Effect of poly(dimethylsiloxane)-block-poly(oligo (ethylene glycol) methacrylate) amphiphilic block copolymers on dermal fibroblast viability and proliferation

Abstract

In this work, well-defined poly(dimethylsiloxane)-b-poly(oligo (ethylene glycol) methacrylate) (PDMS-b-POEGMA) amphiphilic block copolymers were synthesized and their effect on human dermal fibroblast were investigated. Anionic ring opening polymerization (ROP) and atom transfer radical polymerization (ATRP) were used to synthesis the block copolymers. The molecular weight of synthesized copolymers ranged from 1000 to 2300?Da by changing the number of both PDMS and POEGMA units. It was found that the copolymer having low molecular weight decreased the fibroblast viability and proliferation by inducing apoptosis. It was proved by flow cytometry and TUNEL assay that human dermal fibroblast experienced apoptosis after exposure to synthesized amphiphilic copolymers. The results of this work suggest the use of PDMS-b-POEGMA amphiphilic copolymers with low molecular weight for hypertrophic scars remediation.     

ATR-FTIR analysis of protein adsorption on polymeric surfaces

ATR-FTIR spectroscopy was used to study the adsorption of bovine serum albumin on poly(vinyl chloride), poly(vinylidene fluoride), poly(methyl methacrylate), and poly(ethylene glycol)-grafted poly(methyl methacrylate) surfaces. The results were analyzed in terms of the amount of albumin adsorbed on the various polymeric surfaces when immersed in a 1 g/l protein solution. Experimental results were compared with the Van Straaten and Peppas model (1990) and satisfactory agreement was obtained. It was confirmed that poly(ethylene glycol) surfaces exhibited the lowest albumin adsorption patterns.     

New treatments using alginate in order to reduce the calcification of bovine bioprosthetic heart valve tissue

Calcification limits the functional lifetime of cardiac valve substitutes fabricated from glutaraldehyde preserved bovine pericardium. Host factors, mainly younger age, and implant factors, mainly glutaraldehyde cross-linking, are implicated in the calcification process. Glutaraldehyde cross-linking is believed to activate the potential sites in the tissues for biocalcification. In the present work, we investigated the possibility of using alginate azide (AA) instead of glutaraldehyde for the preservation of pericardial tissues in order to enhance the durability of bioprosthetic heart valves. Grafting with poly(GMA-BA) copolymer to the alginate azide cross-linked pericardial (AACPC) tissue was carried out to obtain better stability, strength, and anticalcification properties. The strength property and thermal stability of the AA cross-linked tissues were studied. Calcification studies in rat subdermal models reveal that AA cross-linking reduces the calcification to negligible levels. After 30 days implantation, the calcium content was found to be 10.4 ± 1.2 and 6.1 ± 0.3 μg mg^-1 for untreated AACPC and polymer grafted AACPC, respectively, compared to a value of 100 ± 1.2 μg mg^-1 calcium recorded for control glutaraldehyde cross-linked pericardial (GCPC) tissues.     

Modulating the phase transition temperature and thermosensitivity in N-isopropylacrylamide copolymer gels

—Temperature-responsive copolymer (or ternary copolymer) gels of N-isopropylacrylamide (IPAAm) were synthesized with hydrophobic alkyl methacrylate (RMA), hydrophilic acrylamide (AAm), N,N'-dimethylacrylamide (DMAAm), and N-acryloylpyrrolidine (APy) as comonomers. The effects of these comonomers on the phase transition temperature (LCST) and the thermosensitivity have been discussed. The LCST of poly(IPAAm) gel in phosphate buffered saline (PBS) was lowered by the introduction of hydrophobic RMA, and the change in equilibrium swelling ratio with temperature change became smaller with an increase in RMA content. However, a stable skin layer to achieve complete 'on-off' regulation of drug release was formed at a higher temperature by RMA due to hydrophobic interaction of alkyl chains. The LCST of poly(IPAAm-co-AAm) gel increased with an increase in AAm content. However, the thermosensitivity of the gel became smaller. It was suggested that hydrophilic AAm prevented the formation of a dense skin layer at a higher temperature. It was difficult to obtain a complete 'off' state due to an insufficiently dense skin layer in order to stop the drug release. The LCST was raised and great thermosensitivity was possible by the introduction of DMAAm or APy. Poly(IPAAm-co-DMAAm) enabled 'on-off' drug release in response to smaller temperature changes around the body temperature. The molecular design to control transition temperature and thermosensitivity of gel was established.     

Occupational skin diseases in dental laboratory technicians

In Germans, occupational skin disease (OSD) in dental technician (DT) has been steadily rising in recent years and causing considerable costs for medical care and rehabilitation. Our objective in this study was to: (i) examine affected workers: (ii) perform patch tests to identify causative agents; (iii) develop strategies of prevention. 7 dental laboratories were inspected as to materials used, working habits, safety regulations, etc. A computer data base was developed for products (trade name, active ingredient, additives, etc.). A questionnaire regarding development of OSD was sent out to 1132 dental technicians (45 questions). 55 DT with suspected OSD were examined and patch tested with the standard series, an extensive series of methacrylates, and own materials. Working conditions and knowledge of potential hazards. varied greatly in the laboratories visited. The safety data sheets of working materials were of with use and required supplementation by the computer data base. which provided rapid access to allergological information (e.g., and of aerylate. concentration). In the questionnaire (173 answers). 36% reported skin lesions attributed to work and 1/3 suspected plastic materials as their primary cause. Among the 55 DT examined, allergic contact dermatitis diagnosed in 63.6% and irritant contact dermatitis in 23.6%. Most of the allergens identified (74%) were found in plastic materials (methyl methaerylale (MM A). 9 patients (16%); 2-hydroxyethyl methacrylate (2-HEMA). 18 patients (33%); ethyleneglycol dimethacrylaie (EGDMA), 15 patients (27%)). In 16 patients, multiple sensitizations to various methacrylates were found. The fingertips were primarily involved in allergic contact dermatitis (93%). whereas in irritant contact dermatitis, the dorsa of the fingers (especially of the dominant hand) were affected (80%). 9 patients also showed lesions on the face, neck and forearms. The main irritant factors included wet work, contact with plaster, mechanical friction and thermal changes. Based on experience with DT, various preventive measures have been tried and found to be effect five (reduction of skin contact. 4H Gloves, etc.). In conclusion, better knowledge of OSD in dental laboratories (in physician. D T and their employers) would lead lo a reduced rate of new cases.     

赝复体塑料支架的溶胀对其与SY-1型硅橡胶的粘接性能的影响

目的:评估塑料义齿基托(聚甲基丙烯酸甲酯)的溶胀对其与SY-1型硅橡胶粘接性能的影响. 方法:按照国际标准,用自凝单体(甲基丙烯酸甲酯)溶胀塑料义齿基托表面后,测试其与SY-1型硅橡胶间的拉块强度及剥离强度与溶胀前的差异,进行统计学分析. 结果:塑料义齿基托表面经自凝单体溶胀后,其与SY-1型硅橡胶的粘接强度较溶胀前有显著下降. 拉块强度:溶胀前(0.98±0.04)高于溶胀后(0.53±0.04), P<0.01;剥离强度:溶胀前(0.70±0.03)高于溶胀后(0.33±0.03), P<0.01. 结论:溶胀对塑料表面的处理使得其与SY-1型硅橡胶的粘接强度下降,故建议临床粘接时不用自凝单体处理塑料义齿基托表面.     

Biocompatibility of MPC: in vivo evaluation for clinical application

Biocompatibility is important to assure a mild body reaction to an implanted device and its long-term stability and functionality. In diabetes research, subcutaneously implanted glucose monitoring systems need biocompatible surfaces for long-term application. The biocompatibility of poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate) (MPC), a material similar to the phospholipid layer of a cell membrane, was compared in vivo with the biocompatibility of polyurethane (PU), polyvinyl alcohol (PVA), and cuprophane (CUP). Needle-type glucose sensors and hollow-fiber probes used for microdialysis were coated with these four different biomaterials and implanted subcutaneously in 18 rats and 7 healthy volunteers. At set intervals, the implants and, in the case of the rats, also the surrounding tissue were removed and characterized by light and electron microscopy. MPC-coated sensors and hollow-fiber probes showed smooth and thin deposits in flat layers, whereas the surface deposits on PU- and PVA-coated sensors and those on CUP hollow-fiber probes appeared as rough, irregular, and dense attachments of aggregated cells and protein. This study confirmed results from earlier in vitro tests by showing the biocompatibility and reliability of MPC. Even though the amount of protein and cells attached to the MPC surface was not as low as expected from in vitro experiments, the biocompatibility and long-term stability of the implanted devices were superior to those of PU, PVA, and CUP.     

大孔交联甲基丙烯酸缩水甘油酯共聚物的合成及对血清中ＬＤＬ的吸附性能研究

本文介绍大也交联甲基丙烯酸缩水甘油酸共聚物的合成及经羟基化、磺化制得具亲水性很强的聚阴离子亲和吸附剂,测定了孔结构性能,考察了制备条件及对高脂血症患者血清中低密度脂蛋白（ＬＤＬ）的吸附功效。     

Occupational allergic contact dermatitis from 2-hydroxyethyl methacrylate and ethylene glycol dimethacrylate in a modified acrylic structural adhesive

Acrylates have a broad area of application in various products including glues, sealants and adhesives. Whereas anaerobic acrylic sealants arc well-known sensitizers, acrylate glues that cure in air have only seldom been reported as allergens. Here a patient sensitized to such a glue, and developing hand dermatitis that spread to the lower arms, chest, neck and face, is presented. Her glue was analyzed by gas chroma tography/mass spectrometry (GC/MS) and contained 24,6% 2-hydroxyethyl methacrylate (2-HEMA) and 0.4% ethylene glyol dimethacrylate (EGDMA). These 2 acrylate compounds, as well as her glue, provoked an allergic patch test reaction. Also many other acrylate compounds, e.g., tetrahydrofurfuryl methacrylate, gave an allergic reaction indicating cross-allergy. The patient could not continue in her previous workplace because of severely-relapsing skin symptoms.