Photolabile Polymer Research Articles

Multicolor Light-Induced Immune Activation via Polymer Photocaged Cytokines.

Cytokines act as potent, extracellular signals of the human immune system and can elicit striking treatment responses in patients with autoimmune disease, tissue damage, and cancer. Yet, despite their therapeutic potential, recombinant cytokine-mediated immune responses remain difficult to control as their administration is often systemic, whereas their intended sites of action are localized. To address the challenge of spatially and temporally constraining cytokine signals, we recently devised a strategy whereby recombinant cytokines are reversibly inactivated via chemical modification with photo-labile polymers that respond to visible LED light. Extending this approach to enable both in vivo and multicolor immune activation, here we describe a strategy whereby cytokines appended with heptamethine cyanine-polyethylene glycol are selectively re-activated ex vivo using tissue-penetrating near-infrared (NIR) light. We show that NIR LED light illumination of caged, pro-inflammatory cytokines restores cognate receptor signaling and potentiates the activity of T cell-engager cancer immunotherapies ex vivo. Using combinations of visible- and NIR-responsive cytokines, we further demonstrate multiwavelength optical control of T cell cytolysis ex vivo, as well as the ability to perform Boolean logic using multicolored light and orthogonally photocaged cytokine pairs as inputs and T cell activity as outputs. Together, this work demonstrates a novel approach to control extracellular immune cell signals using light, a strategy that in the future may improve our understanding of and ability to treat cancer and other diseases.

Optical Control of Cytokine Signaling via Bioinspired, Polymer-Induced Latency.

Cytokine signaling is challenging to study and therapeutically exploit as the effects of these proteins are often pleiotropic. A subset of cytokines can, however, achieve signal specificity via association with latency-inducing proteins, which cage the cytokine until disrupted by discreet biological stimuli. Inspired by this precision, here, we describe a strategy for synthetic induction of cytokine latency via modification with photolabile polymers that mimic latency while attached then restore protein activity in response to light, thus controlling the magnitude, duration, and location of cytokine signals. We characterize the high dynamic range of cytokine activity modulation and find that polymer-induced latency, alone, can prolong in vivo circulation and bias receptor subunit binding. We further show that protein derepression can be achieved with a near single-cell resolution and demonstrate the feasibility of transcutaneous photoactivation. Future extensions of this approach could enable multicolor, optical reprogramming of cytokine signaling networks and more precise immunotherapies.

Photo-regulated control of cytokine signaling via bioinspired, polymer-induced latency

Abstract Cytokine signaling is challenging to study or therapeutically modulate as the effects of these protein are often pleotropic and context-dependent. One mechanism by which cytokines with diverse effects can, however, transmit cell type-specific information is via expression in an inactive, or latent, form in which the protein is sterically shielded by a binding partner that is later displaced or degraded (e.g. TGF-β1 association with GARP or LAP). Inspired by this precision, we hypothesized that photo-reversible chemical modification could impart orthogonal specificity to cytokines not expressed in a latent state, such as IL-2, IL-15, or IL-12. Here, we describe a strategy whereby cytokines are modified with photo-labile polymers that mimic the induction of latency while appended, then de-shield to recover protein activity in response to monochromatic light exposure, thus controlling the magnitude, duration, and location of cytokine signals. Using this strategy, we show that latent IL-2 and IL-15 activity can be photo-modulated as much as 103-fold and that polymer-induced IL-2 latency, alone, can bias affinity away from immunosuppressive CD25 binding. We further show that protein de-repression can be achieved with spatial resolution approaching that of a single immune cell and demonstrate the feasibility of transcutaneous IL-2 photoactivation using engineered tissue phantoms. We find that such modifications also prolong the circulation of IL-12 in vivo, thus obviating the need for frequent, high dosing in therapeutic settings. Future extensions of this approach could enable multicolor, optical reprogramming of cytokine signaling networks and lead to immunotherapies that are more tissue-specific and patient-personalized.

Chemical modification strategies for photo-induced control of immune cell signaling

Abstract Cytokine therapies show great potential to induce cancer immune elimination and have demonstrated therapeutic benefit in a subset of patients. However, controlling the pleotropic effects of these immune signal effectors is a challenge. Here, we present an approach to enable optical control of cytokine activity by caging the activity of these proteins via labeling with wavelength-specific, photo-labile polymers (i.e. photo-caging). We create a system to measure light-induced polymer cleavage (uncaging) through fluorescence dequenching and establish: high wavelength-selectivity, protein activation through tissue mimics, and micrometer-scale uncaging resolution (via photopatterning). We focus on cytokines IL-2, IL-12 and IL-15 and demonstrate ability to reversibly modulate cytokine size and activity. We show photo-caging increases cytokine size by up to 20 fold, resulting in increased serum half-life. Additionally, cytokine activity (via T-cell proliferation) is blunted by 1,000 fold and near fully recovered through light-induced uncaging. Affinity measurements demonstrate photo-caging disrupts the bias of IL-2 towards IL-2Rα expressed on immunosuppressive T-regulatory cells. Further, photo-caging negates the ability of IL-2 to increase antigen specific (OT-1) cell activation, but is restored upon uncaging. In summary, we present the synthesis and therapeutic potential of these optically activated cytokines. In future studies we aim to use cytokine photo-caging as a means to provide new insights into the mechanics of cancer immune elimination and achieve tissue exclusive activation by exploiting spatially and temporally constraining cytokine activation in chip-based organoids and in vivo cancer models.

Designing a main-chain visible-light-labile picolinium-caged polymer and its biological applications

A picolinium-caged main-chain photolabile polymer (MCPP) is reported with a high degradation efficiency (∼95%) upon visible light irradiation (452 nm).

Photolabile Hydrogels Responsive to Broad Spectrum Visible Light for Selective Cell Release.

We introduce an efficient method for the preparation of photolabile polymer linkers to be used in the fabrication of bioorthogonal and photodegradable hydrogels. The versatility of this synthesis strategy allows for incorporation of a series of chromophores responsive to addressable wavelengths of UV and broad spectrum visible light. Consequently, selective release of different cell types from composite hydrogels by user-defined timing can be achieved by irradiating the materials with different wavelengths of light.

Chemically Patterned Inverse Opal Created by a Selective Photolysis Modification Process.

Anisotropic photonic crystal materials have long been pursued for their broad applications. A novel method for creating chemically patterned inverse opals is proposed here. The patterning technique is based on selective photolysis of a photolabile polymer together with postmodification on released amine groups. The patterning method allows regioselective modification within an inverse opal structure, taking advantage of selective chemical reaction. Moreover, combined with the unique signal self-reporting feature of the photonic crystal, the fabricated structure is capable of various applications, including gradient photonic bandgap and dynamic chemical patterns. The proposed method provides the ability to extend the structural and chemical complexity of the photonic crystal, as well as its potential applications.

Photodegradable Polymers for Biotechnological Applications

Photodegradable polymers constitute an emerging class of materials that finds numerous applications in biotechnology, biomedicine, and nanoscience. This article highlights some of the emerging applications of photodegradable polymers in the form of homopolymers, particles and self-assembled constructs in solution, hydrogels for tissue engineering, and photolabile polymers for biopatterning applications. Novel photochemistries have been combined with controlled polymerization methods, which result in well-defined photodegradable materials that exhibit light mediated and often controlled fragmentation processes.

Polymer Brushes with Phototriggered and Phototunable Swelling and pH Response

Photolabile polymer brushes with tailored length containing a photoremovable protecting group (NVOC) are prepared via the SI-ATRP method. Upon light irradiation, the NVOC group is removed to generate controlled densities of free amine groups (PAMA) randomly distributed along the brush. The presence of the ionizable groups induces a photo-triggered swelling response. The swelling degree can be tuned by the irradiation dose. A dual (light and pH), tunable response is demonstrated.

Synthesis and Properties of New Poly(urethane-acrylates) With Pendant Triazene Moieties

New triazene urethane methacrylates, 1-(phenyl)-3-(2-methacryloyloxyethyl)-3-methyl triazene-1 (UMA-T1) and 1-(p-methoxyphenyl)-3-(2-methacryloyloxyethyl)-3-methyl triazene-1 (UMA-T2), were synthesized and characterized to be used as co-partners in the radical co-polymerization with methyl methacrylate for achieving triazene-co-polymethacrylates. The synthesized photo-polymers were spectrally and thermally characterized, the results being satisfactory for this class of materials. The most important feature of the co-polyacrylates is their photosensitivity, evaluated by the UV irradiation in DMF solution or thin films, following the disappearance of the π–π* absorption band, corresponding to the triazene chromophore, in the UV spectra. Such photolabile polymers with good film-forming properties could offer new possibilities in printing techniques and nanostructuring on surfaces. In addition, the triazene functions introduced as side-groups may be exploited for the tailoring of novel functional polymeric architectures.

Photolabile and thermally labile polymers as templates and for surface patterning

AbstractThe successful selective metal deposition using a photolabile polymer consisting of a diazosulfonate side chain group has been reported. In addition to 20 mol% diazosulfonate monomer the terpolymer contains 5 mol% of a silane compound, which is necessary for the covalent anchoring of the film onto the substrate. Furthermore, films were prepared using photolabile polymers containing protected amines onto glass and silicon substrates. These films are suitable for imagewise structuring by UV‐light and laser irradiation, and nanoelements like DNA strands could be attached individually in further steps. These polymeric amines with similar structure like the diazosulfonate terpolymers were synthesized by free radical polymerization of three monomer units which are methyl methacrylate (MMA) (spacer), 3‐(trimethoxysilyl)propylmethacrylate (anchoring group) and N‐(N‐nitroveratryloxycarbonyl‐aminopropyl)‐methacrylamide (photolabile compound). The anchoring groups were varied to enable covalent attachment of the polymers, for example, onto gold substrates. Azosulfonates, sulfonate esters, and both protected amines and carboxylic acid groups were used as thermally labile or photolabile functionalities. Selective deprotection using heat or light could be varied. Finally block copolymers based on orthogonally protected hydroxystyrenes could be prepared by controlled radical polymerization. A highly ordered nanostructure could be realized in thin films of these polymers exhibiting strong changes using heat or light treatment. Copyright © 2006 John Wiley & Sons, Ltd.

Optical modification and metal complexation of ultrathin spin-coated polymer films

We report the successful metal salt complexation of ultrathin terpolymer films spin-coated onto glass and silicon substrates and the subsequent reduction of the salt to metal clusters. The photolabile polymer consists of a diazosulfonate side chain polymer which may be decomposed under UV irradiation. Initial, complexed and reduced stages are characterized using optical transmission spectroscopy and X-ray photoelectron spectroscopy, while the film surface roughness, morphology and thickness are determined from atomic force microscopy and ellipsometry. On the one hand, our experiments show that nonirradiated diazosulfonate side groups complex with silver acetate provided from solution, and that silver ions chemically reduce when exposed to a sodium borohydride solution. On the other hand, the complete destruction of the photolabile diazosulfonate unit with UV irradiation was proven. Our experimental investigations are the first successful effort for selective metallization of deposited ultrathin diazosulfonate polymer films. Furthermore, we were able to show that the films can be optically structured by writing micrometer-sized patterns with a focused UV laser beam.

Metal Salt Complexation of Spin-Coated Ultrathin Diazosulfonate Terpolymer Films

We report the successful metal salt complexation of ultrathin terpolymer films spin-coated onto glass and silicon substrates as well as the subsequent reduction of the salt to metal clusters. The photolabile polymer consists of a diazosulfonate side chain polymer which may be decomposed under UV irradiation. All stages, i.e., initial, complexed, and reduced stage, are characterized using optical transmission spectroscopy and X-ray photoelectron spectroscopy. The film surface roughness, morphology, and thickness are determined by atomic force microscopy and ellipsometry. On one hand, our experiments show that nonirradiated diazosulfonate side groups complex with silver acetate provided from solution and that silver ions chemically reduce when exposed to a sodium borohydride solution. On the other hand, the complete destruction of the photolabile diazosulfonate unit under UV irradiation is proven. Our experimental investigations are the first successful efforts demonstrating the selective metallization of d...

Photolysis, thermolysis, and protolytic decomposition of a triazene polymer in solution

AbstractThe depolymerization of a triazeno‐group containing photopolymer, poly[oxy‐1,4‐phenyleneazo(methylimino)hexamethylene(methylimino)azo‐1,4‐phenylene], is investigated in a tetrahydrofuran (THF) solution. Irradiation of the material leads to a clean decomposition of the photolabile polymer, as monitored by UV spectroscopy and gel‐permeation chromatography (GPC). As compared to the photolysis in THF solution, the light‐induced decomposition rate of a polymer in a polymer film is shown to be much slower. The highly photosensitive triazeno group also decomposes thermally at temperatures above approx. 220°C. The kinetics of thermal degradation of the polymer in substance was investigated at a temperature of 256°C, and monitored by GPC measurements. During this decomposition, one first observes the development of higher molar‐mass fractions, which result from grafting reactions of primary radicals. Upon further thermolysis the triazene polymer is completely degraded to low‐molar‐mass products. The volatile decomposition products were identified by gas chromatography/mass spectrometry (GC/MS) analysis. The protolytic decomposition, which represents the retrosynthesis of the triazene polymer, was studied in a 9:1 mixture of tetrahydrofuran and an aqueous citrate buffer solution. Although the decomposition rate in this solvent mixture is slow, as compared to the depolymerization in diluted hydrochloric acid, a clean decomposition of the triazene polymer is obtained.