Allan Hoffman: A 70th Birthday Celebration

Water sorption which is not classically Fickian has been observed in a variety of polymers. Deviation from Fickian kinetics is widely assumed to be caused by rate-limiting polymer relaxation, despite minimal proof of this. To the contrary, the evidence accumulated in this work indicates that water transport in initially glassy poly(2-hydroxyethyl methacrylate) (PHEMA), an important water-swellable biomedical polymer, is controlled by Fickian diffusion. First of all, the fractional water uptake is initially linear and independent of sample thickness when plotted against the square root of time over initial thickness, as expected for a Fickian process. Furthermore, the moving solvent front also advanced with the square root of time. Temperature, polymer thermal history and initial solvent concentration all affected the sorption kinetics of PHEMA in manners consistent with a Fickian process. The invariably Fickian sorption mechanism is believed to be the consequence of the water molecule's small size and affinity for hydrophilic, swellable polymers.     

Universal Bioinert Control of Polystyrene Interfaces via Hydrophobic‐Driven Self‐Assembled Surface PEGylation with a Well‐Defined Block Sequence

This work proposes a new molecular insight of interfacial design in the control of antifouling performance for the versatile biofoulants, including proteins, blood cells, tissue cells, and bacteria. A self‐assembled bioinert interface with universal fouling resistance to general biofoulants via hydrophobic‐driven surface PEGylation is presented. The study systematically discriminates the optimum PEGylated block polymer configuration and hydrophobic/hydrophilic segmental ratio enabling to optimize the surface coverage by the bioinert moieties, thus ensuring the best resistance to biofouling. For similar copolymer molecular weights and similar polystyrene (PS)/poly(ethylene glycol) methacrylate (PEGMA), the coating density obtainable is the highest if a random copolymer is used, while it is the lowest with a triblock copolymer. That measured with a diblock copolymer lies in between. Random copolymers offer more numerous anchoring possibilities than diblock copolymers, while they are importantly fewer if triblock copolymers are used. For similar total number of hydrophilic blocks, the diblock copolymer is more efficient to resist larger cells (leukocytes, fibroblasts) while the triblock is better to promote mitigate biofouling by smaller molecules or cells (proteins, platelets, red blood cells). The length of the hydrophilic PEGylated block seems to dominate fouling resistance of large biofoulants.     

超声乳化联合折叠式人工晶体植入治疗年龄相关性白内障临床观察

目的 探讨年龄相关性白内障患者实施超声乳化术后植入折叠式人工晶体的临床价值.方法 分别选取我院年龄相关性白内障超声乳化术患者植入聚甲基丙烯酸甲酯（PMMA）晶体及折叠式晶体的患者87例和93例.对两组患者术后7 d、14 d以及1个月时的视力进行统计和比较;对两组患者手术前及手术后7 d和1个月时的角膜散光情况进行统计和比较.结果 B组患者在术后7 d、14 d、1个月时视力＞0.8者分别占11.83%、18.28%以及19.35%,均明显优于A组3.45%、5.575%和13.79%,两组比较差异有统计学意义（P＜0.05）.术后7 d两组患者角膜散光分别为（1.20±0.18）D和（0.95±0.21）D,均较术前明显增加,差异有统计学意义（P＜0.05）.术后1个月,A组患者角膜散光为（0.98±0.29）D,仍明显大于术前,差异有统计学意义（P＜0.05）,而B组患者角膜散光为（0.75±0.33）D,与术前相比差别不大,无统计学意义（P＞0.05）.结论 折叠晶体的应用有利于超声乳化术联合人工晶体植入术患者术后视力的提高,如经济状况允许,建议患者选用.     

Effects of acrylic resin monomers on porcine coronary artery reactivity

The purpose of the present investigation was to assess the reactivity of porcine coronary arteries under in vitro conditions following their exposure to methyl methacrylate (MMA) and hydroxyethyl methacrylate (HEMA) monomers. Confirming previous studies using rat aortas, both MMA and HEMA induced acute/direct relaxation of coronary ring preparations, which was partly dependent on the endothelium. With prolonged tissue exposure, both monomers caused time- and concentration-dependent inhibition of receptor-mediated contraction of the vascular smooth muscle caused by prostaglandin F_2∝ (PGF_2∝), with HEMA causing more inhibition than MMA. Hydroxyethyl methacrylate, but not MMA, also produced impairment of non-receptor-mediated contraction of the coronary smooth muscle induced by KCl. On the other hand, neither HEMA nor MMA altered relaxation of the smooth muscle produced by the direct-acting pharmacological agent, sodium nitroprusside (SNP). While exposure to HEMA impaired endothelium-dependent vasorelaxation caused by bradykinin (BK), MMA markedly enhanced this endothelial-mediated response of the arteries. The enhanced endothelial response produced by MMA was linked to nitric oxide (NO) release. In conclusion, with prolonged tissue exposure, MMA causes less pronounced effects/adverse consequences on coronary smooth muscle function relative to the effect of HEMA, while enhancing vasorelaxation associated with release of NO from the endothelium. Accordingly, MMA-containing resin materials appear to be safer for human applications than materials containing HEMA.     

负载抗菌药物的骨水泥的药物释放实验研究

目的 揭示负载抗菌药物的骨水泥的药物释放浓度、持续时间、药物残留程度及低于最小有效抑菌浓度的释放时间,为合理应用抗菌药物提供理论依据。方法 通过对负载盐酸万古霉素和亚胺培南西司他丁钠的骨水泥进行体外洗提实验,采用高效液相色谱法检测分析两种负载抗菌药物的骨水泥的药物释放浓度、释放持续时间和药物残留程度。结果 ①负载抗菌药物的骨水泥第一天药物释放量最大,后逐渐持平,且释放时间较长,释放浓度较低;②截止到第7周盐酸万古霉素、亚胺培南西司他丁释放量分别只占总负载量的15%、25%;③盐酸万古霉素第1周后释放浓度低于最小有效抑菌浓度,亚胺培南西司他丁钠第7周后释放浓度低于最小有效抑菌浓度。结论 载抗菌药物骨水泥存在长时间药物残留现象,是导致持续低于最小有效抑菌浓度的主要原因。此种现象不但对细菌起不到抑菌作用,而且是诱导细菌耐药性的危险因素。     

Thermoresponsive UCST‐Type Behavior of Interpolymer Complexes of Poly(ethylene glycol) and Poly(poly(ethylene glycol) methacrylate) Brushes with Poly(acrylic acid) in Isopropanol

Upper critical solution temperature (UCST)‐type thermoresponsive behavior of poly(ethylene glycol)–poly(acrylic acid) (PEG–PAA) and poly(poly(ethylene glycol) methacrylate)–poly(acrylic acid) (PPEGMA–PAA) interpolymer complexes has been observed in isopropanol. For these investigations, PPEGMA and PAA with various average molecular weights have been synthesized by atom transfer radical polymerization. It has been found that both the PEG and PPEGMA have lower cloud point temperatures (T _cp) than its mixed polymer solutions with PAA, whereas PAA does not show such behavior in the investigated temperature range. These findings indicate the reversible formation of interpolymer complexes with variable structure and composition in the solutions of the polymer mixtures in isopropanol. Increasing the ethylene glycol/acrylic acid molar ratio or the molecular weight of either the PAA or the H‐acceptor PEG component of the interpolymer complexes increases the UCST‐type cloud point temperatures of these interpolymer systems. The polymer–polymer interactions by hydrogen bonds between PAA and PEG or PPEGMA and the correlations between T _cp and structural parameters of the components revealed in the course of these investigations may be utilized for exploring well‐defined UCST‐type material systems for various applications.

     

Photodeformable Microspheres from Methacrylate‐Based Azo Homopolymers

In this study, two methacrylate‐based azo homopolymers are synthesized and used to fabricate photodeformable microspheres through a self‐assembling approach. The methacrylate‐based azo homopolymer with the narrow molecular weight distribution is synthesized by reversible addition fragmentation chain transfer polymerization, while the other with the relatively broad molecular weight distribution is synthesized by conventional radical polymerization. The azo polymers are characterized by proton nuclear magnetic resonance (¹H‐NMR), Fourier transform infrared spectroscopy (FT‐IR), differential scanning calorimetry (DSC), thermal gravimetric analysis TGA, gel permeation chromatography GPC, and ultraviolet‐visible spectroscopy (UV–vis) m. The colloidal spheres are obtained by gradually adding deionized water into the solutions of the azo polymers in N ,N‐dimethylformamide. Laser light scattering analysis and transmission electron microscopy observations show that although both azo polymers can form uniform colloidal spheres in the dispersions, the molecular weight and its distribution show significant effects on the colloid formation process and the sizes of the colloidal spheres formed in the process. Upon irradiation with a linearly polarized Ar⁺ laser beam for a period of time, the azo polymer microspheres show the elongated deformation along the polarization direction of the actinic light.

     

Adding vancomycin to bone cement: research on its influence on mechanical and fixation strength using rabbit femoral prostheses

Objective: To compare the influence of different methods of adding vancomycin on the strength of bone cement used for fixing rabbits' femoral prostheses. Methods: Eighteen New Zealand white rabbits (36 femora) were allocated to three groups of six rabbits (12 femora) each: a control group, an experimental group 1 and experimental group 2. The bone cement used in the control group was mixed manually without vancomycin; in experimental group 1 it was mixed manually with 5% (2 g/40 g) vancomycin; and in experimental group 2 it was mixed in a vacuum with 5% (2 g/40 g) vancomycin. The cement combinations were then used to fill the marrow cavity of rabbit femurs to fix prostheses. An electronic universal testing machine (EUTM) was used to test the pullout force of the prostheses with bone cement 48 hours later. Student's paired t‐test was used for statistical analysis. Results: It was found that the maximum load of pullout force was 559.3 ± 82.3 N in the control group; 523.6 ± 86.5 N in experimental group 1; and 645.1 ± 105.9 N in experimental group 2. Statistical analysis showed there was no significant difference between the control group and experimental group 1 (P > 0.05). However, there were significant differences between the control group and experimental group 2 (P < 0.05); and between experimental group 1 and experimental group 2 (P < 0.05). Conclusion: When bone cement and vancomycin were mixed manually in a low concentration (<5%) vancomycin had no influence on the strength of the bone cement. However, bone cement and vancomycin mixed at the same concentrations in a vacuum did have a statistically significant effect on the strength of the bone cement.     

Polymethyl methacrylate intraocular lens opacification 20 years after cataract surgery: A case report in a tertiary eye hospital in Saudi Arabia

Snowflake degeneration is a slow progressive opacification of polymethyl methacrylate (PMMA) intraocular lenses (IOLs). This late postoperative complication can occur a decade or later after implantation. The deposits are composed of IOL materials that tend to aggregate centrally. There is a relative paucity of the literature on snowflake degeneration of IOLs. Symptoms can range from mild visual disturbance to significant loss of visual acuity. In cases of opacification after IOL implantation, the different diagnosis should include snowflake degeneration to prevent surgical intervention such as lens exchange or explantation unless clinically warranted. We report a case of late optical opacification of a PMMA IOL, the clinical diagnosis and treatment that increased best corrected vision.