An Alginate-based Composite Hydrogel for Heart Tissue Engineering

In this work, ZIF-8 (zeolite imidazolate framework), loaded with dexamethasone (ZLD), were synthesized by dropwise addition of methanol, 2-methylimidazole and dexamethasone solution to methanol and zinc nitrate solution. After stirring the mixed solution for 4 hours, a matt white precipitate was obtained by centrifugation in 8000 rpm for 10 minutes. ZLD nanoparticles were collected after drying the precipitate in oven at 50 0C for 12 hours. Magnetic short nanofibers were produced through electrospinning and mechanical homogenizing. 15 w⁄v% of Polyvinylidene fluoride (PVDF), was dissolved in Dimethylformamide (DMF) solution and Polyvinylpyrrolidone (PVP) coated magnetite nanoparticles in amount of 5 w⁄w % of PVDF was added to the solution. After homogenizing the solution by using an ultrasonic probe, the produced solution was used for electrospinning. Electrospinning parameters like voltage and the distance from tip of spinning needle to rotating drum were varied to find optimum spinning parameters. At last, optimum parameters were found to be voltage of 17 kV, distance of 14 centimeters from needle tip to rotating drum and electrospinning process was carried out through room temperature. Nanofibers mats were cut into 1×1 cm2 and were weighed. Small mats were put into water and acetone solution and by using a mechanical homogenizer in 15000 rpm, they were transformed to magnetic short nanofibers. Through electrospinning process β-phase forms within the fibers which is responsible for piezoelectric properties, known as an important property in heart tissue regeneration. According to some previous studies, magnetite nanoparticles can enhance cell proliferation and differentiation through magnetic properties. They can also, enhance piezoelectric property by making electrical charge transfer to the surface of hydrogel easier, since they are conductive. For making nanocomposite hydrogel, sodium alginate was dissolved in distilled water in amount of 5 w⁄v% , then magnetic short nanofibers and ZLD nanoparticles were added to this solution and by using an ultrasonic probe, the solution was homogenized. Sonication took 10 minutes, helping ZLD nanoparticles and magnetic short nanofibers to disperse in sodium alginate solution. Finally, crosslinking process was carried out through dropwise addition of CaCl2 solution. This nanocomposite hydrogel was characterized through XRD (X-ray diffraction) and FE-SEM (Field emission scanning electron microscopy) images. Hydrogel was tested with different needle gages and showed good injectability, so it can be used as an injectable hydrogel or maybe as a 3D-printed scaffold. This nanocomposite hydrogel has piezoelectric, magnetic and drug delivery properties which can enhance cardiac muscle repair and many studies shows that alginate is a biocompatible and low toxic hydrogel which makes it a good choice for biomedical applications.