Creating three-dimensional hydrogel architectures for biomedical applications

Abstract

Hydrogels are water-soluble polymers which can contain a huge amount of water inside them. This property of hydrogels has attracted specific interests in biomedical fields such as 3D organ/tissue printing, wound dressing, drug delivery, trans-dermal systems, dental materials, implants, injectable polymeric systems, ophthalmic applications, hybrid-type organs, contact lenses etc. Three-dimensional (3D) printing of hydrogels can be considered as a significant advancement in this regard because this may fascilate the use of hydrogels. In this research work, a hydrogel of poly(acrylic acid)- cysteine (PAA-cysteine) conjugates was 3D printed. The hydrogel synthesized was chosen after in-depth literature study. PAA-cysteine conjugates were synthesized by the covalent attachment of L-cysteine to poly(acrylic acid) (PAA). Synthesis followed by purification of the hydrogel. The reaction mixture was dialyzed using Spectra/Por® 2 membrane (MWCO: 12-14 kD) for 3 days in a fume hood under stirring at room temperature. After that, the dialyzed sample was transferred into petri dishes and freeze-dried for two days and stored in a closed desk until use. Swelling test was performed to get the swelling ratio of poly(acrylic acid)- cysteine (PAA-cysteine) conjugated hydrogel. The swelling ratio was found to be ~290% of the dry weight of the hydrogel. This high swelling ratio is very exciting for biomedical application. After that printing of hydrogel was tried. It was very challenging as hydrogel possesses a significant portion of porosity inside them. Inkjet printing and fused deposition modeling (FDM) printing technology were applied for the printing purpose. Inkjet printing was performed successfully with the synthesized hydrogel. A Standard operating procedure (SOP) was prepared for the use of FDM printer. But FDM printing was not possible due to the difficulty in finding the melting point of the hydrogel. Different biomolecules (proitens, amino acids etc.) can be delivered in vivo through the printed hydrogels. This work can be considered as a precursor to facilitate the use of hydrogels in biomedical applications. Keywords: hydrogel, swelling ratio, 3D printing, inkjet printing, fused deposition modeling (FDM).