Sanja Ostojić

Structure and properties of thermoplastic polyurethanes based on poly(dimethylsiloxane): Assessment of biocompatibility

Properties and biocompatibility of a series of thermoplastic poly(urethane-siloxane)s (TPUSs) based on α,ω-dihydroxy ethoxy propyl poly(dimethylsiloxane) (PDMS) for potential biomedical application were studied. Thin films of TPUSs with a different PDMS soft segment content were characterized by (1) H NMR, quantitative (13) C NMR, Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), contact angle, and water absorption measurements. Different techniques (FTIR, AFM, and DMA) showed that decrease of PDMS content promotes microphase separation in TPUSs. Samples with a higher PDMS content have more hydrophobic surface and better waterproof performances, but lower degree of crystallinity. Biocompatibility of TPUSs was examined after attachment of endothelial cells to the untreated copolymer surface or surface pretreated with multicomponent protein mixture, and by using competitive protein adsorption assay. TPUSs did not exhibit any cytotoxicity toward endothelial cells, as measured by lactate dehydrogenase and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide assays. The untreated and proteins preadsorbed TPUS samples favored endothelial cells adhesion and growth, indicating good biocompatibility. All TPUSs adsorbed more albumin than fibrinogen in competitive protein adsorption experiment, which is feature regarded as beneficial for biocompatibility. The results indicate that TPUSs have good surface, thermo-mechanical, and biocompatible properties, which can be tailored for biomedical application requirements by adequate selection of the soft/hard segments ratio of the copolymers.

Poly(urethane‐dimethylsiloxane) copolymers displaying a range of soft segment contents, noncytotoxic chemistry, and nonadherent properties toward endothelial cells

Polyurethane copolymers based on α,ω-dihydroxypropyl poly(dimethylsiloxane) (PDMS) with a range of soft segment contents were prepared by two-stage polymerization, and their microstructures, thermal, thermomechanical, and surface properties, as well as in vitro hemo- and cytocompatibility were evaluated. All utilized characterization methods confirmed the existence of moderately microphase separated structures with the appearance of some microphase mixing between segments as the PDMS (i.e., soft segment) content increased. Copolymers showed higher crystallinity, storage moduli, surface roughness, and surface free energy, but less hydrophobicity with decreasing PDMS content. Biocompatibility of copolymers was evaluated using an endothelial EA.hy926 cell line by direct contact, an extraction method and after pretreatment of copolymers with multicomponent protein mixture, as well as by a competitive protein adsorption assay. Copolymers showed no toxic effect to endothelial cells and all copolymers, except that with the lowest PDMS content, exhibited resistance to endothelial cell adhesion, suggesting their unsuitability for long-term biomedical devices which particularly require re-endothelialization. All copolymers exhibited excellent resistance to fibrinogen adsorption and adsorbed more albumin than fibrinogen in the competitive adsorption assay, suggesting their good hemocompatibility. The noncytotoxic chemistry of these synthesized materials, combined with their nonadherent properties which are inhospitable to cell attachment and growth, underlie the need for further investigations to clarify their potential for use in short-term biomedical devices.

Can mild bilateral sensorineural hearing loss affect developmental abilities in younger school-age children?

The research study was conducted for the purpose of examining the influence of mild bilateral sensorineural hearing loss (MBSNHL) on developmental abilities of younger school-age children. The sample encompassed 144 children with MBSNHL, aged 7.5-11 (M = 8.85). MBSNHL (20-40 dB HL) was identified by pure tone audiometry. The control group encompassed 160 children with normal hearing. The Acadia test of developmental abilities was used for assessment of developmental abilities. Although statistically significant differences between participants with MBSNHL and those with normal hearing were established in the majority of estimated developmental abilities domains, those differences do not indicate any significant delay in development of assessed abilities, except in the domain of auditory discrimination. The obtained results call for a systematic approach to children with MBSNHL in elementary schools.

Characterization of Starch Edible Films with Different Essential Oils Addition

Abstract This study investigated properties of starch-based edible films with oregano and black cumin essential oil addition. Essential oils addition positively affected film swelling (decreased due to essential oil addition), mechanical properties (tensile strength decreased while elongation at break increased), and water vapor barrier properties (decreased along with essential oils addition). Control film did not have any biological activity, which proves the need for essential oils addition in order to obtain active packaging. Oregano oil was more effective in terms of biological activity. Endothermal peak, above 200°C, represents total thermal degradation of edible films. Diffraction pattern of control film showed significant destruction of A-type crystal structure. Addition of essential oils resulted in peak shape change: diffraction peaks became narrower. Principal Component Analysis has been used to assess the effect of essential oils addition on final starch-based edible films characteristics with the aim to reveal directions for the film characteristics improvement, since the next phase will be optimal film application for food packaging.

Incidence of risk factors for hearing impairment in premature babies

According to the World Health Organization, the incidence of hearing impairment in newborn population is 1-3 per 1000 (WHO, 2012). Apart from that, many authors have found that the incidence of hearing impairment is twenty times higher, 2-4%, in neonatal intensive care unit (NICU). Thus, a congenital hearing loss is the most frequent sensory or motor deficit that could be diagnosed immediately upon birth. The objective of this study was to determine the incidence of risk factors for hearing impairment in the population of preterm babies. We were especially interested in the impact of gestational age at birth on the incidence of risk factors for hearing loss. A cohort of 150 preterm babies was enrolled in the study. They were hospitalized in the Institute for Neonatology in Belgrade during 2014 and 2015 and the data were obtained from their medical files. The results of this study indicate high incidence of risk factors for hearing impairment in this population of babies. Gestational age at birth had a strong, statistically significant, correlation with risk factor incidence in lower gestational age and vice versa. High incidence of risk factors and their interaction could account for twenty times higher occurrence of congenital and early acquired hearing loss in population of preterm babies compared to term neonates. These results imply the need for systematic audiological surveillance of prematurely born babies at least until 12 months of corrected age.