S. J. Huang

Synthesis and characterization of a new interpenetrated poly(2-hydroxyethylmethacrylate)—gelatin composite polymer

Poly(2-hydroxyethylmethacrylate) [poly(HEMA)] is a widely used biomaterial which does not allow cell adhesion and growth on its surface, limiting its use in biomedical applications in which cell cohesion is detrimental. We have prepared a poly(HEMA)-gelatin composite hydrogel using a sequential interpenetrating polymer network technique. The properties of this material were compared with poly(HEMA) freeze-dried sponges in terms of morphology, mechanical properties and biocompatibility. Moreover, in vivo biocompatibility experiments highlighted the occurrence of cellular interactions on the surface of the poly(HEMA)-gelatin interpenetrating polymer network, which are usually absent when unmodified poly(HEMA) hydrogels are implanted in the same host organism. These tests also showed a progressive gelatin degradation from the surface to the bulk of the poly(HEMA)-gelatin specimens during short-term (7 d) implantation. Finally, in vitro tests confirmed an improved ability of this composite to scaffold for the cells.

Composite hydrogels for intervertebral disc prostheses

Different PHEMA/PCL semi-IPNs hydrogels and their relative composite systems reinforced with PET fibres have been investigated for potential use as intervertebral disc prostheses. Compression properties and water absorption were evaluated. Uniaxial compression tests on the swollen samples showed an increase of the modulus and maximum stress with increasing content of PCL and PET fibres. In particular, the composite PHEMA/PCL hydrogels showed compression properties similar to those expressed by the canine intervertebral discs in different spinal locations. The equilibrium water content of modified semi-IPNs decreased as function of the PCL and PET fibres. These tests indicate that the use of composite hydrogels as disc prostheses is very promising because it is possible to combine transport and mechanical properties which are crucial for the performance of the intervertebral disc.

A biodegradable composite artificial tendon

The development of a completely biodegradable composite artificial tendon prosthesis that mimics the structure and stress-strain response of natural tendon is presented. The artificial tendon is a composite of water-swollen poly(2-hydroxyethylmethacrylate)/poly(caprolactone) blend hydrogel matrix reinforced with poly(lactic acid) fibres.

Poly(2-hydroxyethyl methacrylate)/Poly(caprolactone) Semi-Interpenetrating Polymer Networks

Semi-interpenetrating polymer networks (semi-IPNs) composed of cross linked poly(2-hydroxyethyl methacrylate) (PHEMA), and linear poly(caprolac tone) (PCL), display improved mechanical properties over pure PHEMA in the water swollen state without covalent bonding between the components.

Hydrophilic-Hydrophobic Binary Systems of Poly(2-hydroxyethyl methacrylate) and Polycaprolactone. Part I: Synthesis and Characterization

Poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels have a potential for broad biomedical applications due to their softness, high water content and high permeability in the water swollen state. Unfortunately, poor mechanical properties limit their use for biomedical applications where mechanical strength is required. Various ways of combining PHEMA with a hydrophobic biodegradable polyester, polycaprolactone (PCL), were in vestigated. The synthesis and physical characterization of the modified hydro gels are discussed.

Biodegradable Polymers Poly(amide-urethanes) [1]:

Poly(amide-urethanes) with long repeating units were prepared from 2-aminoethanol, α,ω-alkylene dicarboxylic acid chlorides, and 1.6-diisocyanatohexane. These partially crystalline polymers undergo slow hydrolysis when suspended in buffered water but were found to be more readily degraded by the enzyme subtilisin.

Synthesis and characterization of saturated and unsaturated poly(alkylene tartrate)s and further cross-linking

Saturated and unsaturated polyesters based on l-tartaric acid were prepared and characterized. Two kinds of low molecular weight polyesters were synthesized by the reaction of l-tartaric acid and 1-12 dodecandiol and 1-8 octanediol. Three different kinds of low molecular weight unsaturated polyesters were synthesized by the reaction of l-tartaric acid, 1-12 dodecandiol, and maleic anhydride. The saturated and unsaturated polymers were characterized by means of proton nuclear magnetic resonance (H NMR), infrared analysis (IR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). These functionalized polymers were thermally cross-linked in the presence of a radical initiator and with 2-hydroxyethyl methacrylate (HEMA) and/or polyethylene glycol ethyl ether methacrylate) (PEGEEM) to prepare cross-linked polymers for biomedical applications. The films were characterized by means of DSC, TGA, and FTIR. The glass transition temperatures (Tg) of the polymers increase with increasing alkene group length and for the presence of the double bonds. The transition temperatures of the cross-linked films range from about -50°C, for the films contraining PEGEEM, to about 90°C, for the film containing HEMA.

Water sorption of glycol-modified cross-linked gelatin-based hydrogels

The water sorption behaviour of several cross-linked gelatin-based systems were investigated and compared. The systems were gelatin, gelatin/ethyleneglycol, gelatin/polyoxypropylenediamine, and gelatin/polyethylene oxide. For all the systems, an increased water gain was obtained by raising the concentration of the second component, while the swelling was reduced by an increase of the cross-linking density.

Effect of Degradation on the Mechanical Properties of Multiphase Polymer Blends: PHBV/PLLA

Abstract The effect of water hydrolysis on the mechanical properties of PHBV/PLLA blends was investigated. The results were interpreted with models able to predict the Youngs modulus of multiphase systems. On the basis of the experimental results relative to the pure components, the models were used to calculate the expected values of the blends; these data were therefore compared with the experimental results in order to verify the theoretical predictions. The results show that the modulus of the degraded blends containing a low amount of PLLA is included in a range individuated from the upper and lower bound models and is close to the Halpin–Tsai prediction. This behavior is not present when PLLA is the continuous phase, and this can be due to the reduction of the degradation kinetics of the PLLA phase when PHBV is added to the polymer and forms a partially miscible system. The strength, which depends on both molecular weight and surface erosion that determine crack initiation, decreases faster than th...

Hydrophilic-Hydrophobic Binary Systems of Poly(2-hydroxyethyl methacrylate) and Polycaprolactone. Part II: Degradation

Poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels can be mechanically reinforced by the incorporation of a hydrophobic biodegradable polyester, polycaprolactone (PCL). The influence of PHEMA on the selective degradability of PCL in the modified hydrogels was investigated by hydrolysis, biodegradation and chemical degradation. The swelling of the PHEMA compo nent in hydrophilic reagents provided hydrolytic exposure to PCL domains. In hydrophobic reagents, the PHEMA component acted as a barrier that retarded the diffusion of hydrophobic acid or base into the network.