Search tips
Search criteria

Results 1-6 (6)

Clipboard (0)

Select a Filter Below

more »
Year of Publication
Document Types
author:("He, lizhong")
1.  pH-Based Regulation of Hydrogel Mechanical Properties Through Mussel-Inspired Chemistry and Processing 
Advanced functional materials  2012;23(9):1111-1119.
The mechanical holdfast of the mussel, the byssus, is processed at acidic pH yet functions at alkaline pH. Byssi are enriched in Fe3+ and catechol-containing proteins, species with chemical interactions that vary widely over the pH range of byssal processing. Currently, the link between pH, Fe3+-catechol reactions, and mechanical function are poorly understood. Herein, we describe how pH influences the mechanical performance of materials formed by reacting synthetic catechol polymers with Fe3+. Processing Fe3+-catechol polymer materials through a mussel-mimetic acidic-to-alkaline pH change leads to mechanically tough materials based on a covalent network fortified by sacrificial Fe3+-catechol coordination bonds. Our findings offer the first direct evidence of Fe3+-induced covalent cross-linking of catechol polymers, reveal additional insight into the pH dependence and mechanical role of Fe3+- catechol interactions in mussel byssi, and illustrate the wide range of physical properties accessible in synthetic materials through mimicry of mussel protein chemistry and processing.
PMCID: PMC3589528  PMID: 23483665
Biomimetics; Hydrogels; Polymeric Materials; Structure-Property Relationships
2.  Mussel-inspired histidine-based transient network metal coordination hydrogels 
Macromolecules  2013;46(3):1167-1174.
Transient network hydrogels cross-linked through histidine-divalent cation coordination bonds were studied by conventional rheologic methods using histidine-modified star poly(ethylene glycol) (PEG) polymers. These materials were inspired by the mussel, which is thought to use histidine-metal coordination bonds to impart self-healing properties in the mussel byssal thread. Hydrogel viscoelastic mechanical properties were studied as a function of metal, pH, concentration, and ionic strength. The equilibrium metal-binding constants were determined by dilute solution potentiometric titration of monofunctional histidine-modified methoxy-PEG and were found to be consistent with binding constants of small molecule analogs previously studied. pH-dependent speciation curves were then calculated using the equilibrium constants determined by potentiometric titration, providing insight into the pH dependence of histidine-metal ion coordination and guiding the design of metal coordination hydrogels. Gel relaxation dynamics were found to be uncorrelated with the equilibrium constants measured, but were correlated to the expected coordination bond dissociation rate constants.
PMCID: PMC3579674  PMID: 23441102
3.  Mussel-Inspired Silver-Releasing Antibacterial Hydrogels 
Biomaterials  2012;33(15):3783-3791.
A silver-releasing antibacterial hydrogel was developed that simultaneously allowed for silver nanoparticle formation and gel curing. Water-soluble polyethylene glycol (PEG) polymers were synthesized that contain reactive catechol moieties, inspired by mussel adhesive proteins, where the catechol containing amino acid 3,4-dihydroxyphenylalanine (DOPA) plays an important role in the ability of the mussel to adhere to almost any surface in an aqueous environment. We utilized silver nitrate to oxidize polymer catechols, leading to covalent cross-linking and hydrogel formation with simultaneous reduction of Ag(I). Silver release was sustained for periods of at least two weeks in PBS solution. Hydrogels were found to inhibit bacterial growth, consistent with the well-known antibacterial properties of silver, while not significantly affecting mammalian cell viability. In addition, thin hydrogel films were found to resist bacterial and mammalian cell attachment, consistent with the antifouling properties of PEG. We believe these materials have a strong potential for antibacterial biomaterial coatings and tissue adhesives, due to the material-independent adhesive properties of catechols.
PMCID: PMC3367767  PMID: 22374454
4.  Clinicopathological Characteristics and Survival Analysis of 87 Male Breast Cancer Cases 
Breast Care  2011;6(6):446-451.
The aim of this study was to investigate the clinicopathologic characteristics, therapy methods, and prognosis of male breast cancer.
Patients and Methods
We retrospectively analyzed the clinicopathological characteristics, recurrence or metastasis, and survival information of 87 male breast cancer patients. Statistical analysis included the Kaplan-Meier method to analyze survivals, log-rank to compare curves between groups, and Cox regression for multivariate prognostic analysis. A p value of <0.05 was considered statistically significant.
5-year disease free survival (DFS) and 5-year overall survival (OS) were 66.3 and 77.0%, respectively. Monofactorial analysis showed tumor size, stage, lymph node involvement, and adjuvant chemotherapy to be prognostic factors with regard to 5-year DFS and 5-year OS. Multivariate Cox regression analysis showed tumor size, stage, and adjuvant chemotherapy to be independent prognostic factors with regard to 5-year DFS and 5-year OS.
Male breast cancer has a lower incidence rate and poor prognosis. Invasive ductal carcinoma is the main pathologic type. Operation-based combined therapy is the standard care for these patients. Tumor size, stage, and adjuvant chemotherapy are independent prognostic factors. More emphasis should be placed on early diagnosis and early therapy, and adjuvant chemotherapy may improve survival.
PMCID: PMC3290016  PMID: 22419898
Male breast cancer; Clinical characteristics; Therapy; Prognosis
5.  Facile, high efficiency immobilization of lipase enzyme on magnetic iron oxide nanoparticles via a biomimetic coating 
BMC Biotechnology  2011;11:63.
Immobilization of lipase on appropriate solid supports is one way to improve their stability and activity, and can be reused for large scale applications. A sample, cost- effective and high loading capacity method is still challenging.
A facile method of lipase immobilization was developed in this study, by the use of polydopamine coated magnetic nanoparticles (PD-MNPs). Under optimal conditions, 73.9% of the available lipase was immobilized on PD-MNPs, yielding a lipase loading capacity as high as 429 mg/g. Enzyme assays revealed that lipase immobilized on PD-MNPs displayed enhanced pH and thermal stability compared to free lipase. Furthermore, lipase immobilized on PD-MNPs was easily isolated from the reaction medium by magnetic separation and retained more than 70% of initial activity after 21 repeated cycles of enzyme reaction followed by magnetic separation.
Immobilization of enzyme onto magnetic iron oxide nanoparticles via poly-dopamine film is economical, facile and efficient.
PMCID: PMC3212977  PMID: 21649934
6.  Quality of Life after Autologous Peripheral Blood Stem Cell Transplantation and High-Dose Chemotherapy in High-Risk Breast Cancer Patients 
Breast Care  2009;4(6):379-386.
As long-term survivors of breast cancer after autologous peripheral blood stem cell transplantation (ASCT) are becoming more numerous, studies addressing the issue of long-term follow-up are necessary. In this study, we report on the quality of life (QOL) after ASCT and high-dose chemotherapy (HDCT).
Patients and Methods
The QOL questionnaire version 3.0 by the European Organization for Research and Treatment of Cancer (EORTC QLQ-C30 version 3.0) was filled in by patients and healthy controls at 5 time points. After obtaining the results, we analyzed the correlation between QOL and the effect factors.
Some functions got significantly worse, and some symptoms got more serious after ASCT and HDCT. However, most of them improved with time and were comparable to the healthy controls after 5 years. QOL was in part related to age, tumor characteristics, educational level, marriage status, and income.
Evaluating QOL allows medical workers to fully understand a patient's state of health, and aid the estimation and selection of clinical treatment methods as well as improve recovery.
PMCID: PMC2942001  PMID: 20877673
Quality of life; Autologous peripheral blood stem cell transplantation; High-risk breast cancer

Results 1-6 (6)