Light is a uniquely powerful tool for controlling molecular events in biology. No other external input (e.g., heat, ultrasound, magnetic field) can be so tightly focused or so highly regulated as a ...clinical laser. Drug delivery vehicles that can be photonically activated have been developed across many platforms, from the simplest “caging” of therapeutics in a prodrug form, to more complex micelles and circulating liposomes that improve drug uptake and efficacy, to large-scale hydrogel platforms that can be used to protect and deliver macromolecular agents including full-length proteins. In this Review, we discuss recent innovations in photosensitive drug delivery and highlight future opportunities to engineer and exploit such light-responsive technologies in the clinical setting.
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Photoresponsive materials have been widely used in vitro for controlled therapeutic delivery and to direct 4D cell fate. Extension of the approaches into a bodily setting requires use of low‐energy, ...long‐wavelength light that penetrates deeper into and through complex tissue. This review details recent reports of photoactive small molecules and proteins that absorb visible and/or near‐infrared light, opening the door to exciting new applications in multiplexed and in vivo regulation.
Light‐responsive materials have made waves on the benchtop, facilitating cutting‐edge research with incredible potential. However, nearly all efforts to translate these new materials into clinical applications have been thwarted by the limitations of light's poor penetration depth in living tissue. This review highlights new biomaterials that respond to lower energy light with better penetration for expanded in vivo applications.
Photodynamic hydrogel biomaterials have demonstrated great potential for user-triggered therapeutic release, patterned organoid development, and four-dimensional control over advanced cell fates in ...vitro. Current photosensitive materials are constrained by their reliance on high-energy ultraviolet light (<400 nm) that offers poor tissue penetrance and limits access to the broader visible spectrum. Here, we report a family of three photolabile material crosslinkers that respond rapidly and with unique tricolor wavelength-selectivity to low-energy visible light (400-617 nm). We show that when mixed with multifunctional poly(ethylene glycol) macromolecular precursors, ruthenium polypyridyl- and ortho-nitrobenzyl (oNB)-based crosslinkers yield cytocompatible biomaterials that can undergo spatiotemporally patterned, uniform bulk softening, and multiplexed degradation several centimeters deep through complex tissue. We demonstrate that encapsulated living cells within these photoresponsive gels show high viability and can be successfully recovered from the hydrogels following photodegradation. Moving forward, we anticipate that these advanced material platforms will enable new studies in 3D mechanobiology, controlled drug delivery, and next-generation tissue engineering applications.
Incorporation of photoresponsive molecules within soft materials can provide spatiotemporal control over bulk properties and address challenges in targeted delivery and mechanical variability. ...However, the kinetics of in situ photochemical reactions are often slow and typically employ ultraviolet wavelengths. Here, we present a novel photoactive crosslinker Ru(bipyridine)2(3‐pyridinaldehyde)2 (RuAldehyde), which was reacted with hydrazide‐functionalized hyaluronic acid to form hydrogels capable of encapsulating protein cargo. Visible light irradiation (400–500 nm) initiated rapid ligand exchange on the ruthenium center, which degraded the hydrogel within seconds to minutes, depending on gel thickness. An exemplar enzyme cargo, TEM1 β‐lactamase, was loaded into and photoreleased from the Ru‐hydrogel. To expand their applications, Ru‐hydrogels were also processed into microgels using a microfluidic platform.
A ruthenium‐containing crosslinker, Ru(bpy)2(3‐pyridinaldehyde)2 was synthesized for reaction with hydrazide‐modified hyaluronic acid to form visible‐light‐responsive macro‐ or microgels. Ru‐hydrogel was formulated to encapsulate active protein until photorelease. This new RuAldehyde crosslinker promotes efficient photodegradation while minimizing toxicity.
Photochemical approaches afford high spatiotemporal control over molecular structure and function, for broad applications in materials and biological science. Here, we present the first example of a ...visible light responsive ruthenium-based photolinker, Ru(bipyridine)
(3-ethynylpyridine)
(RuBEP), which was reacted stoichiometrically with a 25mer DNA or morpholino (MO) oligonucleotide functionalized with 3' and 5' terminal azides, via Cu(I)-mediated 3+2 Huisgen cycloaddition reactions. RuBEP-caged circular morpholinos (Ru-MOs) targeting two early developmental zebrafish genes,
and
, were synthesized and tested
. One-cell-stage zebrafish embryos microinjected with Ru-MO and incubated in the dark for 24 h developed normally, consistent with caging, whereas irradiation at 450 nm dissociated one 3-ethynylpyridine ligand (ϕ = 0.33) and uncaged the MO to achieve gene knockdown. As demonstrated, Ru photolinkers provide a versatile method for controlling structure and function of biopolymers.
Photoresponsive materials afford spatiotemporal control over desirable physical, chemical and biological properties. For advanced applications, there is need for molecular phototriggers that are ...readily incorporated within larger structures, and spatially-sequentially addressable with different wavelengths of visble light, enabling multiplexing. Here we describe spectrally tunable (λ
= 420-530 nm) ruthenium polypyridyl complexes functionalized with two photolabile nitrile ligands that present terminal alkynes for subsequent crosslinking reactions, including hydrogel formation. Two Ru crosslinkers were incorporated within a PEG-hydrogel matrix, and sequentially degraded by irradiation with 592 nm and 410 nm light.
The study of ruthenium polypyridyl complexes can be widely applied across disciplines in the undergraduate curriculum. Ruthenium photochemistry has advanced many fields including dye-sensitized solar ...cells, photoredox catalysis, light-driven water oxidation, and biological electron transfer. Equally promising are ruthenium polypyridyl complexes that provide a sterically bulky, photolabile moiety for transiently “caging” biologically active molecules. Photouncaging involves the use of visible (1-photon) or near-IR (2-photon) light to break one or more bonds between ruthenium and coordinated ligand(s), which can occur on short time scales and in high quantum yields. In this work we demonstrate the use of a model “caged” acetonitrile complex, Ru(2,2′-bipyridine)2(acetonitrile)2, or RuMeCN in an advanced synthesis and physical chemistry laboratory. Students made RuMeCN in an advanced synthesis laboratory course and performed UV–vis spectroscopy and electrochemistry. The following semester students investigated RuMeCN photolysis kinetics in a physical chemistry laboratory. These two exercises may also be combined to create a 2-week module in an advanced undergraduate laboratory course.
Light‐responsive hydrogels show promise in targeted drug delivery, as they can load and deliver sensitive cargo when triggered. To make these hydrogels more amenable for use in vivo, I. J. Dmochowski ...and colleagues have used a nontoxic ruthenium‐based crosslinker to form a hydrogel that degrades upon irradiation with visible light, releasing an active protein cargo. For the full story see the Communication on page 2328 ff.
Ruthenium (Ru) polypyridyl complexes are described that present chemically reactive moieties on one or two photolabile ligands for engineering photoresponsive molecules or materials. Ru-cross-linkers ...can form hydrogels, with proteins or other biomolecules embedded. In this way, the protein is "caged" until released with light. By varying the coordinated ligands, Ru-cross-linkers have 1-photon absorption maxima that are tunable across the visible spectrum and into the near-infrared, which enables photoactivation at multiple, different wavelengths (i.e., multiplexing).
Highlights • DPAT decreased GFAP staining while other 5-HT1A agonists did not. • DPAT remained effective when administered up to 2 h after the toxic challenge. • DPAT reversed the increase in IL-1β ...but did not reduce positive TUNEL staining. • WAY-100635, a silent 5-HT1A antagonist had no effect on DPAT afforded protection. • The effects produced by DPAT appear to lie within its secondary pharmacology.
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