a b s t r a c tThis paper presents a novel approach toward the production of hybrid alginate-lignin aerogels. The key idea of the approach is to employ pressurized carbon dioxide for gelation. Exposure of alginate and lignin aqueous alkali solution containing calcium carbonate to CO 2 at 4.5 MPa resulted in a hydrogel formation. Various lignin and CaCO 3 concentrations were studied. Stable hydrogels could be formed up to 2:1 (w/w) alginate-to-lignin ratio (1.5 wt% overall biopolymer concentration). Upon substitution of water with ethanol, gels were dried in supercritical CO 2 to produce aerogels. Aerogels with bulk density in the range 0.03-0.07 g/cm 3 , surface area up to 564 m 2 /g and pore volume up to 7.2 cm 3 /g were obtained. To introduce macroporosity, the CO 2 induced gelation was supplemented with rapid depressurization (foaming process). Macroporosity up to 31.3 ± 1.9% with interconnectivity up to 33.2 ± 8.3% could be achieved at depressurization rate of 3 MPa/min as assessed by micro-CT. Young's modulus of alginate-lignin aerogels was measured in both dry and wet states. Cell studies revealed that alginate-lignin aerogels are non-cytotoxic and feature good cell adhesion making them attractive candidates for a wide range of applications including tissue engineering and regenerative medicine.

Highlights • alginate-starch Ca-crosslinked aerogels by CO 2 induced gelation and sc-drying; • macroporosity due to CO 2 expansion and intrinsically high mesoporosity; • alginate-starch aerogels are bioactive and non-cytotoxic. ABSTRACT Aerogels are a special class of ultra-light porous materials with growing interest in biomedical applications due to their open pore structure and high surface area. However, they usually lack macroporosity, while mesoporosity is typically high. In this work, carbon dioxide induced gelation followed by expansion of the dissolved CO 2 was performed to produce hybrid calcium-crosslinked alginate-starch hydrogels with dual meso-and macroporosity. The hydrogels were subjected to solvent exchange and supercritical drying to obtain aerogels. Significant increase in macroporosity from 2 to 25 % was achieved by increasing expansion rate from 0.1 to 30 bar/min with retaining mesoporosity (BET surface and BJH pore volume in the range 183-544 m 2 /g and 2.0-6.8 cm 3 /g, respectively). In vitro bioactivity studies showed that the alginate-starch aerogels are bioactive, i.e. they form hydroxyapatite crystals when immersed in a simulated body fluid solution. Bioactivity is attributed to the presence of calcium in the matrix. The assessment of the biological performance showed that the aerogels do not present a cytotoxic effect and the cells are able to colonize and grow on their surface. Results presented in this work provide a good indication of the potential of the alginate-starch aerogels in biomedical applications, particularly for bone regeneration. KEYWORDS aerogels, alginate, starch, tissue engineering, supercritical fluids, CO 2 induced gelation INTRODUCTION An ideal scaffold for tissue engineering must meet particular requirements to achieve the desired biological response: the scaffold should possess interconnecting pores of appropriate size to favor tissue integration and vascularization, be made from material with controlled biodegradability, have appropriate surface chemistry to favor cellular attachment, differentiation and proliferation, possess adequate mechanical properties to match the intended site of implantation and handling, should not induce any adverse response and be easily fabricated into a variety of shapes and sizes [1]. Some attempts have recently been made to address tissue engineering and regenerative medicine (TERM) problems using aerogels as scaffolds. Aerogels are well known ultra-light highly porous materials with an open structure, large specific surface area and pore volume. High mesoporosity comparable to the native extracellular matrix (ca. 80% porosity) is favorable condition for cell growth, making aerogels an ideal candidate for a number of biomedical applications, including tissue engineering. Nevertheless, macroporosity of these structures should be improved to promote cell migration into the matrices and enhance mass transfer between the scaffold and the bulk phase. The fact that biopolymers can be used for aerogel production was recognized by Samuel...

Device-Associated Urinary Tract InfectionsUrological devices are divided into several different market segments managing, for example, urinary incontinence, urinary stones, treatment of prostate hyperplasia or cancer, and erectile dysfunction. Devices aimed to manage urinary incontinence or maintain the ureter or urethra open and unobstructed, include ureteral stents for the upper urinary tract, urethral stents for the lower urinary tract, and urinary catheters. The focus of this paper is on catheter-and ureteral stent-associated UTI (Figure 1) as these are the major device groups and give rise to large numbers of infections worldwide. [10] In this review,

Marine sponges are extremely rich in natural products and are considered a promising biological resource. The major objective of this work is to couple a green extraction process with a natural origin raw material to obtain sponge origin collagen/gelatin for biomedical applications. Marine sponge collagen has unique physicochemical properties, but its application is hindered by the lack of availability due to inefficient extraction methodologies. Traditional extraction methods are time consuming as they involve several operating steps and large amounts of solvents. In this work, we propose a new extraction methodology under mild operating conditions in which water is acidified with carbon dioxide (CO 2) to promote the extraction of collagen/gelatin from different marine sponge species. An extraction yield of approximately 50% of collagen/gelatin was achieved. The results of Fourier transformed infrared spectroscopy (FTIR), circular dichroism (CD), and differential scanning calorimetry (DSC) spectra suggest a mixture of collagen/gelatin with high purity, and the analysis of the amino acid composition has shown similarities with collagen from other marine sources. Additionally, in vitro cytotoxicity studies did not demonstrate any toxicity effects for three of the extracts.

Marine sponges are a rich source of natural bioactive compounds. One of the most abundant valuable products is collagen/ gelatin, which presents an interesting alternative source for pharmaceutical and biomedical applications. We have previously proposed an innovative green technology for the extraction of collagen/gelatin from marine sponges based in water acidified with carbon dioxide. In this work, we have optimized the process operating conditions toward high yields and collagen quality as well as to reduce extraction procedure duration and energy consumption. The process extraction efficiency is higher than 50%, corresponding to a yield of approximately 10% of the sponge dry mass, obtained for mild operating conditions of 10 bar and 3 h. The extracted material was characterized by scanning electron microscopy (SEM), rheology, Fourier transformed infrared spectroscopy (FTIR), circular dichroism (CD), amino acid analysis, and SDS-PAGE. The extracts were found to be composed of highly pure mixtures of collagen and gelatin with similar properties to collagen isolated from other marine sources. The cytotoxicity evaluation, performed with L929 cells, has proven the biocompatibility of the material extracted. Overall, the results obtained demonstrate the efficiency of this approach and the high industrial potential of this technology to obtain marine collagen/gelatin with properties suitable for biomedical applications.