M. I. Vlasov

Preparation of porous ultrahigh-molecular-weight polyethylene using subcritical water

We developed a method of subcritical water extraction of NaCl from ultrahigh-molecular-weight polyethylene (UHMWPE) samples as a step in the preparation of a porous polymeric product, a promising material for implant production. Optimum process conditions were determined to be as follows: pressure 250 bar, temperature 120°C, and water flow rate 3 g/min. This method allows decreasing ten-fold (from 10 to 1 h) the time of salt extraction from the samples. The UHMWPE obtained was shown by scanning electron microscopy to have a porous structure with a main pore diameter from 80 to 700 μm.

Components of supercritical extracts of garlic and synthetic nonsymmetrical allyl disulfides as potential antimicrobial preparations

Extracts of garlic (Allium sativum L.) were obtained using supercritical carbon dioxide extraction and were separated into individual compounds using preparative high performance liquid and gas chromatography. A series of nonsymmetrical allyl disulfides with different substituents were synthesized. The compounds isolated from the supercritical garlic extract and the synthetic nonsymmetrical allyl disulfides (SNA) were tested as potential antimicrobial agents using a number of test objects: Candida utilis, Bacillus cereus, Pseudomonas aurantiaca, and Escherichia coli. It was shown that the SNA exhibit high antimicrobial activity, which was much higher that the activities of individual components of garlic and in some cases were comparable in efficiency with antibiotics of the floxacin series widely used in clinical practice. The data obtained suggest the potential for using SNA as antimicrobial agents.

The solubility of synthetic asymmetric allyl disulfides in subcritical and supercritical media

The solubility of two synthetic asymmetric allyl disulfides, allyl 8-quinolyl disulfide and allyl benzothiazol-2-yl disulfide, in subcritical Freon R22 and Freon R410a, as well as supercritical carbon dioxide, at a temperature of 40°C and a pressure of 200 bar is determined by a dynamic flow method. It is shown that Freon R22 is a promising solvent for practical applications of allyl disulfides.

Xenogenic bone matrix treated with supercritical carbon dioxide as a potential osteoplastic material

A multistage environmentally safe method for processing xenogenic bone matrix using suband supercritical media has been developed. This method provides fast matrix delipidization in a medium of supercritical carbon dioxide and deproteinization by treatment with a 3% hydrogen peroxide solution followed by washing with subcritical water for removal of polar substances. The final treatment with supercritical carbon dioxide serves to remove residual nonpolar components. A method to control the porosity of xenogenic bone matrix at different stages of its purification has been suggested. Preliminary data indicate that a cellular test system based on an allogenic osteoid cell line Th-1 could be used for evaluation of primary adhesion and proliferation of cells on the surface of purified bone matrix.

Impregnation of Ultrahigh-Molecular-Weight Polyethylene with Amoxicillin in Subcritical Freon R22 Media

The method of impregnation of ultrahigh-molecular-weight polyethylene (UHMWPE) with amoxicillin in subcritical Freon R22 media is developed. For the first time, the possibility of polymer impregnation with a polar substance (a standard antibiotic amoxicillin) in the absence of cosolvents is shown. Cosolvents increase the polarity of the medium and removal of them from the polymer matrix is usually a serious problem. Amoxicillin desorption curves from the impregnated UHMWPE samples are obtained by high-performance liquid chromatography (HPLC). Polymeric samples impregnated with amoxicillin are active against gram-positive and gram-negative microorganisms S. aureus, S. epidermidis, E. faecalis, B. subtilis, and E. coli, allowing them to be considered as real implant models for replacement of bone tissue.

Application of Sub- and Supercritical Freons in Xenogenic Bone Matrix Processing

Sub- and supercritical freons can be successfully used in the bone matrix cleaning process. In the case of freon R22 the duration of bone matrix cleaning significantly decreases as compared to the same procedure with supercritical carbon dioxide. Freons R23, R134 and R407c which do not contain chlorine atoms are almost ineffective in this process.

Impregnation of Ultra-High-Density Polyethylene with Unsymmetrical Disulfides in Subcritical Freon Media

For the first time, ultra-high-density polyethylene (UHDPE) samples impregnated with antibacterial unsymmetrical disulfides (allyl benzothiazol-2-yl disulfide and allyl 8-quinolyl disulfide) were obtained in subcritical freon R22 in the absence of organic solvents as modifiers. Freon R22 was completely removed from the impregnated samples that provided a high purity of the final material. Potential implants based on the UHDPE impregnated with unsymmetrical disulfides were shown to manifest antibacterial and antifungal activity.

Sterilization in supercritical media

This review summarizes the achievements in the field of sterilization in supercritical (SC) media in the last 10 years. In particular, new approaches to carrying out the sterilization process are described and the possible use of a wide range of SC media is shown. In addition, some data on microbial inactivation mechanism are presented and new areas of SC sterilization application are discussed.

Sterilization of a porous ultrahigh-molecular-weight polyethylene in supercritical Freons

The possibility of sterilization of porous ultrahigh-molecular-weight polyethylene in subcritical Freons R22 and R410a in the absence of modifiers is for the first time demonstrated. The maximum sterilization effect is achieved when sterilization with Freon R410a is performed in static conditions for 30 min at 50°С and 250 bar or with Freon R22 for 60 min at 70°С and cyclically varied pressure within 100–290 bar (press–depress mode).