Design and evaluation of polar-embedded stationary phases containing triacontyl group for liquid chromatography.

The present work described two triacontyl-bonded silica adsorbents containing different polar embedded groups (i.e. amide- and carbamate-type) for high performance liquid chromatography, which were prepared by covalent surface modification of silica gel with respective pre-synthesized polar-embedded triacontyl (C30) silane. The acylimidazole-mediated method was used for the first time for the synthesis of amide-type alkyl silane, while the carbamate-type silane was obtained via an improved solvent-free procedure. A conventional C30 stationary phase was also developed on the same silica substrate in the similar manner, which was used as a reference column for comparison of the unique mechanisms facilitated and/or furnished by the polar groups. The successful immobilization of the designed C30 species was confirmed by infrared spectroscopy and elemental analysis. In further comparison with an amide-embedded octadecyl (C18) two other conventional C18 stationary phases of different surface chemistry, detailed chromatographic characterization of the C30 series stationary phases was performed in terms of surface density, hydrophobicity, aromatic selectivity, shape selectivity and water tolerance using a diversified range of analytes, including homologous alkylbenzenes, isomeric polycyclic aromatic hydrocarbons, carotenes, congeners of polychlorobiphenyls, aromatic amines, phenolic compounds, estrogens and nucleosides. A high resemblance between the chromatographic behaviors of the two polar-modified C30 stationary phases was observed, meanwhile they demonstrated noticeable differences from non-polar C30 stationary phase. The polar-embedded C30 phases showed satisfactory performance towards the solutes of interest in the studied conditions. The beneficial synergy of the polar groups and the triacontyl chains enabled these polar-enhanced C30 stationary phases to address challenging separation tasks with high selectivity.

[Tracheal reconstruction with memory alloy prosthesis coated with collagen].

OBJECTIVE: To investigate the feasibility of tracheal reconstruction with a prosthesis made of memory alloy coated with collagen sponge in mongrel dogs. METHOD: The basic skeleton of the prosthesis was knitted with Ni-Ti memory alloy wires. The tubular mesh was sealed with polyurethane membrane and then inner and external walls of the lumen were coated with collagen sponge. Cervical trachea segmental reconstruction was performed in 8 mongrel dogs with these prostheses. The efficacy of the implanted prostheses were periodically evaluated after operation using x-ray, tracheoscopy and specimen microscope examinations. RESULTS: One dog died of prosthesis dislocation 10 days after operation, another was killed 45 days later because of anastomotic stenosis. 6 dogs survived more than 90 days and the longest one lived for 150 days. Its implanted prosthesis was completely incorporated with the recipient tissue, where re-epithelialization occluded on anastomotic sites. The tracheal lumen was patent. CONCLUSION: This memory alloy tracheal prosthesis has been proved useful for reconstruction of large, circumferential tracheal defects, although its long-term safety and efficiency need to be confirmed.

[Research progress in tracheal prostheses].

It is difficult to perform a primary anastomosis when a pathological trachea is over-lengnthing resected. Thus the tracheal prosthesis is required to apply in the airway reconstruction. Severe defects in the early tracheal prosthesis result in failure of surgery. Great progress has been achieved in recent years as new materials and tissue-engineering techniques are applied. These efforts bring a bright future to clinical applications of tracheal prostheses.