Modified Au nanoparticles-imprinted sol–gel, multiwall carbon nanotubes pencil graphite electrode used as a sensor for ranitidine determination

Antibacterial self-healing bilayer dressing for epidermal sensors and accelerate wound repair

This study aimed to investigate the effect of the bilayer hydrogel as a wound dressing on the wound-healing rate. We synthesized a self-healing hydrogel with optimized formulation by introducing natural polymer (chitosan) and arginine to the hydrogel composition. We then characterized the hydrogels using FT-IR, thermal analysis, mechanical testing, and in vitro and in vivo assay. The resulting bilayer wound dressing offers a lot of desirable characteristics, including good self-healing and repeatable adhesiveness. Likewise, the conductive bilayer wound dressing could be used to analyze the patient's healthcare data in real-time as epidermal sensors. Bilayer wound dressings remarkably have broad antibacterial efficacy against Gram-positive and Gram-negative bacteria. The potential applications of this bilayer wound dressing are illustrated by detectable body movement and conductivity. The wound-healing rate of bilayer wound dressings containing chitosan and arginine was higher, but those without the aforementioned ingredients had lower wound-healing efficacy. Additionally, promoting collagen synthesis and reducing wound infection has a considerable therapeutic impact on wounds. These results could have significant implications for the development of high-performance wound dressings.

Recent Developments in Voltammetric Analysis of Pharmaceuticals Using Disposable Pencil Graphite Electrodes

The even growing production of both well-known and new derivatives with pharmaceutical action involves the need for developing facile and reliable methods for the analysis of these compounds. Among the widely used instrumental techniques, the electrochemical ones are probably the simplest and the most rapid, also having good performance characteristics. However, the key tool in electroanalysis is the working electrode. Due to the inherent electrochemical and economic advantages of the pencil graphite electrode (PGE), the interest in its applicability in the analysis of different analytes has continuously increased in recent years. Thus, this paper aims to review the scientific reports published in the last 10 years on the use of the disposable eco- and user-friendly PGEs in the electroanalysis of compounds of pharmaceutical importance in different matrices. The PGE characteristics and designs (bare or modified with various types of materials), along with their applications and performance parameters (e.g., linear range, limit of detection, and reproducibility), will be discussed, and their advantages and limitations will be critically emphasized.

L-Menthol-Loadable Electrospun Fibers of PMVEMA Anhydride for Topical Administration

Poly(methyl vinyl ether-alt-maleic anhydride) (PMVEMA) of 119 and 139 molecular weights (P119 and P139, respectively) were electrospun to evaluate the resulting fibers as a topical delivery vehicle for (L-)menthol. Thus, electrospinning parameters were optimized for the production of uniform bead-free fibers from 12% w/w PMVEMA (±2.3% w/w menthol) solutions, and their morphology and size were characterized by field emission scanning electron microscopy (FESEM). The fibers of P119 (F119s) and P139 (F139s) showed average diameter sizes of approximately 534 and 664 nm, respectively, when unloaded, and 837 and 1369 nm when loaded with menthol. The morphology of all types of fibers was cylindrical except for F139s, which mostly displayed a double-ribbon-like shape. Gas chromatography-mass spectrometry (GC-MS) analysis determined that not only was the menthol encapsulation efficiency higher in F139s (92% versus 68% in F119s) but also that its stability over time was higher, given that in contrast with F119s, no significant losses in encapsulated menthol were detected in the F139s after 10 days post-production. Finally, in vitro biological assays showed no significant induction of cytotoxicity for any of the experimental fibers or in the full functionality of the encapsulated menthol, as it achieved equivalent free-menthol levels of activation of its specific receptor, the (human) transient receptor potential cation channel subfamily M (melastatin) member 8 (TRPM8).

Preparation of Dawson heteropolyacid-embedded silver nanoparticles/graphene oxide nanocomposite thin film used to modify pencil graphite electrode as a sensor for trace electrochemical sensing of levodopa

Measurement of levodopa (LD) as the most efficient treatment accessible for controlling the symptoms of Parkinson's disease was investigated. The electrocatalytic measurement of LD was performed at the surface of pencil graphite electrode (PGE) modified with graphene oxide (GO) and silver nanoparticle@Dawson heteropolyacid (AgNPs@DHPA). For this purpose, GO and the intermediate (AgNPs@DHPA) were first synthesized using a simple, cost-effective and straightforward method. The synthetic compounds, morphology, and surface characteristics of the modified sensor were evaluated. The results demonstrated that AgNPs@DHPA well-dispersed on the GO/PGE surface with a mean size of 6.27 nm and thickness of 42 nm. The electrochemical behavior of the modified PGE was also investigated. The heterogeneous charge transfer rate constant (k_s) and transfer coefficient (α) for the electron transfer between AgNPs@DHPA/GO and PGE were obtained as 16.44 s^-1 and 0.59, respectively. Also, the diffusion coefficient of LD for AgNPs@DHPA/GO/PGE thin film was calculated using chronoamperometric experiments (D = 9.05 × 10^-6 cm² s^-1). Optimal parameters were obtained to access the best response for the measurement of LD. The results revealed that the modified PGE was able to measure the trace amounts of LD in phosphate buffer solution (pH = 6.0) in the concentration ranges from 3.0 × 10^-9 to 1.0 × 10^-7 M and 1.0 × 10^-7 to 1.0 × 10^-5 M. The calculated limit of detection was obtained 7.6 × 10^-10 M which was much better than the previously reported electrochemical sensors. The modified electrode was used to measure LD in tablet, blood serum and urine.

Molecularly imprinted sol-gel electrochemical sensor for sildenafil based on a pencil graphite electrode modified by Preyssler heteropolyacid/gold nanoparticles/MWCNT nanocomposite

An electrochemical sensor based on the imprinted sol-gel on pencil graphite electrode (PGE) modified with functionalized multiwalled carbon nanotube (MWCNT), gold nanoparticles (AuNPs), and Preyssler heteropolyacid (PHPA) nanohybrid was fabricated for the determination of trace amounts of sildenafil. The pencil graphite electrode was first deposited by the AuNPs@PHPA-MWCNT nanohybrids, and then, the modified electrode of MIP-sol-gel/AuNPs@PHPA-MWCNTs was prepared by the electrochemical method. The synthesized nanohybrids and prepared modified electrodes were characterized with FE-SEM, FTIR, EDX, XRD, and UV/Vis. Cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry techniques were applied for the electrochemical analysis using the modified electrodes. By measuring the oxidation and reduction currents of the potassium ferricyanide probe, the efficiency of this sensor was evaluated for the detection of sildenafil. The anodic peak current was measured at 0.2 V vs. Ag/AgCl by differential pulse voltammetry in the potential range - 0.1 to 0.5 V (vs. Ag/AgCl). Under the optimum conditions, the current response for the detection of sildenafil was linear in two concentration ranges of 0.1-2 and 2-30 nM and the obtained limit of detection was 0.033 nM. The constructed sensor was used for the measurement of sildenafil in real samples.

Sensitive imprinted optical sensor based on mesoporous structure and green nanoparticles for the detection of methamphetamine in plasma and urine

Methamphetamine (MA), a psychoactive substance with many medicinal applications in different countries, has destructive impacts on the nervous system and brain and can lead to addiction. The optimal system for MA determination must be able to measure the tiny amount of MA in complex matrixes accurately. In the current work, a simple and biocompatible sensitive optical probe was developed based on molecularly imprinted polymers (MIPs) technique and by using green CQDs and mesoporous structured imprinting microspheres (SiO₂@CQDs@ms-MIPs). CQDs (Ф_F = 33%) were synthesized via the hydrothermal method using natural chewing gum as carbon source. SiO₂ nanoparticles were used as the backup substrate for the placement of CQDs. In spite of biocompatibility, porosity and having high specific area are the unique features of SiO₂ nanoparticles. When MA is present, the fluorescence response of MIPs enhances. This is caused by the passivation and adjustment of active clusters that are present on the surface of CQDs. By this optical sensor, the favorable linear dynamic range (5.0-250 μM) and the detection limit (1.6 μM) were obtained. The applicability of the advanced sensor was studied in real samples such as human urine and human blood plasma. Acceptable results were obtained and recovery amounts were in the 92-110% interval.

Voltammetric Techniques for the Analysis of Drugs using Nanomaterials based Chemically Modified Electrodes

Background:

Electroanalytical techniques play a very important role in the areas of medicinal, clinical as well as pharmaceutical research. Amongst these techniques, the voltammetric methods for the determination of drugs using nanomaterials based chemically modified electrodes (CMEs) have received enormous attention in recent years. This is due to the sensitivity and selectivity they provide on qualitative as well as quantitative aspects of the electroactive analyte under study. The aim of the present review was to discuss the work on nanomaterials based CMEs for the analysis of drugs covering the period from 2000 to present employing various voltammetric techniques for different classes of the drugs.

Methods:

The present review deals with the determination of different classes of drugs including analgesics, anthelmentic, anti-TB, cardiovascular, antipsychotics and anti-allergic, antibiotic and gastrointestinal drugs. Also, a special section is devoted for enantioanalysis of certain chiral drugs using voltammetry. The detailed information of the voltammetric determination for the drugs from each class employing various techniques such as differential pulse voltammetry, cyclic voltammetry, linear sweep voltammetry, square wave voltammetry, stripping voltammetry, etc. are presented in tabular form below the description of each class in the review.

Results:

Various nanomaterials including carbon nanotubes, graphene, carbon nanofibers, quantum dots, metal/metal oxide nanoparticles, polymer based nanocomposites have been used by researchers for the development of CMEs over a period of time. The large surface area to volume ratio, high conductivity, electrocatalytic activity and biocompatibility make them ideal modifiers where they produce synergistic effect which helps in trace level determination of pharmaceutical, biomedical and medicinal compounds. In addition, macrocyclic compounds as chiral selectors have been used for the determination of enantiomeric drugs where one of the isomers captured in the cavities of chiral selector shows stronger binding interaction for one of the enantiomorphs.

Conclusion:

arious kinds of functional nanocomposites have led to the manipulation of peak potential due to drug - nanoparticles interaction at the modified electrode surface. This has facilitated the simultaneous determination of drugs with almost similar peak potentials. Also, it leads to the enhancement in voltammetric response of the analytes. It is expected that such modified electrodes can be easily miniaturized and used as portable, wearable and user friendly devices. This will pave a way for in-vivo onsite real monitoring of single as well as multi component pharmaceutical compounds.

A novel optical sensor based on carbon dots embedded molecularly imprinted silica for selective acetamiprid detection

A molecularly imprinted polymer (MIP) on silane-doped carbon dots (Si-CDs) has been synthesized as a novel optical sensor for selective detection of acetamiprid (ACT). Highly fluorescence Si-CDs have been first prepared by hydrothermal method. Subsequently, MIP has been formed on the surface of Si-CDs (MIP@Si-CDs) by a sol-gel process. The properties and structure of the Si-CDs and MIP@Si-CD nanocomposites have been characterized by fluorescence spectroscopy, UV-Vis absorption spectroscopy, transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, and X-ray diffraction techniques. Various parameters, which affect the optical signal, have been optimized. The fluorescence signal of MIP@Si-CDs showed linear response with ACT concentration in the 7-107 nM range with a detection limit of 2 nM and a precision of 2.7% and 3.3% for five replicate detections of 17 and 33 nM ACT under optimal conditions. In addition, the sensor has been satisfactorily utilized for the detection of ACT content in real samples.

Pencil Graphite Electrodes: A Versatile Tool in Electroanalysis

Due to their electrochemical and economical characteristics, pencil graphite electrodes (PGEs) gained in recent years a large applicability to the analysis of various types of inorganic and organic compounds from very different matrices. The electrode material of this type of working electrodes is constituted by the well-known and easy commercially available graphite pencil leads. Thus, PGEs are cheap and user-friendly and can be employed as disposable electrodes avoiding the time-consuming step of solid electrodes surface cleaning between measurements. When compared to other working electrodes PGEs present lower background currents, higher sensitivity, good reproducibility, and an adjustable electroactive surface area, permitting the analysis of low concentrations and small sample volumes without any deposition/preconcentration step. Therefore, this paper presents a detailed overview of the PGEs characteristics, designs and applications of bare, and electrochemically pretreated and chemically modified PGEs along with the corresponding performance characteristics like linear range and detection limit. Techniques used for bare or modified PGEs surface characterization are also reviewed.

Novel flow injection spectrophotometric determination of ranitidine in pharmaceuticals

A novel flow injection spectrophotometric determination of ranitidine in pharmaceuticals is reported. The method is based on a compound formed in a reaction using ranitidine with and potassium permanganate in neutral media, which can be monitored at 430 nm. Under optimal conditions, an analytical curve was constructed, which was linear in the range between 5.0 × 10−5 and 1.0 × 10−3 mol L−1 with a detection limit of 1.0 × 10−5 mol L−1. In addition, the sample throughput was 60 h−1 and the obtained results for commercial formulation samples by applying the proposed method were in good agreement with labeled values and those obtained by a reference method at a 95% confidence level.

Functionalization of Smart Gels with Beta-Cyclodextrin and Release Characteristics to Simulating Drugs

Smart gels have many applications in sensors, actuators, shape memory intelligent devices, recognition, self-healing, drug release, biomimetic soft robot design, biomimetic tactile, neural regeneration, biomimetic membranes, supercapacitor, dye-sensitized solar cells, advanced lithium polymer batteries, environmental fields, biomedical fields, et al. And that cyclodextrins are one of the typical macrocycles with good recognition ability, and endowed with fascinating hydrophobic cavities and hydrophilic surface, which enable the encapsulation of diverse small organic molecules by forming inclusion complexes. In this paper, grafted copolymerization between acrylic acid and N,N-dimethyl acrylamide in the presence of water-soluble cyclodextrins was carried out. The effect of ratio of copolymerization monomer on the grafted polymer was examined. The results indicated that self-crosslinking smart gel with multi-stimuli responsive was obtained by selecting suitable the ratio of copolymerization monomer, its behaviors of swelling/shrinking were examined. The adsorption properties and releasing characteristics of smart gel were performed with simulating drugs. Some meaningful results were obtained. These series grafted copolymer would also be used to modify the surface and interface properties of low-dimensional functional materials or heterostructured nanocomposites for intelligent organic-inorganic functional nanocomposites, some good results were obtained.