Photochemical Acceleration of DNA Strand Displacement by Using Ultrafast DNA Photo-crosslinking

DNA strand displacement is an essential reaction in genetic recombination, biological processes, and DNA nanotechnology. In particular, various DNA nanodevices enable complicated calculations. However, it takes time before the output is obtained, so acceleration of DNA strand displacement is required for a rapid-response DNA nanodevice. Herein, DNA strand displacement by using DNA photo-crosslinking to accelerate this displacement is evaluated. The DNA photo-crosslinking of 3-cyanovinylcarbazole (^CNVK) was accelerated at least 20 times, showing a faster DNA strand displacement. The rate of photo-crosslinking is a key factor and the rate of DNA strand displacement is accelerated through ultrafast photo-crosslinking. The rate of DNA strand displacement was regulated by photoirradiation energy.     

Complete Photochemical Regulation of 8–17 DNAzyme Activity by Using Reversible DNA Photo-crosslinking

The regulation of DNAzyme activity is an important problem for its in vivo applications. We achieved photochemical regulation of DNAzyme activity by using reversible DNA photo-crosslinking of 3-cyanovinylcarbazole (^CNVK). The ODN containing ^CNVK photo-crosslinked to a pyrimidine base in the complementary strand after a few seconds of photoirradiation, and its photoadduct was split by photoirradiation of another wavelength. The activity of photo-crosslinked DNAzyme with ^CNVK was completely inhibited (OFF state). In contrast, after 312 nm irradiation, DNAzyme activity was recovered upon addition of a substrate strand (ON state). In addition, the photo-crosslinked DNAzyme is prone to enzymatic digestion by exonuclease. This photochemical OFF to ON switching with reversible DNA photo-crosslinking was regulated at the desired time and position; therefore, it might be possible to use it for in vivo application.     

Highly Efficient Fluorescent Interstrand Photo‐crosslinking of DNA Duplexes Labeled with 5‐Fluoro‐4‐thio‐2′‐O‐methyluridine

The formation of a fluorescent photoadduct between 5‐fluoro‐4‐thiouridine ( ^FS U ), in the sequence context 5′‐A ^FS U A‐3′ and incorporated into a synthetic oligonucleotide either at its 3′‐ or 5′‐end, and one of the thymines of the TAT motif in a complementary target DNA strand led to photo‐crosslinking of the two strands for several oligonucleotide constructs. Enzymatic digestion, MS, UV, and fluorescence spectral analyses of the interstrand crosslinked oligonucleotides revealed the identity of the thymidine that participates in the photo‐crosslinking reaction as well as the diastereomeric structures of the crosslinks. The proposed pathways of interstrand photo‐crosslinking are supported by experiments with isotopically labeled oligonucleotide constructs and visualized by means of molecular dynamics simulations.     

Chaperone‐Polymer‐Assisted,Photodriven DNA Strand Displacement

Photodriven DNA strand displacement by using a 2′,6′‐dimethylazobenzene‐tethered strand and poly(l ‐lysine)‐graft‐dextran (PLL‐g‐Dex) as a chaperone is reported. Rapid strand displacement was reversibly induced by UV and visible‐light irradiation without any toehold portion. To further improve the method, the concentration of PLL‐g‐Dex and the number of equivalents of the photoresponsive strand were optimised. Optimally, 64 % strand displacement was reversibly induced by alternating UV and visible‐light irradiation.     

Protein Interactions in the T7 DNA Replisome Facilitate DNA Damage Bypass

The DNA replisome inevitably encounters DNA damage during DNA replication. The T7 DNA replisome contains a DNA polymerase (gp5), the processivity factor thioredoxin (trx), a helicase‐primase (gp4), and a ssDNA‐binding protein (gp2.5). T7 protein interactions mediate this DNA replication. However, whether the protein interactions could promote DNA damage bypass is still little addressed. In this study, we investigated strand‐displacement DNA synthesis past 8‐oxoG or O⁶‐MeG lesions at the synthetic DNA fork by the T7 DNA replisome. DNA damage does not obviously affect the binding affinities between helicase, polymerase, and DNA fork. Relative to unmodified G, both 8‐oxoG and O⁶‐MeG—as well as GC‐rich template sequence clusters—inhibit strand‐displacement DNA synthesis and produce partial extension products. Relative to the gp4 ΔC‐tail, gp4 promotes DNA damage bypass. The presence of gp2.5 also promotes it. Thus, the interactions of polymerase with helicase and ssDNA‐binding protein facilitate DNA damage bypass. Accessory proteins in other complicated DNA replisomes also facilitate bypassing DNA damage in similar manner. This work provides new mechanistic information relating to DNA damage bypass by the DNA replisome.     

Synthesis and characterization of photo‐crosslinkable polyfluorene with acrylate side‐chains

A photo‐crosslinkable polymer, poly[2,7‐(9,9‐dioctylfluorene)‐co‐2,7‐(9‐hexyl‐9‐(2‐acrylate ethyl)‐9H‐fluorene)] (P3), was synthesized and the photo‐crosslinkable acrylate groups were introduced into the side‐chains of the polyfluorene derivative after its polymerization. This method avoids the possible crosslinkage of the crosslinkable groups on the monomers during polymerization in the traditional synthesis route by the polymerization of the monomers with the crosslinkable side‐chains. The soluble and processable polymer P3 could be crosslinked via the acrylate groups in its side‐chains upon exposure to UV light in nitrogen atmosphere. The crosslinking was confirmed by IR spectroscopy: the IR peak of C?C bond at 1635 cm^?1 decreased and that of the vinyl C? H bond at 742 cm^?1 disappeared after the UV exposure. The absorption spectra of P3 remain unchanged after crosslinking, but a longer wavelength emission at 517 nm appeared in the photoluminescent and electroluminescent spectra of the crosslinked P3, which could be attributed to the formation of keto defects during the photo crosslinking. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2336–2342, 2006     

Thermal‐ and Photo‐Induced Isomerization of All‐E‐ and Z‐Isomer‐Rich Xanthophylls: Astaxanthin and Its Structurally‐Related Xanthophylls,Adonirubin, and Adonixanthin

The effects of heating and photo‐irradiation on the stability of all‐E‐isomer‐rich and Z‐isomer‐rich xanthophylls, astaxanthin and its structurally related xanthophylls, adonirubin, and adonixanthin, are investigated. The xanthophylls with high Z‐isomer content are prepared from their high‐purity all‐E‐isomers by thermal isomerization and filtering techniques, that is, total Z‐isomer ratios of adonirubin, astaxanthin, and adonixanthin are 80.9%, 89.5%, and 72.5%, respectively. The all‐E‐ and Z‐isomer‐rich xanthophylls dissolved in ethanol are stored at 4, 30, and 50 °C in the dark and at 30 °C under photo‐irradiation using a fluorescent light for 21 days. In the all‐E‐isomer‐rich xanthophylls, as the storage temperature increases, the total Z‐isomer ratio becomes higher, whereas in the Z‐isomer‐rich xanthophylls, the all‐E‐isomer ratio becomes higher. Photo‐irradiation slightly promotes Z‐isomerization in (all‐E)‐xanthophylls, but highly promotes all‐E‐isomerization in Z‐isomer‐rich xanthophylls. In addition, photo‐irradiation prevents thermal Z‐isomerization of (all‐E)‐xanthophylls. Moreover, it is found that some xanthophyll Z‐isomers such as (9Z)‐astaxanthin are more stable than that of the other Z‐isomers against heating and photo‐irradiation. These findings can contribute not only to establishing suitable storage conditions for Z‐isomer‐rich xanthophylls, but also to developing control techniques for the E/Z‐isomer ratio of the xanthophylls. Practical Applications: The fundamental data on the stability of xanthophyll isomers against heating and photo‐irradiation and finding stable xanthophyll Z‐isomers are very important to develop xanthophyll materials rich in the Z‐isomers. Moreover, this study clearly shows that the heat treatment enhances the Z‐isomerization of xanthophylls, whereas the photo‐irradiation enhances the all‐E‐isomerization and prevents thermal Z‐isomerization of them. This information can be utilized in technology for arbitrarily controlling E/Z‐isomerization of xanthophylls.     

Photo‐induced protonation and conductivity of polyaniline/poly(ethylene glycol) and polyaniline/[poly(ethylene glycol)‐grafted polyaniline] composites

Composites of polyaniline in its emeraldine base form (PANI‐EB) and photo‐acid generators (PAG) show an increase in conductivity upon photo‐irradiation due to the protonation of PANI‐EB. Such materials may be utilized to fabricate conducting patterns by photo‐irradiation. However, the conductivity obtained by direct irradiation of PANI‐EB/PAG composites was normally quite low (<10^?3 S/cm) due to aggregation of highly loaded PAG. In this work, poly(ethylene glycol) (PEG), which is a proton transfer polymer, was added to PANI‐EB/PAG. Results showed that addition of low M_w (550) PEG significantly enhance the photo‐induced conductivity. Conductivities as high as 10^?1–10⁰ S/cm were observed after photo‐irradiation. This conductivity is comparable to that of PANI‐salt synthesized by oxidizing aniline in the presence of an acid. High M_w (8000) PEG is much less effective than PEG 550, which is attributed to its lower compatibility with PANI. PEG‐grafted PANI (N‐PEG‐PANI) was also studied as an additive. Composites of PANI‐EB and N‐PEG‐PANI showed conductivity as high as 10² S/cm after treatment with HCl vapor. The photo‐induced conductivity of the N‐PEG‐PANI/PANI‐EB/PAG composite reached 10^?2–10^?1 S/cm. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Photochemical RNA Editing of C to U by Using Ultrafast Reversible RNA Photo-crosslinking in DNA/RNA Duplexes

RNA editing, which is used to edit nucleobases in RNA strands; is more feasible for use in medical applications than DNA editing. We previously reported the photochemical conversion of cytosine to uracil, which required photo-crosslinking, deamination, and photo-splitting. Here, we evaluated the influence of the bases surrounding the target cytosine on the conversion of cytosine to uracil in the RNA strand. The photo-crosslinker 3-carboxyvinylcarbazole(^OHVK), which is more hydrophilic than 3-cyanovinylcarbazole(^CNVK), 3-carboxyamidevinylcarbazole(^NH2VK), and 3-methoxy carbonylvinylcarbazole(^OMeVK), induced faster deamination of cytosine. Furthermore, inosine, which forms two hydrogen bonds with cytosine, was the most efficiently paired base for accelerating photochemical RNA editing. Upon evaluation of the conversion from cytosine to uracil in RNA, the use of oligodeoxynucleotides containing ^OHVK and inosine and the polarity of the bases surrounding the target cytosine were found to be crucial.     

Synthesis and characterization of novel photo‐crosslinkable fluorinated poly(phthalazinone ether)s for optical waveguides

A series of novel photo‐crosslinkable fluorinated poly(phthalazinone ether)s containing 1,1‐diphenylethylene segments in the polymer main chain, used for optical waveguide materials, were synthesized by polycondensation reaction of decafluorobiphenyl with a mixture of 4‐(4‐hydroxylphenyl)(2H)‐phthalazin‐1‐one (DHPZ), 4,4‐(hexafluoroisopropylidene)diphenol and 1,1‐bis(4‐hydroxyphenyl)ethylene (BHPE) as co‐reactant. The feed ratio of DHPZ to total bisphenols varied from 0 to 80 mol%, while that of BHPE remained at 20 mol% for all polymers. The obtained copolymers show good solubility in some common polar organic solvents. The resulting polymers were photo‐crosslinked after UV irradiation for 10 min in the presence of a photoinitiator. The cured polymers show good chemical resistance, high thermal stability (temperatures of 1% mass loss after curing of 472–496 °C under nitrogen) and high glass transition temperatures (160–249 °C) which could be further increased by about 10 °C after photochemical crosslinking. By adjusting the copolymerizing bisphenol content, the refractive indices of transverse electric and transverse magnetic modes (at 1550 nm) of films of the polymers were exactly tuned in the range 1.5029–1.5661 and 1.4950–1.5502, respectively. The propagation losses of the cured films were measured and found to be less than 0.3 dB cm^?1 at 1550 nm, indicating the promise of these materials for passive optical waveguide devices. Copyright © 2011 Society of Chemical Industry     

Triplexes with 8‐Aza‐2′‐Deoxyisoguanosine Replacing Protonated dC: Probing Third Strand Stability with a Fluorescent Nucleobase Targeting Duplex DNA

The fluorescent 8‐aza‐2′‐deoxyisoguanosine ( 4 ) as well as the parent 2′‐deoxyisoguanosine ( 1 ) were used as protonated dCH⁺ surrogates in the third strand of oligonucleotide triplexes. Stable triplexes were formed by Hoogsteen base pairing. In contrast to dC, triplexes containing nucleoside 1 or 4 in place of dCH⁺ are already formed under neutral conditions or even at alkaline pH values. Triplex melting can be monitored separately from duplex dissociation in cases in which the third strand contains the fluorescent nucleoside 4 . Third‐strand binding of oligonucleotides with 4 , opposite to dG, was selective as demonstrated by hybridisation experiments studying mismatch discrimination. Third‐strand binding is more efficient when the stability of the DNA duplex is reduced by mismatches, giving third‐strand binding more flexibility.     

Polymer electrolyte membranes prepared by EB‐crosslinking of sulfonated poly(ether ether ketone) with 1,4‐butanediol

Crosslinked sulfonated poly(ether ether ketone) (SPEEK) membranes were prepared through the electron beam (EB)‐irradiation crosslinking of SPEEK/1,4‐butanediol under various irradiation conditions and used as a proton exchange membrane (PEM) for fuel cell applications. The crosslinked membranes were characterized by gel fraction, a universal testing machine (UTM), dynamic mechanical analysis (DMA), and small‐angle X‐ray scattering (SAXS). The gel fraction of the crosslinked membranes was used to estimate the degree of crosslinking, and the gel fraction was found to be increased with an increase of the crosslinker content and EB‐absorbed dose. The UTM results indicate that a brittle EB‐crosslinked membrane becomes more flexible with an increase in the crosslinker content. The DMA results show that the EB‐crosslinked membranes have well‐developed ionic aggregation regions and the cluster T_g of membranes decrease with an increase in the 1,4‐butanediol crosslinker content. The SAXS results show that the Bragg and persistence distance of crosslinked membranes increase with an increase in the crosslinker content. The proton conductivities of the EB‐crosslinked membranes were more than 9 × 10^?2 S/cm. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41760.     

Transparent photo‐curable co‐polyacrylate/silica nanocomposites prepared by sol‐gel process

This work prepared the highly transparent photo‐curable co‐polyacrylate/silica nanocomposites by using sol‐gel process. The FTIR and ¹³C NMR analyses indicated that during the sol‐gel process, the hybrid precursors transform into composites containing nanometer‐scale silica particles and crosslinked esters/anhydrides. Transmission electron microscopy (TEM) revealed that the silica particles within the average size of 11.5 nm uniformly distributed in the nanocomposite specimen containing about 10 wt % of Si. The nanocomposite specimens exhibited satisfactory thermal stability that they had 5% weight loss decomposition temperatures higher than 150°C and coefficient of thermal expansion (CTE) less than 35 ppm/°C. Analysis via derivative thermogravimetry (DTG) indicated that the crosslinked esters/anhydrides might influence the thermal stability of nanocomposite samples. The UV‐visible spectroscopy indicated that the nanocomposite resins possess transmittance higher than 80% in visible light region. Permeability test revealed a higher moisture permeation resistance for nanocomposite samples, which indicated that the implantation of nano‐scale silica particles in polymer matrix forms effective barrier to moisture penetration. Adhesion test of nanocomposite samples on glass substrate showed at least twofold improvement of adhesion strength compared with oligomer. This evidenced that the silica and the hydrophilic segments in nanocomposite resins might form interchains hydrogen bonds with the ? OH groups on the surface of glass so the substantial enhancement of adhesion strength could be achieved. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Peptide Synthesis on a Next‐Generation DNA Sequencing Platform

Methods for displaying large numbers of peptides on solid surfaces are essential for high‐throughput characterization of peptide function and binding properties. Here we describe a method for converting the >10⁷ flow cell‐bound clusters of identical DNA strands generated by the Illumina DNA sequencing technology into clusters of complementary RNA, and subsequently peptide clusters. We modified the flow‐cell‐bound primers with ribonucleotides thus enabling them to be used by poliovirus polymerase 3D^pol. The primers hybridize to the clustered DNA thus leading to RNA clusters. The RNAs fold into functional protein‐ or small molecule‐binding aptamers. We used the mRNA‐display approach to synthesize flow‐cell‐tethered peptides from these RNA clusters. The peptides showed selective binding to cognate antibodies. The methods described here provide an approach for using DNA clusters to template peptide synthesis on an Illumina flow cell, thus providing new opportunities for massively parallel peptide‐based assays.     

Mineralisation of the antibiotic amoxicillin in pure and surface waters by artificial UVA‐ and sunlight‐induced Fenton oxidation

BACKGROUND: The degradation and mineralisation of the antibiotic amoxicillin by photo‐Fenton reactions, mediated by artificial UVA or solar irradiation, were investigated. Experiments were conducted with 30 mg L^?1 amoxicillin solutions prepared with deionised or surface water at Fe²⁺ and H₂O₂ concentrations in the range 0.0179–0.0895 and 1–10 mmol L^?1, respectively. Black‐light irradiation at 365 nm was provided by a 13 W m^?2 lamp, while samples were exposed to sunlight at 20 W m^?2 for solar experiments. RESULTS: In all cases, quantitative amoxicillin degradation occurred within 5 min and this was accompanied by lower mineralisation rates. Mineralisation followed first‐order kinetics with respect to organic carbon content and it was not affected by the water matrix with either type of illumination. Solar‐induced reactions were only marginally faster than artificial irradiation. Increasing the H₂O₂ to Fe²⁺ concentration ratio increases the extent of mineralisation up to a point beyond which degradation is impeded due to radical scavenging associated with the high concentrations of the Fenton reagents. CONCLUSION: Amoxicillin is readily degradable by homogeneous photocatalysis, being converted to more stable intermediates as indicated by lower mineralisation rates. The process can be driven by solar irradiation, thus providing a sustainable treatment technology. Copyright © 2009 Society of Chemical Industry     

Novel reworkable resins: thermo‐ and photo‐curable di(meth)acrylates

The aim of the study reported in this paper was to develop new di(meth)acrylates having aromatic units and thermally degradable units in their molecules. It was also the aim to clarify the photo‐curing and degradation properties of the new monomers. Di(meth)acrylates having aromatic units and thermally degradable units were synthesized. As thermally cleavable linkages, tertiary ester moieties were incorporated into the di(meth)acrylates. Three types of processes for curing and degradation of the cured resins were studied: thermal curing and thermal degradation; thermal curing and photodegradation; and photo‐curing and thermal degradation. In the thermal curing and photodegradation process, di(meth)acrylate films containing a thermally induced radical initiator and a photoacid generator (PAG) became insoluble in solvents on heating. The cured films became soluble in solvents after ultraviolet irradiation followed by baking. The re‐dissolution behaviors were strongly affected by the structures of the PAGs. A mechanism for the photo‐ or thermo‐curing and photoassisted thermal degradation was studied using Fourier transform infrared, ¹H NMR, thermogravimetric, mass spectrometric and size exclusion chromatographic analyses. Copyright © 2009 Society of Chemical Industry     

Lecithin‐acrylamido‐2‐methylpropane sulfonate based crosslinked phospholipid nanoparticles as drug carrier

In this study, a novel paclitaxel (PTX) loaded and a crosslinked solid phospholipid nanoparticles (SLN‐PTX) with negative surface charge was prepared by UV polymerization for drug delivery. Capping of positive charge of zwitterionic lecithin with negative charge of sodium 2‐acrylamido‐2‐methyl‐1‐propanesulfonate (AMPS‐Na) through cation exchange interaction produced a lecithin‐AMPS (L‐AMPS) complex. The amphiphilic and negative charged lipid complex was emulsified in the presence of emulsifier, paclitaxel, initiator, and methacrylated poly ε‐caprolacton‐diol (PCL‐MAC) as a spacer. The colloidal system was subjected to UV‐irradiation to obtain crosslinked nanoparticles. Completion of the UV‐polymerization was monitored with differential scanning calorimetry (DSC), which indicated the disappearance of exothermic peaks of vinyl groups. The nanoparticle system, having an average size of 200 nm, exhibited high drug encapsulation (96%) with negatively charged surface (zeta potential had an average of ?70 mV). PTX release profiles of the crosslinked and uncrosslinked SLN‐PTXs were studied and their pharmacological properties were compared. The crosslinked nanoparticles exhibited more controlled release behavior with longer release time compared to the uncrosslinked ones. In vitro cytotoxicity test was conducted on MCF‐7 human breast adenocarcinoma cell line, which indicated that the crosslinked SLN‐PTXs have a potential therapeutic effect for breast cancer treatments. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44105.     

Oligonucleotides‐decorated‐poly(N‐vinyl pyrrolidone) nanogels for gene delivery

Pulsed electron‐beam irradiation of a semi‐dilute poly(N‐vinyl pyrrolidone) (PVP) aqueous solution in the presence of acrylic acid has led to a carboxyl functionalized nanogel system. Nanoparticles hydrodynamic size and surface charge density, in water and as a function of pH, were investigated by dynamic light scattering and laser doppler velocimetry, respectively. Nanogels (NGs) were proved not to be cytotoxic at the cellular level. Indeed, they rapidly bypass the cellular membrane to accumulate in specific cell portions of the cytoplasm, in the perinuclear area. The availability of pendant carboxyl groups on the crosslinked PVP NGs core prompted us to attempt their decoration with a single strand oligonucleotide, which holds a terminal amino group. The recognition ability of the attached single helix of its complementary strand was investigated. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39774.     

Fourier‐transform infrared spectroscopic study of plasticization effects on the photodegradation of poly(fluorostyrene) isomers films

The photodegradation of poly(fluorostyrene) isomers with different amounts of phthalate and terephthalate plasticizers has been investigated with the aid of Fourier‐transform infrared spectroscopy. Photo irradiation was carried out with light from a Hydrogen‐Xenon lamp at 265 nm and 293 K. As irradiation time increased, changes occurred in the structure of the polymers due to the destruction of polymeric chains and the formation of new photo products during the degradation. The photo products caused shifts, an increase or decrease of the polymer vibrational frequencies, as well as changes in numerous infrared band intensities. The increase in the intensities of the analyzed ranges is attributed to the formation of carbonyl, hydroxyl, and aliphatic ketones and to the increase in the number of polyene structures that resulted from hydrogen abstraction during photodegradation reactions. The analysis of the Fourier‐transform infrared spectra of the irradiated and nonirradiated samples showed a noticeable formation of a new broad band centered at (1,727 cm^?1, C=O), assigned to the growth of aliphatic ketones formerly from the reaction of reactive alkoxy radicals. Its intensity was found to increase with the increase in irradiation time and also with the increase in the amount of added terephthalate and phthalates plasticizer, indicating an increase in the efficiency of the photo degradation process. Trends of photostability of these isomers were found such that poly(para‐fluorostyrene) > poly(meta‐fluorostyrene) > poly(ortho‐fluorostyrene). The photodegradation process for these plasticized isomers was found to increase by the increase in the bulkiness of the plasticizer molecule . J. VINYL ADDIT. TECHNOL., 24:75–83, 2018. © 2015 Society of Plastics Engineers     

Synthesis of new ionic crosslinked polymer hydrogel combining polystyrene and poly(4‐vinyl pyridine) and its self‐healing through a reshuffling reaction of the trithiocarbonate moiety under irradiation of ultraviolet light

A new ionic crosslinked polymer hydrogel was achieved by the strategy of ionically crosslinking α,ω‐dibromide terminated polystyrene (Br‐PS‐Br) with poly(4‐vinyl pyridine) (P4VP) which was synthesized by reversible addition‐fragmentation chain transfer polymerization using a chain transfer agent containing a trithiocarbonate moiety. The moiety of trithiocarbonate was introduced into the crosslinked network to show the self‐healing characteristics. The chain structure and components of Br‐PS‐Br and P4VP were characterized through ¹H NMR, gel permeation chromatography, Fourier transform IR spectroscopy and elemental analysis. The P4VP (M_n = 25 300 g mol^?1) chains were crosslinked with Br‐PS‐Br (M_n = 2000 g mol^?1) through the quaternization reaction to form a polymer network which was further crosslinked in acetonitrile by irradiation of UV light to fabricate a hydrogel. Such a hydrogel of P4VP/Br‐PS‐Br cut by a razor blade can be rapidly (1 h) and repeatedly (three times) healed through a reshuffling reaction of the trithiocarbonate moiety under irradiation by UV light. © 2018 Society of Chemical Industry