Electrophoretic Deposition of Calcium Phosphates on Carbon-Carbon Composite Implants: Morphology, Phase/Chemical Composition and Biological Reactions.

Despite a long period of application of metal implants, carbon-carbon medical composites are also widely used for bone defect prosthesis in surgery, dentistry, and oncology. Such implants might demonstrate excellent mechanical properties, but their biocompatibility and integration efficiency into the host should be improved. As a method of enhancing, the electrophoretic deposition of fine-dispersed hydroxyapatite (HAp) on porous carbon substrates might be recommended. With electron microscopy, energy dispersion X-ray and Raman spectroscopy, and X-ray diffraction, we found that the deposition and subsequent heat post-treatment (up to the temperature of 400 °C for 1 h) did not lead to any significant phase and chemical transformations of raw non-stoichometric HAp. The Ca/P ratio was ≈1.51 in the coatings. Their non-toxicity, cyto- and biocompatibility were confirmed by in vitro and in vivo studies and no adverse reactions and side effects had been detected in the test. The proposed coating and subsequent heat treatment procedures provided improved biological responses in terms of resorption and biocompatibility had been confirmed by histological, magnetic resonance and X-ray tomographic ex vivo studies on the resected implant-containing biopsy samples from the BDF1 mouse model. The obtained results are expected to be useful for modern medical material science and clinical applications.

Titanium Membranes with Hydroxyapatite/Titania Bioactive Ceramic Coatings: Characterization and In Vivo Biocompatibility Testing.

Titanium membranes and meshes are used for the repair of trauma, tumors, and hernia in dentistry and maxillofacial and abdominal surgery. But such membranes demonstrate the limited effectiveness of integration in recipients due to their bioinertness. In this study, we prepared titania oxide (by microarc oxidation) and/or HAp (by electrophoresis deposition) coatings with alginate soaking. We used annealing at 700 °C for 2.5 h for HAp crystallinity increasing with achievement of an acceptable Ca2+ release rate. The feedstock HAp and prepared coatings were characterized by X-ray diffraction, IR spectroscopy, electron and optical confocal microscopy, and thermal analysis, as well as the in vitro study of solubility in saline and in vivo tests with the animal model of subcutaneous implantation (with Wistar rats). Biocompatible compounds were found for all deposited coatings. We noted that the best biological response was detected for the annealed Ca-P/TiO2 bilayer with alginate binding. In this case, the coating crystallinity was ≈40.5-50.0%. The Ca2+ release rate was 2.042 ± 0.058%/mm2 at 168 h after immersion in saline. Thin and mature tissue capsules with minimal inflammation and vascularization were found in histological sections. We did not detect any unwanted responses around the implants, including inflammation infiltration, suppuration, bacterial infections, tissue lyses, and, finally, implant rejection. This information is expected to be useful for understanding the properties of bioactive ceramic coatings and improving the quality of medical care in dentistry and maxillofacial surgery and other applications of titanium membranes in medicine.

Porcine heart valve, aorta and trachea cryopreservation and thawing using polydimethylsiloxane.

The most common cryopreservation protocols of biological tissues suitable for their further implantation has some disadvantages and limited to one sample per procedure with no possible repeated freezing in case of clinical needs. This study is aimed to improve a biological tissues cryopreservation by adding a new heat transfer fluid - polydimethylsiloxane (PDMS). To evaluate its efficiency the porcine biological tissues (heart valves, aortic and trachea fragments) were cryopreserved and thawed in low-viscous PDMS. According to the computer simulation, the midsection cooling rate was up to 490 °C/min and the midsection thawing rate was up to 1140 °C/min with admissible temperature uniformity. Cryoprotectants and liquid nitrogen were not used. The quality of tissue cryopreservation was evaluated using a number of histological and immunohistochemical methods (Orcein, H&E, Anti-CD34, Anti-Vimentin, Anti-Actin staining). Cryopreserved tissues showed no significant morphological difference in comparison with control group both in case of immediate thawing, and after 2 months of low temperature storage. Computer simulation of heat transfer showed the thermal limitations of used approach for larger specimens. The use of PDMS is proposed for preservation of vascular tissue in order to implant it in the form of homotransplants or biobanking with the possible additional use of an internal hydrophilic coating to prevent hydrophobization.