Cleavage Of Disulfide Bonds Research Articles

An investigation into the possible antibacterial properties of wool fibers

This study shows that using a combination of physical and chemical approaches, wool fiber can be systematically broken down to its constituent components. From this it was possible to investigate the antibacterial nature of wool and its two major subcomponents, the cuticle scales and cortical cells. Wool and its constituent components were subjected to two methods of antibacterial testing, with excess and limited amounts of liquid. From this it was shown that the presence of excess water has a significant impact on the antibacterial properties of the wool fiber and its components. Furthermore, the study shows that on treatment with thioglycolic acid, which cleaves disulfide bonds, the fibers exhibit antibacterial activity.

Focused Ultrasound-Augmented Delivery of Biodegradable Multifunctional Nanoplatforms for Imaging-Guided Brain Tumor Treatment.

The blood brain barrier is the main obstacle to delivering diagnostic and therapeutic agents to the diseased sites of brain. It is still of great challenge for the combined use of focused ultrasound (FUS) and theranostic nanotechnology to achieve noninvasive and localized delivery of chemotherapeutic drugs into orthotopic brain tumor. In this work, a unique theranostic nanoplatform for highly efficient photoacoustic imaging‐guided chemotherapy of brain tumor both in vitro and in vivo, which is based on the utilization of hollow mesoporous organosilica nanoparticles (HMONs) to integrate ultrasmall Cu2− xSe particles on the surface and doxorubicin inside the hollow interior, is synthesized. The developed multifunctional theranostic nanosystems exhibit tumor‐triggered programmed destruction due to the reducing microenvironment‐responsive cleavage of disulfide bonds that are incorporated into the framework of HMONs and linked between HMONs and Cu2− xSe, resulting in tumor‐specific biodegradation and on‐demand drug‐releasing behavior. Such tumor microenvironment‐responsive biodegradable and biocompatible theranostic nanosystems in combination with FUS provide a promising delivery nanoplatform with high performance for orthotopic brain tumor imaging and therapy.

A Single Composition Architecture-Based Nanoprobe for Ratiometric Photoacoustic Imaging of Glutathione (GSH) in Living Mice.

As one of the reduction species, glutathione (GSH) plays a tremendous role in regulating the homeostasis of redox state in living body. Accurate imaging of GSH in vivo is highly desired to provide a real-time visualization of physiological and pathological conditions while it is still a big challenge. Recently developed photoacoustic imaging (PAI) with high resolution and deep penetration characteristics is more promising for in vivo GSH detection. However, its application is dramatically limited by the difficult designation of photoacoustic probes with changeable near-infrared (NIR)-absorption under reductive activation. A cyanine derivative-based activatable probe is developed for in vivo ratiometric PAI of GSH for the first time. The probe is structurally designed to output ratiometric signals toward GSH in NIR-absorption region based on the cleavage of disulfide bond followed by a subsequent exchange between the secondary amine and sulfydryl group formed. Such a ratiometric manner provides high signal-to-noise imaging of blood vessels and their surrounding areas in tumor. Concomitantly, it also exhibits good specificity toward GSH over other thiols. Furthermore, the single composition architecture of the probe effectively overcomes the leakage issue compared with traditional multicomposition architecture-based nanoprobe, thus enhancing the imaging accuracy and fidelity in living body.

Reactivity of hydropersulfides toward the hydroxyl radical unraveled: disulfide bond cleavage, hydrogen atom transfer, and proton-coupled electron transfer.

Hydropersulfides (RSSH) are highly reactive as nucleophiles and hydrogen atom transfer reagents. These chemical properties are believed to be key for them to act as antioxidants in cells. The reaction involving the radical species and the disulfide bond (S-S) in RSSH, a known redox-active group, however, has been scarcely studied, resulting in an incomplete understanding of the chemical nature of RSSH. We have performed a high-level theoretical investigation on the reactions of the hydroxyl radical (˙OH) toward a set of RSSH (R = -H, -CH3, -NH2, -C(O)OH, -CN, and -NO2). The results show that S-S cleavage and H-atom abstraction are the two competing channels. The electron inductive effect of R induces selective ˙OH substitution at one sulfur atom upon S-S cleavage, forming RSOH and ˙SH for the electron donating groups (EDGs), whereas producing HSOH and ˙SR for the electron withdrawing groups (EWGs). The H-Atom abstraction by ˙OH follows a classical hydrogen atom transfer (hat) mechanism, producing RSS˙ and H2O. Surprisingly, a proton-coupled electron transfer (pcet) process also occurs for R being an EDG. Although for RSSH having EWGs hat is the leading channel, S-S cleavage can be competitive or even dominant for the EDGs. The overall reactivity of RSSH toward ˙OH attack is greatly enhanced with the presence of an EDG, with CH3SSH being the most reactive species found in this study (overall rate constant: 4.55 × 1012 M-1 s-1). Our results highlight the complexity in RSSH reaction chemistry, the extent of which is closely modulated by the inductive effect of the substituents in the case of the oxidation by hydroxyl radicals.

Engineering a cleavable disulfide bond into a natural product siderophore using precursor-directed biosynthesis.

An analogue of the bacterial siderophore desferrioxamine B (DFOB) containing a disulfide motif in the backbone was produced from Streptomyces pilosus cultures supplemented with cystamine. Cystamine competed against native 1,5-diaminopentane during assembly. DFOB-(SS)1[001] and its complexes with Fe(iii) or Ga(iii) were cleaved upon incubation with dithiothreitol. Compounds such as DFOB-(SS)1[001] and its thiol-containing cleavage products could expand antibiotic strategies and Au-S-based nanotechnologies.

Activation of disulfide bond cleavage triggered by hydrophobization and lipophilization of functionalized dihydroasparagusic acid.

Concisely synthesized and functionalized dihydroasparagusic acid (DHAA) derivatives were used to show that the introduction of a hydrophobic functional group dramatically reduced air oxidation activity at the dithiol moieties and dominantly activated the cleavage of S-S bonds in proteins, presumably due to the hydrophobization and lipophilization. Notably, the reaction sites of water-reactive dithiol moieties behaved similarly to hydrophobic and lipophilic functional groups, which suggests impersonation of the reaction site.

Redox/temperature responsive nonionic nanogel and photonic crystal hydrogel: Comparison between N, N′-Bis(acryloyl)cystamine and N, N′-methylenebisacrylamide

Redox/temperature responsive poly(N-isopropylacrylamide/N-hydroxyethylacrylamide) (P(NIPA/HEAA)) nonionic nanogels (NP-BAC) crosslinked with N,N′-Bis(acryloyl)cystamine (BAC) have been prepared. An analogous nanogel incorporating N,N′-methylenebisacrylamine (BIS), a reduction-insensitive nanogel (NP-BIS), was chosen as a control nanogel. Compared to the nondegradable NP-BIS nanogel, NP-BAC nanogel particles were found to swell and become less dense due to cleavage of disulfide bonds in BAC. Interestingly, the NP-BAC nanogels preserved their spherical shape after reduction. When loaded with the drug propranolol, NP-BAC nanogels showed accelerated drug release in the presence of 1,4-dithiothreitol (DTT), with rate of release controlled by the DTT concentration. Furthermore, the liquid-crystal-glass phase behavior of these nanogel suspensions were investigated relative to polymer concentration and temperature. Following the liquid-crystal-glass phase diagram, these nanogels can be fabricated into hydrogel by crosslinking with divinylsulfone (DVS). These crosslinked hydrogels exhibited optical diffractions sensitive to temperature and DTT concentration. Several unexpected and distinguishing differences between NP-BAC and NP-BIS nanogels were noted. For example, NP-BAC nanogel formed colloidal crystalline structures faster than NP-BIS nanogels and their reflection signals were much stronger. The reflection peaks of NP-BAC crosslinked hydrogel were blue shifted with rising temperature while that of NP-BIS hydrogel remained unchanged.

Protein Folding in the Presence of Water-Soluble Cyclic Diselenides with Novel Oxidoreductase and Isomerase Activities.

The protein disulfide isomerase (PDI) family, found in the endoplasmic reticulum (ER) of the eukaryotic cell, catalyzes the formation and cleavage of disulfide bonds and thereby helps in protein folding. A decrease in PDI activity under ER stress conditions leads to protein misfolding, which is responsible for the progression of various human diseases, such as Alzheimer's, Parkinson's, diabetes mellitus, and atherosclerosis. Here we report that water-soluble cyclic diselenides mimic the multifunctional activity of the PDI family by facilitating oxidative folding, disulfide formation/reduction, and repair of the scrambled disulfide bonds in misfolded proteins.

Characterization of singly and multiply PEGylated insulin isomers by reversed-phase ultra-performance liquid chromatography interfaced with ion mobility mass spectrometry

Conjugation of poly(ethylene glycol) (PEG) to protein drugs (PEGylation) is increasingly utilized in the biotherapeutics field because it improves significantly the drugs' circulatory half-life, solubility, and shelf-life. The activity of a PEGylated drug depends on the number, size, and location of the attached PEG chain(s). This study introduces a 2D separation approach, including reversed-phase ultra-performance liquid chromatography (RP-UPLC) and ion mobility mass spectrometry (IM-MS), in order to determine the structural properties of the conjugates, as demonstrated for a PEGylated insulin sample that was prepared by random amine PEGylation. The UPLC dimension allowed separation based on polarity. Electrospray ionization (ESI) of the eluates followed by in-source dissociation (ISD) truncated the PEG chains and created insulin fragments that provided site-specific information based on whether they contained a marker at the potential conjugation sites. Separation of the latter fragments by size and charge in the orthogonal IM dimension (pseudo-4D UPLC-ISD-IM-MS approach) enabled clear detection and identification of the positional isomers formed upon PEGylation. The results showed a highly heterogeneous mixture of singly and multiply conjugated isomers plus unconjugated material. PEGylation was observed on all three possible attachment sites (ε-NH2 of LysB29, A- and B-chain N-termini). Each PEGylation site was validated by analysis of the same product after disulfide bond cleavage, so that the PEGylated A- and B- chain could be individually characterized with the same pseudo-4D UPLC-ISD-IM-MS method.

Fabrication of Hyperbranched Block-Statistical Copolymer-Based Prodrug with Dual Sensitivities for Controlled Release.

Dendrimer with hyperbranched structure and multivalent surface is regarded as one of the most promising candidates close to the ideal drug delivery systems, but the clinical translation and scale-up production of dendrimer has been hampered significantly by the synthetic difficulties. Therefore, there is considerable scope for the development of novel hyperbranched polymer that can not only address the drawbacks of dendrimer but maintain its advantages. The reversible addition-fragmentation chain transfer self-condensing vinyl polymerization (RAFT-SCVP) technique has enabled facile preparation of segmented hyperbranched polymer (SHP) by using chain transfer monomer (CTM)-based double-head agent during the past decade. Meanwhile, the design and development of block-statistical copolymers has been proven in our recent studies to be a simple yet effective way to address the extracellular stability vs intracellular high delivery efficacy dilemma. To integrate the advantages of both hyperbranched and block-statistical structures, we herein reported the fabrication of hyperbranched block-statistical copolymer-based prodrug with pH and reduction dual sensitivities using RAFT-SCVP and post-polymerization click coupling. The external homo oligo(ethylene glycol methyl ether methacrylate) (OEGMA) block provides sufficient extracellularly colloidal stability for the nanocarriers by steric hindrance, and the interior OEGMA units incorporated by the statistical copolymerization promote intracellular drug release by facilitating the permeation of GSH and H+ for the cleavage of the reduction-responsive disulfide bond and pH-liable carbonate link as well as weakening the hydrophobic encapsulation of drug molecules. The delivery efficacy of the target hyperbranched block-statistical copolymer-based prodrug was evaluated in terms of in vitro drug release and cytotoxicity studies, which confirms both acidic pH and reduction-triggered drug release for inhibiting proliferation of HeLa cells. Interestingly, the simultaneous application of both acidic pH and GSH triggers promoted significantly the cleavage and release of CPT compared to the exertion of single trigger. This study thus developed a facile approach toward hyperbranched polymer-based prodrugs with high therapeutic efficacy for anticancer drug delivery.

Smart pH-sensitive micelles based on redox degradable polymers as DOX/GNPs carriers for controlled drug release and CT imaging

An amphiphilic copolymer poly(ε-caprolactone)-ss-poly(2-(dimethylamino) ethyl methacrylate), PCL-SS-PDMAEMA, was designed and synthesized using ROP and ARGET ATRP methods. Dual stimulus responsive micelles were prepared by the self-assembly of PCL-SS-PDMAEMA. PDMAEMA could respond to acid conditions with protonation, followed by enhanced hydrophilicity and swelling of the micellar shell. In addition, the cleavable joint disulfide bond between the core and shell was disrupted when exposed to an abundance of the reductant reductive glutathione GSH, leading to the disassembly of the micellar structure. The smart response behavior can be used for intracellular controlled drug release in tumor cells. In terms of “theranostics” with higher therapy effect, the tool for tumor imaging and diagnose through computed tomography (CT) was considered with the loading of gold nanoparticles (GNPs). GNPs with good distribution were prepared by means of in situ reduction by PDMAEMA block and stabilized by the micelles. Polymeric micelles were used to load the anticancer drug doxorubicin (DOX) in the hydrophobic core and GNPs in the hydrophilic PDMAEMA shell. Subsequently, the micellar theranostics platform combining chemotherapy and CT diagnose was obtained. The pH- or redox-triggered drug release profiles suggesting that the DOX/GNPs-loaded micelles facilitated controlled release in response to different simulated microenvironments. Cellular uptake study was carried out, indicating that the micelles could be fast internalized within several hours. MTT assay showing significant inhibition against HepG2 and MCF-7 cells for the DOX/GNPs-loaded micelles. Finally, the in vitro CT imaging assay indicated the good CT diagnosis potential of DOX/GNPs-loaded micelles. The micelle simultaneously loaded with DOX and GNPs represent a promising theranostics platform for efficient cancer chemotherapy and diagnosis.

Effect of Oxidation and Protein Unfolding on Cross-Linking of β-Lactoglobulin and α-Lactalbumin.

Oxidation and heat treatment can initiate changes in the amino acid composition, structure, solubility, hydrophobicity, conformation, function, and susceptibility to proteolysis of proteins. These can result in adverse consequences for mammals, plants, foodstuffs, and pharmaceuticals. This study investigated whether and how individual or combined treatment with heat, a commonly encountered factor in industrial processing, and H2O2 alters the structure and composition of two major milk whey proteins, α-lactalbumin and β-lactoglobulin, and mixtures of these. Thermal treatment induced reducible cross-links in isolated β-lactoglobulin, but not isolated α-lactalbumin under the conditions employed. Cross-linking occurred at lower temperatures and to a greater extent in the presence of low concentrations of H2O2. H2O2 did not induce cross-linking in the absence of heat. Mixtures of α-lactalbumin and β-lactoglobulin showed similar behavior, except that mixed α-lactalbumin-β-lactoglobulin dimers were detected. Cross-linking was associated with formation of sulfenic acids (RS-OH species), oxidation of methionine residues, cleavage of disulfide bonds in α-lactalbumin, altered conformation of disulfide bonds in β-lactoglobulin, alterations in the fluorescence intensity and maximum emission wavelength of endogenous tryptophan residues, and binding of the hydrophobic probe 8-anilinonaphthalenesulfonate. These data are consistent with increased unfolding and subsequent aggregation of the protein, with these changes being maximized in the presence of both heat and H2O2. The enhanced aggregation detected with H2O2 is consistent with additional pathways to aggregation above that induced by heat alone. These mechanistic insights provide potential strategies for modulating the extent and nature of protein modification induced by thermal and oxidant treatment.

Rational Design of a New Self-Codelivery System from Redox-Sensitive Camptothecin-Cytarabine Conjugate Assembly for Effectively Synergistic Anticancer Therapy.

Herein, two careful selected anticancer drugs camptothecin (CPT) and cytarabine (Ara-C) with different biological action mechanisms and different water solubility are conjugated together through a glutathione (GSH) cleavable disulfide bond to construct a redox-sensitive drug-drug conjugate, which can self-assemble into nanoparticles, thus notably improving the water solubility of CPT and the cell membrane permeability of Ara-C. Compared with free drugs, the self-assembled CPT-ss-Ara nanoparticles can concentrate in tumor tissues through the enhanced permeability and retention (EPR) effect, then they can be rapidly internalized by tumor cells and degrade into free drugs for killing the tumor cells when exposed to the reductive environment (GSH) of tumor cells, thereby reducing the injury to normal cells. Meanwhile, the CPT-ss-Ara nanoparticles can effectively protect CPT and Ara-C molecules from biological inactivation before their arrival in tumor microenvironment since free CPT and Ara-C are easy to partly lose their therapy efficacy due to their structure degradation in blood circulation. The in vitro and in vivo anticancer experimental results indicate that simultaneous release of free CPT and Ara-C can realize synergistic chemotherapy effects, thus markedly improve their anticancer activity. Therefore, our designed carrier-free, redox-sensitive CPT-ss-Ara nanoparticles might have promising clinical application to combat cancers.

Reductive nanocomplex encapsulation of cRGD-siRNA conjugates for enhanced targeting to cancer cells.

In this study, through covalent conjugation and lipid material entrapment, a combined modification strategy was established for effective delivery of small interfering RNA (siRNA). Single strands of siRNA targeting to BRAFV600E gene (siMB3) conjugated with cRGD peptide at 3′-terminus or 5′-terminus via cleavable disulfide bond was synthesized and then annealed with corresponding strands to obtain single and bis-cRGD-siRNA conjugates. A cationic lipid material (CLD) developed by our laboratory was mixed with the conjugates to generate nanocomplexes; their uniformity and electrical property were revealed by particle size and zeta potential measurement. Compared with CLD/siBraf, CLD/cRGD-siBraf achieved higher cell uptake and more excellent tumor-targeting ability, especially 21 (sense-5′/antisense-3″-cRGD-congjugate) nanocomplex. Moreover, they can regulate multiple pathways to varying degree and reduce acidification of endosome. Compared with the gene silencing of different conjugates, single or bis-cRGD-conjugated siRNA showed little differences except 22 (5/5) which cRGD was conjugated at 5′-terminus of antisense strand and sense strand. However bis-cRGD conjugate 21 nanocomplex exhibited better specific target gene silencing at multiple time points. Furthermore, the serum stabilities of the bis-cRGD conjugates were higher than those of the single-cRGD conjugates. In conclusion, all these data suggested that CLD/bis-conjugates, especially CLD/21, can be an effective system for delivery of siRNA to target BRAFV600E gene for therapy of melanoma.

Predictable Peptide Conjugation Ratios by Activation of Proteins with Succinimidyl Iodoacetate (SIA).

The small heterobifunctional linker succinimidyl iodoacetate (SIA) was examined for the preparation of peptide–protein bioconjugates with predicable conjugation ratios. For many conjugation protocols, the protein is either treated with a reductant to cleave disulfide bonds or is reacted with thiolation chemicals, such as Traut’s reagent. Both approaches are difficult to control, need individual optimization and often lead to unsatisfactory results. In another popular approach, a heterobifunctional linker with a N-hydroxysuccinimide (NHS) and a maleimide functionality is applied to the protein. After the activation of some lysine ε-amino groups with the NHS ester functionality, a cysteine-containing peptide is attached to the activated carrier protein via maleimide. Particularly, the maleimide reaction leads to some unwanted byproducts or even cleavage of the linker. Many protocols end up with conjugates with unpredictable and irreproducible conjugation ratios. In addition, the maleimide-thiol addition product should be assumed immunogenic in vivo. To avoid these and other disadvantages of the maleimide approach, we examined the known linker succinimidyl iodoacetate (SIA) in more detail and developed two protocols, which lead to peptide–protein conjugates with predefined average conjugation ratios. This holds potential to eliminate tedious and expensive optimization steps for the synthesis of a bioconjugate of optimal composition.

A Pre-Treatment Coating with Redox-Responsive Self-Healing Function for AZ31B Magnesium Alloy

Benefiting the major advantages such as high strength to weight ratio and good formability, magnesium alloy, as a significant light alloy, has shown great potential in modern machine manufacturing field. Unfortunately, limited by their poor corrosion resistance and fast degradation rate, magnesium alloy materials face predicament in stability and durability. Considering that the degradation rate of magnesium alloy is very quick, the repairing speed should also be fast enough to overtake the corrosion process. Hence, sensitive, rapid responsiveness and fast repair process is necessary for magnesium alloy protection. Electrochemical potential was chosen as indicator to monitor the corrosion process: It decreases as soon as the corrosion took place, and it only declined with corrosion reaction. This character guarantees the sensitivity of self-healing coating based on electrochemical potential mechanism to sense the very beginning of corrosion reaction. Disulfide bond unit was frequently introduced into controlled release systems for redox-responsiveness due to that they could easily be reduced and cleaved into thiol groups. Inside human body, there exists abundant glutathione (GSH) in the cytosol. This reducing substance could realize rapid cleavage of disulfide bonds. According to previous literatures, the half-cell potential of GSSG/GSH was -0.26 V, while for magnesium alloy, their corrosion potential is much lower. Therefore, it is expected that the redox reactions during corrosion of magnesium alloy would have the same effect in cleaving disulfide bond as GSH. Following this biomimetic idea, corrosion environment combined with disulfide could realize redox-responsive self-healing agent release, composing the most dependable self-healing mechanism. Herein, we report a sensitive, intelligent anticorrosion sol-gel pre-treatment coating based on redox-responsive motif. As key component, self-healing agent, the inhibitor molecules benzotriazole (BTA) was located inside mesoporous silica materials, sealed by supramolecular complex gate. Composed by novel macrocyclic molecules, water soluble pillar[5]arenes (WP5) and pyridine cation derivative molecules (G), the formation of supramolecular complex is driven by electrostatic force and hydrophobic function. Disulfide bonds were used as linker connecting surface of mesoporous silica nanospheres and the “gate” molecules. To shorten the travel path of inhibitor molecules, we added Fe3O4 nanoparticles inside mesoporous silica layer to fabricate magnetic intelligent nanocontainers. To our knowledge, the magnetic properties have been widely used for controlling the location of materials. Therefore, under the effect of external magnetic field, the magnetic nanocontainer with BTA wrapped inside could be enriched to coating-metal interface. Through shortening the travel path, the inhibitor molecules could reach the corroded areas in minimal time, further accelerating repairing speed. Through evaluations by in-situ scanning kelvin probe technique (SKP), the reported coating exhibit the rapid self-healing functionality, give the timely feedback and maintain the reliable long-term protection of magnesium alloy. 15 μL of 0.05 M NaCl electrolyte was covered on artificial defect (deep into the alloy layer, simulating the coating deterioration at the beginning of corrosion) and NiCr SKP probe was positioned 100μm above the sample surface. Through non-destructive, in-situ measurement of electrode potential at metal surface, a function of the potential over time was recorded (Figure 1B). At the beginning of immersion, the potential at defect site remains level, at the corrosion potential of AZ31B (-1.5 V), indicating that the contact between metal and electrolyte leads to active corrosion in all the samples. After four hours of immersion, the corrosion potential of doped sample rockets to -1.05 V, entering into the passivation range, while for undoped sample, it did not display self-healing function. This is the first time that precise control over location of repair factor inside coatings is achieved. Figure 1

Enzymatic PEG-Poly(amine-co-disulfide ester) Nanoparticles as pH- and Redox-Responsive Drug Nanocarriers for Efficient Antitumor Treatment.

We have designed and constructed novel multifunctional nanoparticle drug-delivery systems that are stable under physiological conditions and responsive to tumor-relevant pH and intracellular reduction potential. The nanoparticles were fabricated from enzymatically synthesized poly(ethylene glycol) (PEG)-poly(ω-pentadecalactone-co-N-methyldiethyleneamine-co-3,3'-dithiodipropionate) (PEG-PPMD) and PEG-poly(ε-caprolactone-co-N-methyldiethyleneamine-co-3,3'-dithiodipropionate) (PEG-PCMD) block copolymers via self-assembly processes in aqueous solution. At acidic pH and in the presence of a reductant (e.g., d,l-dithiothreitol or glutathione), the nanosized micelle particles rapidly swell and disintegrate due to the protonation of amino groups and reductive cleavage of disulfide bonds in the micelle cores. Consistently, docetaxel (DTX)-loaded PEG-PPMD and PEG-PCMD micelles can be triggered synergistically by acidic endosomal pH and a high intracellular reduction potential to rapidly release the drug for efficient killing of cancer cells. The drug formulations based on PEG-PPMD and PEG-PCMD copolymers exhibited a substantially higher potency than free DTX in inhibiting tumor growth in mice, whereas their therapeutic effects on important organ tissues were minimal. These results demonstrate that PEG-PPMD and PEG-PCMD nanoparticles have a great potential to serve as site-specific, controlled drug-delivery vehicles for safe and efficient antitumor treatment.

GSH-Activated NIR Fluorescent Prodrug for Podophyllotoxin Delivery.

Theranostic prodrug therapy enables the targeted delivery of anticancer drugs with minimized adverse effects and real-time in situ monitoring of activation of the prodrugs. In this work, we report the synthesis and biological assessment of the near-infrared (NIR) prodrug DCM-S-PPT and its amphiphilic copolymer (mPEG-DSPE)-encapsulated nanoparticles. DCM-S-PPT is composed of podophyllotoxin (PPT) as the anticancer moiety and a dicyanomethylene-4H-pyran (DCM) derivative as the NIR fluorescent reporter, which are linked by a thiol-specific cleavable disulfide bond. In vitro experiments indicated that DCM-S-PPT has low cytotoxicity and that glutathione (GSH) can activate DCM-S-PPT resulting in PPT release and a concomitant significant enhancement in NIR fluorescence at 665 nm. After being intravenously injected into tumor-bearing nude mice, DCM-S-PPT exhibited excellent tumor-activated performance. Furthermore, we have demonstrated that mPEG-DSPE as a nanocarrier loaded with DCM-S-PPT (mPEG-DSPE/DCM-S-PPT) showed even greater tumor-targeting performance than DCM-S-PPT on account of the enhanced permeability and retention effect. Its tumor-targeting ability and specific drug release in tumors make DCM-S-PPT a promising prodrug that could provide a significant strategy for theranostic drug delivery systems.

Cyclometalated Iridium(III)-Complex-Based Micelles for Glutathione-Responsive Targeted Chemotherapy and Photodynamic Therapy

The integration of chemotherapy and photodynamic therapy (PDT) in a single delivery system is highly desirable for enhancing anticancer therapeutic efficacy. Herein, two cyclometalated Ir(III) complex-constructed micelles FIr-1 and FIr-2 were demonstrated for glutathione (GSH) activated targeted chemotherapy and PDT. The cyclometalated Ir(III) complexes were prepared by conjugating phosphorescent Ir(III) compounds with chemotherapeutic drug camptothecin (CPT) through GSH responsive disulfide bond linkages, and the Ir(III) complexes were then assembled with amphiphilic surfactant pluronic F127 via noncovalent encapsulation to afford micelles. The surfaces of the micelles were further decorated with folic acid as a targeting group. The micelles showed intense fluorescence that renders them with excellent real-time imaging capability. The release of free anticancer drug CPT from the micelles was realized through GSH-activated disulfide bond cleavage in tumor cells. In addition, the micelles were capable of generating singlet oxygen used for PDT upon visible light irradiation. On account of having folic acid targeting ligand, the micelles displayed greater cellular accumulation in folate receptor (FR) overexpressed HeLa cells than FR low-expressed MCF-7 cells, leading to selective cancer cell killing effect. As compared with solo therapeutic systems, the micelles with targeted combinational chemotherapy and PDT presented superior potency and efficacy in killing tumor cells at a low dosage. On the basis of these findings, the multifunctional micelles could serve as a versatile theranostic nanoplatform for cancer cell targeted imaging and combinational therapy.

Improvement of the water resistance of soybean protein-based wood adhesive by a thermo-chemical treatment approach

In order to extend the applications of wood composites and products bonded by soybean protein adhesive from interior to exterior fields of application, this study proposes a novel approach for improving the water resistance of soybean protein-based wood adhesives using thermo-chemical treatment of soybean protein. The soybean protein formed stable three-dimensional networks due to repolymerization or self-crosslinking during thermo-chemical treatment, confirmed by both increases in the water-insoluble content of the treated soybean protein and the improved hydrothermal-aged wet bond strength of the resulting soybean protein adhesive. Thermo-chemical treatment in the presence of 1wt% sodium sulfite (which cleaves disulfide bonds) and 1wt% sodium dodecyl sulfate (which destroys the hydrophobic interactions of proteins) released active groups buried within the globular structure of soybean protein via unfolding. This release both promoted the repolymerization of the soybean protein molecules and exposed more active sites for effective crosslinking by the post-added crosslinker EMPA. Plywood bonded by the optimal soybean protein adhesive possessed a good hydrothermal-aged bond strength of 1.22MPa, exceeding the value required for structural use according to the JIS K6806-2003 commercial standard.