Thiolated chitosan nanoparticles encapsulated nisin and selenium: antimicrobial/antibiofilm/anti-attachment/immunomodulatory multi-functional agent.

BACKGROUND: The increase in the resistance of bacterial strains to antibiotics has led to research into the bactericidal potential of non-antibiotic compounds. This study aimed to evaluate in vitro antibacterial/ antibiofilm properties of nisin and selenium encapsulated in thiolated chitosan nanoparticles (N/Se@TCsNPs) against prevalent enteric pathogens including standard isolates of Vibrio (V.) cholerae O1 El Tor ATCC 14,035, Campylobacter (C.) jejuni ATCC 29,428, Salmonella (S.) enterica subsp. enterica ATCC 19,430, Shigella (S.) dysenteriae PTCC 1188, Escherichia (E.) coli O157:H7 ATCC 25,922, Listeria (L.) monocytogenes ATCC 19,115, and Staphylococcus (S.) aureus ATCC 29,733. METHODS: The synthesis and comprehensive analysis of N/Se@TCsNPs have been completed. Antibacterial and antibiofilm capabilities of N/Se@TCsNPs were evaluated through broth microdilution and crystal violet assays. Furthermore, the study included examining the cytotoxic effects on Caco-2 cells and exploring the immunomodulatory effects of N/Se@TCsNPs. This included assessing the levels of both pro-inflammatory (IL-6 and TNFα) and anti-inflammatory (IL-10 and TGFß) cytokines and determining the gene expression of TLR2 and TLR4. RESULTS: The N/Se@TCsNPs showed an average diameter of 136.26 ± 43.17 nm and a zeta potential of 0.27 ± 0.07 mV. FTIR spectroscopy validated the structural features of N/Se@TCsNPs. Scanning electron microscopy (SEM) images confirmed their spherical shape and uniform distribution. Thermogravimetric Analysis (TGA)/Differential Scanning Calorimetry (DSC) tests demonstrated the thermal stability of N/Se@TCsNPs, showing minimal weight loss of 0.03%±0.06 up to 80 °C. The prepared N/Se@TCsNPs showed a thiol content of 512.66 ± 7.33 µmol/g (p < 0.05), an encapsulation efficiency (EE) of 69.83%±0.04 (p ≤ 0.001), and a drug release rate of 74.32%±3.45 at pH = 7.2 (p ≤ 0.004). The synthesized nanostructure demonstrated potent antibacterial activity against various isolates, with effective concentrations ranging from 1.5 ± 0.08 to 25 ± 4.04 mg/mL. The ability of N/Se@TCsNPs to reduce bacterial adhesion and internalization in Caco-2 cells underscored their antibiofilm properties (p ≤ 0.0001). Immunological studies indicated that treatment with N/Se@TCsNPs led to decreased levels of inflammatory cytokines IL-6 (14.33 ± 2.33 pg/mL) and TNFα (25 ± 0.5 pg/mL) (p ≤ 0.0001), alongside increased levels of anti-inflammatory cytokines IL-10 (46.00 ± 0.57 pg/mL) and TGFß (42.58 ± 2.10 pg/mL) in infected Caco-2 cells (p ≤ 0.0001). Moreover, N/Se@TCsNPs significantly reduced the expression of TLR2 (0.22 ± 0.09) and TLR4 (0.16 ± 0.05) (p < 0.0001). CONCLUSION: In conclusion, N/Se@TCsNPs exhibited significant antibacterial/antibiofilm/anti-attachment/immunomodulatory effectiveness against selected Gram-positive and Gram-negative enteric pathogens. However, additional ex-vivo and in-vivo investigations are needed to fully assess the performance of nanostructured N/Se@TCsNPs.

Discovering of Atomically Precise Metal Nanoclusters by High-Throughput Syntheses Platform.

Understanding the complete structure of noble metal nanoclusters is both academically and practically significant. However, progress has been hindered by the low synthetic efficiency of many nanocluster syntheses. In this study, we present the first high-throughput syntheses of homo-gold, homo-copper, and gold-copper alloy nanoclusters in dichloromethane at room temperature. Through high-throughput screening, we successfully obtained three nanoclusters in a single reaction: Au18(SC6H11)14, [Au41Cu66(SC6H11)44](SbF6)3, and an unidentified copper cluster (referred to as Au18, Au41Cu66 , and Cu-NC). The optimized synthesis route was achieved with the assistance of machine learning for experimental data analysis, which also guided the synthesis of other metal nanoclusters such as Au40Cu34(4-S-PhF)40 (Au40Cu34), [Au6Cu6(SPh)12]n ([Au6Cu6]n), and Au18Cu32(3,5-C8H9S)36 (Au18Cu32)). This research demonstrates that high-throughput screening can be a valuable tool in accelerating the development of nanocluster syntheses.

Equipment-Free Fabrication of Thiolated Reduced Graphene Oxide Langmuir-Blodgett Films: A Novel Approach for Versatile Surface Engineering.

This research presents a novel method for the fabrication of mercapto reduced graphene oxide (m-RGO) Langmuir-Blodgett (LB) films without the need for specialized equipment. The conventional LB technique offers precise control over the deposition of thin films onto solid substrates, but its reliance on sophisticated instrumentation limits its accessibility. In this study, we demonstrate a simplified approach that circumvents the necessity for such equipment, thereby democratizing the production of m-RGO LB films. Thiolation of reduced graphene oxide (rGO) imparts enhanced stability and functionality to the resulting films, rendering them suitable for a wide range of applications in surface engineering, sensing, and catalysis. The fabricated m-RGO LB films exhibit favorable morphological, structural, and surface properties, as characterized by various analytical techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). Furthermore, the performance of the m-RGO LB films is evaluated in terms of their surface wettability, electrochemical behavior, and chemical reactivity. The equipment-free fabrication approach presented herein offers a cost-effective and scalable route for the production of functionalized graphene-based thin films, thus broadening the scope for their utilization in diverse technological applications.

A General Protocol for Synthesizing Thiolated Folate Derivatives.

Folic acid (FA) has shown great potential in the fields of targeted drug delivery and disease diagnosis due to its highly tumor-targeting nature, biocompatibility, and low cost. However, FA is generally introduced in targeted drug delivery systems through macromolecular linkage via complex synthetic processes, resulting in lower yields and high costs. In this work, we report a general protocol for synthesizing thiolated folate derivatives. The small molecule thiolated folate (TFa) was first synthesized with a purity higher than 98.20%. First, S-S-containing diol was synthesized with a purity higher than 99.44 through a newly developed green oxidation protocol, which was carried out in water with no catalyst. Then, folic acid was modified using the diol through esterification, and TFa was finally synthesized by breaking the disulfide bond. Further, the synthesized TFa was utilized to modify silver nanoparticles. The results showed that TFa could be easily bonded to metal particles. The protocol could be extended to the synthesis of a series of thiolated derivatives of folate, such as mercaptohexyl folate, mercaptoundecyl folate, etc., which would greatly benefit the biological applications of FA.

Formulation and characterization of thiolated chitosan/polyvinyl acetate based microneedle patch for transdermal delivery of dydrogesterone.

Microneedle patches are promising transdermal drug delivery platforms with minimal invasiveness in a painless manner. Microneedle patch could be a promising alternate route for delivery of drugs having poor solubility and low bioavailability. This research work therefore, aimed to develop and characterize microneedle patch of thiolated chitosan (TCS) and polyvinyl acetate (PVA) for the systemic delivery of dydrogesterone (DYD). TCS-PVA-based microneedle patch was fabricated with 225 needles having a length of 575 µm with the sharp pointed end. Different ratios of TCS-PVA-based patch were employed to investigate the effects of mechanical tensile strength and percentage elongation. The scanning electron microscopy (SEM) revealed intact sharp-pointed needles. In vitro dissolution studies of microneedle patch (MN-P) were carried out by modified Franz-diffusion cell revealing the sustained release of DYD 81.45 ± 2.768 % at 48 hrs as compared to pure drug that showed 96.7 ± 1.75 % at 12 hrs. The transport of DYD (81%) across skin reaching the systemic circulation was evaluated through ex vivo permeation studies of MN-P. The skin penetration study through the parafilm M method showed good penetration with no deformation and breakage of needles along with no visible signs of skin irritation. Histological study of mice skins clearly showed the deeper penetration of needles into the skin. In summary, as-prepared MN-P show potential in developing an effective transdermal delivery system for DYD.

Partial Phosphorization: A Strategy to Improve Some Performance(s) of Thiolated Metal Nanoclusters Without Notable Reduction of Stability.

Thiolates endow metal nanoclusters with stability while sometimes inhibit the catalytic activity due to the strong M-S interaction (M: metal atom). To improve the catalytic activity and keep the stability to some extent, one strategy is the partial phosphorization of thiolated metal nanoclusters. This is demonstrated by successful partial phosphorization of Au23 (SC6 H11 )16 and by revealing that the products Au22 (SC6 H11 )14 (PPh3 )2 and Au22 (SC6 H11 )12 (PPh3 )4 , with varied degree of phosphorization, both show excellent activity in the photocatalytic oxidation of thioanisole without notable reduction of stability. Furthermore, Au22 (SC6 H11 )12 (PPh3 )4 exhibits better photoluminescence performance than the mother nanocluster Au23 (SC6 H11 )16 , indicating that partial phosphorization can also improve some other performance(s) except for the catalytic performance. The intermediates Au22-x Cux (SC6 H11 )12 (PPh3 )4 (x=1, 2) in the transformation from Au23 (SC6 H11 )16 (Au22 (SC6 H11 )14 (PPh3 )2 ) to Au22 (SC6 H11 )12 (PPh3 )4 were captured and identified by mass spectrometry and single crystal X-ray diffraction, which throws light on the understanding of the non-alloyed anti-galvanic reaction.

Evaluation of antimicrobial activity of thiolated methylated N-(4-N,N-dimethylaminobenzyl) chitosan as a new derivative of chitosan.

Despite chitosan, a natural cationic polysaccharide derived from chitin, being applied as an antimicrobial agent, many studies are being performed for enhancing its capability to fight against pathogens. The aim of this study was to investigate the antibacterial effect of thiolated methylated N-(4-N,N-dimethylaminobenzyl) chitosan (TTMAC) polymer and its nanoparticles as a novel derivation of chitosan. The polymer derivative was synthetized and characterized via 1 H NMR, Fourier transform infrared and the Elman test. The nanoparticles with different N/P ratios were prepared by the ionic gelation method and were characterized by dynamic light scattering and transmission electron microscopy. The cellular toxicity of polymer and nanoparticles at different concentrations were evaluated on human MCF-7 cell line. Antimicrobial assay was performed on Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923) and Candida albicans (ATCC 10231) as Gram-negative, Gram-positive and yeast pathogens, respectively. The obtained results have shown the TTMAC polymer has a higher inhibition activity against microbial pathogens and also lower cellular toxicity in comparison with chitosan polymer. Furthermore, chitosan nanoparticles in comparison with TTMAC nanoparticles have lower size and highest zeta potential in different ratio and chitosan nanoparticles have more inhibitory effects against microbial pathogens. In conclusion, TTMAC derivative in polymeric form can be a promising tool against microbial pathogens.

Blood Thiol Redox State in Chronic Kidney Disease.

Thiols (sulfhydryl groups) are effective antioxidants that can preserve the correct structure of proteins, and can protect cells and tissues from damage induced by oxidative stress. Abnormal levels of thiols have been measured in the blood of patients with moderate-to-severe chronic kidney disease (CKD) compared to healthy subjects, as well as in end-stage renal disease (ESRD) patients on haemodialysis or peritoneal dialysis. The levels of protein thiols (a measure of the endogenous antioxidant capacity inversely related to protein oxidation) and S-thiolated proteins (mixed disulphides of protein thiols and low molecular mass thiols), and the protein thiolation index (the molar ratio of the S-thiolated proteins to free protein thiols in plasma) have been investigated in the plasma or red blood cells of CKD and ESRD patients as possible biomarkers of oxidative stress. This type of minimally invasive analysis provides valuable information on the redox status of the less-easily accessible tissues and organs, and of the whole organism. This review provides an overview of reversible modifications in protein thiols in the setting of CKD and renal replacement therapy. The evidence suggests that protein thiols, S-thiolated proteins, and the protein thiolation index are promising biomarkers of reversible oxidative stress that could be included in the routine monitoring of CKD and ESRD patients.

Improved Mucoadhesion, Permeation and In Vitro Anticancer Potential of Synthesized Thiolated Acacia and Karaya Gum Combination: A Systematic Study.

Thiolation of polymers is one of the most appropriate approaches to impart higher mechanical strength and mucoadhesion. Thiol modification of gum karaya and gum acacia was carried out by esterification with 80% thioglycolic acid. FTIR, DSC and XRD confirmed the completion of thiolation reaction. Anticancer potential of developed thiomer was studied on cervical cancer cell lines (HeLa) and more than 60% of human cervical cell lines (HeLa) were inhibited at concentration of 5 µg/100 µL. Immobilized thiol groups were found to be 0.8511 mmol/g as determined by Ellman's method. Cytotoxicity studies on L929 fibroblast cell lines indicated thiomers were biocompatible. Bilayered tablets were prepared using Ivabradine hydrochloride as the model drug and synthesized thiolated gums as mucoadhesive polymer. Tablets prepared using thiolated polymers in combination showed more swelling, mucoadhesion and residence time as compared to unmodified gums. Thiol modification controlled the release of the drug for 24 h and enhanced permeation of the drug up to 3 fold through porcine buccal mucosa as compared to tablets with unmodified gums. Thiolated polymer showed increased mucoadhesion and permeation, anticancer potential, controlled release and thus can be utilized as a novel excipient in formulation development.

Nanotechnology based solutions for anti-leishmanial impediments: a detailed insight.

As a neglected tropical disease, Leishmaniasis is significantly instigating morbidity and mortality across the globe. Its clinical spectrum varies from ulcerative cutaneous lesions to systemic immersion causing hyperthermic hepato-splenomegaly. Curbing leishmanial parasite is toughly attributable to the myriad obstacles in existing chemotherapy and immunization. Since the 1990s, extensive research has been conducted for ameliorating disease prognosis, by resolving certain obstacles of conventional therapeutics viz. poor efficacy, systemic toxicity, inadequate drug accumulation inside the macrophage, scarce antigenic presentation to body's immune cells, protracted length and cost of the treatment. Mentioned hurdles can be restricted by designing nano-drug delivery system (nano-DDS) of extant anti-leishmanials, phyto-nano-DDS, surface modified-mannosylated and thiolated nano-DDS. Likewise, antigen delivery with co-transportation of suitable adjuvants would be achievable through nano-vaccines. In the past decade, researchers have engineered nano-DDS to improve the safety profile of existing drugs by restricting their release parameters. Polymerically-derived nano-DDS were found as a suitable option for oral delivery as well as SLNs due to pharmacokinetic re-modeling of drugs. Mannosylated nano-DDS have upgraded macrophage internalizing of nanosystem and the entrapped drug, provided with minimal toxicity. Cutaneous Leishmaniasis (CL) was tackling by the utilization of nano-DDS designed for topical delivery including niosomes, liposomes, and transfersomes. Transfersomes, however, appears to be superior for this purpose. The nanotechnology-based solution to prevent parasitic resistance is the use of Thiolated drug-loaded and multiple drugs loaded nano-DDS. These surfaces amended nano-DDS possess augmented IC50 values in comparison to conventional drugs and un-modified nano-DDS. Phyto-nano-DDS, another obscure horizon, have also been evaluated for their anti-leishmanial response, however, more intense assessment is a prerequisite. Impoverished Cytotoxic T-cells response followed by Leishmanial antigen proteins delivery have also been vanquished using nano-adjuvants. The eminence of nano-DDS for curtailment of anti-leishmanial chemotherapy and immunization associated challenges are extensively summed up in this review. This expedited approach is ameliorating the Leishmaniasis management successfully. Alongside, total to partial eradication of this disease can be sought along with associated co-morbidities.

Novel Chitosan-Silica Hybrid Hydrogels for Cell Encapsulation and Drug Delivery.

Hydrogels constructed from naturally derived polymers provide an aqueous environment that encourages cell growth, however, mechanical properties are poor and degradation can be difficult to predict. Whilst, synthetic hydrogels exhibit some improved mechanical properties, these materials lack biochemical cues for cells growing and have limited biodegradation. To produce hydrogels that support 3D cell cultures to form tissue mimics, materials must exhibit appropriate biological and mechanical properties. In this study, novel organic-inorganic hybrid hydrogels based on chitosan and silica were prepared using the sol-gel technique. The chemical, physical and biological properties of the hydrogels were assessed. Statistical analysis was performed using One-Way ANOVAs and independent-sample t-tests. Fourier transform infrared spectroscopy showed characteristic absorption bands including amide II, Si-O and Si-O-Si confirming formation of hybrid networks. Oscillatory rheometry was used to characterise the sol to gel transition and viscoelastic behaviour of hydrogels. Furthermore, in vitro degradation revealed both chitosan and silica were released over 21 days. The hydrogels exhibited high loading efficiency as total protein loading was released in a week. There were significant differences between TC2G and C2G at all-time points (p < 0.05). The viability of osteoblasts seeded on, and encapsulated within, the hydrogels was >70% over 168 h culture and antimicrobial activity was demonstrated against Pseudomonas aeruginosa and Enterococcus faecalis. The hydrogels developed here offer alternatives for biopolymer hydrogels for biomedical use, including for application in drug/cell delivery and for bone tissue engineering.

Attachment of Single-Stranded DNA to Certain SERS-Active Gold and Silver Substrates: Selected Practical Tips.

Layers formed from single-stranded DNA on nanostructured plasmonic metals can be applied as "working elements" in surface-enhanced Raman scattering (SERS) sensors used to sensitively and accurately identify specific DNA fragments in various biological samples (for example, in samples of blood). Therefore, the proper formation of the desired DNA layers on SERS substrates is of great practical importance, and many research groups are working to improve the process in forming such structures. In this work, we propose two modifications of a standard method used for depositing DNA with an attached linking thiol moiety on certain SERS-active structures; the modifications yield DNA layers that generate a stronger SERS signal. We propose: (i) freezing the sample when forming DNA layers on the nanoparticles, and (ii) when forming DNA layers on SERS-active macroscopic silver substrates, using ω-substituted alkanethiols with very short alkane chains (such as cysteamine or mercaptopropionic acid) to backfill the empty spaces on the metal surface unoccupied by DNA. When 6-mercapto-1-hexanol is used to fill the unoccupied places on a silver surface (as in experiments on standard gold substrates), a quick detachment of chemisorbed DNA from the silver surface is observed. Whereas, using ω-substituted alkanethiols with a shorter alkane chain makes it possible to easily form mixed DNA/backfilling thiol monolayers. Probably, the significantly lower desorption rate of the thiolated DNA induced by alkanethiols with shorter chains is due to the lower stabilization energy in monolayers formed from such compounds.

Thiolated Chitosan-Centella asiatica Nanocomposite: A Potential Brain Targeting Strategy Through Nasal Route.

The major challenge associated with the treatment of neurological disorders is the inefficiency of drugs to enter the Central Nervous System (CNS). Polymer-drug conjugates are now being tailored to overcome this hindrance associated with conventional drugs. The study aimed at developing polymer hybrid nasal nanocomposite for enhanced delivery of Centella to the CNS. Thiolated chitosan was complexed with Centella to form a composite using EDAC hydrochloride. The composite was characterized by FTIR, XRD, NMR, and MS. Further, this composite was converted into a nanoformulation by the ionic-gelation method, characterized, and subjected to ex vivo permeation studies. Additionally, MTT assay was performed using Human Uumbilical cord Vein Endothelial Cells (HUVECs) mimicking Blood-Brain Barrier (BBB) to establish the safety of nanocomposite. The targeting efficacy was predicted by molecular docking studies against receptors associated with BBB. The FTIR, XRD, NMR, and MS studies confirmed the chemical conjugation of thiolated chitosan with Centella. Nanocomposite characterization through SEM, AFM, and DLS confirmed the size and stability of the developed nanocomposite having a zeta potential of - 14.5 mV and PDI of 0.260. The nanocomposite showed no signs of nasal ciliotoxicity and good permeation of 89.44 ± 1.75% (mean ± SD, n = 3) at 8 h across the nasal mucosa. MTT assay showed that the nanocomposite had lesser toxicity compared to the free drug (IC50 of Centella-269.1 µg/mL and IC50 of CTC nanocomposite-485.375 µg/mL). The affinity of polymer to the BBB receptors as proved by docking studies suggests the ability of polymer-based nanocomposite to concentrate in the brain post nasal administration.

Bioadhesive hydrogel comprising bilirubin/ß-cyclodextrin inclusion complexes promote diabetic wound healing.

CONTEXT: Chronic non-healing diabetic wound therapy is an important clinical challenge. Manipulating the release of bioactive factors from an adhesive hydrogel is an effective approach to repair chronic wounds. As an endogenous antioxidant, bilirubin (BR) has been shown to promote wound healing. Nonetheless, its application is limited by its low water solubility and oxidative degradation. OBJECTIVE: This study developed a bilirubin-based formulation for diabetic wound healing. MATERIALS AND METHODS: Bilirubin was incorporated into ß-CD-based inclusion complex (BR/ß-CD) which was then loaded into a bioadhesive hydrogel matrix (BR/ß-CD/SGP). Scratch wound assays were performed to examine the in vitro pro-healing activity of BR/ß-CD/SGP (25 µg/mL of BR). Wounds of diabetic or non-diabetic rats were covered with BR or BR/ß-CD/SGP hydrogels (1 mg/mL of BR) and changed every day for a period of 7 or 21 days. Histological assays were conducted to evaluate the in vivo effect of BR/ß-CD/SGP. RESULTS: Compared to untreated (18.7%) and BR (55.2%) groups, wound closure was more pronounced (65.0%) in BR/ß-CD/SGP group. In diabetic rats, the wound length in BR/ß-CD/SGP group was smaller throughout the experimental period than untreated groups. Moreover, BR/ß-CD/SGP decreased TNF-α levels to 7.7% on day 3, and elevated collagen deposition and VEGF expression to 11.9- and 8.2-fold on day 14. The therapeutic effects of BR/ß-CD/SGP were much better than those of the BR group. Similar observations were made in the non-diabetic model. DISCUSSION AND CONCLUSION: BR/ß-CD/SGP promotes wound healing and tissue remodelling in both diabetic and non-diabetic rats, indicating an ideal wound-dressing agent.

Thiolated Nanoparticles Overcome the Mucus Barrier and Epithelial Barrier for Oral Delivery of Insulin.

Oral administration is an ideal alternative for drug delivery due to its convenience and safety. However, oral protein delivery is limited by biological barriers such as the mucus barrier and epithelial barrier, which hamper drugs from entering the blood successfully. Here we presented PC6/CS NPs, a thiolated-polymer-based nanodrug delivery system in the form of poly(acrylic acid)-cysteine-6-mercaptonicotinic acid (PAA-Cys-6MNA, PC6), which is a kind of preactivated thiolated polymer, coated on chitosan (CS) nanoparticles (NPs). Its ability to overcome the mucus barrier and epithelial barrier was investigated. The existence of PC6 made the NPs prone to penetrate the mucus layer as well as strengthened the transcellular transport of insulin on epithelial cells. PC6/CS NPs efficiently enhanced the oral bioavailability of insulin to 16.2%. The improvement resulted from the function of PC6: (1) "diluting" mucus to promote nanoparticle penetration, (2) opening a tight junction to help insulin transport via the paracellular pathway, (3) making the nanoparticle more electrically neutral during the penetration process, and (4) uncoating from PC6/CS NPs so that positive CS NPs were adhered and uptaken by epithelial cells. Our study proves that PC6/CS NPs, which can achieve mucus penetration and epithelial permeation efficiently, are a potential nanocarrier for oral protein delivery.

Polydopamine coated copper nanoclusters with aggregation-induced emission for fluorometric determination of phosphate ion and acid phosphatase activity.

The preparation of aggregation-induced emission-type copper nanoclusters (CuNCs) capped with polydopamine (PDA) is described. PDA was formed via in situ polymerization of dopamine in the presence of alkaline polyethylenimine. The PDA-capped CuNCs (PDA-CuNCs) exhibit orange fluorescence with maximal emission at 580 nm upon excitation at 340 nm, a storage stability of at least 2 weeks, and a quantum yield (QY) of 2.54% in aqueous solution. The QY is 28-fold higher than that of sole CuNCs. The fluorescence of the PDA-CuNCs is quenched by Fe3+ ion while it is recovered by PO43- due to its stronger affinity for Fe3+. On this basis, a fluorometric phosphate assay was developed that has a 1.5 nM detection limit and a linear range over 0.003-70 µM. The method was satisfactorily applied to the determination of phosphate in local tap water and human sera, and the results agreed well with those obtained by a colorimetric method. In the presence of acid phosphatase (ACP), PO43- is produced by the catalytic hydrolysis of adenosine triphosphate (ACP substrate). Thus, a fluorogenic assay for screening ACP activity was established. Response is linear over the activity range 0.0012-25 U L-1, with a detection limit of 0.001 U L-1 (at S/N = 3). Graphic abstract We proposed an effective polydopamine-templating strategy for the in situ synthesis of highly emissive and stable CuNCs and demonstrated its use as an ion-driven fluorescence switch for the determination of phosphate and acid phosphatase activity.

Ultra-sensitive amperometric determination of quercetin by using a glassy carbon electrode modified with a nanocomposite prepared from aminated graphene quantum dots, thiolated ß-cyclodextrin and gold nanoparticles.

Thiolated ß-cyclodextrin functionalized gold nanoparticles (Au-ß-CDs) with layered wrinkled flower structure were prepared. Au-ß-CDs were electrostatically combined with protonated aminated graphene quantum dots (NH2-GQDs) to form a nanocomposite with better supramolecular recognition, conductivity, catalysis and dispersion properties. For constructing a quercetin (QU) sensor, the nanocomposites were one-step electrodeposited by a cyclic voltammetry (CV) method onto a glassy carbon electrode to form a stable film. Under optimized conditions, the sensor showed a wide linear response range of 1-210 nM, with a lower detection limit of 285 pM. At the same time, flavonoids with similar structures hardly interfere with the determination of QU. The sensor has been used to determine QU in honey, tea, honeysuckle and human serum with satisfactory results. Graphical abstractSchematic representation of the fabrication of an ultrasensitive quercetin electrochemical sensor based on aminated graphene quantum dots, thiolated ß-cyclodextrin and gold nanoparticles (NH2-GQDs/Au-ß-CD/GCE).

Simultaneous electrochemical determination of ochratoxin A and fumonisin B1 with an aptasensor based on the use of a Y-shaped DNA structure on gold nanorods.

A complementary DNA (cDNA) was designed to simultaneously hybridize with the ochratoxin A (OTA) aptamer and the fumonisin B1 (FB1) aptamer to form a unique Y-shaped DNA structure and to achieve simultaneous detection. Gold nanorods (AuNRs) were used to immobilize thionine (Th), thiolated ferrocene (Fc), thiolated OTA aptamer (Apt1), and thiolated FB1 aptamer (Apt2), to form an amplified signal element and a recognition element. The Apt1-AuNRs-Th complex and the Apt2-AuNRs-Fc complex hybridize with cDNA to form a unique Y-DNA structure on a gold electrode. This produces two initial electrochemical signals [with 177 µΑ cm-2 near -0.2 V, and 3121 µΑ cm-2 near +0.46 V (vs. Ag/AgCl)] by differential pulse voltammetry. Upon addition of 0.1 ng mL-1 OTA and 0.1 ng mL-1 FB1, the aptamers bind the two toxins. This results in the release of Apt1-AuNRs-Th and Apt2-AuNRs-Fc, so the peak currents densities decrease to 115 µΑ cm-2 and 209 µΑ cm-2. The assay allows simultaneous determination of OTA and FB1 in the 1.0 pg·mL-1 to 100 ng·mL-1 concentration ranges, with LODs of 0.47 and 0.26 pg·mL-1. The assay is reproducible, stable and specific. It was applied to the determination of OTA and FB1 in spiked beer, with recoveries between 89.0% and 102.0%. Graphical abstractSchematic representation of OTA and FB1 detection based on Apt2-AuNRs-Fc/Apt1-AuNRs-Th/cDNA/AuE. (AuNRs: Gold nanorods; Th: thionine; Fc: ferrocene; SH: thiol; BSA: Bovine serum albumin; cDNA: Complementary DNA; Apt1: Aptamer1; Apt2: Aptamer2; OTA: Ochratoxin A; FB1: Fumonisin B1).

Fabrication and Characterization of Thiolated Chitosan Microneedle Patch for Transdermal Delivery of Tacrolimus.

Microneedle patch is a prominent strategy with minimal invasion and painless application to improve skin penetration of drug molecules. Herein, we report microneedle patch (MNP) as an alternative to the oral route for the systemic delivery of tacrolimus (TM), an immunosuppressant drug. Thiolated chitosan (TCS) based microneedle patch was fabricated and characterized in vitro and in vivo for its mechanical strength, skin penetration, drug release, and skin irritation. The MNP having 225 needles with 575 µm showed good mechanical properties in terms of tensile strength and percentage elongation. The skin penetration showed 84% penetration with no breakage. Histology of the mice skin after insertion showed the penetration of needles into the dermis. In vitro release and ex vivo permeation studies through Franz diffusion cell showed the sustained release (82.5%) of TM from the MNP with significantly higher (p < 0.05) skin permeation as compared with controls, respectively. Moreover, in vivo biocompatibility in rats showed the safety of the material and patch. Thus, the TCS microneedle patch has the potential to be developed as a transdermal delivery system for tacrolimus with improved bioavailability and sustained release over a longer period.

Development and Characterization of Bioadhesive Film Embedded with Lignocaine and Calcium Fluoride Nanoparticles.

The formation of biofilm by Streptococcus mutans on the tooth surface is the primary cause of dental caries and periodontal diseases, and fluoride (F) has shown tremendous potential as a therapeutic moiety against these problems. Herein, we report an efficient multi-ingredient bioadhesive film-based delivery system for oral cavity to combat dental problems with an ease of administration. Thiolated chitosan-based bioadhesive film loaded with calcium fluoride nanoparticles (CaF2 NPs) and lignocaine as a continuous reservoir for prolonged delivery was successfully prepared and characterized. The polygonal CaF2 NPs with an average particle size less than 100 nm, PDI 0.253, and + 6.10 mV zeta potential were synthesized and loaded in film. The energy dispersive x-ray (EDX) spectroscopy confirmed the presence 33.13% F content in CaF2 NPs. The characterization of the three film trials for their mechanical strength, bioadhesion, drug release, and permeation enhancement suggested film B as better among the three trials and showed significant outcomes, indicating the potential application of the medicated bioadhesive film. In vitro dissolution studies revealed sustained release pattern of lignocaine and CaF2 NP following Krosmeyer-Peppas model over 8 h. Franz diffusion studies showed the prolonged contact time of film with mucosa that facilitated the transport of CaF2 NPs and lignocaine across the mucosa. Hence, the prepared bioadhesive film-based system showed good potential for better management of dental problems. Graphical Abstract.