Modeling Zinc Complexes Using Neural Networks.

Understanding the energetic landscapes of large molecules is necessary for the study of chemical and biological systems. Recently, deep learning has greatly accelerated the development of models based on quantum chemistry, making it possible to build potential energy surfaces and explore chemical space. However, most of this work has focused on organic molecules due to the simplicity of their electronic structures as well as the availability of data sets. In this work, we build a deep learning architecture to model the energetics of zinc organometallic complexes. To achieve this, we have compiled a configurationally and conformationally diverse data set of zinc complexes using metadynamics to overcome the limitations of traditional sampling methods. In terms of the neural network potentials, our results indicate that for zinc complexes, partial charges play an important role in modeling the long-range interactions with a neural network. Our developed model outperforms semiempirical methods in predicting the relative energy of zinc conformers, yielding a mean absolute error (MAE) of 1.32 kcal/mol with reference to the double-hybrid PWPB95 method.

Superelastic carbon aerogels with anisotropic and hierarchically-enhanced cellular structure for wearable piezoresistive sensors.

Elastic carbon aerogels have promising applications in the field of wearable sensors. Herein, a new strategy for preparing carbon aerogels with excellent compressive strength and strain, shape recovery, and fatigue resistance was proposed based on the structure design and carbonization optimization of nanocellulose-based precursor aerogels. By the combination of directional freezing and zinc ion cross-linking, bacterial cellulose (BC)/alginate (SA) composite aerogels with high elasticity and compressive strength were first achieved. The existance of zinc ions also significantly improved the carbon retention rate and inhibited structural shrinkage, thus making the carbon aerogels retain ultra-high elasticity and fatigue resistance after compression. Moreover, the carbon aerogel possessed excellent piezoresistive pressure sensing performance with a wide detection range of 0-7.8 kPa, high sensitivity of 11.04 kpa-1, low detection limit (2 % strain), fast response (112 ms), and good durability (over 1,000 cycles). Based on these excellent properties, the carbon aerogel pressure sensors were further successfully used for human motion monitoring, from joint motion to and speech recognition.

Novel Ag3PO4/ZnWO4-modified graphite felt electrode for photoelectrocatalytic removal of harmful algae: Performance and mechanism.

A novel Ag3PO4/ZnWO4-modified graphite felt electrode (AZW@GF) was prepared by drop coating method and applied to photoelectrocatalytic removal of harmful algae. Results showed that approximately 99.21% of chlorophyll a and 91.57% of Microcystin-LR (MCLR) were degraded by the AZW@GF-Pt photoelectrocatalytic system under the optimal operating conditions with a rate constant of 0.02617 min-1 and 0.01416 min-1, respectively. The calculated synergistic coefficient of photoelectrocatalytic algal removal and MC-LR degradation by the AZW@GF-Pt system was both larger than 1.9. In addition, the experiments of quenching experiments and electron spin resonance (ESR) revealed that the photoelectrocatalytic reaction mainly generated •OH and •O2- for algal removal and MC-LR degradation. Furthermore, the potential pathway for photoelectrocatalytic degradation of MC-LR was proposed. Finally, the photoelectrocatalytic cycle algae removal experiments were carried out on AZW@GF electrode, which was found to maintain the algae removal efficiency at about 91% after three cycles of use, indicating that the photoelectrocatalysis of AZW@GF electrode is an effective emergency algae removal technology.

Potentiating Activity of GmhA Inhibitors on Gram-Negative Bacteria.

Inhibition of the biosynthesis of bacterial heptoses opens novel perspectives for antimicrobial therapies. The enzyme GmhA responsible for the first committed biosynthetic step catalyzes the conversion of sedoheptulose 7-phosphate into d-glycero-d-manno-heptose 7-phosphate and harbors a Zn2+ ion in the active site. A series of phosphoryl- and phosphonyl-substituted derivatives featuring a hydroxamate moiety were designed and prepared from suitably protected ribose or hexose derivatives. High-resolution crystal structures of GmhA complexed to two N-formyl hydroxamate inhibitors confirmed the binding interactions to a central Zn2+ ion coordination site. Some of these compounds were found to be nanomolar inhibitors of GmhA. While devoid of HepG2 cytotoxicity and antibacterial activity of their own, they demonstrated in vitro lipopolysaccharide heptosylation inhibition in Enterobacteriaceae as well as the potentiation of erythromycin and rifampicin in a wild-type Escherichia coli strain. These inhibitors pave the way for a novel treatment of Gram-negative infections.

Construction of a Zn(II)-Eu(III) Nanoring with Temperature-Dependent Luminescence for the Qualitative and Quantitative Detection of Neopterin as an Inflammatory Marker.

A nine-metal Zn(II)-Eu(III) nanoring 1 with a diameter of about 2.3 nm was constructed by the use of a long-chain Schiff base ligand. It shows a luminescence response to neopterin (Neo) through the enhancement of lanthanide emission with high selectivity and sensitivity, which can be used to quantitatively analyze the concentrations of Neo in fetal calf serum and urine. The luminescence sensing of 1 to Neo is temperature-dependent, and it displays more obvious response behavior at lower temperatures. Filter paper strips bearing 1 can be used to qualitatively detect Neo by the color change from chartreuse to red under a UV lamp. The limit of detection is as low as 3.77 × 10-2 nM.

Constructing porous ZnFC-PA/PSF composite spheres for highly efficient Cs+ removal.

Radioisotope leaking from nuclear waste has become an intractable problem due to its gamma radiation and strong water solubility. In this work, a novel porous ZnFC-PA/PSF composite sphere was fabricated by immobilization of ferrocyanides modified zinc phytate into polysulfone (PSF) substrate for the treatment of Cs-contaminated water. The maximum adsorption capacity of ZnFC-PA/PSF was 305.38 mg/g, and the removal efficiency of Cs+ was reached 94.27% within 2 hr. The ZnFC-PA/PSF presented favorable stability with negligible dissolution loss of Zn2+ and Fe2+ (< 2%). The ZnFC-PA/PSF achieved high-selectivity towards Cs+ (Kd = 2.24×104 mL/g) even in actual geothermal water. The adsorption mechanism was inferred to be the ion-exchange between Cs+ and K+. What's more, ZnFC-PA/PSF worked well in the fixed-bed adsorption (E = 91.92%), indicating the application potential for the hazardous Cs+ removal from wastewater.

Zinc shields against copper phytotoxicity in a contaminated soil.

While zinc protects plants from copper in hydroponics, its behavior in soil remains unclear. We investigated the potential of zinc sulfate to protect ryegrass from copper toxicity in contaminated soil. Twelve soil treatments combined varying levels of copper oxide (CuO) and zinc sulfate (ZnSO4). Increasing CuO significantly stunted ryegrass, but adding ZnSO4 mitigated the effects at each CuO level. ZnSO4 had no effect in unpolluted conditions. These results, supported by the Terrestrial Biotic Ligand Model, indicate that zinc competes with copper for binding sites, reducing copper uptake by ryegrass and mitigating its toxicity. Application of zinc sulfate to copper-contaminated soils appears promising for ryegrass growth, although field studies are critical to confirm real-world efficacy.

Pyridine appended pyrimidine bis hydrazone: Zn2+/ATP detection, bioimaging and functional properties of its dinuclear Zn(II) complex.

A pyridine functionalized pyrimidine-based system, H2P was successfully synthesized, characterized, and evaluated for its remarkable selective characteristics towards Zn2+ and ATP ions. The chemical sensing capabilities of H2P were demonstrated through absorption, fluorescence, and NMR spectroscopic techniques. The probe exhibited outstanding sensitivity when interacting with the ions, demonstrating relatively strong association constants and impressively low detection limits. The comprehensive binding mechanism of H2P with respect to Zn2+ and ATP ions was investigated using a combination of analytical methods, including Job's plot, NMR spectroscopy, mass spectrometry, and density functional theory (DFT) experiments. The interesting sensing ability of H2P for Zn2+/ATP ions was harnessed for live cell bioimaging and other diverse on-site detection purposes, including paper strips, cotton swabs, and applications involving mung bean sprouts. Further, the fluorescent probe demonstrated its effectiveness in detecting Zn2+ and ATP within live cells, indicating its significant potential in the realm of biological imaging applications. Moreover, the molecular configuration of the zinc complex (H2P-Zn2Cl4), derived from H2P, was elucidated using X-ray crystallography. This complex exhibited intriguing multifunctional attributes, encompassing its capability for detecting picric acid and for reversible acid/base sensing responses. The enhanced conducting behavior of the complex as well as its resistance properties were investigated by performing I-V characteristics and electrochemical impedance spectroscopic (EIS) experiments respectively.

Indole-based NNN donor Schiff base ligand and its complexes: Sonication-assisted synthesis, characterization, DNA binding, anti-cancer evaluation and in-vitro biological assay.

A novel indole based NNN donor Schiff base ligand and its Ni(II), Zn(II) and Cd(II) complexes have been synthesized using sonication-assisted method which is a highly efficient eco-friendly mechanism. The synthesized complexes have been characterized using elemental analysis, UV-Vis spectroscopy, mass spectrometry, FT-IR, and NMR and are optimized using DFT approach, which provided their theoretical framework. The stoichiometry between the ligand and the metal ions was also determined using Job's method. The thermogravimetric (TGA/DSC) analyses confirm the stability for all complexes at room temperature followed by thermal decomposition in different steps. DNA binding activities have been assessed by employing UV-visible and fluorescence spectra using the CT-DNA. The estimated intrinsic binding constant (Kb) for NiL, ZnL, and CdL complexes was 6.00 × 105, 5.58 × 105, and 4.7 × 105, respectively. In accordance with the Kb value, the quenching constant (Ksv) values of NiL, ZnL, and CdL are 5.59 × 105 M-1, 4.3 × 105 M-1, and 4.08 × 105 M-1 respectively. The anticancer properties have been assessed using MTT Assay. It has been found that the Ni(II) complex (NiL) is the most potent among the series with IC50 of 169 µg/mL. An in-vitro antioxidant experiment using DPPH was used to evaluate the synthesizedcomplexes' ability to scavenge free radicals. The findings indicated that the complexes exhibited notable antioxidant properties. The antioxidant property ZnL has been found to be the highest with an IC50 of 2.91 µg/mL and it follows the order is ZnL > NiL > CdL > L. Using the egg albumin denaturation technique, the anti-inflammatory property have been assessed, and the amount of protein denaturation inhibition has been computed. NiL has the highest % inhibition among the series studied. Comparatively, the metal complexes have been reported to exhibit higher biological activities than the prepared Schiff base ligand. The reason for the excellent biological properties observed in the metal complexes could be attributed to the incorporation of the electron-withdrawing CH3COO- during complexation. Molecular docking studies have been performed on the 2GYT protein and it has been found that the complexes have excellent binding affinity, with NiL having the lowest binding energy of -6.93 Kcal mol-1. The values suggested that NiL is more effective against HePG2 cancer cells, which is also in accordance with the MTT Assay results.

Chemical Versatility in Catalysis and Inhibition of the Class IIb Histone Deacetylases.

ConspectusThe zinc-dependent histone deacetylases (HDACs 1-11) belong to the arginase-deacetylase superfamily of proteins, members of which share a common α/ß fold and catalytic metal binding site. While several HDACs play a role in epigenetic regulation by catalyzing acetyllysine hydrolysis in histone proteins, the biological activities of HDACs extend far beyond histones. HDACs also deacetylate nonhistone proteins in the nucleus as well as the cytosol to regulate myriad cellular processes. The substrate pool is even more diverse in that certain HDACs can hydrolyze other covalent modifications. For example, HDAC6 is also a lysine decrotonylase, and HDAC11 is a lysine-fatty acid deacylase. Surprisingly, HDAC10 is not a lysine deacetylase but instead is a polyamine deacetylase. Thus, the HDACs are biologically and chemically versatile catalysts as they regulate the function of diverse protein and nonprotein substrates throughout the cell.Owing to their critical regulatory functions, HDACs serve as prominent targets for drug design. At present, four HDAC inhibitors are FDA-approved for cancer chemotherapy. However, these inhibitors are active against multiple HDAC isozymes, and a lack of selectivity is thought to contribute to undesirable side effects. Current medicinal chemistry campaigns focus on the development of isozyme-selective inhibitors, and many such studies largely focus on HDAC6 and HDAC10. HDAC6 is a target for therapeutic intervention due to its cellular role as a tubulin deacetylase and tau deacetylase, and selective inhibitors are being studied in cancer chemotherapy and the treatment of peripheral neuropathy. Crystal structures of enzyme-inhibitor complexes reveal how various features of inhibitor design, such as zinc-coordinating groups, bifurcated capping groups, and aromatic fluorination patterns, contribute to affinity and isozyme selectivity. The polyamine deacetylase HDAC10 is also an emerging target for cancer chemotherapy. Crystal structures of intact substrates trapped in the HDAC10 active site reveal the molecular basis of strikingly narrow substrate specificity for N8-acetylspermidine hydrolysis. Active site features responsible for substrate specificity have been successfully exploited in the design of potent and selective inhibitors.In this Account, I review the structural chemistry and inhibition of HDACs, highlighting recent X-ray crystallographic and functional studies of HDAC6 and HDAC10 in my laboratory. These studies have yielded fascinating snapshots of catalysis as well as novel chemical transformations involving bound inhibitors. The zinc-bound water molecule in the HDAC active site is the catalytic nucleophile in the deacetylation reaction, but this activated water molecule can also react with inhibitor C═O or C═N groups to yield unanticipated reaction products that bind exceptionally tightly. Versatile active site chemistry unleashes the full inhibitory potential of such compounds, and X-ray crystallography allows us to view this chemistry in action.

Bio-sorption capacity of cadmium and zinc by Pseudomonas monteilii with heavy-metal resistance isolated from the compost of pig manure.

The tolerance of Pseudomonas monteilii X1, isolated from pig manure compost, to Cd and Zn, as well as its capacity for biosorption, were investigated. The minimum inhibitory concentrations (MIC) of Cd and Zn for the strain were 550 mg/L and 800 mg/L, respectively. Untargeted metabolomics analysis revealed that organic acids and derivatives, lipids and lipid-like molecules, and organic heterocyclic compounds were the main metabolites. The glyoxylate and dicarboxylate metabolism pathway were significantly enriched under Cd2+ stress. The isothermal adsorption and adsorption kinetics experiments determined that the strain had adsorption capacities of 9.96 mg/g for Cd2+ and 23.4 mg/g for Zn2+. Active groups, such as hydroxyl, carboxyl, and amino groups on the cell surface, were found to participate in metal adsorption. The strain was able to convert Zn2+ into Zn3(PO4)2·4H2O crystal. Overall, this study suggested that Pseudomonas monteilii has potential as a remediation material for heavy metals.

Insights into the G-quadruplex DNA interaction landscape: Comparative analysis of anionic Zn(II) and Co(II) phthalocyanine-tetrasulfonate complexes.

G-quadruplexes play a pivotal role in regulating various cellular processes, including gene expression and replication, making them essential structures in understanding, and manipulating cellular functions. The development of G-quadruplex ligands holds significant promise in therapeutic and research applications, offering targeted tools to modulate G-quadruplex structures and potentially influence critical biological pathways. An exciting frontier in G-quadruplex research lies in the exploration of anionic ligands, and their profound impact on stabilizing and modulating G-quadruplex DNA. In this study, the interaction of two anionic phthalocyanine compounds (Zinc (II) phthalocyanine 3,4',4″,4‴-tetrasulfonic acid, tetrasodium salt, ZnAPC; cobalt (II) phthalocyanine 3,4',4″,4‴-tetrasulfonic acid, tetrasodium salt, CoAPC) and three separate G-quadruplex-forming DNA sequences was investigated. Interactions were carried out by DNA polymerase stop studies along with spectroscopic studies. According to the results of experimental data, it was determined that ZnAPC actively interacts with the G-quadruplex DNA structures. On the other hand, it was thought that the interaction with CoAPC was less and even occurred in simple electrostatic interactions. KD constants and Bmax constants for the interaction with ZnAPC were calculated. The KD constants for ZnAPC were found to be (1.16 ± 0.07) × 10-5, (9.75 ± .24) × 10-6 and (1.00 ± 0.36) × 10-4 M for AS1411, Vegf, and Tel21, respectively. Accordingly, it was concluded that ZnAPC interacts with G-quadruplex DNA ligands effectively.

Investigating the effect of Zn doping and temperature on the photoluminescence behaviour of CuLaSe2 quantum dots.

In this study, CuLaSe2 and ZnCuLaSe2 quantum dots (QDs) with a mean size of ~4 nm were synthesized and characterized, and their temperature-dependent photoluminescence (PL) properties were studied in the temperature range from 90 to 300 K for the first time. The results show that the obtained QDs were spherical and revealed excitonic band gaps. The PL intensity for both types of materials decreased when increasing the temperature to 300 K, which was attributed to the nonradiative relaxation and thermal escape mechanisms. As the temperature was increased, the PL linewidths broadened, and PL peak energies were red shifted for both types of QDs due to the exciton-phonon coupling and lattice deformation potential mechanisms. In addition, we found that as the temperature was decreased, the PL spectrum of ZnCuLaSe2 QDs contained two extra components, which could be attributed to the shallow defect sites (low energy peak) and the crystal phase transition process (high energy peak). The spectrum of CuLaSe2 QDs contained one extra component, which could be attributed to the crystal phase transition process.

Dual Emissive Zn(II) Naphthalocyanines: Synthesis, Structural and Photophysical Characterization with Theory-Supported Insights towards Soluble Coordination Compounds with Visible and Near-Infrared Emission.

Metal phthalocyaninates and their higher homologues are recognized as deep-red luminophores emitting from their lowest excited singlet state. Herein, we report on the design, synthesis, and in-depth characterization of a new class of dual-emissive (visible and NIR) metal naphthalocyaninates. A 4-N,N-dimethylaminophen-4-yl-substituted naphthalocyaninato zinc(II) complex (Zn-NMe2Nc) and the derived water-soluble coordination compound (Zn-NMe3Nc) exhibit a near-infrared fluorescence from the lowest ligand-centered state, along with a unique push-pull-supported luminescence in the visible region of the electromagnetic spectrum. An unprecedentedly broad structural (2D-NMR spectroscopy and mass spectrometry) as well as photophysical characterization (steady-state state and time-resolved photoluminescence spectroscopy) is presented. The unique dual emission was assigned to two independent sets of singlet states related to the intrinsic Q-band of the macrocycle and to the push-pull substituents in the molecular periphery, respectively, as predicted by TD-DFT calculations. In general, the elusive chemical aspects of these macrocyclic compounds are addressed, involving both reaction conditions, thorough purification, and in-depth characterization. Besides the fundamental aspects that are investigated herein, the photoacoustic properties were exemplarily examined using phantom gels to assess their tomographic imaging capabilities. Finally, the robust luminescence in the visible range arising from the push-pull character of the peripheral moieties demonstrated a notable independence from aggregation and was exemplarily implemented for optical imaging (FLIM) through time-resolved multiphoton micro(spectro)scopy.

Organophosphate Detoxification and Acetylcholinesterase Reactivation Triggered by Zeolitic Imidazolate Framework Structural Degradation.

Organophosphate (OP) toxicity is related to inhibition of acetylcholinesterase (AChE) activity, which plays a key role in the neurotransmission process. In this work, we report the ability of different zinc zeolitic imidazolate frameworks (ZIFs) to behave as potential antidotes against OP poisoning. The Zn-L coordination bond (L = purine, benzimidazole, imidazole, or 2-methylimidazole) is sensitive to the G-type nerve agent model compounds diisopropylfluorophosphate (DIFP) and diisopropylchlorophosphate, leading to P-X (X = F or Cl) bond breakdown into nontoxic diisopropylphosphate. P-X hydrolysis is accompanied by ZIF structural degradation (Zn-imidazolate bond hydrolysis), with the concomitant release of the imidazolate linkers and zinc ions representing up to 95% of ZIF particle dissolution. The delivered imidazolate nucleophilic attack on the OP@AChE adduct gives rise to the recovery of AChE enzymatic function. P-X bond breakdown, ZIF structural degradation, and AChE reactivation are dependent on imidazolate linker nucleophilicity, framework topology, and particle size. The best performance is obtained for 20 nm nanoparticles (NPs) of Zn(2-methylimidazolate)2 (sod ZIF-8) exhibiting a DIFP degradation half-life of 2.6 min and full recovery of AChE activity within 1 h. 20 nm sod ZIF-8 NPs are not neurotoxic, as proven by in vitro neuroblastoma cell culture viability tests.

Anticancer, antioxidant, and antimicrobial studies and molecular docking of a new hexanuclear Zn(II) complex, together with its X-ray crystal analysis.

A new hexanuclear Zn(II) complex with the ligand 2,2'-(piperazine-1,4-diyl)bis(ethan-1-amine), [L3Zn6(OH)6][ClO4]6·3MeOH·7H2O, was synthesized. The crystal structure of this complex showed that each Zn atom is in a distorted tetrahedral coordination environment, surrounded by two nitrogen atoms from each ligand and two hydroxide groups, each of which bridges to another Zn atom. The anticancer activities of the ligand and its metal complex against the breast cancer cell line (MCF-7) indicated that the zinc complex had a greater anticancer activity. The free ligand and its metal complex were evaluated for antioxidant activity using the DPPH scavenging method. In addition, the antibacterial activities of both compounds were screened against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The interaction of these compounds with DNA and AChE was also investigated using molecular docking.

Understanding the nanoscale adhesion forces between the fungal pathogen Candida albicans and antimicrobial zinc-based layered double hydroxides using single-cell and single-particle force spectroscopy.

Antifungal resistance has become a very serious concern, and Candida albicans is considered one of the most opportunistic fungal pathogens responsible for several human infections. In this context, the use of new antifungal agents such as zinc-based layered double hydroxides to fight such fungal pathogens is considered one possible means to help limit the problem of antifungal resistance. In this study, we show that ZnAl LDH nanoparticles exhibit remarkable antifungal properties against C. albicans and cause serious cell wall damage, as revealed by growth tests and atomic force microscopy (AFM) imaging. To further link the antifungal activity of ZnAl LDHs to their adhesive behaviors toward C. albicans cells, AFM-based single-cell spectroscopy and single-particle force spectroscopy were used to probe the nanoscale adhesive interactions. The force spectroscopy analysis revealed that antimicrobial ZnAl LDHs exhibit specific surface interactions with C. albicans cells, demonstrating remarkable force magnitudes and adhesion frequencies in comparison with non-antifungal negative controls, e.g., Al-coated substrates and MgAl LDHs, which showed limited interactions with C. albicans cells. Force signatures suggest that such adhesive interactions may be attributed to the presence of agglutinin-like sequence (Als) adhesive proteins at the cell wall surface of C. albicans cells. Our findings propose the presence of a strong correlation between the antifungal effect provided by ZnAl LDHs and their nanoscale adhesive interactions with C. albicans cells at both the single-cell and single-particle levels. Therefore, ZnAl LDHs could interact with C. albicans fungal pathogens by specific adhesive interactions through which they adhere to fungal cells, leading to their damage and subsequent growth inhibition.

Exploring the Influence of Zinc Ions on the Conformational Stability and Activity of Protein Disulfide Isomerase.

The interplay between metal ion binding and the activity of thiol proteins, particularly within the protein disulfide isomerase family, remains an area of active investigation due to the critical role that these proteins play in many vital processes. This research investigates the interaction between recombinant human PDIA1 and zinc ions, focusing on the subsequent implications for PDIA1's conformational stability and enzymatic activity. Employing isothermal titration calorimetry and differential scanning calorimetry, we systematically compared the zinc binding capabilities of both oxidized and reduced forms of PDIA1 and assessed the structural consequences of this interaction. Our results demonstrate that PDIA1 can bind zinc both in reduced and oxidized states, but with significantly different stoichiometry and more pronounced conformational effects in the reduced form of PDIA1. Furthermore, zinc binding was observed to inhibit the catalytic activity of reduced-PDIA1, likely due to induced alterations in its conformation. These findings unveil a potential regulatory mechanism in PDIA1, wherein metal ion binding under reductive conditions modulates its activity. Our study highlights the potential role of zinc in regulating the catalytic function of PDIA1 through conformational modulation, suggesting a nuanced interplay between metal binding and protein stability in the broader context of cellular redox regulation.

Preventing biofilm formation and eradicating pathogenic bacteria by Zn doped histidine derived carbon quantum dots.

Bacterial infections are of major medical concern due to antibiotic resistance. Carbon quantum dots (CDs) have emerged as potentially excellent biomaterials for multifunctional applications due to their low toxicity, outstanding water solubility, high fluorescence, and high biocompatibility. All of these properties allow CDs to be exceptional biomaterials for inhibiting the growth of bacteria and stopping biofilm formation due to their strong binding affinity, cell wall penetration, and solubilizing biofilm in water. Here, we describe a strategy for one-pot synthesis of histidine-derived zinc-doped N-doped CDs (Zn-NCDs) by a hydrothermal method for inhibiting the growth of both Gram-positive and Gram-negative bacteria without harming mammalian cells. The NCDs and Zn-NCDs showed uniform sizes (∼6 nm), crystallinity, good photostability, high quantum yield (76%), and long decay time (∼5 ns). We also studied their utilization for live cell bio-imaging and the antimicrobial properties towards the Gram-positive Staphylococcus aureus and the Gram-negative Pseudomonas aeruginosa. Importantly, the Zn-NCDs could penetrate the biofilm and bacterial cell wall to effectively inhibit the growth of bacteria and subsequently inhibit biofilm formation. Thus, the structure, chemical composition, and low toxicity properties of the newly-developed Zn-NCDs exemplify a promising novel method for the preparation of nano-level antibacterial drugs.

Bioactive chitosan-citral Schiff base zinc complex: A pH-responsive platform for potential therapeutic applications.

The application of CO2 supercritical fluid (SCF) technology has developed rapidly because of its non-toxic, environmentally friendly, mild reaction conditions and safety. The SCF technology can effectively speed up the reaction process of nano-material synthesis, and maintains a high degree of controllability and repeatability. This study mainly included carboxymethyl chitosan sodium salt (CCS), citral (CT), p-coumaric acid (CA), and ZnSO4 as raw materials to prepare CCS-CT-CA-Zn complex as a pH-responsive agent and was investigated using supercritical fluid technique. The coordination structure of Bridge-CCS-CT-CH3COO-CA-Zn-Schiff base/OH and the morphology of the complex agents were verified. The prepared CCS-CT-CA-Zn complex showed good dispersion and uniformity (mean size: 852 ± 202 nm, PdI: 0.301, and mean zeta potential: -31 ± 6 mV). Also, it has a good pH responsive release in an acid environment. Besides, both of CCS-CT-CA-Zn complex (DS-B) and its decomposed mixture in acid (DS-A) demonstrated significant antioxidant and anti-vibrio activity. Moreover, both DS-B complex and DS-A mixture inhibited biofilm formation, swimming, and swarming motilities of V. parahaemolyticus in a dose-dependent manner. This work will provide a scientific basis for the further design and development of natural products derived antibacterial-antioxidant complex agents, food additives and feed additives.