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International audience; 3D bioprinted hydrogel constructs are advanced systems of a great drug delivery application potential. One of the bioinks that has recently gained a lot of attention is gelatin methacrylate (GelMA) hydrogel exhibiting specific properties, including UV cross-linking possibility. The present study aimed to develop a new bioink composed of GelMA and gelatin modified by addition of polymer (polycaprolactone or polyethersulfone) microspheres serving as bioactive substance carriers. The prepared microspheres suspension in GelMA/gelatin bioink was successfully bioprinted and subjected to various tests, which showed that the addition of microspheres and their type affects the physicochemical properties of the printouts. The hydrogel stability and structure was examined using scanning electron and optical microscopy, its thermal properties with differential scanning calorimetry and thermogravimetric analysis and its biocompatibility on HaCaT cells using viability assay and electron microscopy. Analyses also included tests of hydrogel equilibrium swelling ratio and release of marker substance. Subsequently, the matrices were loaded with ampicillin and the antibiotic release was validated by monitoring the antibacterial activity on Staphylococcus aureus and Escherichia coli. It was concluded that GelMA/gelatin bioink is a good and satisfying material for potential medical use. Depending on the polymer used, the addition of microspheres improves its structure, thermal and drug delivery properties.

Developing accurate methods for the assessment of therapeutic protein release from polymer drug delivery systems (microcapsules, microspheres, nanoparticles, 3D-printed systems) is of paramount importance for new formulation development. The most straightforward method for protein release assessment is spectrophotometric analysis of the release medium surrounding the formulation. However, direct spectrophotometric analysis is inapplicable to formulations releasing interfering compounds (co-encapsulated drugs, additives) absorbing light in the same spectrum as proteins. Conventional protein release assays also require frequent release medium sampling and replacement, which reduces their accuracy. We propose a one-step method to assess protein release from core/shell microcapsules eliminating the need for sampling and allowing selective real-time protein quantitation in the release medium. To prevent spectral interferences, released protein is differentiated from interfering compounds by employing a colorimetric protein assay reagent, forming a colour complex selectively with the protein, as the release medium. To eliminate sampling, we employed a continuous flow closed loop set-up, where the release medium is constantly circulating between microcapsule-containing tank and spectrophotometer. A series of colorimetric protein assay reagents (bromocresol green, tetrabromophenol blue, eosin B, eosin Y, biuret) were evaluated in terms of their applicability as the release medium in described system. Only biuret reagent was found compatible with proposed method due to formation of color complex stable over extended period of time and low adsorption to microcapsules. Presented method allowed effective evaluation of albumin release from alginate-polyethersulfone microcapsules with accuracy equal to conventional ‘sample and separate’ technique. Albumin release followed first-order kinetics with plateau reached after 19 h.

3D bioprinting uses bioink deposited directly on a collector to create any previously designed 3D model. One of the most common and the easiest to operate bioinks is gelatin-alginate hydrogel. The present study aimed to combine 3D bioprinting with different cross-linking techniques to develop a new stable and biodegradable gelatin-alginate hydrogel matrix for drug delivery applications. The matrix-building biopolymers were crosslinked by ionotropic gelation with Ca

The method of preparation of partly degradable polysulfone/polyurethane (PSf/PU) asymmetric hollow fiber membranes is presented. The membranes built of PSf and polyurethane polymer containing degradable ester groups were obtained by dry/wet-spinning phase-inversion technique then treated with sodium hydroxide solution using the flowing method. The membrane hydraulic permeability (UFC) for pure water and retention coefficients were evaluated for chosen markers before and after applied hydrolysis. An increase in ultrafiltration coefficient was observed while retention coefficient did not change significantly in post-treatment membranes. Hydrolysis caused the partial removal of PU from the membrane structure resulting in the opening of the pore passages and the permeability increase without increasing the pore size. The morphology of the PSf/PU hollow fiber membranes was analyzed using scanning electron microscopy before and after hydrolysis.

Application of computer-aided image analysis to quality assessment of inner structure of alginate-polyethersulfone microcapsule is presented. The microcapsules are provided for analysis in the form of optical microscope images of their cross-sections. A specialized computer program APEK makes it possible to measure and calculate a set of morphological parameters describing microcapsules’ outer and inner size and shape, as well as the thickness of a polyethersulfone membrane which covers hydrogel microcapsule core. It is described a method of thickness profile of microcapsule's membrane measuring based on skeleton line. Calculations are illustrated by an example. Suggestions concerning future works have been formulated.

We present a method for retrieval of cells encapsulated in alginate-polyethersulfone (AP) microcapsules. AP microcapsules consist of alginate hydrogel core and a semi-permeable polymer membrane. Proposed method is based on chemical destruction of microcapsule structure that is, polymer membranes are removed by dissolution in 1-methyl-2-pyrrolidone subsequently the cells immobilized in the cores are released by liquefaction of alginate gel. The viability of Saccharomyces cerevisiae cells retrieved by this technique exceeds 98%, while the concentration of recovered cells reaches 98%-102% of cell concentration in suspension used for microencapsulation, which proves that proposed method allows to effectively and quantitatively retrieve encapsulated cells without compromising their viability.

The current methods allow for encapsulation of cells inside spherical microcapsules made of a matrix covered by a permselective membrane using an electrostatic droplet generator with 1-nozzle or 2-nozzle heads. However, some potentially useful materials for the outer membranes cannot be put into direct contact with hydrophilic core filled by cells during the manufacturing process. Therefore, we designed a novel 3-coaxial-nozzle head that allows for the third fluid to separate the core material from the membrane material. The equipment was applied for manufacturing spherical microcapsules comprised of cell-friendly alginate core surrounded by semipermeable polyethersulfone membrane. The obtained microcapsules had a diameter between 0.84 mm and 1.79 mm, and the diameter correlated negatively with the applied electric voltage. The thickness of the membrane varied from 171 µm to 450 µm. The SEM images of the interior of microcapsules revealed highly porous membrane structure typical for synthetic membranes ob...