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Biomedical subjects

Changyou Gao

Publications and source records attributed to Changyou Gao.

13 recordsLinked to original sources
PubMed2003

Swelling and shrinking of polyelectrolyte microcapsules in response to changes in temperature and ionic strength.

Swelling and shrinking of polyelectrolyte microcapsules consisting of poly(styrene sulfonate, sodium salt) (PSS) and poly(diallyldimethyl ammonium) chloride (PDADMAC) multilayers have been observed in response to temperature and electrolyte exposure, respectively. Heat-induced capsule swelling and capsule wall volume reduction were observed by confocal laser scanning microscopy (CLSM) and scanning force microscopy (SFM). On the other hand, pronounced shrinking in diameter induced by exposure to an electrolyte was observed in parallel to increases in the thickness of the capsule wall. The estimated wall volume was reduced to two thirds of the control for the salt-exposed capsules and one half for the salt-exposed and simultaneously annealed capsules. This reduction in volume was supposedly mainly caused by the compression of the capsule wall due to the ionic screening from the electrolyte. The highly porous microstructure of the multilayers and loosely bound PSS/PDADMAC complex are thought to be responsible for the structure of the PSS/PDADMAC capsules being easily modulated upon annealing and salt-exposure.

Journal Article↗
PubMed2003

Chondrocyte behaviors on poly-L-lactic acid (PLLA) membranes containing hydroxyl, amide or carboxyl groups.

Hydrophilic groups, i.e. hydroxyl (-OH), carboxyl (-COOH) or amide (-CONH(2)) were introduced onto the poly-L-lactic acid (PLLA) membrane surfaces via the photo-induced grafting copolymerization of the corresponding monomers, i.e. hydroxyethyl methacrylate, methacrylic acid or acrylamide, respectively. Chondrocyte culture was used to study the correlation between the cell behaviors and the hydrophilic functional groups. The results showed that the cytocompatibility of the PLLA membranes with hydroxyl or amide groups on the surface was greatly improved compared to that of the original PLLA membrane. However, the PLLA membrane with carboxyl groups on the surface had even worse cytocompatibility though possessed a similar hydrophilicity.

Animals↗
PubMed2003

Surface modification of poly-L-lactic acid (PLLA) membrane by grafting acrylamide: an effective way to improve cytocompatibility for chondrocytes.

Poly-L-lactic acid (PLLA) membranes were photo-oxidized in hydrogen peroxide solution under ultraviolet light (UV) to introduce hydroperoxide groups onto the PLLA membrane surfaces. The photo-oxidized membranes were then immersed in acrylamide (AAm) solution containing Fe2+ to graft polyacrylamide (PAAm) onto the PLLA membrane surfaces. The density of the hydroperoxide groups introduced on the PLLA membrane surfaces varied with the temperature and the photo-oxidization time. The occurrence of grafting was verified by X-ray photoelectron spectroscopy (XPS). The degree of grafting increased with the monomer concentration and the polymerization time. Water contact angle measurements showed that the wettability of the modified PLLA membranes had improved. Chondrocytes proliferated more rapidly and were more spread out on the modified membrane than on the control PLLA membrane, indicating that the PAAm-grafted PLLA membrane has better cytocompatibility for chondrocytes.

Acrylamide↗
PubMed2003

[Polymeric materials for tissue engineering].

As regeneration scaffolds or templates in tissue engineering, polymeric materials play key roles in inducing tissue regeneration, and mediating cell growth and differentiation, i.e. functioning as artificial extracellular matrix. The polymeric materials including biological derived biopolymers and synthetic polymers, which are usually employed in tissue engineering, are reviewed in this paper.

Biocompatible Materials↗
PubMed2002

Surface engineering of poly(D,L-lactic acid) by entrapment of chitosan-based derivatives for the promotion of chondrogenesis.

Chitosan and chitosan-amino acid derivatives were explored to engineer poly(D,L-lactic acid) (PDL-LA) as an extracellular matrix-like surface to promote cell adhesion and growth. Four kinds of chitosan-amino acid derivatives were prepared to mimic the carbohydrate moieties of cell matrix glycoprotein. The chitosan-amino acid derivatives were characterized by using Fourier transform infrared and ultraviolet spectra. The amino acid content on chitosan-amino acid derivatives was determined by using a ninhydrin-ultraviolet method. A new strategy, entrapment, was therefore used to modify the PDL-LA membrane with chitosan and chitosan-amino acid derivatives. The results of X-ray photoelectron spectroscopy, attenuated total reflectance-Fourier transform infrared, and contact angle confirmed that a stable thin film of chitosan and its derivatives can be entrapped on the surface of the PDL-LA membrane. From the results of chondrocyte cytocompatibility, MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assays, and cell morphology, the chitosan-amino acid derivative modified PDL-LA membranes were shown to promote chondrogenesis. The novel surface treatment method combines the good mechanical property of PDL-LA with the good cytocompatibility of chitosan derivatives, which may have potential for tissue engineering.

Amino Acids↗
PubMed2002

Immobilization of natural macromolecules on poly-L-lactic acid membrane surface in order to improve its cytocompatibility.

With the use of a grafting-coating method, three kinds of natural macromolecules, that is, gelatin, collagen, or chitosan, were immobilized on poly-L-lactic acid (PLLA) membrane surfaces with the goal of improving of cellular interactions. Attenuated total reflectance infrared spectroscopy (ATR-IR), x-ray photoelectron spectroscopy (XPS) and surface morphology analysis using scanning electronic microscopy (SEM) confirmed that the natural macromolecule layers adhered tightly to the hydrophobic PLLA membrane surfaces. Chondrocyte culture showed that the modified PLLA membranes had higher cell attachment, higher cell proliferation rate, and higher cell activity than the control PLLA membrane. Moreover, the chondrocytes were more spread out on the modified PLLA membranes than on the control PLLA membranes.

Animals↗
PubMed2002

Surface engineering of poly(DL-lactic acid) by entrapment of alginate-amino acid derivatives for promotion of chondrogenesis.

Alginate-amino acid derivatives were explored to engineer poly(DL-lactic acid)(PDL-LA) as glycocalyx-like surface to promote cell adhesion and growth. Four different kinds of alginate-amino acid derivatives were synthesized to mimic the glycocalyx of cell membrane to promote chondrogenesis. The alginate-amino acid derivatives were characterized by FT-IR, 1H NMR and UV spectra and the amino acid content on alginate-amino acid derivatives was given by ninhydrin-UV method. A new strategy, entrapment, was then employed to modify PDL-LA membranes with alginate and its amino acid derivatives. The results of XPS, ATR-FTIR and contact angle confirmed that a stable thin film of alginate and its amino acid derivatives can be entrapped on the surface of PDL-LA membrane. The chondrocyte cytocompatibility test and MTT assays indicated that the alginate-amino acid derivatives modified PDL-LA membranes could promote chondrogenesis. The novel surface treatment method may have potentials for tissue engineering and other biomedical applications.

Alginates↗
PubMed2002

Surface modification of polycaprolactone with poly(methacrylic acid) and gelatin covalent immobilization for promoting its cytocompatibility.

Polycaprolactone (PCL) membrane was modified by grafting copolymerization of methacrylic acid (MAA) initiated under UV light. The covalent immobilization of gelatin on PCL-g-PMAA surface was consequently performed by using condensing agent, 1-ethyl-3-(3-dimethylamino propyl) carbodiimide hydrochloride. The occurrence of grafting copolymerization of PMAA and further immobilization of gelatin was confirmed by ATR-FTIR and X-ray photoelectron spectroscopy characterizations. The existence of carboxyl groups grafted on PCL surface was verified quantitatively by absorbance spectroscopy where rhodamine 6G was employed to react with carboxyl groups to generate an absorbance at 512 nm. The endothelial cell culture proved that the PCL membrane slightly modified with suitable amount of PMAA or gelatin had better cytocompatibility than control PCL or PCL membrane heavily modified with PMAA or gelatin.

Biocompatible Materials↗
PubMed2002

[Materials and structure design of artificial dermis equivalent based on collagen].

The schematic structure model, materials selection and microstructure modulation are introduced for the design of artificial dermis equivalent. The artificial skin should also possess a bilayer structure that imitates then natural skin, i.e. the top layer functions as a temporary epidermis which is composed of polymer elastomer that is permeable for moisture but not for water, the bottom layer is the skin regeneration template employing collagen based sponge. In addition to collagen, polysaccharides like glycosaminoglycan is also used in the artificial dermis equivalent in order to simulate the natural extracellular matrix of skin and to modulate the degradation rate. The pore size and morphology of collagen porous membranes can be controlled by variation of the pH value, concentration and freezing temperature. Hence, the microstructure of the dermis equivalent can be optimized. The collagen based artificial dermis equivalent thus fabricated may be an option to skin graft in the clinical treatment of full skin injuries and ulcers.

Biocompatible Materials↗
PubMedDate not supplied

Surface modification of polycaprolactone membrane via aminolysis and biomacromolecule immobilization for promoting cytocompatibility of human endothelial cells.

Amino groups were covalently introduced onto a polycaprolactone (PCL) surface by the reaction between 1,6-hexanediamine and the ester groups of PCL. The occurrence of the aminolysis and the introduction of free NH(2) groups were verified qualitatively by fluorescence spectroscopy, where rhodamine B isothiocyanate was employed to label NH(2) groups, and quantitatively by absorbance spectroscopy, where ninhydrin was used to react with NH(2) to generate a blue product. Due to the presence of deep pores on the PCL membrane, the aminolysis reaction could penetrate as deep as 50 microm to yield NH(2) density as high as 2 x 10(-7) mol/cm(2). By use of the NH(2) groups as active sites, biocompatible macromolecules such as gelatin, chitosan, or collagen were further immobilized on the aminolyzed PCL membrane via a cross-linking agent, glutaraldehyde. X-ray photoelectron spectroscopy (XPS) and surface wettability measurements confirmed the coupling of the biomacromolecules. The endothelial cell culture proved that the cytocompatibility of the aminolyzed PCL was improved slightly regardless of the NH(2) amount on the surface. After immobilization of the biomacromolecules, however, the cell attachment and proliferation ratios were obviously improved and the cells showed a similar morphology to those on tissue culture polystyrene. Measurement of the von Willebrand factor (vWF) secreted by these endothelial cells (ECs) verified the endothelial function. Hence, a better EC-compatible PCL was produced.

Amination↗
PubMedDate not supplied

Layer-by-layer assembly to modify poly(l-lactic acid) surface toward improving its cytocompatibility to human endothelial cells.

A novel technique to introduce free amino groups onto polyester scaffolds via aminolyzing the ester groups with diamine has been developed recently. Positively charged chitosan was then deposited onto the aminolyzed poly(l-lactic acid) (PLLA) membrane surface in a layer-by-layer assembly manner using poly(styrene sulfonate, sodium salt) (PSS) as a negatively charged polyelectrolyte. The layer-by-layer deposition process of PSS and chitosan was monitored by UV-vis absorbance spectroscopy, energy transfer by fluorescence spectroscopy, and advancing contact angle measurements. The existed chitosan obviously improved the cytocompatibility of PLLA to human endothelial cells. The cell attachment, activity, and proliferation on the PLLA membranes assembled with three or five bilayers of PSS/chitosan with chitosan as the outermost layer were better than those with one bilayer of PSS/chitosan or the control PLLA. The cells also showed morphology of an elongated shape with abundant cytoplasm, and a confluent cell layer was reached after being cultured for 4 days. Measurement of von Willebrand factor secreted by these endothelial cells (ECs) verified the endothelial function. Hence, better ECs compatible PLLA were produced.

Cells, Cultured↗