Surface characteristics and biofunctionality of a novel high-performance, hydrophilic Jeffamine-added fluoro-containing polyimide for biomedical applications

Design of polymer-based antimicrobial hydrogels through physico-chemical transition

The antimicrobial activity represents a cornerstone in the development of biomaterials: it is a leading request in many areas, including biology, medicine, environment and industry. Over the years, different polymeric scaffolds are proposed as solutions, based on the encapsulation of metal ions/particles, antibacterial agents or antibiotics. However, the compliance with the biocompatibility criteria and the concentration of the active principles to avoid under- and over-dosing are being debated. In this work, we propose the synthesis of a versatile hydrogel using branched polyacrylic acid (carbomer 974P) and aliphatic polyetherdiamine (elastamine®) through physico-chemical transition, able to show its ability to counteract the bacterial growth and infections thanks to the polymers used, that are not subjected to further chemical modifications. In particular, the antimicrobial activity is clearly demonstrated against Staphyloccoccus aureus and Candida albicans, two well-known opportunistic pathogens. Moreover, we discuss the hydrogel use as drug carrier to design a unique device able to combine the antibacterial/antimicrobial properties to the controlled drug delivery, as a promising tool for a wide range of biomedical applications.

High thermally stable thermosetting polyimides derived from a carborane-containing tetramine

In this study, we report the preparation of thermosetting polyimides (PIs) based on carborane-containing tetramine and their characterizations. The novel tetramine 1,2-bis(4-(3,5-diaminobenzoic acid phenyl ester))carborane (CBNH) was synthesized and characterized firstly. Then, it was used in the preparation of two kinds of branched imide oligomers via the method of thermal imidization. The cure behavior of the obtained phenylethynyl-terminated oligomers was investigated by differential scanning calorimetry. The effect of carborane substituent on the thermal properties of PIs was studied by comparing with a similar structure without the carborane group. The thermal properties of PIs and carbon fiber/PI composites were investigated by thermal gravimetric analysis and dynamic mechanical analysis, respectively. Because of the introduction of high steric hindrance of carborane structure, the resulting thermosets and carbon fiber/PI composites had excellent thermal property with a high char yield at 800°C (>66.5%) and a high glass transition temperature (up to 500°C), respectively.

An Injectable System for Local and Sustained Release of Antimicrobial Agents in the Periodontal Pocket

Periodontitis treatments usually require local administration of antimicrobial drugs with the aim to reduce the bacterial load inside the periodontal pocket. Effective pharmaceutical treatments may require sustained local drug release for several days in the site of interest. Currently available solutions are still not able to fulfill the clinical need for high-quality treatments, mainly in terms of release profiles and patients' comfort. This work aims to fill this gap through the development of an in situ gelling system, capable to achieve controlled and sustained release of antimicrobial agents for medium-to-long-term treatments. The system is composed of micrometer-sized β-cyclodextrin-based hydrogel (bCD-Jef-MPs), featured by a strong hydrophilic character, suspended in a synthetic block-co-polymer solution (Poloxamer 407), which is capable to undergo rapid thermally induced sol-gel phase transition at body temperature. The chemical structure of bCD-Jef-MPs was confirmed by cross-correlating data from Fourier transform infrared (FTIR) spectroscopy, swelling test, and degradation kinetics. The thermally induced sol-gel phase transition is demonstrated by rheometric tests. The effectiveness of the described system to achieve sustained release of antimicrobial agents is demonstrated in vitro, using chlorhexidine digluconate as a drug model. The results achieved in this work disclose the potential of the mentioned system in effectively treating periodontitis lesions.

Comparative study of cytotoxicity and genotoxicity of commercial Jeffamines® and polyethylenimine in CHO-K1 cells

Jeffamines^® are a family of polymers containing primary amine groups attached to the extremities of polyether backbone which can be used as biomaterials. They have been used in combination with polyethylenimine (PEI) to improve biocompatibility in drug and gene delivery systems. Despite these facts, very few studies have been done on cytotoxicity and genotoxicity of pure Jeffamines^® or compared with PEI. The present study aimed to evaluate and compare the cytotoxic and genotoxic effects of Jeffamines^® and PEI in CHO-K1 cells. Specifically, polypropylene oxide 2000 (PPO 2000, Jeffamine^® D series), polyethylene oxide 1900 (PEO 1900, Jeffamine^® ED series), branched 25 kDa PEI, and linear 20 kDa PEI were evaluated at different concentrations. Cell viability and proliferation were assessed by 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) and 5-bromo-2'-deoxyuridine (BrdU) assays, respectively. Genotoxicity was evaluated using single cell gel electrophoresis assay and the cytokinesis-blocked micronucleus assay. PPO 2000 was the most cytotoxic Jeffamine^® , whereas PEO 1900 did not caused significant cell death at any tested concentration. Branched PEI was more cytotoxic than linear PEI (LPEI) and both were more cytotoxic than Jeffamines^® . Only PPO 2000 induced DNA damage when evaluated in comet assay probably due to its cytotoxicity. PPO 2000, PEO 1900, and PEI did not increase the frequency of micronuclei when tested at sub-cytotoxic concentrations. This work provides new insights about biocompatibility of Jeffamines^® and PEI and suggests the genotoxicological safety for further investigations of PEO 1900 in drug and gene delivery systems. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 742-750, 2018.

In vitro mesenchymal stem cell response to a CO2 laser modified polymeric material

With an ageing world population it is becoming significantly apparent that there is a need to produce implants and platforms to manipulate stem cell growth on a pharmaceutical scale. This is needed to meet the socio-economic demands of many countries worldwide. This paper details one of the first ever studies in to the manipulation of stem cell growth on CO2 laser surface treated nylon 6,6 highlighting its potential as an inexpensive platform to manipulate stem cell growth on a pharmaceutical scale. Through CO2 laser surface treatment discrete changes to the surfaces were made. That is, the surface roughness of the nylon 6,6 was increased by up to 4.3μm, the contact angle was modulated by up to 5° and the surface oxygen content increased by up to 1atom %. Following mesenchymal stem cell growth on the laser treated samples, it was identified that CO2 laser surface treatment gave rise to an enhanced response with an increase in viable cell count of up to 60,000cells/ml when compared to the as-received sample. The effect of surface parameters modified by the CO2 laser surface treatment on the mesenchymal stem cell response is also discussed along with potential trends that could be identified to govern the mesenchymal stem cell response.