible Applications in Pharmacoresistant Schizophrenia Therapy 
BioMed Research International  2015;2015:484963.
The efficient noninvasive treatment of neurodegenerative disorders is often constrained by reduced permeation of therapeutic agents into the central nervous system (CNS). A vast majority of bioactive agents do not readily permeate into the brain tissue due to the existence of the blood-brain barrier (BBB) and the associated P-glycoprotein efflux transporter. The overexpression of the MDR1 P-glycoprotein has been related to the occurrence of multidrug resistance in CNS diseases. Various research outputs have focused on overcoming the P-glycoprotein drug efflux transporter, which mainly involve its inhibition or bypassing mechanisms. Studies into neurodegenerative disorders have shown that the P-glycoprotein efflux transporter plays a vital role in the progression of schizophrenia, with a noted increase in P-glycoprotein function among schizophrenic patients, thereby reducing therapeutic outcomes. In this review, we address the hypothesis that methods employed in overcoming P-glycoprotein in cancer and other disease states at the level of the BBB and intestine may be applied to schizophrenia drug delivery system design to improve clinical efficiency of drug therapies. In addition, the current review explores polymers and drug delivery systems capable of P-gp inhibition and modulation.
doi:10.1155/2015/484963
PMCID: PMC4600488  PMID: 26491671
4.  Synthesis of a Semi-Interpenetrating Polymer Network as a Bioactive Curcumin Film 
AAPS PharmSciTech  2014;15(6):1476-1489.
This study focused on the synthesis and characterization of a natural polymeric system employing the interpenetrating polymer network (IPN) comprising curcumin as a bioactive. Biopolymers and actives such as chitosan, hypromellose, citric acid, genipin, and curcumin were used to develop an effective, biodegradable, and biocompatible film employed therapeutically as a wound healing platform. The semi-IPN films were investigated for their physicochemical, physicomechanical, and biological properties by quantification by FTIR, DSC, and Young’s modulus. Following characterization, an optimum candidate formulation was produced whereby further in vitro and ex vivo studies were performed. Results revealed a burst release occurring at the first hour with 1.1 mg bioactive released when in contact with the dissolution medium and 2.23 mg due to bioactive permeation through the skin, thus suggesting that the lipophilic nature of skin greatly impacted the bioactive release rate. Furthermore, chemical and mechanical characterization and tensile strength analysis revealed that the degree of crosslinking and concentration of polymeric material used significantly influenced the properties of the film.
doi:10.1208/s12249-014-0170-3
PMCID: PMC4245434  PMID: 24984920
biomaterials; crosslinker; curcumin; films; semi-interpenetrating polymer network; wound healing
5.  An Epichlorohydrin-Crosslinked Semi-Interpenetrating GG-PEO Network as a Xerogel Matrix for Sustained Release of Sulpiride 
AAPS PharmSciTech  2014;15(5):1292-1306.
The current study involved the development of a novel sustained release crosslinked semi-IPN xerogel matrix tablet prepared by chemical crosslinking of poly(ethylene) oxide (PEO) and gellan gum (GG) employing epichlorohydrin (EPI) as crosslinker. A Box–Behnken design was employed for the statistical optimization of the matrix system to ascertain the ideal combination of native polymeric and crosslinking agents. Characterization studies were performed by employing standard polymer characterization techniques such as Fourier transform infrared spectrometry, differential scanning calorimetry, and scanning electron microscopy. Formulated matrix tablets displayed zero-order release kinetics, extending over 24 h. The mechanism of drug release was primarily by swelling and surface erosion. Crosslinked semi-IPN xerogel matrix tablets were compared to non-crosslinked polymer blends; results from the study conducted showed that the physiochemical properties of the PEO and GG were sufficiently modified to allow for sustained release of sulpiride with a 100% drug release at 24 h in a controlled manner as compared to non-crosslinked formulations which displayed further release beyond the test period. Crosslinked formulations displayed water uptake between 450 and 500% indicating a controlled rate of swelling and erosion allowing for sustained release. Surface morphology of the crosslinked system depicted a porous structure formed by interpenetrating networks of polymers, allowing for a greater degree of controlled penetration into the system affording it the ability to sustain drug release. Therefore, conclusively, based on the study performed, crosslinked PEO-GG allows for the sustained release of sulpiride from a hydrophilic semi-IPN xerogel matrix system.
doi:10.1208/s12249-014-0153-4
PMCID: PMC4179658  PMID: 24920521
epichlorohydrin; matrix tablet; semi-interpenetrating polymer network; sustained release; sulpiride
6.  Parameters and characteristics governing cellular internalization and trans-barrier trafficking of nanostructures 
Cellular internalization and trans-barrier transport of nanoparticles can be manipulated on the basis of the physicochemical and mechanical characteristics of nanoparticles. Research has shown that these factors significantly influence the uptake of nanoparticles. Dictating these characteristics allows for the control of the rate and extent of cellular uptake, as well as delivering the drug-loaded nanosystem intra-cellularly, which is imperative for drugs that require a specific cellular level to exert their effects. Additionally, physicochemical characteristics of the nanoparticles should be optimal for the nanosystem to bypass the natural restricting phenomena of the body and act therapeutically at the targeted site. The factors at the focal point of emerging smart nanomedicines include nanoparticle size, surface charge, shape, hydrophobicity, surface chemistry, and even protein and ligand conjugates. Hence, this review discusses the mechanism of internalization of nanoparticles and ideal nanoparticle characteristics that allow them to evade the biological barriers in order to achieve optimal cellular uptake in different organ systems. Identifying these parameters assists with the progression of nanomedicine as an outstanding vector of pharmaceuticals.
doi:10.2147/IJN.S75615
PMCID: PMC4370919  PMID: 25834433
nanoparticles; transport mechanisms; cellular uptake; size; shape; charge
7.  A Review of the Advancements in Probiotic Delivery: Conventional vs. Non-conventional Formulations for Intestinal Flora Supplementation 
AAPS PharmSciTech  2013;15(1):29-43.
Probiotic delivery systems are widely used nutraceutical products for the supplementation of natural intestinal flora. These delivery systems vary greatly in effectiveness to exert health benefits for a patient. Probiotic delivery systems can be categorized into conventional, pharmaceutical formulations, and non-conventional, mainly commercial food-based, products. The degree of health benefits provided by these probiotic formulations varies in their ability to deliver viable, functional bacteria in large enough numbers (effectiveness), to provide protection against the harsh effects of the gastric environment and intestinal bile (in vivo protection), and to survive formulation processes (viability). This review discusses the effectiveness of these probiotic delivery systems to deliver viable functional bacteria focusing on the ability to protect the encapsulated probiotics during formulation process as well as against harsh physiological conditions through formulation enhancements using coatings and polymer enhancements. A brief overview on the health benefits of probiotics, current formulation, patient and legal issues facing probiotic delivery, and possible recommendations for the enhanced delivery of probiotic bacteria are also provided. Newer advanced in vitro analyses that can accurately determine the effectiveness of a probiotic formulation are also discussed with an ideal probiotic delivery system hypothesized through a combination of the two probiotic delivery systems described.
doi:10.1208/s12249-013-0027-1
PMCID: PMC3909163  PMID: 24222267
conventional and non-conventional formulations; drug delivery systems design; intestinal flora; nutraceutical products; probiotics
8.  Evaluation of the Impacts of Formulation Variables and Excipients on the Drug Release Dynamics of a Polyamide 6,10-Based Monolithic Matrix Using Mathematical Tools 
AAPS PharmSciTech  2013;14(4):1349-1359.
Drug release from hydrophilic matrices is regulated mainly by polymeric erosion, disentanglement, dissolution, swelling front movement, drug dissolution and diffusion through the polymeric matrix. These processes depend upon the interaction between the dissolution media, polymeric matrix and drug molecules, which can be significantly influenced by formulation variables and excipients. This study utilized mathematical parameters to evaluate the impacts of selected formulation variables and various excipients on the release performance of hydrophilic polyamide 6,10 (PA 6,10) monolithic matrix. Amitriptyline HCl and theophylline were employed as the high and low solubility model drugs, respectively. The incorporation of different excipient concentrations and changes in formulation components influenced the drug release dynamics as evidenced by computed mathematical quantities (tx%, MDTx%,f1, f2, k1, k2, and КF). The effects of excipients on drug release from the PA 6,10 monolithic matrix was further elucidated using static lattice atomistic simulations wherein the component energy refinements corroborates the in vitro and in silico experimental data. Consequently, the feasibility of modulating release kinetics of drug molecules from the novel PA 6,10 monolithic matrix was well suggested.
doi:10.1208/s12249-013-0021-7
PMCID: PMC3840780  PMID: 23990121
excipients; formulation variables; mathematical tools; monolithic matrix; polyamide 6,10
9.  A Review of Bioactive Release from Nerve Conduits as a Neurotherapeutic Strategy for Neuronal Growth in Peripheral Nerve Injury 
BioMed Research International  2014;2014:132350.
Peripheral nerve regeneration strategies employ the use of polymeric engineered nerve conduits encompassed with components of a delivery system. This allows for the controlled and sustained release of neurotrophic growth factors for the enhancement of the innate regenerative capacity of the injured nerves. This review article focuses on the delivery of neurotrophic factors (NTFs) and the importance of the parameters that control release kinetics in the delivery of optimal quantities of NTFs for improved therapeutic effect and prevention of dose dumping. Studies utilizing various controlled-release strategies, in attempt to obtain ideal release kinetics, have been reviewed in this paper. Release strategies discussed include affinity-based models, crosslinking techniques, and layer-by-layer technologies. Currently available synthetic hollow nerve conduits, an alternative to the nerve autografts, have proven to be successful in the bridging and regeneration of primarily the short transected nerve gaps in several patient cases. However, current research emphasizes on the development of more advanced nerve conduits able to simulate the effectiveness of the autograft which includes, in particular, the ability to deliver growth factors.
doi:10.1155/2014/132350
PMCID: PMC4131113  PMID: 25143934
10.  Physicomechanical Characterization and Optimization of EDTA–mPEG and Avicel®–EDTA–mPEG In Situ Melt Dispersion Mini-Pellets 
AAPS PharmSciTech  2013;14(3):935-949.
The purpose of this study was to develop a physicomechanically customizable oral metal chelatory in situ hot melt dispersion mini-pellet entity which could be utilized within a binary drug delivery system. Avicel® RC/CL type R-591 was included within the in situ hot melt dispersion mini-pellet formulations to determine the physicomechanical effect this compound would have on the mini-pellet formulations. The physicomechanical properties of the hot melt in situ mini-pellet formulations were mathematically fitting to regression curves. Physicomechanical adjustment of the in situ hot melt dispersion mini-pellet formulations could be mathematically predicted with the derived regression curve equations. The addition of Avicel® RC/CL type R-591 increased the physicomechanical properties such as matrix hardness and increased total disintegration of the in situ hot melt dispersion mini-pellet formulations. The utilization of a physicomechanically customizable oral metal chelatory in situ hot melt dispersion mini-pellet entity within a binary drug delivery system would to achieve a synergistically enhance the activity of a drug-carrying entity or a permeation enhancing entity within a single drug delivery unit. The experimental results indicated that weights of the pellets that achieved optimal hardness ranged between 35 and 45 mg. The melt–dispersion formulations disintegrated within shorter time periods and maintained higher ethylenediaminetetraacetic acid (EDTA) concentrations whereas melt–dispersion formulations which included Avicel® had superior physicomechanical properties. Disintegration times ranged between 1,000 s for melt–dispersions containing EDTA and methyloxy polyethylene glycol 2000 (mPEG) only, to >6,000 s for melt–dispersions comprising EDTA, mPEG, and Avicel®.
Electronic supplementary material
The online version of this article (doi:10.1208/s12249-013-9979-4) contains supplementary material, which is available to authorized users.
doi:10.1208/s12249-013-9979-4
PMCID: PMC3755157  PMID: 23733514
chelation therapy; disintegration studies; mini-pellets; oral drug delivery; polymer melts; solid dosage forms; textual analysis
11.  A Review of Polymeric Refabrication Techniques to Modify Polymer Properties for Biomedical and Drug Delivery Applications 
AAPS PharmSciTech  2013;14(2):692-711.
Polymers are extensively used in the pharmaceutical and medical field because of their unique and phenomenal properties that they display. They are capable of demonstrating drug delivery properties that are smart and novel, such properties that are not achievable by employing the conventional excipients. Appropriately, polymeric refabrication remains at the forefront of process technology development in an endeavor to produce more useful pharmaceutical and medical products because of the multitudes of smart properties that can be attained through the alteration of polymers. Small alterations to a polymer by either addition, subtraction, self-reaction, or cross reaction with other entities have the capability of generating polymers with properties that are at the level to enable the creation of novel pharmaceutical and medical products. Properties such as stimuli-responsiveness, site targeting, and chronotherapeutics are no longer figures of imaginations but have become a reality through utilizing processes of polymer refabrication. This article has sought to review the different techniques that have been employed in polymeric refabrication to produce superior products in the pharmaceutical and medical disciplines. Techniques such as grafting, blending, interpenetrating polymers networks, and synthesis of polymer complexes will be viewed from a pharmaceutical and medical perspective along with their synthetic process required to attain these products. In addition to this, each process will be evaluated according to its salient features, impeding features, and the role they play in improving current medical devices and procedures.
doi:10.1208/s12249-013-9955-z
PMCID: PMC3665995  PMID: 23543606
alteration; blending; drugs; grafting; interpenetrating polymer networks; medicine; pharmaceutical; polymer complexes; polymer modification
12.  Design of an Interpolyelectrolyte Gastroretentive Matrix for the Site-Specific Zero-Order Delivery of Levodopa in Parkinson’s Disease 
AAPS PharmSciTech  2013;14(2):605-619.
This study focused on developing a gastroretentive drug delivery system employing a triple-mechanism interpolyelectrolyte complex (IPEC) matrix comprising high density, swelling, and bioadhesiveness for the enhanced site-specific zero-order delivery of levodopa in Parkinson’s disease. An IPEC was synthesized and directly compressed into a levodopa-loaded matrix employing pharmaceutical technology and evaluated with respect to its physicochemical and physicomechanical properties and in vitro drug release. The IPEC-based matrix displayed superior mechanical properties in terms of matrix hardness (34–39 N/mm) and matrix resilience (44–47%) when different normality’s of solvent and blending ratios were employed. Fourier transform infrared spectroscopy confirmed the formation of the IPEC. The formulations exhibited pH and density dependence with desirable gastro-adhesion with Peak Force of Adhesion ranging between 0.15 and 0.21 N/mm, densities from 1.43 to 1.54 g/cm3 and swellability values of 177–234%. The IPEC-based gastroretentive matrix was capable of providing site-specific levodopa release with zero-order kinetics corroborated by detailed mathematical and molecular modeling studies. Overall, results from this study have shown that the IPEC-based matrix has the potential to improve the absorption and subsequent bioavailability of narrow absorption window drugs, such as levodopa with constant and sustained drug delivery.
doi:10.1208/s12249-013-9945-1
PMCID: PMC3666024  PMID: 23494468
gastroretention; interpolyelectrolyte complex; levodopa; narrow absorption window drugs; Parkinson’s disease
13.  Overview of the role of nanotechnological innovations in the detection and treatment of solid tumors 
Nanotechnology, although still in its infantile stages, has the potential to revolutionize the diagnosis, treatment, and monitoring of disease progression and success of therapy for numerous diseases and conditions, not least of which is cancer. As it is a leading cause of mortality worldwide, early cancer detection, as well as safe and efficacious therapeutic intervention, will be indispensable in improving the prognosis related to cancers and overall survival rate, as well as health-related quality of life of patients diagnosed with cancer. The development of a relatively new field of nanomedicine, which combines various domains and technologies including nanotechnology, medicine, biology, pharmacology, mathematics, physics, and chemistry, has yielded different approaches to addressing these challenges. Of particular relevance in cancer, nanosystems have shown appreciable success in the realm of diagnosis and treatment. Characteristics attributable to these systems on account of the nanoscale size range allow for individualization of therapy, passive targeting, the attachment of targeting moieties for more specific targeting, minimally invasive procedures, and real-time imaging and monitoring of in vivo processes. Furthermore, incorporation into nanosystems may have the potential to reintroduce into clinical practice drugs that are no longer used because of various shortfalls, as well as aid in the registration of new, potent drugs with suboptimal pharmacokinetic profiles. Research into the development of nanosystems for cancer diagnosis and therapy is thus a rapidly emerging and viable field of study.
doi:10.2147/IJN.S50941
PMCID: PMC3904834  PMID: 24489467
nanosystems; targeted drug delivery; nanotheranostics; antineoplastic drugs; poor aqueous solubility; solid tumors
14.  Prolonged Delivery of Ciprofloxacin and Diclofenac Sodium from a Polymeric Fibre Device for the Treatment of Peridontal Disease 
BioMed Research International  2013;2013:460936.
In vitro analysis of drug release and antimicrobial activity of the coblended crosslinked polymeric fibre device (PFD) were investigated. The fibre loaded with ciprofloxacin and diclofenac sodium was comprised of alginate and glycerol crosslinked with barium cations. The pH dependent drug release was evident with ciprofloxacin and diclofenac sodium diffusing from the fibre at pH 4.0 compared to pH 6.8, where the fibre swelled and eroded resulting in zero-order drug release. Agar diffusion studies followed by minimum inhibitory assays were conducted to determine the antimicrobial activity of the device against Escherichia coli, Enterococcus faecalis, and Streptococcus mutans. The antimicrobial activity of the PFD was confirmed in both test assays against all test pathogens. The MIC ranges at pH 4.0 for E. coli, E. faecalis, and S. mutans were 0.5–0.8, 0.4–1.1, and 0.7–2.1 μg/mL, respectively. At pH 6.8, similar efficacies (0.3–0.5 μg/mL for E. coli and E. faecalis and 0.6–1.0 μg/mL for S. mutans) were observed. The effect of varying the plasticizer and crosslinking ion concentration on drug release profile of the fibers was further elucidated and conceptualized using molecular mechanics energy relationships (MMER) and by exploring the spatial disposition of geometrically minimized molecular conformations.
doi:10.1155/2013/460936
PMCID: PMC3845435  PMID: 24324962
15.  A Novel Multilayered Multidisk Oral Tablet for Chronotherapeutic Drug Delivery 
BioMed Research International  2013;2013:569470.
A Multilayered Multidisk Tablet (MLMDT) comprising two drug-loaded disks enveloped by three drug-free barrier layers was developed for use in chronotherapeutic disorders, employing two model drugs, theophylline and diltiazem HCl. The MLMDT was designed to achieve two pulses of drug release separated by a lag phase. The polymer disk comprised hydroxyethylcellulose (HEC) and ethylcellulose (EC) granulated using an aqueous dispersion of EC. The polymeric barrier layers constituted a combination of pectin/Avicel (PBL) (1st barrier layer) and hydroxypropylmethylcellulose (HPMC) (HBL1 and HBL2) as the 2nd and 3rd barrier layers, respectively. Sodium bicarbonate was incorporated into the diltiazem-containing formulation for delayed drug release. Erosion and swelling studies confirmed the manner in which the drug was released with theophylline formulations exhibiting a maximum swelling of 97% and diltiazem containing formulations with a maximum swelling of 119%. FTIR spectra displayed no interactions between drugs and polymers. Molecular mechanics simulations were undertaken to predict the possible orientation of the polymer morphologies most likely affecting the MLMDT performance. The MLMDT provided two pulses of drug release, separated by a lag phase, and additionally it displayed desirable friability, hardness, and uniformity of mass indicating a stable formulation that may be a desirable candidate for chronotherapeutic drug delivery.
doi:10.1155/2013/569470
PMCID: PMC3762207  PMID: 24024200
16.  Integration of Biosensors and Drug Delivery Technologies for Early Detection and Chronic Management of Illness 
Sensors (Basel, Switzerland)  2013;13(6):7680-7713.
Recent advances in biosensor design and sensing efficacy need to be amalgamated with research in responsive drug delivery systems for building superior health or illness regimes and ensuring good patient compliance. A variety of illnesses require continuous monitoring in order to have efficient illness intervention. Physicochemical changes in the body can signify the occurrence of an illness before it manifests. Even with the usage of sensors that allow diagnosis and prognosis of the illness, medical intervention still has its downfalls. Late detection of illness can reduce the efficacy of therapeutics. Furthermore, the conventional modes of treatment can cause side-effects such as tissue damage (chemotherapy and rhabdomyolysis) and induce other forms of illness (hepatotoxicity). The use of drug delivery systems enables the lowering of side-effects with subsequent improvement in patient compliance. Chronic illnesses require continuous monitoring and medical intervention for efficient treatment to be achieved. Therefore, designing a responsive system that will reciprocate to the physicochemical changes may offer superior therapeutic activity. In this respect, integration of biosensors and drug delivery is a proficient approach and requires designing an implantable system that has a closed loop system. This offers regulation of the changes by means of releasing a therapeutic agent whenever illness biomarkers prevail. Proper selection of biomarkers is vital as this is key for diagnosis and a stimulation factor for responsive drug delivery. By detecting an illness before it manifests by means of biomarkers levels, therapeutic dosing would relate to the severity of such changes. In this review various biosensors and drug delivery systems are discussed in order to assess the challenges and future perspectives of integrating biosensors and drug delivery systems for detection and management of chronic illness.
doi:10.3390/s130607680
PMCID: PMC3715220  PMID: 23771157
biosensor; BioMEMS; biomarkers; closed loop system; illness management; implantable systems
17.  In vivo evaluation of a conjugated poly(lactide-ethylene glycol) nanoparticle depot formulation for prolonged insulin delivery in the diabetic rabbit model 
Poly(ethylene glycol) (PEG) and polylactic acid (PLA)-based copolymeric nanoparticles were synthesized and investigated as a carrier for prolonged delivery of insulin via the parenteral route. Insulin loading was simultaneously achieved with particle synthesis using a double emulsion solvent evaporation technique, and the effect of varied PEG chain lengths on particle size and insulin loading efficiency was determined. The synthesized copolymer and nanoparticles were analyzed by standard polymer characterization techniques of gel permeation chromatography, dynamic light scattering, nuclear magnetic resonance, and transmission electron microscopy. In vitro insulin release studies performed under simulated conditions provided a near zero-order release pattern up to 10 days. In vivo animal studies were undertaken with varied insulin loads of nanoparticles administered subcutaneously to fed diabetic rabbits and, of all doses administered, nanoparticles containing 50 IU of insulin load per kg body weight controlled the blood glucose level within the physiologically normal range of 90–140 mg/dL, and had a prolonged effect for more than 7 days. Histopathological evaluation of tissue samples from the site of injection showed no signs of inflammation or aggregation, and established the nontoxic nature of the prepared copolymeric nanoparticles. Further, the reaction profiles for PLA-COOH and NH2-PEGDA-NH2 were elucidated using molecular mechanics energy relationships in vacuum and in a solvated system by exploring the spatial disposition of various concentrations of polymers with respect to each other. Incorporation of insulin within the polymeric matrix was modeled using Connolly molecular surfaces. The computational results corroborated the experimental and analytical data. The ability to control blood glucose levels effectively coupled with the nontoxic behavior of the nanoparticles indicates that these nanoparticles are a potential candidate for insulin delivery.
doi:10.2147/IJN.S38011
PMCID: PMC3575164  PMID: 23429428
parenteral delivery; insulin; nanoparticles; poly(lactide-ethylene glycol) diblock copolymer; molecular mechanics energy relationship
18.  Optimization of a Dual Mechanism Gastrofloatable and Gastroadhesive Delivery System for Narrow Absorption Window Drugs 
AAPS PharmSciTech  2011;13(1):1-15.
In order to overcome poor bioavailability of narrow absorption window drugs, a gastrosphere system comprising two mechanisms of gastric retention, namely buoyancy and gastroadhesion, has been investigated in this study employing poly(lactic-co-glycolic acid) (PLGA), polyacrylic acid (PAA), alginate, pectin, and a model drug metformin hydrochloride. Fifteen formulations were obtained using a Box–Behnken statistical design. The gastrosphere yield was above 80% in all cases; however, due to the high water solubility of metformin, drug entrapment efficacy was between 18% and 54%. Mean dissolution time and gastroadhesive strength were used as the formulation responses in order to optimize the formulation. Furthermore, the molecular mechanics force field simulations were performed to corroborate the experimental findings. Drug release profiles revealed three different release kinetics, namely, burst, first-order and zero-order release. Varying gastroadhesive results were obtained, and were highly sensitive to changes in polymer concentrations. FTIR revealed that strong bonds of PAA and PLGA were retained within the gastrosphere. Surface area and porosity analysis provided supporting evidence that the lyophilization process resulted in a significant increase in the porosity. Analysis of the surface morphology by SEM revealed that air pockets were spread over the entire surface of the gastrosphere, providing a visual proof of the high porosity and hence low density of the gastrosphere. The spatial disposition and energetic profile of the sterically constrained and geometrically optimized multi-polymeric complex of alginate, pectin, PAA, and PLGA corroborated the experimental results in terms of in vitro drug release and gastroadhesive strength of the fabricated gastrospheres.
doi:10.1208/s12249-011-9711-1
PMCID: PMC3299464  PMID: 22048877
Box–Behnken design; gastroretentive drug delivery; molecular mechanics simulations; narrow absorption window drugs; polymeric gastrosphere synthesis
19.  Composite Polylactic-Methacrylic Acid Copolymer Nanoparticles for the Delivery of Methotrexate 
Journal of Drug Delivery  2012;2012:579629.
The purpose of this study was to develop poly(lactic acid)-methacrylic acid copolymeric nanoparticles with the potential to serve as nanocarrier systems for methotrexate (MTX) used in the chemotherapy of primary central nervous system lymphoma (PCNSL). Nanoparticles were prepared by a double emulsion solvent evaporation technique employing a 3-Factor Box-Behnken experimental design strategy. Analysis of particle size, absolute zeta potential, polydispersity (Pdl), morphology, drug-loading capacity (DLC), structural transitions through FTIR spectroscopy, and drug release kinetics was undertaken. Molecular modelling elucidated the mechanisms of the experimental findings. Nanoparticles with particle sizes ranging from 211.0 to 378.3 nm and a recovery range of 36.8–86.2 mg (Pdl ≤ 0.5) were synthesized. DLC values were initially low (12 ± 0.5%) but were finally optimized to 98 ± 0.3%. FTIR studies elucidated the comixing of MTX within the nanoparticles. An initial burst release (50% of MTX released in 24 hours) was obtained which was followed by a prolonged release phase of MTX over 84 hours. SEM images revealed near-spherical nanoparticles, while TEM micrographs revealed the presence of MTX within the nanoparticles. Stable nanoparticles were formed as corroborated by the chemometric modelling studies undertaken.
doi:10.1155/2012/579629
PMCID: PMC3418700  PMID: 22919501
20.  Oral Drug Delivery Systems Comprising Altered Geometric Configurations for Controlled Drug Delivery 
Recent pharmaceutical research has focused on controlled drug delivery having an advantage over conventional methods. Adequate controlled plasma drug levels, reduced side effects as well as improved patient compliance are some of the benefits that these systems may offer. Controlled delivery systems that can provide zero-order drug delivery have the potential for maximizing efficacy while minimizing dose frequency and toxicity. Thus, zero-order drug release is ideal in a large area of drug delivery which has therefore led to the development of various technologies with such drug release patterns. Systems such as multilayered tablets and other geometrically altered devices have been created to perform this function. One of the principles of multilayered tablets involves creating a constant surface area for release. Polymeric materials play an important role in the functioning of these systems. Technologies developed to date include among others: Geomatrix® multilayered tablets, which utilizes specific polymers that may act as barriers to control drug release; Procise®, which has a core with an aperture that can be modified to achieve various types of drug release; core-in-cup tablets, where the core matrix is coated on one surface while the circumference forms a cup around it; donut-shaped devices, which possess a centrally-placed aperture hole and Dome Matrix® as well as “release modules assemblage”, which can offer alternating drug release patterns. This review discusses the novel altered geometric system technologies that have been developed to provide controlled drug release, also focusing on polymers that have been employed in such developments.
doi:10.3390/ijms13010018
PMCID: PMC3269670  PMID: 22312236
controlled drug delivery; geometrically altered devices; multilayered tablets; polymeric materials; release modules assemblage
21.  Novel High-Viscosity Polyacrylamidated Chitosan for Neural Tissue Engineering: Fabrication of Anisotropic Neurodurable Scaffold via Molecular Disposition of Persulfate-Mediated Polymer Slicing and Complexation 
Macroporous polyacrylamide-grafted-chitosan scaffolds for neural tissue engineering were fabricated with varied synthetic and viscosity profiles. A novel approach and mechanism was utilized for polyacrylamide grafting onto chitosan using potassium persulfate (KPS) mediated degradation of both polymers under a thermally controlled environment. Commercially available high molecular mass polyacrylamide was used instead of the acrylamide monomer for graft copolymerization. This grafting strategy yielded an enhanced grafting efficiency (GE = 92%), grafting ratio (GR = 263%), intrinsic viscosity (IV = 5.231 dL/g) and viscometric average molecular mass (MW = 1.63 × 106 Da) compared with known acrylamide that has a GE = 83%, GR = 178%, IV = 3.901 dL/g and MW = 1.22 × 106 Da. Image processing analysis of SEM images of the newly grafted neurodurable scaffold was undertaken based on the polymer-pore threshold. Attenuated Total Reflectance-FTIR spectral analyses in conjugation with DSC were used for the characterization and comparison of the newly grafted copolymers. Static Lattice Atomistic Simulations were employed to investigate and elucidate the copolymeric assembly and reaction mechanism by exploring the spatial disposition of chitosan and polyacrylamide with respect to the reactional profile of potassium persulfate. Interestingly, potassium persulfate, a peroxide, was found to play a dual role initially degrading the polymers—“polymer slicing”—thereby initiating the formation of free radicals and subsequently leading to synthesis of the high molecular mass polyacrylamide-grafted-chitosan (PAAm-g-CHT)—“polymer complexation”. Furthermore, the applicability of the uniquely grafted scaffold for neural tissue engineering was evaluated via PC12 neuronal cell seeding. The novel PAAm-g-CHT exhibited superior neurocompatibility in terms of cell infiltration owing to the anisotropic porous architecture, high molecular mass mediated robustness, superior hydrophilicity as well as surface charge due to the acrylic chains. Additionally, these results suggested that the porous PAAm-g-CHT scaffold may act as a potential neural cell carrier.
doi:10.3390/ijms131113966
PMCID: PMC3509560  PMID: 23203044
neural tissue engineering; polymer composite; polyacrylamidated chitosan; potassium persulphate; polymer grafting; neurodurable scaffold; molecular modeling and simulation
22.  Investigation of the Physicochemical and Physicomechanical Properties of a Novel Intravaginal Bioadhesive Polymeric Device in the Pig Model 
AAPS PharmSciTech  2010;11(2):793-808.
The purpose of this study was to develop and evaluate the bioadhesivity, in vitro drug release, and permeation of an intravaginal bioadhesive polymeric device (IBPD) loaded with 3′-azido-3′-deoxythymidine (AZT) and polystyrene sulfonate (PSS). Modified polyamide 6,10, poly(lactic-coglycolic acid), polyacrylic acid, polyvinyl alcohol, and ethylcellulose were blended with model drugs AZT and PSS as well as radio-opaque barium sulfate (BaSO4) and then compressed into caplet devices on a tableting press. One set of devices was coated with 2% w/v pentaerythritol polyacrylic acid (APE-PAA) while another remained uncoated. Thermal analysis was performed on the constituent polymers as well the IBPD. The changes in micro-environmental pH within the simulated human vaginal fluid due to the presence of the IBPD were assessed over a period of 30 days. Textural profile analysis indicated that the bioadhesivity of the APE-PAA-coated devices (3.699 ± 0.464 N; 0.0098 ± 0.0004 J) was higher than that of the uncoated devices (1.198 ± 0.150 N; 0.0019 ± 0.0001 J). In addition, BaSO4-facilitated X-ray imaging revealed that the IBPD adhered to pig vaginal tissue over the experimental period of 30 days. Controlled drug release kinetics was obtained over 72 days. During a 24-h permeation study, an increase in drug flux for both AZT (0.84 mg cm−2 h−1) and PSS (0.72 mg cm−2 h−1) was realized up to 12 h and thereafter a steady-state was achieved. The diffusion and dissolution dynamics were mechanistically deduced based on a chemometric and molecular structure modeling approach. Overall, results suggested that the IBPD may be sufficiently bioadhesive with desirable physicochemical and physicomechanical stability for use as a prolonged intravaginal drug delivery device.
doi:10.1208/s12249-010-9439-3
PMCID: PMC2902328  PMID: 20446071
bioadhesivity; controlled release; intravaginal drug delivery; microbicidal polymeric device; physicochemical and physicomechanical characterization
23.  A Review of Multi-Responsive Membranous Systems for Rate-Modulated Drug Delivery 
AAPS PharmSciTech  2010;11(1):441-459.
Membrane technology is broadly applied in the medical field. The ability of membranous systems to effectively control the movement of chemical entities is pivotal to their significant potential for use in both drug delivery and surgical/medical applications. An alteration in the physical properties of a polymer in response to a change in environmental conditions is a behavior that can be utilized to prepare ‘smart’ drug delivery systems. Stimuli-responsive or ‘smart’ polymers are polymers that upon exposure to small changes in the environment undergo rapid changes in their microstructure. A stimulus, such as a change in pH or temperature, thus serves as a trigger for the release of drug from membranous drug delivery systems that are formulated from stimuli-responsive polymers. This article has sought to review the use of stimuli-responsive polymers that have found application in membranous drug delivery systems. Polymers responsive to pH and temperature have been extensively addressed in this review since they are considered the most important stimuli that may be exploited for use in drug delivery, and biomedical applications such as in tissue engineering. In addition, dual-responsive and glucose-responsive membranes have been also addressed as membranes responsive to diverse stimuli.
doi:10.1208/s12249-010-9403-2
PMCID: PMC2850454  PMID: 20300895
Dual-responsive membranes; Glucose-responsive membranes; Membranous drug delivery systems; “On–off” gating mechanisms; pH; Stimuli-responsive polymers; Temperature
24.  A Review on Composite Liposomal Technologies for Specialized Drug Delivery 
Journal of Drug Delivery  2011;2011:939851.
The combination of liposomes with polymeric scaffolds could revolutionize the current state of drug delivery technology. Although liposomes have been extensively studied as a promising drug delivery model for bioactive compounds, there still remain major drawbacks for widespread pharmaceutical application. Two approaches for overcoming the factors related to the suboptimal efficacy of liposomes in drug delivery have been suggested. The first entails modifying the liposome surface with functional moieties, while the second involves integration of pre-encapsulated drug-loaded liposomes within depot polymeric scaffolds. This attempts to provide ingenious solutions to the limitations of conventional liposomes such as short plasma half-lives, toxicity, stability, and poor control of drug release over prolonged periods. This review delineates the key advances in composite technologies that merge the concepts of depot polymeric scaffolds with liposome technology to overcome the limitations of conventional liposomes for pharmaceutical applications.
doi:10.1155/2011/939851
PMCID: PMC3065812  PMID: 21490759
25.  In Silico Theoretical Molecular Modeling for Alzheimer’s Disease: The Nicotine-Curcumin Paradigm in Neuroprotection and Neurotherapy 
The aggregation of the amyloid-β-peptide (AβP) into well-ordered fibrils has been considered as the key pathological marker of Alzheimer‘s disease. Molecular attributes related to the specific binding interactions, covalently and non-covalently, of a library of compounds targeting of conformational scaffolds were computed employing static lattice atomistic simulations and array constructions. A combinatorial approach using isobolographic analysis was stochastically modeled employing Artificial Neural Networks and a Design of Experiments approach, namely an orthogonal Face-Centered Central Composite Design for small molecules, such as curcumin and glycosylated nornicotine exhibiting concentration-dependent behavior on modulating AβP aggregation and oligomerization. This work provides a mathematical and in silico approach that constitutes a new frontier in providing neuroscientists with a template for in vitro and in vivo experimentation. In future this could potentially allow neuroscientists to adopt this in silico approach for the development of novel therapeutic interventions in the neuroprotection and neurotherapy of Alzheimer‘s disease. In addition, the neuroprotective entities identified in this study may also be valuable in this regard.
doi:10.3390/ijms12010694
PMCID: PMC3039975  PMID: 21340009
amyloid-β protein; Alzheimer‘s disease; molecular mechanics; artificial neural networks; curcumin; nicotine; isobolographic analysis; docking; central composite design; constraint optimization; ligand-protein complexes; synergism

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