Hydrophilicity of 3-D biomaterials: the Washburn equation

Adhesion, proliferation, and osteogenic differentiation of human mesenchymal stem cells on additively manufactured Ti6Al4V alloy scaffolds modified with calcium phosphate nanoparticles

In the present study, biocomposites based on 3D porous additively manufactured Ti6Al4V (Ti64) scaffolds modified with biocompatible calcium phosphate nanoparticles (CaPNPs) were investigated. Ti64 scaffolds were manufactured via electron beam melting technology using an Arcam machine. Electrophoretic deposition was used to modify the scaffolds with CaPNPs, which were synthesized by precipitation in the presence of polyethyleneimine (PEI). Dynamic light scattering revealed that the CaP/PEI nanoparticles had an average size of 46 ± 18 nm and a zeta potential of +22 ± 9 mV. Scanning electron microscopy (SEM) revealed that the obtained spherical CaPNPs had an average diameter of approximately 90 nm. The titanium-based scaffolds coated with CaPNPs exhibited improved hydrophilic surface properties, with a water contact angle below 5°. Cultivation of human mesenchymal stem cells (hMSCs) on the CaPNPs-coated Ti64 scaffolds indicated that the improved hydrophilicity was beneficial for the attachment and growth of cells in vitro. The Ti6Al4V/CaPNPs scaffold supported an increase in the alkaline phosphatase (ALP) activity of cells. In addition to the favourable cell proliferation and differentiation, Ti6Al4V/CaPNPs scaffolds displayed increased mineralization compared to non-coated Ti6Al4V scaffolds. Thus, the developed composite 3D scaffolds of Ti6Al4V functionalized with CaPNPs are promising materials for different applications related to bone repair.

Electrospun biocomposite nanofibrous patch for cardiac tissue engineering

A bioengineered construct that matches the chemical, mechanical, biological properties and extracellular matrix morphology of native tissue could be suitable as a cardiac patch for supporting the heart after myocardial infarction. The potential of utilizing a composite nanofibrous scaffold of poly(dl-lactide-co-glycolide)/gelatin (PLGA/Gel) as a biomimetic cardiac patch is studied by culturing a population of cardiomyocyte containing cells on the electrospun scaffolds. The chemical characterization and mechanical properties of the electrospun PLGA and PLGA/Gel nanofibers were studied by Fourier transform infrared spectroscopy, scanning electron microscopy and tensile measurements. The biocompatibility of the scaffolds was also studied and the cardiomyocytes seeded on PLGA/Gel nanofibers were found to express the typical functional cardiac proteins such as alpha-actinin and troponin I, showing the easy integration of cardiomyocytes on PLGA/Gel scaffolds. Our studies strengthen the application of electrospun PLGA/Gel nanofibers as a bio-mechanical support for injured myocardium and as a potential substrate for induction of endogenous cardiomyocyte proliferation, ultimately reducing the cardiac dysfunction and improving cardiac remodeling.

The importance of particle size in porous titanium and nonporous counterparts for surface energy and its impact on apatite formation

The importance of particle size in titanium (Ti) fabricated by powder metallurgy for the surface energy and its impact on the apatite formation was investigated. Four sorts of Ti powders of different mean particle size were realized through 20min, 2h, 5h and 8h of ball milling, respectively. Each sort of Ti powder was used to fabricate porous Ti and its nonporous counterparts sharing similar surface morphology, grain size and chemical composition, and then alkali-heat treatment was conducted on them. Surface energy was measured on the surfaces of the nonporous Ti counterparts due to the difficulty in measuring the porous surfaces directly. The surface energy increase on the alkali-heat-treated porous and nonporous Ti was observed due to the decrease in the particle size of the Ti powders and the presence of Ti-OH groups brought by the alkali-heat treatment. The apatite-inducing ability of the alkali-heat-treated porous and nonporous Ti with different surface energy values was evaluated in modified simulated body fluid and results indicated that there was a strong correlation between the apatite-inducing ability and the surface energy. The alkali-heat-treated porous and nonporous Ti discs prepared from the powders with an average particle size of 5.89+/-0.76microm possessed the highest surface energy and the best apatite-inducing ability when compared to the samples produced from the powders with the average particle size varying from 19.79+/-0.31 to 10.25+/-0.39microm.

Culture of dermal fibroblasts and protein adsorption on block conetworks of poly(butyl methacrylate-block-(2,3 propandiol-1-methacrylate-stat-ethandiol dimethacrylate))

Amphiphilic block terpolymer conetworks composed of butyl methacrylate (BMA), 2,3 propandiol-1-methacrylate (GMMA) and ethandiol dimethacrylate (EDMA) were synthesized. Telechelic oligomers with the carboxylic acid end groups were made via ozonolysis of poly(BMA-co-butadiene) and then these were reacted with glycidyl methacrylate to obtain cross-linkable vinyl groups at both chain ends. Networks were then formed via free radical copolymerization with EDMA and GMMA or 2-methyl-acrylic acid 2,2-dimethyl-[1,3]dioxolan-4-ylmethyl ester (GMAc). The acetonide groups of the GMAc units were then removed, by reaction with selenium dioxide and hydrogen peroxide, to give networks with the same molecular structure as the GMMA terpolymers but different cell adhesion and protein adsorption properties. Protein adsorption was maximised in networks prepared with GMMA rather than with GMAc followed by removal of the acetonide. Block conetworks that were synthesised with GMAc were poor substrates for cell proliferation whilst the GMMA class support good levels of both cell viability and proliferation. It is suggested that the difference in behaviour is derived from changes in the surface composition.

Use of Polyurethane Minisponges to Collect Human Tear Fluid

PURPOSE

To characterize a method of tear collection based on the use of amphiphilic polyurethane absorbing minisponges.

METHODS

Tear fluid was collected from 17 healthy volunteers. A preweighed polyurethane dry minisponge was laid on the margin of the lower eyelid. Once wet (5-10 minutes), the fluid was transferred to a preweighed Eppendorf tube after squeezing the sponge by centrifugation. The amount of fluid absorbed and fluid recovered were determined by reweighing the sponge and the tube after absorption and centrifugation steps, respectively. The fluid was qualitatively characterized by electrophoretic polypeptide profiling in Coomassie blue-stained SDS-polyacrylamide gels.

RESULTS

Per eye, 14.6 +/- 5.3 microL tear fluid was collected. That volume was about 90% of the fluid absorbed by polyurethane minisponges, almost doubling the fraction recovered from other more hydrophilic absorbing polymers. Major bands characterizing the electrophoretic profile of this fluid were those of 79, 66, 27, 18, and 14 kd. This profile was indistinguishable from that of tear fluid aspirated into glass microcapillaries. Tear fluid collected simultaneously from both eyes displayed the same profiles. Successive tear samples from a single eye showed the same profile except for the 66-kd band, which increased steadily as collection proceeded. Tear donors rarely complained of discomfort.

CONCLUSIONS

Tear collection by absorbing polyurethane minisponges is highly advantageous in efficiency (recovery) and reproducibility (invariant electrophoretic polypeptide profiles). Tear donor comfort, simultaneous bilateral collection, and collections from several donors at once are additional major advantages of this collection method in studies involving single subjects and populations in health and disease.