Journal of Biomedical Materials Research - Part A

An ideal gene carrier is required both in safety and efficiency for transfection. Polyethylenimine (PEI), a well‐studied cationic polymer, has been proved with high transfection efficiency, but is reported as toxicity in many cell lines. In this study, PEI was coupled with polyethylene glycol (PEG) to reduce its cytotoxicity. PEG–PEI copolymers were synthesized with isoporon diisocyanate (IPDI) in two steps. A set of PEG–PEI with different PEG molecular weights (MWs) and amounts of PEG were synthesized. The molecular structure of the resulting copolymers was evaluated by nuclear magnetic resonance spectroscopy (¹H NMR), infrared spectroscopy (IR), and gel permeation chromatography (GPC), all of which had successfully verified formation of the copolymers. The particle size and zeta potential of polymer/DNA complexes were measured, and their cytotoxicity and transfection efficiency in Hela cells were evaluated. We found that the copolymer block structure significantly influenced not only the physicochemical properties of complexes, but also their cytotoxicity and transfection efficiency. PEG (5 kDa) significantly reduced the diameter of the spherical complexes. The zeta potential of complexes was reduced with increasing amount of PEG grafting. Cytotoxicity was dependent not on PEG MW but on the amount of PEG grafting. Copolymer PEG–PEI (2‐25‐1) with 1.89 PEG (2 kDa) was proved to be more efficient for in vitro gene transfer. In conclusion, PEG MW and the degree of PEGylation were found to significantly influence the biological activity of PEG–PEI/DNA complexes. These results provide new sights into the studies using block copolymer as gene delivery systems. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008

Articular cartilage has limited potential for repair. Current clinical treatments for articular cartilage damage often result in fibrocartilage and are associated with joint pain and stiffness. To address these concerns, researchers have turned to the engineering of cartilage grafts. Tissue engineering, an emerging field for the functional restoration of articular cartilage and other tissues, is based on the utilization of morphogens, scaffolds, and responding progenitor/stem cells. Because articular cartilage is a water‐laden tissue and contains within its matrix hydrophilic proteoglycans, an engineered cartilage graft may be based on synthetic hydrogels to mimic these properties. To this end, we have developed a polymer system based on the hydrophilic copolymer poly(propylene fumarate‐co‐ethylene glycol) [P(PF‐co‐EG)]. Solutions of this polymer are liquid below 25°C and gel above 35°C, allowing an aqueous solution containing cells at room temperature to form a hydrogel with encapsulated cells at physiological body temperature. The objective of this work was to determine the effects of the hydrogel components on the phenotype of encapsulated chondrocytes. Bovine articular chondrocytes were used as an experimental model. Results demonstrated that the components required for hydrogel fabrication did not significantly reduce the proteoglycan synthesis of chondrocytes, a phenotypic marker of chondrocyte function. In addition, chondrocyte viability, proteoglycan synthesis, and type II collagen synthesis within P(PF‐co‐EG) hydrogels were investigated. The addition of bone morphogenetic protein‐7 increased chondrocyte proliferation with the P(PF‐co‐EG) hydrogels, but did not increase proteoglycan synthesis by the chondrocytes. These results indicate that the temperature‐responsive P(PF‐co‐EG) hydrogels are suitable for chondrocyte delivery for articular cartilage repair. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 268–274, 2004

The increasing interest in using chitosan nanoparticles for controlled drug delivery is hampered by its blood incompatibility, especially for intravenous applications. This study investigated the effects of processing solvents (acetic acid/lactic acid), dispersing media (acidic medium/saline), and surface modifiers (polyethylene glycol, polyvinyl alcohol, and ethylenediaminetetraacetatic acid) on the hemocompatibility of chitosan. Blood compatibility of chitosan nanoparticles prepared by ionotropic gelation with altered surface chemistry was evaluated by assessing their hemolytic activity, platelet aggregation, coagulation, and cytokine induction. It was observed that nanoparticles prepared in lactic acid and dispersed in saline did not show hemolysis, platelet aggregation, or coagulation, whereas nanoparticles prepared in acetic acid showed strong hemolysis. Surface modifiers were not observed to significantly affect blood compatibility, with the exception of EDTA, which delayed blood clotting times. Thus, chitosan nanoparticles prepared in lactic acid and dispersed in saline may be an ideal nanocarrier for parenteral applications. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A:2957–2966, 2013.

Bệnh van tim là một vấn đề sức khỏe cộng đồng nghiêm trọng và ngày càng gia tăng, trong đó việc thay thế bằng bộ phận giả là điều thường thấy. Các thiết bị giả hiện tại không đủ tốt cho người lớn trẻ tuổi và trẻ em đang phát triển. Các kênh van động mạch chủ sống được thiết kế mô có tiềm năng để tái cấu trúc, tái tạo, và phát triển, nhưng việc chế tạo độ phức tạp giải phẫu tự nhiên với tính không đồng nhất của tế bào vẫn còn là thách thức. Trong nghiên cứu hiện tại, chúng tôi áp dụng công nghệ sinh học in 3D để chế tạo các kênh van bằng chất dẻo alginate/gelatin sống với cấu trúc giải phẫu và việc kết hợp trực tiếp các loại tế bào kép theo cách bị hạn chế vùng. Các tế bào cơ trơn xoang gốc động mạch (SMC) và tế bào mô liên kết của nắp van động mạch (VIC) được bao bọc trong các đĩa hydrogels alginate/gelatin có khả năng sống qua 7 ngày trong môi trường nuôi cấy. Các hydrogels không có tế bào in 3D thể hiện sự giảm xu hướng, sức mạnh tối đa, và ứng suất tối đa giảm nhẹ trong suốt thời gian nuôi cấy 7 ngày, trong khi sinh học cơ học kéo của hydrogel chứa tế bào vẫn được duy trì. Các kênh van động mạch được in sinh học thành công với sự bao bọc trực tiếp SMC ở gốc van và VIC ở các nắp. Cả hai loại tế bào đều có khả năng sống (81,4 ± 3,4% đối với SMC và 83,2 ± 4,0% đối với VIC) trong các mô được in 3D. Tế bào SMC bao bọc biểu hiện mức alpha‐sợi cơ trơn cao, trong khi VIC biểu hiện mức vimentin cao. Những kết quả này chứng minh rằng các kênh van động mạch sống có độ phức tạp giải phẫu và bao bọc không đồng nhất có thể được chế tạo bằng công nghệ sinh học in 3D. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Phần A, 2013.

Functionally graded material (FGM) is a heterogeneous composite material including a number of constituents that exhibit a compositional gradient from one surface of the material to the other subsequently, resulting in a material with continuously varying properties in the thickness direction. FGMs are gaining attention for biomedical applications, especially for implants, owing to their reported superior composition. Dental implants can be functionally graded to create an optimized mechanical behavior and achieve the intended biocompatibility and osseointegration improvement. This review presents a comprehensive summary of biomaterials and manufacturing techniques researchers employ throughout the world. Generally, FGM and FGM porous biomaterials are more difficult to fabricate than uniform or homogenous biomaterials. Therefore, our discussion is intended to give the readers about successful and obstacles fabrication of FGM and porous FGM in dental implants that will bring state‐of‐the‐art technology to the bedside and develop quality of life and present standards of care. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A: 3046‐3057, 2013.

The experiments were designed to use photochemically cross‐linked plastically compressed collagen (PCPCC) gel to support corneal epithelial cells. A plastically compressed collagen (PCC) scaffold was photo cross‐linked by UVA in the presence of riboflavin to form a biomaterial with optimal mechanical properties. The breaking force, rheology, surgical suture strength, transparency, ultrastructure, and cell‐based biocompatibility were compared between PCPCC and PCC gels. The breaking force increased proportionally with an increased concentration of riboflavin. The stress required to reach breaking point of the PCPCC scaffolds was over two times higher compared to the stress necessary to break PCC scaffolds in the presence of 0.1% riboflavin. Rheology results indicated that the structural properties of PCC remain unaltered after UVA cross‐linking. The PCC gels were more easily broken than PCPCC gels when sutured on to bovine corneas. The optical density values of PCPCC and PCC showed no significant differences (p > 0.05). SEM analyses showed that the collagen fibres within the PCPCC gels were similar in morphology to PCC gels. No difference in cell‐based biocompatibility was seen between the PCPCC and PCC scaffolds in terms of their ability to support the ex vivo expansion of corneal epithelial cells or their subsequent differentiation evidenced by similar levels of cytokeratin 14. In conclusion, PCPCC scaffold is an optimal biomaterial for use in therapeutic tissue engineering of the cornea. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 99A: 1–8, 2011.

In this study, we investigated the suitability of microjet impingement for use on hydrogel materials to determine the cellular adhesion strength of corneal epithelial cells grown on novel hydrogels with extracellular matrix proteins (laminin and/or fibronectin) or a peptide sequence (fibronectin adhesion promoting peptide, FAP) tethered to their surface with poly(ethylene glycol) chains. The deformation of the hydrogel surface in response to the force of the microjet was analyzed both visually and mathematically. After the results of these experiments and calculations determined that no deformation occurred and that the pressure required for indentation (1.25 × 10⁶ Pa) was three factors of 10 greater than the maximum pressure of the microjet, the relative mean adhesion strength of primary rabbit corneal epithelial cells grown on the novel poly(2‐hydroxyethyl methacrylate‐co‐methacrylic acid) hydrogels was determined and compared with that of the same type of cells grown on control glass surfaces. Only confluent cell layers were tested. Cells grown on control glass surfaces adhered with a mean relative adhesion strength of 488 ± 28 dynes/cm². Under identical conditions, cells grown on laminin‐ and FAP‐tethered hydrogel surfaces were unable to be removed, indicating an adhesion strength greater than 516 dynes/cm². Cells grown on fibronectin‐ and fibronectin/laminin (1:1)‐tethered surfaces showed significantly lower relative adhesion strengths (201 ± 50 and 189 ± 11 dynes/cm², respectively), compared with laminin‐ and FAP‐tethered surfaces (p = 0.001). Our results demonstrate that the microjet impingement method of cell adhesion analysis is applicable to hydrogel substrates. Additionally, analysis of our test surfaces indicates that fibronectin tethered to this hydrogel in the quantity and by the method used here does not induce stable ligand/receptor bonding to the epithelial cell membrane to the same degree as does laminin or FAP. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 72A: 19–24, 2005

Polypropyleneimine octaamine dendrimers were studied as an alternative means of generating highly crosslinked collagen. Crosslinking was effected by using the water‐soluble carbodiimide 1‐ethyl‐3‐(3‐dimethyl aminopropyl) carbodiimide hydrochloride (EDC). The multifunctional dendrimers were introduced as novel crosslinkers after the activation of the carboxylic acid groups of glutamic and aspartic acid residues in collagen. The conventional crosslinker glutaraldehyde was used as a control. EDC, itself an alternative crosslinker, which forms zero‐length crosslinks by directly covalently binding collagen molecules, as well as a low molecular weight diamine and a low molecular weight triamine, were also studied. All of the resultant gels were freeze‐dried to obtain sponges for characterization. Water uptake of the gels decreased from 90% to 60% after dendrimer crosslinking compared with EDC crosslinking. DSC results showed an increase of denaturation temperature of collagen after crosslinking with the various methods. The generation 2 and 3 dendrimer‐crosslinked collagen samples had the highest denaturation temperature, at up to 90°C compared with 50°C in the uncrosslinked collagen control. The dendrimer‐crosslinked collagen also showed unique thermal characteristics, with multiple denaturation temperature peaks in contrast to the single peak noted with the other crosslinked collagens. This is thought to be due to the heterogeneous nature of dendrimer crosslinking. Collagenase results revealed that the dendrimer‐crosslinked collagen had a comparative resistance to proteolysis to glutaraldehyde‐crosslinked collagen. Measurement of activated carboxylic acid groups before and after crosslinking indicated that 40–70% of the activated carboxylic acid was consumed during crosslinking with dendrimers. The results suggest that dendrimer crosslinking of collagen produces stable gels. The presence of a large number of excess amine groups in the dendrimers may also be useful for subsequent modification with biologically relevant groups. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005

The purpose of this study was to introduce newly synthesized nanomaterials as an alternative to superparamagnetic ironoxide based particles (SPIO) and thus to launch a new platform for highly controllable hyperthermia cancer therapy and imaging. The new material that forms the basis for this article is lanthanum manganite particles with silver ions inserted into the perovskite lattice: La_1−xAg_xMnO_3+δ. Adjusting the silver doping level, it is possible to control the Curie temperature (T_c) in the hyperthermia range of interest (41–44°C). A new class of nanoparticles based on silver‐doped manganites La_1–xAg_xMnO_3+δ is suggested. New nanoparticles are stable, and their properties were not affected by the typical ambient conditions in the living tissue. It is possible to monitor the particle uptake and retention by MRI. When these particles are placed into an alternating magnetic field, their temperature increases to the definite value near T_c and then remains constant if the magnetic field is maintained. During the hyperthermia procedure, the temperature can be restricted, thereby preventing the necrosis of normal tissue. A new class of nanoparticles based on silver‐doped manganites La_1–xAg_xMnO_3+δ was suggested. Ag‐doped perovskite manganites particles clearly demonstrated the effect of adjustable Curie temperature necessary for highly controllable cellular hyperthermia. The magnetic relaxation properties of the particles are comparable with that of SPIO, and so we were able to monitor the particle movement and retention by MRI. Thus, the new material combines the MRI contrast enhancement capability with targeted hyperthermia treatment. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009

Tissue engineering aims at resolving problems such as donor shortage and immune rejection faced by transplantation. Scaffolds (artificial extracellular matrices) have critical roles in tissue engineering. Recently, we developed nano‐fibrous poly(L‐lactic acid) scaffolds under the hypothesis that synthetic nano‐fibrous scaffolding, mimicking the structure of natural collagen fibers, could create a more favorable microenvironment for cells. This is the first report that the nano‐fibrous architecture built in three‐dimensional scaffolds improved the features of protein adsorption, which mediates cell interactions with scaffolds. Scaffolds with nano‐fibrous pore walls adsorbed four times more serum proteins than scaffolds with solid pore walls. More interestingly, the nano‐fibrous architecture selectively enhanced protein adsorption including fibronectin and vitronectin, even though both scaffolds were made from the same poly(L‐lactic acid) material. Furthermore, nano‐fibrous scaffolds also allowed >1.7 times of osteoblastic cell attachment than scaffolds with solid pore walls. These results demonstrate that the biomimetic nano‐fibrous architecture serves as superior scaffolding for tissue engineering. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 531–537, 2003