Release Step Research Articles

Electrokinetics of CO2 Reduction in Imidazole Medium Using RuO2.SnO2-Immobilized Glassy Carbon Electrode

The pursuit of electrochemical carbon dioxide reduction reaction (CO2RR) as a means of energy generation and mitigation of global warming is of considerable interest. In this study, a novel RuO2-incorporated SnO2-fabricated glassy carbon electrode (GCE) with a Nafion binder was used for the electrochemical reduction of CO2 in an aqueous alkaline imidazole medium. The electrode fabrication process involved the drop-casting method, where RuO2.SnO2 was incorporated onto the surface of the GCE. Electrochemical studies demonstrated that the GCE-RuO2.SnO2 electrode facilitated CO2 reduction at −0.58 V vs. the reversible hydrogen electrode (RHE) via a diffusion-controlled pathway with the transfer of two electrons. Importantly, the first electron transfer step was identified as the rate-determining step (RDS). A Tafel slope of 144 mV dec−1 confirmed the association of two-electron transfer kinetics with CO2RR. Moreover, the standard rate constant (ko) and formal potential (E°′) were evaluated as 2.89 × 10−5 cm s−1 and 0.0998 V vs. RHE, respectively. Kinetic investigations also reveal that the deprotonation and electron release steps took place simultaneously in the CO2RR. Based on the reported results, the GCE-RuO2.SnO2 electrode could be a promising candidate for CO2 reduction, applicable in renewable energy generation.

Enzymatic ester bond formation strategies in fungal macrolide skeletons.

Covering: up to August 2024Macrolides, the core skeletons of numerous marketed drugs and bioactive natural products, have garnered considerable scientific interest owing to their structural diversity and broad spectrum of pharmaceutical activities. The formation of intramolecular ester bonds is a critical biocatalytic step in constructing macrolide skeletons. Here, we summarised enzymatic ester bond formation strategies in fungal polyketide (PK)-type, nonribosomal peptide (NRP)-type, and PK-NRP hybrid-type macrolides. In PK-type macrolides, ester bond formation is commonly catalysed by a trans-acting thioesterase (TE) or a cis-acting TE domain during the product release process. In NRP-type and PK-NRP hybrid-type macrolides, the ester bond is usually introduced through condensation (C) domain-catalysed esterification during the elongation or product release step. Although the TE and C domains share similarities in their catalytic mechanism, using hydroxyl groups as nucleophiles in an intramolecular nucleophilic attack, they differ in terms of the hydroxyl origin, the timing of ester bond formation, and domain location. Furthermore, some TE domains are utilized as chemoenzymatic catalysts to construct macrolides with different ring sizes. A comparison of ester bond formation between fungi and bacteria is also discussed. Exploring the biosynthetic pathways of fungal macrolides, elucidating the diverse strategies employed in the formation of ester bonds, and understanding the application of enzymes/domains in chemoenzymatic synthesis hold promise for the discovery of new bioactive macrolides in the future.

Green Light Activated Dual-Action Pt(IV) Prodrug With Enhanced PDT activity.

Light induced release of cisplatin from Pt(IV) prodrugs is a promising tool for precise spatiotemporal control over the antiproliferative activity of Pt-based chemotherapeutic drugs. A combination of light-controlled chemotherapy (PACT) and photodynamic therapy (PDT) in one molecule has the potential to overcome crucial drawbacks of both Pt-based chemotherapy and PDT via a synergetic effect. Herein we report green-light-activated Pt(IV) prodrug GreenPt with BODIPY-based photosentitizer in the axial position with an incredible high light response and singlet oxygen generation ability. GreenPt demonstrated the ability to release cisplatin under low-dose green light irradiation up to 1 J/cm2. The investigation of the photoreduction mechanism of GreenPt prodrug using DFT modeling and ΔG0 PET estimation revealed that the anion-radical formation and substituent photoinduced electron transfer from the triplet excited state of the BODIPY axial ligand to the Pt(IV) center is the key step in the light-induced release of cisplatin. Green-light-activated BODIPY-based photosentitizers 5 and 8 demonstrated outstanding photosensitizing properties with an extraordinary phototoxicity index (PI) >1300. GreenPt prodrug demonstrated gradual intracellular accumulation and light-induced phototoxicity with PI > 100, thus demonstrating dual action through light-controlled release of both cisplatin and a potent BODIPY-based photosensitizer.

Effects of linkers on the development of liposomal docetaxel-glutathione prepared by active click loading.

Loading drug-maleimide (MAL) conjugates into liposomes preloaded with glutathione (GSH) can prepare the liposome encapsulating GSH-conjugated prodrugs, which serve as a feasible way to construct liposomal formulation. However, the effects ofthelinker on the development of this liposomal system remained unclear. Herein, docetaxel (DTX)-MAL conjugates linked by various linkers were used for such studies. It was found that the linker influenced the aqueous solubility of DTX-MALs, which further affected their loading efficiency in liposomes. The linker significantly influenced the DTX release from liposomal DTX-GSH (DTX-LIPs) by impacting the activation rate of DTX-GSH outside liposomes. Notably, DTX-LIPs containing the rapidly-activated DTX-GSH exhibited much more potent antitumor activity in the 4T1 breast cancer xenograft than other DTX-LIPs and commercial DTX injections. Analysis of the drug release mechanism revealed that DTX-GSH was first released from theliposome and consequently activated into DTX, and the prodrug activation was the rate-limiting step for DTX release. These results highlighted the crucial role of linkers in the drug loading, drug release, and antitumor activity of DTX-LIPs prepared by active click loading, which would effectively guide the rational design of liposomal drugs for improved antitumor efficacy.

Molecular dynamics model of mechanophore sensors for biological force measurement.

Cellular forces regulate an untold spectrum of living processes, such as cell migration, gene expression, and ion conduction. However, a quantitative description of mechanical control remains elusive due to the lack of general, live-cell tools to measure discrete forces between biomolecules. Here we introduce a computational pipeline for force measurement that leverages well-defined, tunable release of a mechanically activated small molecule fluorophore. These sensors are characterized using a multiscale approach combining equilibrium and steered QM/MM molecular dynamics models to capture the chemical, mechanical, and conformational transitions underlying force activation thresholds on a nano Newton scale. We find that chemical modification of the mechanophore and variation of its biomolecular tethers can tune the rate-determining step for fluorophore release and adjust the mechanochemical activation barrier. The models offer a new molecular framework for calibrated, programmable biomolecular force reporting within the live-cell regime, opening new opportunities to study mechanical phenomena in biological systems.

Operando Characterization of CO2 Reduction Interfaces by Electrochemical Atomic Force Microscopy

The electrode-electrolyte interface is perhaps the most important interface of an electrochemical device. At this interface, the electrochemical reactions of interest occur, and the local microenvironment (e.g. pH, reactant concentrations, water activity) can differ significantly from bulk electrolyte conditions due to double layer formation, migration, mass transport effects, catalyst restructuring, and more. In addition, common electrode materials such as polycrystalline metal foils and nanoparticle catalyst layers are heterogeneous with regions of differing activity, making the interface vary across the surface of the electrode both spatially and temporally. Understanding the electrode-electrolyte interface, its local microenvironment, and the evolution of the heterogeneous electrode surface is crucial to the development of high performing electrochemical devices. However, traditional electrochemical methods average current and potential measurements across the electrode surface. Thus, combining electrochemistry with advanced in situ and operando is necessary for a holistic view of the electrode-electrolyte interface.Scanning probe techniques are well-suited for operando studies of electrode-electrolyte interfaces due to their compatibility with liquid environments and suitable spatial (µm to nm scale) and temporal (minutes to seconds) resolutions. One popular operando technique for the study of electrode-electrolyte interfaces is electrochemical atomic force microscopy (EC-AFM). EC-AFM measures the interaction forces between a sharp physical probe and sample surface to map the surface topography. These measurements can also extract information about the sample’s mechanical properties by generating force-distance curves across the surface. EC-AFM measurements are readily performed in a three-electrode cell under potential bias, thereby allowing spatially and temporally resolved imaging of the electrode-electrolyte interface in operando.Here, we applied EC-AFM to two studies of the electrode-electrolyte interface during the electrochemical CO2 reduction reaction (CO2RR). First, we present EC-AFM measurements of a common degradation mode for CO2RR electrolyzers: salt precipitation. CO2RR produces OH-, which accumulates at the electrode-electrode interface and causes the local pH to shift more alkaline. However, this alkaline environment also promotes the formation and precipitation of (bi)carbonate salts by the reaction of OH- and CO2. Herein, we conducted EC-AFM measurements on a Ag electrode in calcium-containing bicarbonate electrolytes. CO2RR was catalyzed at the Ag surface to cause a local pH shift at the electrode surface and result in the formation of CaCO3 crystallites on the electrode surface. Through EC-AFM measurements, we investigated the effect of applied current and bulk electrolyte pH on this deleterious mineralization process.Second, we studied the interactions between polyethylenimine (PEI) and a Ag catalyst. PEI is a polymer that can capture CO2 from the atmosphere by forming a carbamate. Recent work has shown that CO2 bound in PEI can be directly converted to CO without an intermediate CO2 release step. However, very little information is known about the interaction of the polymer with the electrode surface during CO2RR. We studied the morphology and mechanical properties of a Ag electrode surface in PEI-containing electrolytes as a function of applied potential and electrolyte composition for the conversion of CO2 to CO. Both variables significantly affected the mechanical properties (i.e. modulus) of the electrode surface, suggesting polymer chain reorganization at the interface due to interactions with electrolyte species and charged electrode surfaces. Overall, these examples demonstrate that EC-AFM is a powerful operando technique for building fundamental understanding of the electrode-electrolyte interface.

An Aqueous Redox Flow Battery Using CO2 as an Active Material

H2 storage system utilizing the interconversion of CO2 and formate, named a chemical hydrogen battery, has been proposed. The system stores H2 via CO2 hydrogenation to produce formic acid (or formate) and releases H2 via formic acid (or formate) dehydrogenation. Beller et al. reported a catalytic system combining lysine with Mn based homogeneous catalysts and pincer ligands to achieve 10 charging-discharging cycles1. In the H2 release step, lysine acted as a base and trapped CO2, generating >99% pure H2. In addition, our research group developed Ir-based homogeneous catalysts that could drive a chemical hydrogen battery2. The Ir-based homogeneous catalyst enabled H2 storage under ambient conditions and produced 1 MPa of H2 in the H2 release step. However, in the chemical hydrogen battery, energy losses are inevitable in the conversion of electrical energy to H2 as chemical energy and H2 to electrical energy, resulting in a loss of more than half of the input electricity.Thus, we considered that the significant energy loss could be overcome by directly storing and generating electrical energy without using H2. In this presentation, we introduce an aqueous redox flow battery in which the anolyte involves a CO2–formate redox pair based on homogeneous Ir catalysts, while the catholyte involves an MnII–MnIII redox pair. The system exhibited a maximum discharge capacity of 10.5 mAh (1.5 AhL-1), capacity decay of 0.2% per cycle, and total turnover number of 2550 after 50 cycles3. In the redox flow battery system, the formation of IrIV and high-valence hydride species, in contrast to the case of the chemical hydrogen battery, worked as active species and was supported by the in situ fluorescence Ir L III-edge XAFS spectroscopic analysis using the newly constructed online setup.

Role of Complexin 2 in the regulation of hormone secretion from the islet of Langerhans.

Regulated secretion of insulin from β-cells, glucagon from α-cells, and somatostatin from δ-cells is necessary for the maintenance of glucose homeostasis. The release of these hormones from pancreatic islet cells requires the assembly and disassembly of the SNARE protein complex to control vesicle fusion and exocytosis. Complexin 2 (Cplx 2) is a small soluble synaptic protein that participates in the priming and release steps of vesicle fusion. It plays a dual role as a molecular switch that first clamps and prevents fusion pore opening, and subsequently undergoes a conformational change upon Ca 2+ binding to synaptotagmin to facilitate exocytosis. Using a Cplx 2 knockout (KO) mouse model, we show a direct inhibitory role of Cplx 2 for glucagon and somatostatin secretion, along with an indirect role in the paracrine inhibition of insulin secretion by somatostatin. Deletion of Cplx 2 increases glucagon and somatostatin secretion from intact mouse islets, while there is no difference in insulin secretion between WT and Cplx 2 KO islets. The normal paracrine inhibition of insulin secretion by somatostatin is disrupted in Cplx 2 KO islets. On the contrary, deletion of Cplx 2 did not affect the known role of somatostatin in the paracrine inhibition of glucagon at elevated glucose levels, since the paracrine inhibition of glucagon secretion by somatostatin is similar for both WT and Cplx 2 KO islets. In both β- and α-cells, the secretion profiles are parallel to Ca 2+ activity changes following somatostatin treatment of WT and Cplx 2 KO islets. The loss of paracrine inhibition of insulin secretion is substantiated by direct measurements of insulin vesicle fusion events in Cplx 2 KO islets. Together, these data show a differential role for Cplx 2 in regulating hormone secretion from pancreatic islets.

Releasing Preferentially Sequestered Na+ from Its Confinement by Beauvericin: A Single Water Molecule is the Accomplice.

Beauvericin (Bv) is a natural ionophore capable of transporting ions across biological membranes. Mass spectrometry and infrared spectroscopy show that Bv specifically captures sodium ions with a unique 6-fold coordination in its cavity, which illustrates how ions are carried through the membrane. But with no reports on how ions are released from Bv at the interface, a complete picture of the ion transport process has yet to be established. In this study, conformational changes of Bv complexes with alkali metal ions upon hydration were investigated using infrared spectroscopy and computational calculations. The addition of a single water molecule to Na+Bv pries the ion away from the 6-fold cavity to the amide face of the ionophore, evidence of the first step of ion release. In contrast, there is little impact on the other M+Bv complexes, with the ion bound to the three carbonyl groups on the amide face. Analysis of the carbonyl C═O and water OH stretching modes reveals the competition between ion-ionophore, ion-water, and water-ionophore interactions and demonstrates how water actively participates in ion transport by initiating ion release from the ionophore.

On the Control of Directionality of Myosin.

The origin of the unique directionality of myosin has been a problem of fundamental and practical importance. This work establishes in a conclusive way that the directionality is controlled by tuning the barrier for the rate-determining step, namely, the ADP release step. This conclusion is based on exploring the molecular origin behind the reverse directionality of myosins V and VI and the determination of the origin of the change in the barriers of the ADP release for the forward and backward motions. Our investigation is performed by combining different simulation methods such as steer molecular dynamics (SMD), umbrella sampling, renormalization method, and automated path searching method. It is found that in the case of myosin V, the ADP release from the postrigor (trailing head) state overcomes a lower barrier than the prepowerstroke (leading head) state, which is also evident from experimental observation. In the case of myosin VI, we noticed a different trend when compared to myosin V. Since the directionality of myosins V and VI follows a reverse trend, we conclude that such differences in the directionality are controlled by the free energy barrier for the ADP release. Overall, the proof that the directionality of myosin is determined by the activation barrier of the rate-determining step in the cycle, rather than by some unspecified dynamical effects, has general importance.

Antiviral activity of the water extract and ethanol extract of Sorbus commixta against influenza A virus in vitro

Although vaccines and antivirals are currently available, influenza virus infections continually present major threats to human health. Due to genetic diversity and variability of influenza viruses, the development of new antiviral agents against the virus remains as a considerable challenge. In this study, we evaluated the antiviral activity of the water extract and ethanol extract of Sorbus commixta Hedl. (SCH), widely used as a medical herb, against influenza A viruses and identified molecular mechanisms for the antiviral activity. The water extract and ethanol extract of SCH demonstrated virucidal activity against influenza A virus at the noncytotoxic concentrations. In addition, cytopathic effect reduction assay and GFP fluorescence image analysis suggest that SCH extracts have inhibitory activity on multiple stages during influenza virus life cycle. Mechanisms studies showed that SCH extracts inhibited the biological functions of influenza viral surface hemagglutinin and neuraminidase proteins that play critical roles in the viral entry and release steps. SCH extracts not only prevented the receptor binding of influenza viral HA to the cellular receptors but also inhibited the HA-mediated membrane fusion. In addition, SCH extracts suppressed the enzyme activity of the viral neuraminidase. The results together suggest that SCH extracts contain antiviral natural compounds that inhibit multiple influenza viral proteins including the viral surface proteins. Our findings suggest that SCH extracts could be promising resources for the development of novel antiviral agents against influenza A viruses.

Structural and mechanistic insights into a mesophilic prokaryotic Argonaute.

Argonaute (Ago) proteins are programmable nucleases found in all domains of life, playing a crucial role in biological processes like DNA/RNA interference and gene regulation. Mesophilic prokaryotic Agos (pAgos) have gained increasing research interest due to their broad range of potential applications, yet their molecular mechanisms remain poorly understood. Here, we present seven cryo-electron microscopy structures of Kurthia massiliensis Ago (KmAgo) in various states. These structures encompass the steps of apo-form, guide binding, target recognition, cleavage, and release, revealing that KmAgo employs a unique DDD catalytic triad, instead of a DEDD tetrad, for DNA target cleavage under 5'P-DNA guide conditions. Notably, the last catalytic residue, D713, is positioned outside the catalytic pocket in the absence of guide. After guide binding, D713 enters the catalytic pocket. In contrast, the corresponding catalytic residue in other Agos has been consistently located in the catalytic pocket. Moreover, we identified several sites exhibiting enhanced catalytic activity through alanine mutagenesis. These sites have the potential to serve as engineering targets for augmenting the catalytic efficiency of KmAgo. This structural analysis of KmAgo advances the understanding of the diversity of molecular mechanisms by Agos, offering insights for developing and optimizing mesophilic pAgos-based programmable DNA and RNA manipulation tools.

Characterizing and Tailoring the Substrate Profile of a γ-Glutamyltransferase Variant.

Xenobiology is an emerging field that focuses on the extension and redesign of biological systems through the use of laboratory-derived xenomolecules, which are molecules that are new to the metabolism of the cell. Despite the enormous potential of using xenomolecules in living organisms, most noncanonical building blocks still need to be supplied externally, and often poor uptake into cells limits wider applicability. To improve the cytosolic availability of noncanonical molecules, a synthetic transport system based on portage transport was developed, in which molecules of interest "cargo" are linked to a synthetic transport vector that enables piggyback transport through the alkylsulfonate transporter (SsuABC) of Escherichia coli. Upon cytosolic delivery, the vector-cargo conjugate is enzymatically cleaved by GGTxe, leading to the release of the cargo molecule. To deepen our understanding of the synthetic transport system, we focused on the characterization and further development of the enzymatic cargo release step. Hence, the substrate scope of GGTxe was characterized using a library of structurally diverse vector-cargo conjugates and MS/MS-based quantification of hydrolysis products in a kinetic manner. The resulting substrate tolerance characterization revealed that vector-amino acid conjugates were significantly unfavored. To overcome this shortcoming, a selection system based on metabolic auxotrophy complementation and directed evolution of GGTxe was established. In a directed evolution campaign, we improved the enzymatic activity of GGTxe for vector-amino acid conjugates and revealed the importance of residue D386 in the cargo unloading step.

Achieving high geometric fidelity in vat photopolymerization additive manufacturing through liquid surface support

The top-down vat photopolymerization (VPP) printing process, known for its extensive material adaptability and elimination of the release step between the printed object and the separation film, is widely used in 3D printing of advanced functional materials. However, for slurries that cannot achieve rapid self-leveling, edge morphology distortion in printed objects reduces geometric precision. This study investigated the issue of edge morphology distortion in the top-down VPP printing process, and proposes a liquid surface support (LSS) printing method that can be applied to general VPP printers. The results show that the protective slurry fence printed simultaneously with the object can provide excellent liquid surface support for the uncured layer above the printed object, which shifts the edge morphology distortion issue from the target object to the fence. The gap distance between the fence and the target sample is identified as the primary factor affecting edge morphology fidelity, which is influenced by surface tension. Finally, we successfully validated the application of the LSS printing method in the printing of ceramic dental prostheses and slender rod structures. This novel method significantly enhances the geometric precision of printed samples and is expected to promote the advancement of VPP printing applications for advanced functional materials.

Positive feedback in Ras activation by full-length SOS arises from autoinhibition release mechanism

Signaling through the Ras-MAPK pathway can exhibit switch-like activation, which has been attributed to the underlying positive feedback and bimodality in the activation of RasGDP to RasGTP by SOS. SOS contains both catalytic and allosteric Ras binding sites, and a common assumption is that allosteric activation selectively by RasGTP provides the mechanism of positive feedback. However, recent single-molecule studies have revealed that SOS catalytic rates are independent of the nucleotide state of Ras in the allosteric binding site, raising doubt about this as a positive feedback mechanism. Here, we perform detailed kinetic analyses of receptor-mediated recruitment of full-length SOS to the membrane while simultaneously monitoring its catalytic activation of Ras. These results, along with kinetic modeling, expose the autoinhibition release step in SOS, rather than either recruitment or allosteric activation, as the underlying mechanism giving rise to positive feedback in Ras activation.

Atg8/LC3 controls systemic nutrient surplus signaling in flies and humans

Organisms experience constant nutritional flux. Mechanisms at the interface of opposing nutritional states-scarcity and surplus-enable organismal energy homeostasis. Contingent on nutritional stores, adipocytes secrete adipokines, such as the fat hormone leptin, to signal nutrient status to the central brain. Increased leptin secretion underlies metabolic dysregulation during common obesity, but the molecular mechanisms regulating leptin secretion from human adipocytes are poorly understood. Here, we report that Atg8/LC3 family proteins, best known for their role in autophagy during nutrient scarcity, play an evolutionarily conserved role during nutrient surplus by promoting adipokine secretion. We show that in a well-fed state, Atg8/LC3 promotes the secretion of the Drosophila functional leptin ortholog unpaired 2 (Upd2) and leptin from human adipocytes. Proteomic analyses reveal that LC3 directs leptin to a secretory pathway in human cells. We identified LC3-dependent extracellular vesicle (EV) loading and secretion (LDELS) as a required step for leptin release, highlighting a unique secretory route adopted by leptin in human adipocytes. In Drosophila, mutations to Upd2's Atg8 interaction motif (AIM) result in constitutive adipokine retention. Atg8-mediated Upd2 retention alters lipid storage and hunger response and rewires the bulk organismal transcriptome in a manner conducive to starvation survival. Thus, Atg8/LC3's bidirectional role in nutrient sensing-conveying nutrient surplus and responding to nutrient deprivation-enables organisms to manage nutrient flux effectively. We posit that decoding how bidirectional molecular switches-such as Atg8/LC3-operate at the nexus of nutritional scarcity and surplus will inform therapeutic strategies to tackle chronic metabolic disorders.

Cleaving Folded RNA by Multifunctional DNAzyme Nanomachines.

Both tight and specific binding of folded biological mRNA is required for gene silencing by oligonucleotide gene therapy agents. However, this is fundamentally impossible using the conventional oligonucleotide probes according to the affinity/specificity dilemma. This study addresses this problem for cleaving folded RNA by using multicomponent agents (dubbed 'DNA nanomachine' or DNM). DNMs bind RNA by four short RNA binding arms, which ensure tight and highly selective RNA binding. Along with the improved affinity, DNM maintain the high sequence selectivity of the conventional DNAzymes. DNM enabled up to 3-fold improvement in DNAzymes catalytic efficiency (kcat/Km) by facilitating both RNA substrate binding and product release steps of the catalytic cycle. This study demonstrates that multicomponent probes organized in sophisticated structures can help to achieve the balance between affinity and selectivity in recognizing folded RNA and thus creates a foundation for applying complex DNA nanostructures derived by DNA nanotechnology in gene therapy.

Direct Glycan Analysis of Biological Samples and Intact Glycoproteins by Integrating Machine Learning-Driven Surface-Enhanced Raman Scattering and Boronic Acid Arrays.

Frequent monitoring of glycan patterns is a critical step in studying glycan-mediated cellular processes. However, the current glycan analysis tools are resource-intensive and less suitable for routine use in standard laboratories. We developed a novel glycan detection platform by integrating surface-enhanced Raman spectroscopy (SERS), boronic acid (BA) receptors, and machine learning tools. This sensor monitors the molecular fingerprint spectra of BA binding to cis-diol-containing glycans. Different types of BA receptors could yield different stereoselective reactions toward different glycans and exhibit unique vibrational spectra. By integration of the Raman spectra collected from different BA receptors, the structural information can be enriched, eventually improving the accuracy of glycan classification and quantification. Here, we established a SERS-based sensor incorporating multiple different BA receptors. This sensing platform could directly analyze the biological samples, including whole milk and intact glycoproteins (fetuin and asialofetuin), without tedious glycan release and purification steps. The results demonstrate the platform's ability to classify milk oligosaccharides with remarkable classification accuracy, despite the presence of other non-glycan constituents in the background. This sensor could also directly quantify sialylation levels of a fetuin/asialofetuin mixture without glycan release procedures. Moreover, by selecting appropriate BA receptors, the sensor exhibits an excellent performance of differentiating between α2,3 and α2,6 linkages of sialic acids. This low-cost, rapid, and highly accessible sensor will provide the scientific community with an invaluable tool for routine glycan screening in standard laboratories.

New Hydrophilic Matrix Tablets for the Controlled Released of Chlorzoxazone.

The modified release of active substances such as chlorzoxazone from matrix tablets, based on Kollidon®SR and chitosan, depends both on the drug solubility in the dissolution medium and on the matrix composition. The aim of this study is to obtain some new oral matrix tablet formulations, based on Kollidon®SR and chitosan, in order to optimize the low-dose oral bioavailability of chlorzoxazone, a non-steroidal anti-inflammatory drug of class II Biopharmaceutical Classification System. Nine types of chlorzoxazone matrix tablets were obtained using the direct compression method by varying the components ratio as 1:1, 1:2, and 1:3 chlorzoxazone/excipients, 20-40 w/w % Kollidon®SR, 3-7 w/w % chitosan while the auxiliary substances: Aerosil® 1 w/w %, magnesium stearate 0.5 w/w % and Avicel® up to 100 w/w % were kept in constant concentrations. Pharmaco-technical characterization of the tablets included the analysis of flowability and compressibility properties (flow time, friction coefficient, angle of repose, Hausner ratio, and Carr index), and pharmaco-chemical characteristics (such as mass and dose uniformity, thickness, diameter, mechanical strength, friability, softening degree, and in vitro release profiles). Based on the obtained results, only three matrix tablet formulations (F1b, F2b, and F3b, containing 30 w/w % KOL and 5 w/w % CHT, were selected and further tested. These formulations were studied in detail by Fourier-transform infrared spectrometry, X-ray diffraction, thermogravimetry, and differential scanning calorimetry. The three formulations were comparatively studied regarding the release kinetics of active substances using in vitro release testing. The results were analyzed by fitting into four representative mathematical models for the modified-release oral formulations. In vitro kinetic study revealed a complex mechanism of release occurring in two steps of drug release, the first step (0-2 h) and the second (2-36 h). Two factors were calculated to assess the release profile of chlorzoxazone: f1-the similarity factor, and f2-the factor difference. The results have shown that both Kollidon®SR and chitosan may be used as matrix-forming agents when combined with chlorzoxazone. The three formulations showed optima pharmaco-technical properties and in vitro kinetic behavior; therefore, they have tremendous potential to be used in oral pharmaceutical products for the controlled delivery of chlorzoxazone. In vitro dissolution tests revealed a faster drug release for the F2b sample.

Light-Responsive Pt(IV) Prodrugs with Controlled Photoactivation and Low Dark Toxicity.

Light-induced release of cisplatin from Pt(IV) prodrugs represents a promising approach for precise control over the antiproliferative activity of Pt-based chemotherapeutic drugs. This method has the potential to overcome crucial drawbacks of conventional cisplatin therapy, such as high general toxicity toward healthy organs and tissues. Herein, we report two Pt(IV) prodrugs with BODIPY-based photoactive ligands Pt-1 and Pt-2, which were designed using carbamate and triazole linkers, respectively. Both prodrugs demonstrated the ability to release cisplatin under blue light irradiation without the requirement of an external reducing agent. Dicarboxylated Pt-2 prodrug turned out to be more stable in the dark and more sensitive to light than its monocarbamate Pt-1 counterpart; these observations were explained using DFT calculations. The investigation of the photoreduction mechanism of Pt-1 and Pt-2 prodrugs using DFT modeling and ΔG0 PET estimation suggests that the photoinduced electron transfer from the singlet excited state of the BODIPY axial ligand to the Pt(IV) center is the key step in the light-induced release of cisplatin from the complexes. Cytotoxicity studies demonstrated that both prodrugs were nontoxic in the dark and toxic to MCF-7 cells under low-dose irradiation with blue light, and the observed effect was solely due to the cisplatin release from the Pt(IV) prodrugs. Our research presents an elegant synthetic approach to light-activated Pt(IV) prodrugs and presents findings that may contribute to the future rational design of photoactivatable Pt(IV) prodrugs.