Lighting the Path: Light Delivery Strategies to Activate Photoresponsive Biomaterials In Vivo

Abstract

Photoresponsive biomaterials are experiencing a transition from in vitro models to in vivo demonstrations that point toward clinical translation. Dynamic hydrogels for cell encapsulation, light-responsive carriers for controlled drug delivery, and nanomaterials containing photosensitizers for photodynamic therapy are relevant examples. Nonetheless, the step to the clinic largely depends on their combination with technologies to bring light into the body. This review highlights the challenge of photoactivation in vivo, and presents strategies for light management that can be adopted for this purpose. The authors' focus is on technologies that are materials-driven, particularly upconversion nanoparticles that assist in "direct path" light delivery through tissue, and optical waveguides that "clear the path" between external light source and in vivo target. The authors' intention is to assist the photoresponsive biomaterials community transition toward medical technologies by presenting light delivery concepts that can be integrated with the photoresponsive targets. The authors also aim to stimulate further innovation in materials-based light delivery platforms by highlighting needs and opportunities for in vivo photoactivation of biomaterials.

Photoswitchable assembly of long-lived azobenzenes in water using visible light

“…Moreover, the reverse cis-trans isomerization using blue light (via n→π* excitation) is typically far from complete due to overlapping of the n→π* absorption bands of each isomer. For biological applications, the toxicity and poor penetration depth of UV light is particularly restrictive, [23] limiting the application of traditional azobenzenes in vivo. Water solubility is also usually limited, [24,25] and is obtained by the introduction of polar groups such as carboxylate [26] or ether groups.…”

Solution‐Based Synthesis Routes for the Preparation of Noncentrosymmetric 0‐D Oxide Nanocrystals with Perovskite and Nonperovskite Structures

“…[14] NCO nanocrystals thus behave as nonlinear point-like dipoles and their use in the biomedical imaging field further pushes some of the limits of the traditional fluorescence microscopy based on dyes, proteins, quantum dots, and upconverting nanoparticles: low penetration depth due to tissue/ living cell absorption and autofluorescence, optically resonant conditions, photobleaching and blinking. Harmonic signals from NCO nanocrystals used as exogenous bio-labeling probes thus hold great promise in the bioimaging and theranostic fields [15][16][17][18][19][20] and especially for very long term and fast in vivo imaging in the four NIR biological transparency windows. [21][22][23][24] As nonlinear optics is concerned, both Rayleigh and Mie scattering from all-dielectric nanostructures [25,26] and metal-NCO core-shell cavities [27,28] have also stimulated a lot of interest for the tailored and on-demand enhancement of the wavelengthdependent emission of harmonic signals when size control of these (hybrid)-nanostructures is achieved.…”

Nanoplatforms with donor-acceptor Stenhouse adduct molecular switch for enzymatic reactions remotely controlled with near-infrared light

“…Upconversion nanoparticles (UCNPs) are a new generation of anti-Stokes-shift-type photoluminescent nanoconverters [28], which can efficiently convert long-wavelength near-infrared (NIR) light into high-energy UV or visible light while minimizing the side effects of UV light [29]. Owing to their unique optical conversion capacity, UCNPs have been used in deep osmotic photodynamic therapy and to activate photoresponsive systems for specific biomedical applications [30][31][32].…”