PMC

(a) Schematic illustration of the synthesis of photodegradable coordination polymer particles (CPPs). The cargos can be encapsulated in CPPs for a light-controlled release via photolysis of the organic linkers. (b) Chemical structure of the photocleavable organic ligand used in the synthesis of CPPs and cleavage of the ligand under UV light irradiation.

Structures of star polymer 1, diMOFO, diDIFO, MN from diDIFO and 1, and the corresponding linear polymer photodegradation product. To clearly depict their location in the MN structure, photodegradable NBOC groups are shown in red and diDIFO is shown in orange.

(a) The chemical structure of photodegradable PEG diacrylate (PEGdiPDA) where green indicates the acrylate groups, blue the o-nitrobenzyl photodegradable groups, and black the PEG backbone. In the presence of a photoinitiator and 405 nm light the polymer undergoes a free radical initiated polymerization reaction to form a hydrogel network. The hydrogel network can then be degraded by irradiation with 365 nm light to cleave the o-nitrobenzyl groups. (b) Schematic of the fabrication and degradation process of patterned photodegradable hydrogel films. To form the hydrogel thin films by micromolding, a PDMS master is filled with the hydrogel forming polymer solution and irradiated with 405 nm light. A flow channel is then bonded over the top of the hydrogel film which can then be degraded under flow conditions by irradiation with 365 nm light. (c) The PDMS molds used to pattern the hydrogel capture surface demonstrating the difference in size between the flat and herringbone (HB) patterned surfaces. Scale bar 1 cm. (d) Representative images of flat (top) and HB (bottom) micromolded hydrogel surfaces. Scale bar 1 mm. (e) A three-dimensional confocal image of a photodegradable hydrogel HB patterned surface to show the replication of the HB pattern using the micromolding process. Scale bar 100 µm.

Photodegradable polyurethane nanoparticle. a) Structure of a photolabile polyurethane; b) A hydrophobic model drug and photolabile polyurethane self-assemble into a drug-loaded nanoparticle. Upon UV irradiation, the polymer backbones degrade, releasing the encapsulated drug. Adapted with permission from []. Copyright 2012 American Chemical Society.