Study of the influence of β-radiation on the properties and mineralization of different starch-based biomaterials

Supercritical CO2 technology: The next standard sterilization technique?

Sterilization of implantable medical devices is of most importance to avoid surgery related complications such as infection and rejection. Advances in biotechnology fields, such as tissue engineering, have led to the development of more sophisticated and complex biomedical devices that are often composed of natural biomaterials. This complexity poses a challenge to current sterilization techniques which frequently damage materials upon sterilization. The need for an effective alternative has driven research on supercritical carbon dioxide (scCO₂) technology. This technology is characterized by using low temperatures and for being inert and non-toxic. The herein presented paper reviews the most relevant studies over the last 15 years which cover the use of scCO₂ for sterilization and in which effective terminal sterilization is reported. The major topics discussed here are: microorganisms effectively sterilized by scCO₂, inactivation mechanisms, operating parameters, materials sterilized by scCO₂ and major requirements for validation of such technique according to medical devices' standards.

Chondrogenic potential of injectable κ-carrageenan hydrogel with encapsulated adipose stem cells for cartilage tissue-engineering applications

Due to the limited self-repair capacity of cartilage, regenerative medicine therapies for the treatment of cartilage defects must use a significant amount of cells, preferably applied using a hydrogel system that can promise their delivery and functionality at the specific site. This paper discusses the potential use of κ-carrageenan hydrogels for the delivery of stem cells obtained from adipose tissue in the treatment of cartilage tissue defects. The developed hydrogels were produced by an ionotropic gelation method and human adipose stem cells (hASCs) were encapsulated in 1.5% w/v κ-carrageenan solution at a cell density of 5 × 10(6) cells/ml. The results from the analysis of the cell-encapsulating hydrogels, cultured for up to 21 days, indicated that κ-carrageenan hydrogels support the viability, proliferation and chondrogenic differentiation of hASCs. Additionally, the mechanical analysis demonstrated an increase in stiffness and viscoelastic properties of κ-carrageenan gels with their encapsulated cells with increasing time in culture with chondrogenic medium. These results allowed the conclusion that κ-carrageenan exhibits properties that enable the in vitro functionality of encapsulated hASCs and thus may provide the basis for new successful approaches for the treatment of cartilage defects.

Effect of γ-Radiation on Thermal and Chemical Properties of Starch/Polystyrene Biopolymer Blend

In this study, the starch/polystyrene (PS) biopolymer blend is prepared by utilizing an in solution polymerization process. Two different ratios (50/50 and 80/20) of starch/PS were dissolved in toluene associated with mechanical mixing to maintain the homogeneity of the blend. Thereafter, the blend was exposed to γ-radiation using Cobalt 60 (Co60) at different dosing rates. The thermal and chemical properties were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), enzymatic degradation, and disclosure of starch by iodine, respectively. The deviation of glass transition temperature (Tg ( and the IR peaks indicate that a good interaction between starch and polystyrene was achieved in the blend. Exposure of the starch/PS blend to the α-amylase enzyme and to iodine demonstrated that the γ-rays have affected the amylopectin part with no distinct effect on the amylose part of the starch. Moreover, the colour has completely disappeared at 100 kGray irradiation dose since the blend becomes more responsive to enzymatic degradation at higher irradiation dose, which in turn causes in breaking down of the amylose part in the starch.

Microhardness of starch based biomaterials in simulated physiological conditions

In this work the variation of the surface mechanical properties of starch-based biomaterials with immersion time was followed using microhardness measurements. Two blends with very distinct water uptake capabilities, starch/cellulose acetate (SCA) and starch/poly(epsilon-caprolactone) (SPCL), were immersed in a phosphate buffer solution (PBS) at 37.5 degrees C for various times. The microhardness of the blends decreased significantly ( approximately 50% for SPCL and approximately 94% for SCA), within a time period of 30 days of immersion, reflecting the different hydrophilic character of the synthetic components of the blends. The dependence of microhardness on the applied loading time and load was also analysed and showed a power law dependency for SCA. Water uptake and weight loss measurements were performed for the same immersion times used in the microhardness experiments. The different swelling/degradation behaviour presented by the blends was related to the respective variation in microhardness. Moreover, complementary characterization of the mechanical properties of SCA and SPCL was accomplished by dynamic mechanical analysis (DMA) and creep measurements. Microhardness measurements proved to be a useful technique for characterizing the mechanical behaviour near the surface of polymeric biomaterials, including in simulated physiological conditions.