Biocompatibility and paclitaxel/cisplatin dual-loading of nanotubes prepared from poly(ethylene glycol)-polylactide-poly(ethylene glycol) triblock copolymers for combination cancer therapy

Nanotubes were prepared by self-assembly of the copolymer using co-solvent evaporation method. The biocompatibility of the nanotubes was assessed in comparison with spherical micelles and filomicelles prepared from poly(ethylene glycol)-poly(L-lactide-co-glycolide) (PEG-PLGA) and poly(ethylene glycol)-poly(L-lactide) (PEG-PLA), respectively. Several aspects of biocompatibility of the aggregates were considered, including agar diffusion and MTT assay, release of cytokines, hemolysis, protein adsorption, dynamic clotting in vitro, and Zebrafish embryonic compatibility in vivo. The nanotubes present good cell compatibility and blood compatibility in vitro, and almost no toxicity towards Zebrafish embryos development in vivo. Furthermore, dual-loading of hydrophilic cisplatin and hydrophobic paclitaxel was achieved in the nanotubes with high loading content and loading efficiency. The release of both drugs was slower from dual-loaded nanotubes than from single-loaded ones, but the total amount of released drugs in higher for dual-loaded nanotubes than from single-loaded ones. Cellular uptake and inhibition tests showed that the nanotubes were successfully taken up by tumor cells and effectively inhibited cell growth. It is thus concluded that PEG-PLA-PEG nanotubes with outstanding biocompatibility could be promising for co-delivery of hydrophilic and hydrophobic agents in combination cancer therapy.     

Synergistic hierarchical silicone-modified polysaccharide hybrid as a soft scaffold to control cell adhesion and proliferation

In this study, a new type of polydimethylsiloxane-modified chitosan (PMSC) amphiphilic hydrogel was developed as a soft substrate to explore cellular responses for dermal reconstruction. The hydrogel wettability, mechanical stiffness and topography were controllable through manipulation of the degree of esterification (DE) between hydrophobic polydimethylsiloxane (PDMS) and hydrophilic N,O-(carboxymethyl)-chitosan (NOCC). Based on microphase separation, the incorporation of PDMS into NOCC increased the stiffness of the hybrid through the formation of self-assembled aggregates, which also provided anchor sites for cell adhesion. As the DE exceeded 0.39, the size of the PDMS-rich aggregates changed from nanoscale to microscale. Subsequently, the hierarchical architecture resulted in an increase in the tensile modulus of the hybrid gel up to fourfold, which simultaneously provided mechano-topographic guidance and allowed the cells to completely spread to form spindle shapes instead of forming a spherical morphology, as on NOCC (DE = 0). The results revealed that the incorporation of hydrophobic PDMS not only impeded acidic damage resulting from NOCC but also acted as an adhesion modification agent to facilitate long-term cell adhesion and proliferation on the soft substrate. As proved by the promotion on long-term type-I collagen production, the PMSC hybrid with self-assembled mechano-topography offers great promise as an advanced scaffold material for use in healing applications.     

Characterization and bacterial anti-adherent effect on modified PMMA denture acrylic resin containing platinum nanoparticles

PURPOSE

This study characterized the synthesis of a modified PMMA (Polymethyl methacrylate) denture acrylic loading platinum nanoparticles (PtN) and assessed its bacterial inhibitory efficacy to produce novel antimicrobial denture base material.

MATERIALS AND METHODS

Polymerized PMMA denture acrylic disc (20 mm × 2 mm) specimens containing 0 (control), 10, 50, 100 and 200 mg/L of PtN were fabricated respectively. The obtained platinum-PMMA nanocomposite (PtNC) was characterized by TEM (transmission electron microscopy), SEM/EDX (scanning electron microscope/energy dispersive X-ray spectroscopy), thermogravimetric and atomic absorption spectrophotometer analysis. In antimicrobial assay, specimens were placed on the cell culture plate, and 100 µL of microbial suspensions of S. mutans (Streptococcus mutans) and S. sobrinus (Streptococcus sobrinus) were inoculated then incubated at 37℃ for 24 hours. The bacterial attachment was tested by FACS (fluorescence-activated cell sorting) analysis after staining with fluorescent probe.

RESULTS

PtN were successfully loaded and uniformly immobilized into PMMA denture acrylic with a proper thermal stability and similar surface morphology as compared to control. PtNC expressed significant bacterial anti-adherent effect rather than bactericidal effect above 50 mg/L PtN loaded when compared to pristine PMMA (P=.01) with no or extremely small amounts of Pt ion eluted.

CONCLUSION

This is the first report on the synthesis and its antibacterial activity of Pt-PMMA nanocomposite. PMMA denture acrylic loading PtN could be a possible intrinsic antimicrobial denture material with proper mechanical characteristics, meeting those specified for denture bases. For clinical application, future studies including biocompatibility, color stability and warranting the long-term effect were still required.     

Dual Thermo- and Photo-Responsive Micelles Based on Azobenzene-Containing Random Copolymer

Amphiphilic random copolymer poly(methacrylamido-azobenzene)-ran-poly(2-hydroxyethylacrylate) (PMAAAB-ran-PHEA) was synthesized via hydrolysis of poly(methacrylamido-azobenzene)-ran-poly[2-((2′-tetrahydropyranyl)oxy)ethylacrylate] (PMAAAB-ran-P(THP-HEA)), which was prepared by conventional radical polymerization. PMAAAB-ran-PHEA micelles were then prepared via dialysis method against water with DMF as solvent. The structure, morphology, size, and low critical solution temperature (LCST) of PMAAAB-ran-PHEA and its micelles were determined by ¹H-NMR, GPC, TEM, and DLS. The thermo- and photo-responsive behaviors of the resulting polymer micelles were investigated with Nile red as a fluorescence probe. The results showed that PMAAAB-ran-PHEA micelles were porous or bowl-shaped and its size was 135–150 nm, and its LCST was 55 °C when F_MAAAB of the random copolymer was 0.5351; the hydrophobicity of the micellar core was changed reversibly under the irradiation of UV light and visible light without release of Nile red or disruption of micelles; the size and solubilization capacity of the micelles were dependent on temperature, and Nile red would migrate for many times between the water phase and the micelles, and finally increasingly accumulated during the repeated heating and cooling processes.     

3种消毒剂浸泡消毒对甲基丙烯酸树脂基托机械性能的影响

目的:测量3种消毒剂浸泡过的甲基丙烯酸树脂的机械性能,了解消毒剂对树脂基托机械性能的影响,为临床应用提供依据.方法:制备80 mm×15 mm×4 mm丙烯酸树脂试样40个,随机分成A、B、C、D 4组,每组10个,分别浸泡于1：200"84"消毒液、体积分数为0.1%的过氧乙酸、体积分数为2%的戊二醛消毒液和蒸馏水中,30 min后从每组取出5个(共20个)试样为组1,分别测试每组树脂基托的弯曲强度和弯曲模量;取出每组中的另外5个(共20个)为组2,测试其冲击强度.结果:1：200"84"消毒液、体积分数为0.1%的过氧乙酸、体积分数为2%的戊二醛3种消毒液浸泡前后,反映材料机械性能的弯曲强度和弯曲模量及冲击强度3项指标差异均无统计学意义,且与蒸馏水浸泡组差异无统计学意义.结论:甲基丙烯酸树脂在1：200"84"消毒液、体积分数为0.1%的过氧乙酸、体积分数为2%的戊二醛中浸泡30 min,其机械性能均不受影响.     

Assembly of Semiconductor Nanorods into Circular Arrangements Mediated by Block Copolymer Micelles

The collective properties of ordered ensembles of anisotropically shaped nanoparticles depend on the morphology of organization. Here, we describe the utilization of block copolymer micelles to bias the natural packing tendency of semiconductor nanorods and organize them into circularly arranged superstructures. These structures are formed as a result of competition between the segregation tendency of the nanorods in solution and in the polymer melt; when the nanorods are highly compatible with the solvent but prefer to segregate in the melt to the core-forming block, they migrate during annealing toward the core–corona interface, and their superstructure is, thus, templated by the shape of the micelle. The nanorods, in turn, exhibit surfactant-like behavior and protect the micelles from coalescence during annealing. Lastly, the influence of the attributes of the micelles on nanorod organization is also studied. The circular nanorod arrangements and the insights gained in this study add to a growing list of possibilities for organizing metal and semiconductor nanorods that can be achieved using rational design.     

Graft copolymer emulsions of sodium alginate with hydroxyallsyl methacrylates for microencapsulation

A hybrid material with interesting capsule forming properties has been prepared by γ-initiated polymerization of hydroxyethyl methacrylate (HEMA) or other acrylic monomers in the presence of aqueous sodium alginate. For example, an aqueous solution of HEMA (1 wt%) and sodium alginate (1 wt%) was irradiated in a γ-source at a dose of 0.15 MR, to produce a stable emulsion which coalesced in the form of a homogeneous precipitate when added to 0.1 M CaCI₂. Polymerization of HEMA was presumed to be initiated by free radicals generated in the alginate by γ-irradiation. The emulsion consisted largely of polyHEMA homopolymer stabilized by an alginate-polyacrylate graft (or block) copolymer of highly branched and ill-defined character, which acts as surfactant to prevent coagulation of the emulsion. Erythrocytes were encapsulated in such an emulsion by extrusion of cell/copolymer emulsion mixture into HEPES buffered CaCI₂ (10 mM Ca). Cells appeared intact and functional after encapsulation. By SEM it appeared that the capsule wall consisted of microspheres of polyHEMA on the inner and outer surfaces held together by the alginate. Furthermore the capsule did not contain the internal meshwork, characteristic of calcium alginate homopolymer gels. Although much remains to be learned about these materials, the combination of the easy gelling characteristics of the alginate with the range of desirable properties (e.g. biocompatibility) afforded by the acrylic monomers may have a significant impact on the development of cell microencapsulation technology.     

Evaluation of staining susceptibility of resin artificial teeth and stain removal efficacy of denture cleansers

Objective. To assess the staining susceptibility of four acrylic resin (Ivostar, SR Vivodent PE, Major Dent, Integral) and a nanocomposite resin (Veracia) artificial teeth and to evaluate the stain removal efficacy of denture cleansers. Materials and methods. Sixty maxillary incisors of each brand (total = 300) were divided into three groups according to staining solution as coffee, red wine and tea. Baseline color measurements were performed with a spectrophotometer. Specimens were immersed in staining solutions for 14 h (2 h × 7 days) and then second color measurements were performed. Each group was further divided into four sub-groups according to denture cleanser as Corega tabs, Fittydent, NaOCl (0.5%) and distilled water (control) (n = 5). Specimens were immersed in denture cleansers for 8 h and third color measurements were made. Thus, the weekly simulation period was completed. This cycle was repeated 12 times to simulate a 3-month time period and measurements were performed at the end of the 4th, 8th and 12th cycles. ΔE values were calculated and data were analyzed with 3-way repeated measures ANOVA and Bonferroni tests. Results. Significant color differences were found among the teeth and staining solutions, but all of the color differences were in the clinically acceptable range (ΔE < 5.5). Integral showed the highest ΔE values for all solutions, while Ivostar and Vivodent demonstrated the lowest ΔE values for red wine and tea solutions. There was no significant difference among the denture cleansers in terms of stain removal efficacy. Conclusions. Cross-linked acrylic (Integral) and nanocomposite (Veracia) resin teeth were more susceptible to staining. Denture cleansers were efficient on stain removal from artificial teeth.