A Modular Approach to Sensitized Two‐Photon Patterning of Photodegradable Hydrogels

Abstract

Photodegradable hydrogels have emerged as useful platforms for research on cell function, tissue engineering, and cell delivery as their physical and chemical properties can be dynamically controlled by the use of light. The photo-induced degradation of such hydrogel systems is commonly based on the integration of photolabile o-nitrobenzyl derivatives to the hydrogel backbone, because such linkers can be cleaved by means of one- and two-photon absorption. Herein we describe a cytocompatible click-based hydrogel containing o-nitrobenzyl ester linkages between a hyaluronic acid backbone, which is photodegradable in the presence of cells. It is demonstrated for the first time that by using a cyclic benzylidene ketone-based small molecule as photosensitizer the efficiency of the two-photon degradation process can be improved significantly. Biocompatibility of both the improved two-photon micropatterning process as well as the hydrogel itself is confirmed by cell culture studies.

Dynamic Supramolecular Ruthenium‐Based Gels Responsive to Visible/NIR Light and Heat

“…While materials responsive to UV‐light have long been established, there has been a recent shift in the field towards the use of photochemical processes, which respond in the visible and NIR region due to the poor penetration of high‐energy UV‐light as well as its incompatibility with biological environments . Also light‐sensitive ruthenium‐based complexes have been shown to be responsive to light with long wavelengths, for example, for photodynamic therapy with deep‐tissue penetration.…”

Hydrogels: soft matters in photomedicine

“…387 For example, the enhanced fluorescence intensity achieved with hydrogel formulations facilitates their use in imaging-guided PDT. 347 Additional benefits arise from specific hydrogel properties (injectable, self-healing), the ability to pattern the gels, 293 control of the sol-gel transition, 500 and from advanced drug delivery techniques. For example, recently, the permeability and oral bioavailability of non-permeable drugs such as acyclovir was significantly enhanced by encapsulating the drug into the photocross-linked hydrogel matrix of PMMA in a microdevice.…”

“…291 Thiolene photopolymerization has also been used for biochemical 3D pattern of photoreactive polypeptides in hydrogels 292 and two-photon patterning of photodegradable hydrogels has recently been achieved as well. 293 Near-IR irradiation was used to induce gel-sol transitions -in hydrogels containing core-shell upconversion nanoparticles (NaYF 4 :TmYb) which result in the release of the encapsulated biomolecules.…”

Biomaterials-based approaches to model embryogenesis

“…5c). 84,85 Additionally, biochemically patterned hydrogels provide fine 3D control over the distribution and availability of the signals to the cells through light-mediated approaches 86 whereby the molecules are presented or removed through photocaging and photocleaving respectively. In photocaging, the bioligand is bound to the hydrogel with its active site masked by a photodegradable moiety and becomes activated upon light irradiation (Fig.…”