Gregory Cheng-Chie Niu

Preparation and characterization of hyaluronan/collagen II microspheres under an electrostatic field system with disc electrodes.

Collagen II and hyaluronan are the two major components of the native extracellular matrix (ECM). Both biopolymers are responsible for providing the associated tissues with tensile strength, and also serve as a structural scaffold for cell adhesion and growth. Over the years, many researchers have focused on the preparation and evaluation of man-made ECM comprising the two polymers in the form of a membrane for chondrocyte culture applications. Here, a simple and in situ method, involving the injection of the hyaluronan/collagen II (HA/Col II) mixture solution through a pair of hollow-centered parallel disc electrodes (HCPDEs) of a high-voltage electrostatic field system, was developed and employed to prepare HA/Col II microspheres in watery phase. The HA/Col II microspheres were firmed up by a two-step cross-linking treatment (first by FeCl(3) and then by 1-ethyl-3-(3-dimethyl aminopropyl) carbodimide, EDC) to secure the spherical structure shape. Then, at 37 degrees C, reconstitution treatment of the Col II molecules was conducted to further strengthen the microspheres. Depending on treatment conditions, the resulting series of HA/Col II microspheres all exhibited good sphericity in the range of 486+/-43 to 679+/-24microm in diameter. Furthermore, the ratio and amount of HA/Col II in the mixture solutions would affect the morphological structure and basic characteristics, including mechanical strength, thermal properties and water content. In the preliminary study, the HA/Col II microspheres have shown to provide favorable ECM characteristics, with appropriate mechanical strength, and exhibited a 3D inclination.

Evaluation of nanoarchitectured collagen type II molecules on cartilage engineering.

Scaffold architecture, including the geometry and dimension of scaffolds, is an important parameter in cell adhesion, migration, proliferation, and differentiation. Following the characterization of collagen type II nanoarchitectured molecules, collagen fibrils (CNFs) and collagen spheres (CNPs) prepared using a high-voltage electric field in our laboratory, we proposed to use these nanoarchitectured molecules to assess their influence on the culturing of chondrocytes in stirred bioreactors. The results demonstrate that chondrocytes rapidly formed more and larger chondrocyte pellets (spheroids) after the addition of nanoarchitectured molecules into the culture medium. The maintenance of chondrocytes with round morphology and increased glycosaminoglycan secretion indicated that these spheroids contained viable and un-dedifferentiated chondrocytes. No significant increases in DNA content were detected. These results show that the introduction of these molecules did not affect chondrocyte proliferation during a 3-day culture period. After the addition of CNPs and CNFs into the culture medium, the expression levels of collagen type II and aggrecan genes in chondrocytes increased significantly as demonstrated by real-time PCR analysis. Interestingly, chondrocytes exhibited distinct collagen type II and aggrecan gene expression profiles in culture with CNPs and CNFs. The aggrecan gene expression level of the chondrocytes was 2.5-fold greater following CFN addition than following the addition of CNPs. In contrast, the collagen type II expression level of the chondrocytes was 2.2-fold greater following the addition of CNPs than following the addition of CNFs. The chondrocyte pellets rapidly restored defects in articular cartilage during a 1-month implantation period in a rabbit model.

CHITOSAN IN APPLICATIONS OF BIOMEDICAL DEVICES

Chitosan is a natural polysaccharide with great potential for biomedical applications due to its biocompatibility, biodegradable capability, and nontoxicity. Various techniques used for preparing chitosan microspheres/membranes and evaluations of these fabrications have also been reviewed. The hydrophilicity of chitosan provides unique characteristics of hydrogel formation with the acidic media and may entrap the drug content inside of the matrix for controlled release. In order to improve upon the scope of preparation of chitosan microspheres, we had successfully employed and incorporated a high-voltage system into the direct pumping injection process. The wide range of drug release profiles could be attributed to the surface characteristics, porosities, and various structures of chitosan microspheres upon treatment with Na5P3O10/NaOH solutions of various volume ratios. We also demonstrated that with the addition of chitosan/β-TCP microspheres as a constituent into the PMMA cement significantly decreases the curing peak temperature and increases the setting time. The excellent gelforming property of chitosan offers another biomedical application in membrane separation fields. Chitosan membranes were prepared by a thermal induced phase separation method, following treatment with nontoxic NaOH gelating and Na5P3O10, Na2SO3 crosslinking agents. In order to further improve the mechanical strength and biocompatibility and to expand the potential of chitosan GTR membranes in periodontal applications, various chitosan membranes incorporating with negatively charged alginate, bioactive tricalcium phosphate, and platelet rich plasma, respectively, were also prepared and characterized. Moreover, we had also utilized chitosan, which with good blood-clotting, cheap, and easy preparation characteristics, as the raw material to prepare rapid clotting wound dressing and tooth plug.

EFFECTS OF CHITOSAN/β-TCP MICROSPHERES ON RABBIT CRANIAL AND CONDYLE DEFECTS HEALING: A PRELIMINARY STUDY

Two kinds of chitosan/β-TCP microspheres were prepared; one was by a traditional emulsion technique (Group A), and the other was by a high-voltage electrostatic system (Group B). Both of the microspheres exhibited good sphericity and the β-TCP fine particles were well trapped inside the chitosan based particles. After 60-day shaking, Group A and Group B degraded by about 40% and 80% of initial weight, respectively. Two models of bone defects were created in rabbits included for a series of randomized blind pilot study. In the cranial model, two equal 10 mm diameter cranial defects were created. In condyle model, two equal 5 mm femur condyle defects were created on each hind leg, and underwent the same grafting treatment. After 4 weeks of implantation, both the cranial and condyle sites filled with Group A were shown to be surrounded by fibrous tissues with the presence of osteoblasts. In Group B, only condyle site showed the presence of osteoblasts. In contrast, fibrous tissue formation was seen on the control group after 4 weeks of healing. After 8 weeks of implantation, the condyle sites filled with Group A and Group B showed the presence of new bone formation as compared to control group. However, there was no obvious new bone formations in the cranial sites filled with both Group A and Group B. The same events were observed in the cranial sites after 12 weeks of implantation. In contrast, new bone formation was seen on the condyle sites in all three groups after 12 weeks of implantation.

The integration of 3-D hip-shape anthropometric data bank and human-engineered seat-cushion: The classification of hip shapes and category of seat cushions

Custom fitted seat cushions work to improve posture, alleviate fatigue and prevent bedsores by evenly distributing body mass and relieving single or multiple points of pressure. Existing commercially-available bedding and seating is unsatisfactory to patients and professionals alike. Three-dimensional anthropometric measurement technology is employed to establish a database of hip-form profiles. This database includes 400 individuals grouped into five categories based on the shapes and measurements of 3-D hip-forms analogous to womens brassiere cup sizes. Each class is matched within a range of a anthropomtric values such as height, weight, hip-circumference and thigh-diameter. With such human factor engineering considerations, the preliminary 3-D hip-form database has created practical distinctions between the five hip-form classes that could help to design patient specific seating that is both comfortable and healthy.