Two-photon polymerization of hydrogels – versatile solutions to fabricate well-defined 3D structures

Abstract

Hydrogels are cross-linked water-containing polymer networks that are formed by physical, ionic or covalent interactions. In recent years, they have attracted significant attention because of their unique physical properties, which make them promising materials for numerous applications in food and cosmetic processing, as well as in drug delivery and tissue engineering. Hydrogels are highly waterswellable materials, which can considerably increase in volume without losing cohesion, are biocompatible and possess excellent tissue-like physical properties, which can mimic in vivo conditions. When combined with highly precise manufacturing technologies, such as two-photon polymerization (2PP), well-defined three-dimensional structures can be obtained. These structures can become scaffolds for selective cell-entrapping, cell/drug delivery, sensing and prosthetic implants in regenerative medicine. 2PP has been distinguished from other rapid prototyping methods because it is a non-invasive and efficient approach for hydrogel cross-linking. This review discusses the 2PP-based fabrication of 3D hydrogel structures and their potential applications in biotechnology. A brief overview regarding the 2PP methodology and hydrogel properties relevant to biomedical applications is given together with a review of the most important recent achievements in the field.

Functionalized 3D Architected Materials via Thiol‐Michael Addition and Two‐Photon Lithography

“…[35] A more modern approach has been to synthesize monomers with the functional groups of interest. By carefully designing the monomers such that the desired functional groups are not consumed during the polymerization process, structures with unique properties such as photo-reactive surfaces, [37-39] intrinsic chemical sensing, [40] chemical resistance, [41] bioactivity [42-43] and biodegradability [44-45] can be fabricated. Since the functional groups are directly installed onto the monomer, they should exhibit a higher surface density of functional groups.…”

Engineered 3D Polymer and Hydrogel Microenvironments for Cell Culture Applications

“…Two-photon polymerization (TPP) uses the non-linearity of two-photon absorption to polymerize extremely confined regions (voxels have a characteristic dimension in the order of 100 nm) of resin since only the focal spot receives sufficient light intensity for triggering the two-photon process. TPP has much higher 3D resolution than SLA but the writing time is much slower, making it suitable for special applications and rapid prototyping but not for high throughput production [60][61][62][63], although the integration of galvanometric mirrors and moving-beam fixed-sample (MBFS) strategies are starting to fill this gap.…”

Biomaterial-based microstructures fabricated by two-photon polymerization microfabrication technology

“…However, the biodegradability and biocompatibility as well as immunogenicity of the microstructures can not meet the requirement in biomedical application. 79 Unlike synthetic polymers, biomacromolecules including proteins, sugars and so on have excellent biodegradability, biocompatibility and low immunogenicity.…”