Key Engineering Materials Vols. 288-289

Abstract: A novel process was developed to fabricate polymer/ceramic composites for bone tissue engineering. The mixture of polylactic acid (PLA), calcium metaphosphate (CMP), and NaCl were compressed and subsequently heated. After dissolving the NaCl salts, porous biodegradable polymer/ceramic composite scaffolds were formed. The characteristics of the scaffolds were compared to those of scaffolds fabricated using a conventional solvent casting method, in terms of pore structure, pore size distribution, and mechanical properties. The scaffolds were seeded by osteoblasts and cultured in vitro or implanted into nude mice subcutaneously for up to 5 weeks. Cells were better grown to form tissue-like structures on CMP/PLA composites fabricated by the Press-and-Baking method. In addition, the alkaline phosphatase activity of and calcium deposition in the scaffolds explanted from mice were enhanced significantly for the scaffolds by Press-and-Baking compared to them by solvent casting. Taken together, these results suggest that CMP promote cell differentiation and proliferation via direct interaction with cells in the CMP/PLA composites. This novel PLA/CMP composite will be applicable for bone tissue engineering to support and cell differentiation and growth.

Abstract: Repair of osteochondral defects created in rabbit femoral trochlea were studied using a water-soluble sulfated p-GlcNAc formulation, (Marine Polymer Technologies, Danvers, MA, USA). After 12 weeks of healing empty defects were compared to defects filled with sulfated p-GlcNAc sponge alone and sulfated p-GlcNAc sponge seeded with autologous chondrocytes. The chondrocyte seeded sponge provided the best healing of both cartilage and subchondral bone. The sulfated p-GlcNAc sponge alone did not provide as good healing as the chondrocyte seeded sponge, but healing was still superior to that of the empty defect. This study supports the use of p-GlcNAc sponge to augment healing of osteochondral defects in animal models.

Abstract: The porous poly（β-hydroxybutyrate-co-β-hydroxyvalerate）（PHBV）/bioactive glasses （BG） tissue engineering scaffold was prepared in this article. The mineralization behavior of the porous PHBV/BG scaffold was observed in simulated body fluid (SBF). The ion concentration of calcium, silicon and phosphorus in different mineralization periods were tested by inductively coupled plasma (ICP). The formation of the hydroxyl carbonate apatite(HCA) layer on the scaffold surface was confirmed by the Fourier transform infrared(FTIR) spectroscopy and X-ray diffraction(XRD) apparatus. The micro morphology and porosity of the scaffold before and after mineralization were observed by scanning electron microscopy(SEM). The in vivo biological evaluation of the porous PHBV/BG scaffolds was carried out by implanting the scaffold into the rat muscle to test the biocompatibility. The in vivo result shows that the composite exhibit good biocompatibility. The porous PHBV/BG scaffold is suitable for tissue engineering.

Abstract: Chitosan is considered to be a very promising biopolymer for various biomedical and pharmaceutical uses because of its nontoxic and biocompatible nature [1]. In this paper, we introduced and discussed chitosan-based biomaterials used for hepatocyte culture, including chitosan microcarriers, heparin and alginate modified chitosan scaffolds, collagen-chitosan complex and sugar-modified chitosan scaffold

Abstract: Chitosan has been considered to be a good candidate for gene delivery system, since it is already known as a biocompatible, biodegradable, and low toxic material with high cationic potential. However, low specificity and low transfection efficiency of chitosan need to be overcome prior to clinical trial. In this review paper, chemical modification of chitosan for enhancement of cell specificity and transfection efficiency was explained. Also, chemical modification of chitosan for the stability of chitosan/DNA complexes was reviewed.

Abstract: Films composed of alternating layers of protamine and DNA were constructed using the layer-by-layer method on quartz and subsequently studied the enzymic degradation in vitro. UV-visible spectrometry measurement indicated the uniform assembly of Protamine/DNA multilayer films. UV-visible spectrometry and fluorescence spectrometry results revealed that the Protamine/DNA multilayer films were in vitro enzymic biodegradable. The novel biodegradable multilayer of Protamine/DNA may have great potential for gene therapy applications in tissue engineering, medical implant etc.

Abstract: Tumor targeting of plasmid DNA was achieved through the conjugation of dextran derivative with chelate residue based on metal coordination. Spermine (Sm) was chemically introduced to the hydroxyl groups of dextran to obtain dextran-Sm derivative. A negative zeta potential of plasmid DNA became almost 0 mV by the Zn2+-coordinated conjugation with the dextran-Sm When the dextran-Sm-plasmid DNA conjugate with Zn2+ coordination was intravenously injected to mice subcutaneously bearing Meth-AR-1 fibrosarcoma, the dextran- Sm-plasmid DNA conjugate significantly enhanced the level of gene expression in the tumor, in contrast to free plasmid DNA..

Abstract: In this paper, DNA hybrid polyethersulfone (PES) microspheres, including DNA-loaded porous particles and DNA-encapsulated hollow particles, are fabricated using a liquid-liquid phase separation method based on precipitation technique; the microspheres are then used for the removal of poisonous organic chemicals and endocrine disruptors. With the increase of the DNA amount incorporated into the spheres, the removal ratios increased both for the poisonous organic chemicals and endocrine disruptors. The particles without DNA also remove and accumulate poisonous organic chemicals due to the high porosity of the spheres. The results suggested that DNA hybrid PES particles could be prepared by a liquid-liquid phase separation method, and have potential to serve as a useful functional biomaterial for medical, engineering, and environmental application.

Abstract: Of many polymeric biomaterials, hydrogels are of special importance because of their favorable biocompatibility and pertinence in delivering delicate bioactive agents such as proteins. Physical hydrogels have attracted much attention for controlled drug delivery because of the mild and aqueous conditions involved in trapping bioactive agents. This paper reviews our recent progress on developing a new class of physical hydrogels based on the supramolecular self-assembly between cyclodextrins and bioabsorbable poly(ethylene oxide) (PEO) or its copolymers. Being thixotropic, the hydrogels can be injected through needles and applied as injectable drug delivery systems. The properties of the hydrogels also can be fine-tuned with triblock copolymers where PEO segments flank hydrophobic or biodegradable segments in the middle.