Search tips
Search criteria

Results 1-25 (32)

Clipboard (0)

Select a Filter Below

Year of Publication
Document Types
1.  Role of Branching of Hydrophilic Domain on Physicochemical Properties of Amphiphilic Macromolecules 
Polymer chemistry  2014;5(4):1457-1462.
A novel series of amphiphilic macromolecules (AMs) composed of a sugar backbone, aliphatic chains, and branched, hydrophilic poly(oligoethylene glycol) methyl ether methacrylate (POEGMA)were developed for drug delivery applications. The branched, hydrophilic domains (POEGMA homopolymers with one hydroxyl group) were prepared via atom transfer radical polymerization (ATRP) of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) monomers using 2-hydroxyethyl-2-bromoisobutyrate (HEBiB) as an initiator and copper bromide/bipyridine (CuBr/Bpy) as the catalyst system. To form the amphiphilic structures, the branched POEGMAs were coupled to hydrophobic domains that were formed via acylation of a sugar backbone. The impact of branching in the hydrophilic domain was investigated by comparing the AMs’ solution and thermal properties with those of the linear counterparts. Although these highly branched AMs showed similar critical micelle concentration (CMC) values as compared to linear analogues, they possessed quite low glass transition (Tg) temperatures. Consequently, these novel AMs with branched hydrophilic domain combine the desirable thermal properties of POEGMA with favorable solution properties of amphiphilic architectures, which make them suitable for injectable drug delivery systems.
PMCID: PMC3920977  PMID: 24533034
2.  Biodegradable polyesters containing ibuprofen and naproxen as pendant groups 
Biomacromolecules  2013;14(10):10.1021/bm400889a.
Controlled release of non-steroidal anti-inflammatory drugs such as ibuprofen and naproxen could be beneficial for the treatment of inflammatory diseases while reducing the side effects resulting from their continuous use. Novel biodegradable polyesters solely comprised of biocompatible components (e.g., tartaric acid, 1,8-octanediol, and ibuprofen or naproxen as pendant groups) have been synthesized using tin (II) 2-ethylhexanoate as catalyst at 130 °C and subsequently characterized to determine their structures and physicochemical properties. The polymers release the free drug (ibuprofen or naproxen) in vitro in a controlled manner without burst release, unlike the release rates achieved when the drugs are encapsulated in other polymers. These new biomaterials are not cytotoxic towards mouse fibroblasts up to 0.10 mg/mL. The drugs retain their chemical structure following hydrolytic degradation of the polymer, suggesting that bioactivity is preserved.
PMCID: PMC3812688  PMID: 23957612
ibuprofen; naproxen; tartaric acid; biodegradable; polyester; prodrug
3.  Locally Delivered Salicylic Acid from a Poly(anhydride-ester): Impact on Diabetic Bone Regeneration 
Diabetes mellitus (DM) involves metabolic changes that can impair bone repair, including a prolonged inflammatory response. A salicylic acid-based poly(anhydride-ester) (SA-PAE) provides controlled and sustained release of salicylic acid (SA) that locally resolves inflammation. This study investigates the effect of polymer-controlled SA release on bone regeneration in diabetic rats where enhanced inflammation is expected. Fifty-six Sprague-Dawley rats were randomly assigned to two groups: diabetic group induced by streptozotocin (STZ) injection or normoglycemic controls injected with citrate buffer alone. Three weeks after hyperglycemia development or vehicle injection, 5 mm critical sized defects were created at the rat mandibular angle and treated with SA-PAE/bone graft mixture or bone graft alone. Rats were euthanized 4 and 12 weeks after surgery, then bone fill percentage in the defect region was assessed by micro-computed tomography (CT) and histomorphometry. It was observed that bone fill increased significantly at 4 and 12 weeks in SA-PAE/bone graft-treated diabetic rats compared to diabetic rats receiving bone graft alone. Accelerated bone formation in normoglycemic rats caused by SA-PAE/bone graft treatment was observed at 4 weeks but not at 12 weeks. This study shows that treatment with SA-PAE enhances bone regeneration in diabetic rats and accelerates bone regeneration in normoglycemic animals.
PMCID: PMC3757941  PMID: 23827476
poly(anhydride-ester); salicylic acid; diabetes; bone regeneration
4.  Biodegradable Coumaric Acid-based Poly(anhydride-ester) Synthesis and Subsequent Controlled Release 
Macromolecular rapid communications  2013;34(15):1231-1236.
p-Coumaric acid (pCA), a naturally occurring bioactive, has been chemically incorporated into a poly(anhydride-ester) backbone through solution polymerization following a Knoevenagel synthetic approach to overcome drug delivery issues associated with its short half-life in vivo. Nuclear magnetic resonance and Fourier transform infrared spectroscopies indicated that pCA was successfully incorporated without noticeable alterations in structural integrity. The weight-average molecular weight and thermal properties were determined for the polymer, which exhibited a molecular weight of over 26,000 Da and a glass transition temperature of 57 °C. In addition, in vitro pCA release via hydrolytic anhydride and ester bond cleavage demonstrated pCA release over 30 days and maintained its antioxidant activity, demonstrating its potential as a controlled release system.
PMCID: PMC3789234  PMID: 23836606
biodegradable; polymer; poly(anhydride-ester); coumaric acid; drug delivery systems
5.  Formulation of salicylate-based poly(anhydride-ester) microspheres for short- and long-term salicylic acid delivery 
The formulation of salicylate-based poly(anhydride-ester) (PAE) microspheres was optimized by altering polymer concentration and homogenization speed to improve the overall morphology. The microspheres were prepared using three salicylate-based PAEs with different chemical compositions comprised of either a heteroatomic, linear aliphatic, or branched aliphatic moiety. These PAEs broadened the range of complete salicylic acid release to now include days, weeks and months. The molecular weight (Mw), polydispersity index (PDI) and glass transition temperature (Tg) of the formulated polymers were compared to the unformulated polymers. In general, the Mw and PDI exhibited decreased and increased values, respectively, after formulation, whereas the Tg changes did not follow a specific trend. Microsphere size and morphology were determined using scanning electron microscopy. These microspheres exhibited smooth surfaces, no aggregation, and size distributions ranging from 2-34 m in diameter. In vitro release studies of the chemically incorporated salicylic acid displayed widely tunable release profiles.
PMCID: PMC3571728  PMID: 23420391
drug delivery; microspheres; salicylic acid; biodegradable
6.  PolyMorphine: an innovative biodegradable polymer drug for extended pain relief 
Morphine, a potent narcotic analgesic used for the treatment of acute and chronic pain, was chemically incorporated into a poly(anhydride-ester) backbone. The polymer termed “PolyMorphine”, was designed to degrade hydrolytically releasing morphine in a controlled manner to ultimately provide analgesia for an extended time period. PolyMorphine was synthesized via melt-condensation polymerization and its structure was characterized using proton and carbon nuclear magnetic resonance spectroscopies, and infrared spectroscopy. The weight-average molecular weight and the thermal properties were determined. The hydrolytic degradation pathway of the polymer was determined by in vitro studies, showing that free morphine is released. In vitro cytocompatibility studies demonstrated that PolyMorphine is non-cytotoxic towards fibroblasts. In vivo studies using mice showed that PolyMorphine provides analgesia for 3 days, 20 times the analgesic window of free morphine. The animals retained full responsiveness to morphine after being subjected to an acute morphine challenge.
PMCID: PMC3455147  PMID: 22877734
morphine; biodegradable; polymer; extended release; pain treatment; prodrug
7.  Tunable drug release profiles from salicylate-based poly(anhydride-ester) matrices using small molecule admixtures 
Poly(anhydride-esters) with salicylic acid, a nonsteroidal anti-inflammatory drug, chemically incorporated into the polymer backbone provide high inherent drug loading. These poly(anhydride-esters) hydrolytically degrade to release salicylic acid over extended time periods (>30 days); however, an initial lag period of no salicylic acid release is observed. This lag period could be unfavorable in applications where immediate salicylic acid release is desired. Poly(anhydride-esters) with short (2 days) and long (11 days) lag periods were admixed with various small molecules as a means to shorten or eliminate the lag period. Salicylic acid, larger salicylic acid prodrugs, and 1:1 combinations of the two were physically admixed, each at 1%, 5%, and 10% (w/w). All admixtures resulted in immediate salicylic acid release and a decrease in glass transition temperatures compared to polymer alone. By varying the amounts of salicylic acid and salicylic acid prodrugs incorporated into the polymer matrix, immediate and constant salicylic acid release profiles over varied time periods were achieved.
PMCID: PMC3782750  PMID: 24078768
Biodegradable; polymer; salicylic acid; salicylic acid prodrugs; drug delivery; sustained release; poly(anhydride-ester); timed release
8.  Impact of ionizing radiation on physicochemical and biological properties of an amphiphilic macromolecule 
Polymer degradation and stability  2012;97(9):1686-1689.
An amphiphilic macromolecule (AM) was exposed to ionizing radiation (both electron beam and gamma) at doses of 25 kGy and 50 kGy to study the impact of these sterilization methods on the physicochemical properties and bioactivity of the AM. Proton nuclear magnetic resonance and gel permeation chromatography were used to determine the chemical structure and molecular weight, respectively. Size and zeta potential of the micelles formed from AMs in aqueous media were evaluated by dynamic light scattering. Bioactivity of irradiated AMs was evaluated by measuring inhibition of oxidized low-density lipoprotein uptake in macrophages. From these studies, no significant changes in the physicochemical properties or bioactivity were observed after the irradiation, demonstrating that the AMs can withstand typical radiation doses used to sterilize materials.
PMCID: PMC3496278  PMID: 23162175
amphiphilic macromolecule; electron beam radiation; gamma radiation; oxLDL inhibition; stability
9.  Stability of a salicylate-based poly(anhydride-ester) to electron beam and gamma radiation 
Polymer degradation and stability  2011;96(9):1625-1630.
The effect of electron beam and gamma radiation on the physicochemical properties of a salicylate-based poly(anhydride-ester) was studied by exposing polymers to 0 (control), 25 and 50 kGy. After radiation exposure, salicylic acid release in vitro was monitored to assess any changes in drug release profiles. Molecular weight, glass transition temperature and decomposition temperature were evaluated for polymer chain scission and/or crosslinking as well as changes in thermal properties. Proton nuclear magnetic resonance and infrared spectroscopies were also used to determine polymer degradation and/or chain scission. In vitro cell studies were performed to identify cytocompatibility following radiation exposure. These studies demonstrate that the physicochemical properties of the polymer are not substantially affected by exposure to electron beam and gamma radiation.
PMCID: PMC3167163  PMID: 21909173
polyanhydride; sterilization; drug release; gamma irradiation; electron beam; stability
10.  Microscale Plasma-Initiated Patterning of Electrospun Polymer Scaffolds 
Microscale plasma-initiated patterning (μPIP) is a novel micropatterning technique used to create biomolecular micropatterns on polymer surfaces. The patterning method uses a polydimethylsiloxane (PDMS) stamp to selectively protect regions of an underlying substrate from oxygen plasma treatment resulting in hydrophobic and hydrophilic regions. Preferential adsorption of the biomolecules onto either the plasma-exposed (hydrophilic) or plasma-protected (hydrophobic) regions leads to the biomolecular micropatterns. In the current work, laminin-1 was applied to an electrospun polyamide nanofibrillar matrix following plasma treatment. Radial glial clones (neural precursors) selectively adhered to these patterned matrices following the contours of proteins on the surface. This work demonstrates that textured surfaces, such as nanofibrillar scaffolds, can be micropatterned to provide external chemical cues for cellular organization.
PMCID: PMC3062666  PMID: 21345656
Extracellular matrix; micropatterning; nanofibers; laminin-1; glial cells; nerve regeneration
11.  Salicylic acid-derived poly(anhydride-ester) electrospun fibers designed for regenerating the peripheral nervous system 
Continuous biomaterial advances and the regenerating potential of the adult human peripheral nervous system offer great promise for restoring full function to innervated tissue following traumatic injury via synthetic nerve guidance conduits. To most effectively facilitate nerve regeneration, a tissue engineering scaffold within a conduit must be similar to the linear microenvironment of the healthy nerve. To mimic the native nerve structure, aligned poly(lactic-co-glycolic acid)/bioactive polyanhydride fibrous substrates were fabricated through optimized electrospinning parameters with diameters of 600 ± 200 nm. Scanning electron microscopy images show fibers with a high degree of alignment. Schwann cells and dissociated rat dorsal root ganglia demonstrated elongated and healthy proliferation in a direction parallel to orientated electrospun fibers with significantly longer Schwann cell process length and neurite outgrowth when compared to randomly orientated fibers. Results suggest that an aligned polyanhydride fiber mat holds tremendous promise as a supplement scaffold for the interior of a degradable polymer nerve guidance conduit. Bioactive salicylic acid based polyanhydride fibers are not limited to nerve regeneration and offer exciting promise for a wide variety of biomedical applications.
PMCID: PMC3096072  PMID: 21442724
Nerve regeneration; electrospinning; fibers; polyanhydride; salicylic acid
12.  Storage Stability Study of Salicylate-based Poly(anhydride-esters) 
Polymer degradation and stability  2010;95(9):1778-1782.
Storage stability was evaluated on a biodegradable salicylate-based poly(anhydride-ester) to elucidate the effects of storage conditions over time. The hydrolytically labile polymer samples were stored in powdered form at five relevant storage temperatures (−12 °C, 4 °C, 27 °C, 37 °C, 50 °C) and monitored over four weeks for changes in color, glass transition temperature, molecular weight, and extent of hydrolysis. Samples stored at lower temperatures remained relatively constant with respect to bond hydrolysis and molecular weight. Whereas, samples stored at higher temperatures displayed significant hydrolysis. For hydrolytically degradable polymers, such as these poly(anhydride-esters), samples are best stored at low temperatures under an inert atmosphere.
PMCID: PMC2997568  PMID: 21152105
Polyanhydride; Stability; Degradation; Biodegradable; Hydrolysis
13.  Nanoscale amphiphilic macromolecules as lipoprotein inhibitors: the role of charge and architecture 
A series of novel amphiphilic macromolecules composed of alkyl chains as the hydrophobic block and poly(ethylene glycol) as the hydrophilic block were designed to inhibit highly oxidized low density lipoprotein (hoxLDL) uptake by synthesizing macromolecules with negatively charged moieties (ie, carboxylic acids) located in the two different blocks. The macromolecules have molecular weights around 5,500 g/mol, form micelles in aqueous solution with an average size of 20–35 nm, and display critical micelle concentration values as low as 10−7 M. Their charge densities and hydrodynamic size in physiological buffer solutions correlated with the hydrophobic/hydrophilic block location and quantity of the carboxylate groups. Generally, carboxylate groups located in the hydrophobic block destabilize micelle formation more than carboxylate groups in the hydrophilic block. Although all amphiphilic macromolecules inhibited unregulated uptake of hoxLDL by macrophages, inhibition efficiency was influenced by the quantity and location of the negatively charged-carboxylate on the macromolecules. Notably, negative charge is not the sole factor in reducing hoxLDL uptake. The combination of smaller size, micellar stability and charge density is critical for inhibiting hoxLDL uptake by macrophages.
PMCID: PMC2676825  PMID: 18203436
polymeric micelles; amphiphilic macromolecules; highly oxidized low-density lipoproteins; scavenger receptor inhibition
14.  In silico design of anti-atherogenic biomaterials 
Biomaterials  2013;34(32):10.1016/j.biomaterials.2013.07.011.
Atherogenesis, the uncontrolled deposition of modified lipoproteins in inflamed arteries, serves as a focal trigger of cardiovascular disease (CVD). Polymeric biomaterials have been envisioned to counteract atherogenesis based on their ability to repress scavenger mediated uptake of oxidized lipoprotein (oxLDL) in macrophages. Following the conceptualization in our laboratories of a new library of amphiphilic macromolecules (AMs), assembled from sugar backbones, aliphatic chains and poly(-ethylene glycol) tails, a more rational approach is necessary to parse the diverse features such as charge, hydrophobicity, sugar composition and stereochemistry. In this study, we advance a computational biomaterials design approach to screen and elucidate anti-atherogenic biomaterials with high efficacy. AMs were quantified in terms of not only 1D (molecular formula) and 2D (molecular connectivity) descriptors, but also new 3D (molecular geometry) descriptors of AMs modeled by coarse-grained molecular dynamics (MD) followed by all-atom MD simulations. Quantitative structure-activity relationship (QSAR) models for anti-atherogenic activity were then constructed by screening a total of 1164 descriptors against the corresponding, experimentally measured potency of AM inhibition of oxLDL uptake in human monocyte-derived macrophages. Five key descriptors were identified to provide a strong linear correlation between the predicted and observed anti-atherogenic activity values, and were then used to correctly forecast the efficacy of three newly designed AMs. Thus, a new ligand-based drug design framework was successfully adapted to computationally screen and design biomaterials with cardiovascular therapeutic properties.
PMCID: PMC3880781  PMID: 23891521
Amphiphilic macromolecules; Macrophages; Atherosclerosis; Molecular modeling; Structure-activity relations
15.  Nanoscale Amphiphilic Macromolecules with Variable Lipophilicity and Stereochemistry Modulate Inhibition of Oxidized Low-Density Lipoprotein Uptake 
Biomacromolecules  2013;14(8):2463-2469.
Amphiphilic macromolecules (AMs) based on carbohydrate domains functionalized with poly(ethylene glycol) can inhibit the uptake of oxidized low density lipoprotein (oxLDL) and counteract foam cell formation, a key characteristic of early atherogenesis. To investigate the influence of lipophilicity and stereochemistry on the AMs' physicochemical and biological properties, mucic acid-based AMs bearing four aliphatic chains (2a) and tartaric acid-based AMs bearing two (2b and 2l) and four aliphatic chains (2g and 2k) were synthesized and evaluated. Solution aggregation studies suggested that both the number of hydrophobic arms and the length of the hydrophobic domain impact AM micelle sizes, whereas stereochemistry impacts micelle stability. 2l, the meso analogue of 2b, elicited the highest reported oxLDL uptake inhibition values (89%), highlighting the crucial effect of stereochemistry on biological properties. This study suggests that stereochemistry plays a critical role in modulating oxLDL uptake and must be considered when designing biomaterials for potential cardiovascular therapies.
PMCID: PMC3773991  PMID: 23795777
Amphiphilic polymer; atherosclerosis; self-assembled micelle; oxLDL inhibition
16.  Biodegradable Ferulic Acid-containing Poly(anhydride-ester): Degradation Products with Controlled Release and Sustained Antioxidant Activity 
Biomacromolecules  2013;14(3):854-861.
Ferulic acid (FA) is an antioxidant and photoprotective agent used in biomedical and cosmetic formulations to prevent skin cancer and senescence. Although FA exhibits numerous health benefits, physicochemical instability leading to decomposition hinders its efficacy. To minimize inherent decomposition, a FA-containing biodegradable polymer was prepared via solution polymerization to chemically incorporate FA into a poly(anhydride-ester). The polymer was characterized using nuclear magnetic resonance and infrared spectroscopies. The molecular weight and thermal properties were also determined. In vitro studies demonstrated that the polymer was hydrolytically degradable, thus providing controlled release of the chemically incorporated bioactive with no detectable decomposition. The polymer degradation products were found to exhibit antioxidant and antibacterial activity comparable to free FA and in vitro cell viability studies demonstrated that the polymer is non-cytotoxic towards fibroblasts. This renders the polymer a potential candidate for use as a controlled release system for skin care formulations.
PMCID: PMC3595371  PMID: 23327626
biodegradable; polymer; poly(anhydride-ester); ferulic acid; antioxidant; controlled release
17.  Synthesis and Characterization of 5-Aminosalicylic Acid Based Poly(anhydride-esters) by Solution Polymerization 
PMCID: PMC3889020  PMID: 24431483
5-aminosalicylic acid; polyanhydride; polymer drug; solution polymerization; triphosgene
18.  Carbohydrate Composition of Amphiphilic Macromolecules Influences Physicochemical Properties and Binding to Atherogenic Scavenger Receptor A 
Acta biomaterialia  2012;8(11):3956-3962.
Amphiphilic macromolecules (AMs) based on carbohydrate domains functionalized with poly(ethylene glycol) can inhibit the uptake of oxidized low density lipoprotein (oxLDL) mediated by scavenger receptor A (SR-A) and counteract foam cell formation, the characteristic “atherosclerotic” phenotype. A series of AMs were prepared by altering the carbohydrate chemistry to evaluate the influence of backbone architecture on the physicochemical and biological properties. Upon evaluating the degree of polymer-based inhibition of oxLDL uptake in human embryonic kidney cells expressing SR-A, two AMs (2a and 2c) were found to have the most efficacy. Molecular modeling and docking studies show that these same AMs have the most favorable binding energies and most close interactions with the molecular model of SR-A collagen-like domain. Thus, minor changes in the AMs architecture can significantly affect the physicochemical properties and inhibition of oxLDL uptake. These insights can be critical for designing optimal AM-based therapeutics for management of cardiovascular disease.
PMCID: PMC3462273  PMID: 22835678
Amphiphilic polymer; atherosclerosis; self-assembled micelle; oxLDL inhibition
19.  Synthesis and characterization of antiseptic-based poly(anhydride-esters) 
Poly(anhydride-esters) were prepared from catechol, fenticlor and hexachlorophene. The molecular weights (Mw) of the polymers were typically > 10,000 Da with glass transition temperatures (Tg) ranging from 23 to 84 °C. The thermal characteristics of the polymers paralleled the melting temperatures of the chemically incorporated antiseptic molecules. The in vitro release of the chemically incorporated antiseptic molecules were monitored over a 12 week period. For comparison, the in vitro release of physically admixed antiseptic molecules were also observed. After 12 weeks, the polymers were not completely degraded with drug release ranging from less than 1 to 55 %. Sessile-drop contact angles indicated that the polymers were relatively hydrophobic, contributing to the slow polymer degradation rates.
PMCID: PMC3769797  PMID: 24039323
20.  Optimized Synthesis of Salicylate-based Poly(anhydride-esters) 
The synthesis of a salicylate-based poly(anhydride-ester) was optimized to improve the overall efficiency and quality of the polymer. First, a new approach for the preparation of the polymer precursor minimizes the overall number of synthetic steps and increases the overall yield. Second, the melt-polymerization apparatus was modified to include dynamic mixing, which yields polymer with increased molecular weights on both the milligram and gram scale.
PMCID: PMC3748603  PMID: 23976808
21.  Effect of Linker Structure on Salicylic Acid-Derived Poly(anhydride–esters) 
Macromolecules  2005;38(16):6895-6901.
A series of salicylic acid-derived poly(anhydride–esters) were synthesized by melt polym erization methods, in which the structures of the molecule (“linker”) linking together the two salicylic acids were varied. To determine the relationship between the linker and the physical properties of the corresponding poly(anhydride–ester), several linkers were evaluated including linear aliphatic, aromatic, and aliphatic branched structures. For the linear aliphatic linkers, higher molecular weights were obtained with longer linear alkyl chains. The most sterically hindered linkers yielded lower molecular weight polymers. The thermal decomposition temperature increased with the alkyl chain length, but the glass transition temperature decreased, due to the enhanced flexibility of the polymer. The highest glass transition temperatures were obtained by using aromatic linkers as a result of increased π–π interactions. Water contact angles determined the relative hydrophobicity of the polymers, which correlated to hydrolytic degradation rates; i.e., the highest contact angle values yielded the slowest degrading polymers.
PMCID: PMC3748625  PMID: 23976793
22.  Synthesis and Characterization of Salicylic Acid-Based Poly(Anhydride-Ester) Copolymers 
A series of poly(anhydride-esters) based on poly(1,10-bis(o-car-boxyphenoxy)decanoate) (CPD) and poly(1,6-bis(p-carboxyphenoxy)hexane) (p-CPH) were synthesized by melt-condensation polymerization. Poly-(anhydride-esters) that contain CPD hydrolytically degraded into salicylic acid, however, these homopolymers have mechanical and thermal characteristics that limit their use in clinical applications. The synthesis and characterization of copolymers of CPD with p-CPH, a monomer known to generate mechanically stable homopolymers, was investigated. By changing the CPD to p-CPH monomer ratios, the salicylic acid loading and thermal/mechanical properties of the copolymers was a controlling factor; increasing the CPD concentration increased the salicylate loading but decreased the polymer stability; whereas increasing the p-CPH concentration increased the thermal and mechanical stability of the copolymers. Specifically, decreasing the CPD:p-CPH ratio resulted in lower salicylate loading and increased thermal decomposition temperatures. The glass transition temperatures (°C) varied from 27 to 38°C, a desirable range for elastomeric biomedical implants.
PMCID: PMC3744112  PMID: 23956492
poly(anhydride-ester); salicylic acid; drug loading; thermal properties; degradation; polyanhydride stability
23.  Kinetically Assembled Nanoparticles of Bioactive Macromolecules Exhibit Enhanced Stability and Cell-Targeted Biological Efficacy 
Kinetically assembled nanoparticles are fabricated from an advanced class of bioactive macromolecules that have potential utility in counteracting atherosclerotic plaque development via receptor-level blockage of inflammatory cells. In contrast to micellar analogs that exhibit poor potency and structural integrity under physiologic conditions, these kinetic nanoparticle assemblies maintain structural stability and demonstrate superior bioactivity in mediating oxidized low-density lipoprotein (oxLDL) uptake in inflammatory cells.
PMCID: PMC3495129  PMID: 22223224
Nanomedicine; Cardiovascular Disease; Macrophages; Atherosclerosis; Flash NanoPrecipitation; Biomedical Applications
24.  Thermodynamic and Physical Interactions between Novel Polymeric Surfactants and Lipids: Toward Designing Stable Polymer–Lipid Complexes 
Surfactant amphiphilic macromolecules (AMs) were complexed with a 1:1 ratio of 1,2-dioleoyl-3-trimethyl-ammonium-propane (DOTAP) and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), either by a coevaporation (CE) or postaddition (PA) method, to form AM–lipid complexes with enhanced drug delivery applications. By characterizing the surfactant–lipid interactions, these heterogeneous drug delivery systems can be better controlled and engineered for optimal therapeutic outcomes. In this study, the physical interactions between DOPE:DOTAP liposomes and AM surfactants were investigated. Langmuir fllm balance and isothermal calorimetry studies showed cooperative intermolecular interactions between pure lipids and AM in monolayers and high thermostability of structure formed by the addition of AM micelles to DOTAP: DOPE vesicles in buffer solution respectively. Increasing the AM weight ratio in the complexes via the CE method led to complete vesicle solubilization—from lamellar aggregates, to a mixture of coexisting vesicles and micelles, to mixed micelles. Isothermal calorimetry evaluation of AM-lipid complexes shows that, at higher AM weight ratios, PA-produced complexes exhibit greater stability than complexes at lower AM weight ratios. Similar studies show that AM-lipid complexes produced by the CE methods display stronger interactions between AM-lipid components than complexes produced by the PA method. The results suggest that the PA method produces vesicles with AM molecules associated with its outer leaflet only (i.e., an AM-coated vesicle), while the CE method produces complexes ranging from mixed vesicles to mixed micelle in which the AM-lipid components are more intimately associated. These results will be helpful in the design of AM-lipid complexes as structurally defined, stable, and effective drug delivery systems.
PMCID: PMC3566872  PMID: 21732646
25.  Preferential cellular uptake of amphiphilic macromolecule–lipid complexes with enhanced stability and biocompatibility 
Amphiphilic macromolecules (AM) were electrostatically complexed with a 1:1 ratio of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) to form AM–lipid complexes with drug delivery applications. The complexes exist as AM-coated liposomes and their drug delivery properties can be tuned by altering the AM–lipid weight ratio. The complexation and tuning are achieved in a simple, efficient, and scalable manner. The gradual increase in lipid ratios concurrently increased the zeta potential of the complexes, which directly correlates to increased cell uptake of the complexes in vitro with preferential uptake noted in BT-20 carcinoma cells versus normal fibroblasts. Increasing AM content increased complex steric stability in the presence of serum proteins and reduced the inherent cytotoxicity towards fibroblasts in vitro. AM–lipid complexes solubilized paclitaxel and showed drug-mediated, dose-dependent cytotoxicity towards target BT-20 cells in vitro. AM–lipid complexes make good candidates as drug delivery systems due to their tunable zeta potential, steric stability, inherently low cytotoxicity, and ability to load and deliver insoluble chemotherapeutic agents. Significantly, their preferential uptake in a carcinoma cell line over normal cells in vitro demonstrates a unique, passive targeting approach to delivery anti-cancer therapeutics.
PMCID: PMC3564574  PMID: 21510986
Liposomes; Amphiphilic macromolecules; Preferential cell uptake; Drug delivery; Paclitaxel

Results 1-25 (32)