Determination of the critical micelle concentration by absorbance and fluorescence techniques using fluorescein probe

Micelle-mediated synthesis of quinoxaline, 1,4-benzoxazine and 1,4-benzothiazine scaffolds from styrenes

A range of heterocycles based on quinoxalines, 1,4-benzoxazines and 1,4-benzothiazines have been accessed from styrenes by reacting them with benzene-1,2-diamine, 2-aminophenol and 2-aminothiophenol respectively in micellar medium. This reaction occurring in a less explored cetylpyridinium bromide (CPB) micellar medium operates in the presence of NBS through a tandem hydrobromination-oxidation cascade, converting styrenes to phenacyl bromides. Its subsequent nucleophilic addition with aromatic 1,2-dinucleophiles and further transformations led to the formation of heterocyclic constructs. The locus of the reaction site was confirmed through NMR studies and the types of interactions between the CPB and solubilizates were established by DFT calculations.

Presenting a new fluorescent probe, methyl(10-phenylphenanthren-9-yl)sulfane sensitive to the polarity and rigidity of the microenvironment: applications toward microheterogeneous systems

A molecule, methyl(10-phenylphenanthren-9-yl)sulfane (MPPS), with a straightforward structure, has been synthesized, characterized, and explored as a new fluorescent probe for microheterogeneous systems. The photophysical properties of MPPS have been studied through experimental and theoretical calculations using the range-separated hybrid functional CAM-B3LYP in conjunction with a 6-311++g(d,p) basis set. Theoretical calculations show that the freely rotating phenyl ring forms a 94° dihedral angle with the phenanthrene ring in the ground state. Experimentally found two absorption bands correspond to the n → π* and π → π* transitions supported by the frontier molecular orbital calculations. Two excited singlet states, E-1 and E-2 (the former being more stable than the latter in the gas phase), exist with dihedral angles between the phenyl and phenanthrene rings as 142° and 133°, respectively, in the gas phase. Two emitting states in a condensed medium of varying polarities are supported by the steady-state fluorescence and fluorescence intensity decay data. Emission energies, fluorescence intensities, and excited singlet state lifetimes change with the polarity of the solvents. To support that the free rotation in the molecule is responsible for these changes, the fluorescence properties of another molecule, methyl(10-(o-tolyl)phenanthren-9-yl)sulfane (MTPS), with restricted rotation of the substituted benzene, i.e., o-tolyl ring have been studied. The fast-intensity decay component of MPPS is ascribed to the conformer in the E-1 state. The molecule has proved to be an excellent polarity probe explored to determine the critical micelle concentrations (cmc) values of different surfactants, which agree well with the literature reports. Different regions of binding isotherm (specific, non-cooperative, cooperative, and massive binding) of a gemini surfactant, 12-6-12,2Br- with bovine serum albumin (BSA) have been successfully demonstrated by the steady-state and time-resolved fluorescence and fluorescence anisotropic properties of MPPS. Docking results show that MPPS resides in the hydrophobic pocket of BSA. The fluorescence quenching of BSA by MPPS reveals the location of Trp residues of BSA. Thus, a polarity and molecular rigidity-sensitive fluorescent molecule, MPPS has been presented here that can potentially be used to monitor the changes in the microenvironment of biomolecules in different processes.

Preparation of pH-sensitive carboxymethyl chitosan nanoparticles loaded with ginsenoside Rb1 and evaluation of drug release in vitro

Oral absorption of ginsenoside Rb1 (Rb1) is often hindered by the gastrointestinal tract. Carboxymethyl chitosan deoxycholic acid loaded with ginsenoside Rb1 nanoparticles (CMDA@Rb1-NPs), were prepared as a delivery system using a self-assembly technique with amphipathic deoxycholic acid grafted carboxymethyl chitosan as the carrier, which improved the stability and embedding rate of Rb1. In addition, the CMDA@Rb1-NPs was encapsulated with sodium alginate by ion crosslinking method with additional layer (CMDAlg@Rb1-NPs). Scanning electron microscopy showed that the nanoparticles were spherical, evenly distributed, smooth and without obvious adhesion. By evaluating drug loading, entrapment efficiency, the encapsulation efficiency of Rb1 increased from 60.07 % to 72.14 % after grafting deoxycholic acid improvement and optimization. In vitro release results showed that the cumulative release of Rb1 by CMDAlg-NPs showed a pH dependent effect, which was <10 % in simulated gastric juice with pH 1.2, completely released with pH 7.4 for about 48 h. In addition, Rb1 and CMDAlg@Rb1-NPs had inhibitory effects on A549 cells, and the inhibitory effect of CMDAlg@Rb1-NPs was better. Therefore, all results indicated that CMDA/Alg@Rb1 nanoparticles might be a novel drug delivery system to improve the stability and embedding rate of Rb1, and has the potential to be applied in oral pharmaceutical preparations.

A novel amidine-based fluorescent probe TPE-4+ for rapid detection of anionic surfactant sodium dodecyl sulfate

An accurate, fast, and simple surfactant detection method is of great significance for monitoring surfactants pollution. Sodium dodecyl sulfate (SDS) is one of the most commonly used anionic surfactants and has been listed as an important monitoring pollutant for surfactant residues. Herein, a novel fluorescent probe named TPE-4+ with four amidines as the recognition functional group and tetraphenylethene as the fluorophore was fabricated. Due to the special intramolecular environment, the probe showed selectively identification towards SDS which made an aggregation induced fluorescence enhencement. Under the optimum conditions, the fluorescence enhencement of TPE-4+ is linearly related to the concentration of SDS in the range of 5.0-60.0 μM with limit of detection (LOD) of 0.010 μM and limit of quantification (LOQ) of 0.034 μM. Relative to the reported methods, the probe in our work showed better selectivity and sensitivity. The proposed method was successfully applied for the SDS determination of disinfecting bowls.

Innovative Real-Time Flow Sensor Using Detergent-Free Complex Emulsions with Dual-Emissive Semi-Perfluoroalkyl Substituted Α-Cyanostilbene

In this study, the potential of complex emulsions is investigated as transducers in sensing applications. Complex emulsions are stabilized without external detergents by developing a novel α-cyanostilbene substituted with PEG and semi-perfluoroalkyl chain (CNFCPEG). CNFCPEG exhibits unique variable emission properties depending on its aggregation state, allowing dual blue and green emissions in complex emulsions with hydrocarbon-in-fluorocarbon-in-water (H/F/W) morphology. The green excimer emissions result from the self-assembly of CNFCPEG at the fluorocarbon/water interface, while the blue emission observed is due to aggregation in the organic phase. A novel flow-injection method is developed by incorporating complex emulsions with CNFCPEG into multiple-well flow chips (MWFC). Iodine is successfully detected in a mobile aqueous solution by monitoring morphology changes. The findings demonstrate that self-stabilized complex emulsions with MWFC hold great promise for real-time sensing without costly instruments.

PEG Gels Significantly Improve the Storage Stability of Nucleic Acid Preparations

Currently, nucleic acid preparations have gained much attention due to their unique working principle and application value. However, as macromolecular drugs, nucleic acid preparations have complex construction and poor stability. The current methods to promote stability face problems such as high cost and inconvenient operatios. In this study, the hydrophilic pharmaceutical excipient PEG was used to gelate nucleic acid preparations to avoid the random movements of liquid particles. The results showed that PEG gelation significantly improved the stability of PEI25K-based and liposome-based nucleic acid preparations, compared with nucleic acid preparations without PEG gelation. After being stored at 4 °C for 3 days, non-PEG gelled nucleic acid preparations almost lost transfection activity, while PEGylated preparations still maintained high transfection efficiency. Fluorescence experiments showed that this effect was caused by inhibiting particle aggregation. The method described in this study was simple and effective, and the materials used had good biocompatibility. It is believed that this study will contribute to the better development of gene therapy drugs.

Direct and Reverse Pluronic Micelles: Design and Characterization of Promising Drug Delivery Nanosystems

Pluronics are a family of amphiphilic block copolymers broadly explored in the pharmaceutical field. Under certain conditions, Pluronics self-assemble in different structures including nanosized direct and reverse micelles. This review provides an overview about the main parameters affecting the micellization process of Pluronics, such as polymer length, fragments distribution within the chain, solvents, additives and loading of cargo. Furthermore, it offers a guide about the most common techniques used to characterize the structure and properties of the micelles. Finally, it presents up-to-date approaches to improve the stability and drug loading of Pluronic micelles. Special attention is paid to reverse Pluronics and reverse micelles, currently underexplored in the literature. Pluronic micelles present a bright future as drug delivery agents. A smart design and thorough characterization will improve the transfer to clinical applications.

Dual acting acid-cleavable self-assembling prodrug from hyaluronic acid and ciprofloxacin: A potential system for simultaneously targeting bacterial infections and cancer

The incidence and of bacterial infections, and resulting mortality, among cancer patients is growing dramatically, worldwide. Several therapeutics have been reported to have dual anticancer and antibacterial activity. However, there is still an urgent need to develop new drug delivery strategies to improve their clinical efficacy. Therefore, this study aimed to develop a novel acid cleavable prodrug (HA-Cip) from ciprofloxacin and hyaluronic acid to simultaneously enhance the anticancer and antibacterial properties of Cip as a superior drug delivery system. HA-Cip was synthesised and characterised (FT-IR, HR-MS, and H1 NMR). HA-Cip generated stable micelles with an average particle size, poly dispersion index (PDI) and zeta potential (ZP) of 237.89 ± 25.74 nm, 0.265 ± 0.013, and -17.82 ± 1.53 mV, respectively. HA-Cip showed ≥80 % cell viability against human embryonic kidney 293 cells (non-cancerous cells), ˂0.3 % haemolysis; and a faster pH-responsive ciprofloxacin release at pH 6.0. HA-Cip showed a 5.4-fold improvement in ciprofloxacin in vitro anticancer activity against hepatocellular cancer (HepG2) cells; and enhanced in vitro antibacterial activity against Escherichia coli and Klebsiella pneumoniae at pH 6.0. Our findings show HA-Cip as a promising prodrug for targeted delivery of ciprofloxacin to efficiently treat bacterial infections associated, and/or co-existing, with cancer.

Supramolecular self-associating amphiphiles: determination of molecular self-association properties and calculation of critical micelle concentration using a high-throughput, optical density based methodology

Supramolecular self-associating amphiphiles are a class of amphiphilic salt, the anionic component of which is 'frustrated' in nature, meaning multiple hydrogen bonding modes can be accessed simultaneously. Here we derive critical micelle concentration values for four supramolecular self-associating amphiphiles using the standard pendant drop approach and present a new high-throughput, optical density measurement based methodology, to enable the estimation of critical micelle concentrations over multiple temperatures. In addition, we characterise the low-level hydrogen bonded self-association events in the solid state, through single crystal X-ray diffraction, and in polar organic DMSO-d₆ solutions using a combination of ¹H NMR techniques. Moving into aqueous ethanol solutions (EtOH/H₂O or EtOH/D₂O (1 : 19 v/v)), we also show these amphiphilic compounds to form higher-order self-associated species through a combination of ¹H NMR, dynamic light scattering and zeta potential studies.

Effect of amino acid on the surface adsorption and micellar properties of surface active ILs varying in cationic head groups

The interfacial along with bulk characteristics of the aqueous solutions of ILs with dissimilar cationic head group viz. 1-dodecyl-3-methylimidazolium bromide ([C₁₂mim][Br]), and N-dodecyl-N-methylmorpholinium bromide ([Mor_1,12][Br]) in the absence and the presence of an amino acid L-Methionine as an external additive have been examined by electrical conductivity, UV-Visible, surface tension, and DLS measurements. The CMC values, and the lowest maximum surface excess concentration (Г_max) achieved from all three techniques, and surface tension measurements respectively displayed more surface activity of the [C₁₂mim][Br] than the [Mor_1,12][Br]. Also, the morpholinium head group is less hazardous than imidazolium, it can be utilised to design ILs that are greener, mainly in combination with polar, small, and non-toxic side chains and anions.

N-acetylneuraminic acid and chondroitin sulfate modified nanomicelles with ROS-sensitive H2S donor via targeting E-selectin receptor and CD44 receptor for the efficient therapy of atherosclerosis

Currently, very limited therapeutic approaches are available for the drug treatment of atherosclerosis(AS). H2S-donor is becoming a common trend in much life-threatening research. Several studies have documented that H2S-lyase is predominantly present in endothelial cells. N-Acetylneuraminic acid (SA), natural carbohydrate, binds specifically to the E-selectin receptor of endothelial cells. Meanwhile, recent studies related to Chondroitin sulfate have excellent target binding ability with CD44 receptor. We conjecture that the N-Acetylneuraminic acid and Chondroitin sulfate modified nanomicelles not only enhances the accumulation of the drug but also cleaves the H2S donor in the lesion, thus one stone two birds. Given these findings, we synthesized two kinds of nanoparticles, Carrier I (SCCF) and Carrier II (SCTM), for atherosclerosis to validate our guesses. Initially, S-allyl-L-cysteine and 4-methoxyphenylthiourea were used as H2S donors for SCCF and SCTM, respectively. After the introduction of ROS-sensitive groups. Then, micelles with N-Acetylneuraminic acid and Chondroitin sulfate were prepared to load rapamycin(RAP). Further, in atherosclerosis Oil Red O staining (ORO) results confirmed remarkable treatment effect with SCCF@RAP and SCTM@RAP. Thus, we conclude that the effect of dual-targeting nanomicelles with ROS-sensitive H2S donor based on N-Acetylneuraminic acid and Chondroitin sulfate will have a better role in atherosclerosis.

A Review of Polymeric Micelles and Their Applications

Self-assembly of amphiphilic polymers with hydrophilic and hydrophobic units results in micelles (polymeric nanoparticles), where polymer concentrations are above critical micelle concentrations (CMCs). Recently, micelles with metal nanoparticles (MNPs) have been utilized in many bio-applications because of their excellent biocompatibility, pharmacokinetics, adhesion to biosurfaces, targetability, and longevity. The size of the micelles is in the range of 10 to 100 nm, and different shapes of micelles have been developed for applications. Micelles have been focused recently on bio-applications because of their unique properties, size, shape, and biocompatibility, which enhance drug loading and target release in a controlled manner. This review focused on how CMC has been calculated using various techniques. Further, micelle importance is explained briefly, different types and shapes of micelles are discussed, and further extensions for the application of micelles are addressed. In the summary and outlook, points that need focus in future research on micelles are discussed. This will help researchers in the development of micelles for different applications.

Melatonin photoreactivity: phosphorescence formation and quenching processes

Studies of melatonin photoreactivity in water solutions: An effect of an external heavy atom I− on UV/Vis absorption, fluorescence and phosphorescence spectra is explored. The data allowed determination of relevant energetics for the system.The heavy atom effect (HAE) of I− on melatonin is clearly found to induce an intersystem crossing from the lowest energy singlet state to the lowest energy triplet state (T1) by a state mixing. Lifetime for the first excited triplet states of melatonin in association with I− and quenching rates for halomethanes (CH2X2, CHX3, CY4, X = Cl, Br, Y = Cl) are determined from Time-Correlated Single-Photon Counting decay curves for the phosphorescence. Dramatic alterations in quenching rate constants with quenchers as CH2X2 < CHX3 < CX4 and Cl < Br are attributed to energy transfer from an I−…Me*(T1) complex to low-lying electronic states of the halomethanes followed by dissociation to form R and X fragments. Relevance of the melatonin photoreactivity to photosensitizer properties in organic media is discussed.

Graphical abstract

Poloxamer 188 as surfactant in biological formulations - An alternative for polysorbate 20/80?

Surfactants are used to stabilize biologics. Particularly, polysorbates (Tween® 20 and Tween® 80) dominate the group of surfactants in protein and especially antibody drug products. Since decades drug developers rely on the ethoxylated sorbitan fatty acid ester mixtures to stabilize sensitive molecules such as proteins. Reasons are (i) excellent stabilizing properties, and (ii) well recognized safety and tolerability profile of these polysorbates in humans, especially for parenteral applications. However, over the past decade concerns regarding the stability of these two polysorbates were raised. The search of alternatives with preferably less reservations concerning degradation and product quality reducing issues leads, among others, to poloxamer 188 (e.g. Kolliphor® P188), a nonionic triblock-copolymer surfactant. This review sums up our current knowledge related to the characterization and physico-chemical properties of poloxamer 188, its analytics and stability properties for biological formulations. Furthermore, the advantages and disadvantages as a suitable polysorbate-alternative for the stabilization of biologics are discussed.

Novel β-cyclodextrin based copolymers: fabrication, characterization and in vitro release behavior

A novel cyclodextrin-contained copolymer poly(AAc-co-SA-AC-co-allyl-β-CD) was synthesized based on the method of redox radical polymerization. Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (¹H NMR) spectra were used to study the structure of the obtained copolymer. The molecular weight of the copolymer was studied by gel permeation chromatography (GPC). The polymeric nanoparticles (NPs) were fabricated by a solvent evaporation method. The morphology and particle size distribution of the cargo-free NPs were investigated with transmission electron microscope (TEM), atomic force microscope (AFM), and laser particle analyzer, respectively. Curcumin (Cur) was selected as a model drug and encapsulated into the above NPs. The distribution of Cur in the drug-loaded NPs was analyzed by the method of differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Moreover, the release profiles of Cur from Cur-loaded NPs were studied in pH 6.8 and 7.4 buffers. The results of FTIR and ¹H NMR spectra confirmed the successful synthesis of poly(AAc-co-SA-AC-co-allyl-β-CD). GPC curve proved that the molecular weight of the copolymer was more than 60 kDa. TEM and AFM images illustrated that the cargo-free NPs were in spherical shape with a diameter about 40 nm. XRD patterns and DSC curves indicated that most of Cur distributed in the Cur-loaded NPs with amorphous state. Importantly, the medicated NPs showed sustained release characteristics toward Cur.

Novel dual labelled nanoprobes for nanosafety studies: Quantification and imaging experiment of CuO nanoparticles in C. elegans

Metal oxide nanoparticles have been extensively studied for their toxicological impacts. However, accurate tracing/quantification of the nanomaterials and their biological responses are difficult to measure at low concentrations. To overcome the challenge, we developed a dual-labelling technique of CuO nanoparticles with a stable isotope of ⁶⁵Cu, and with rhodamine dye. In vivo experiments on C. elegans were performed using natural feeding of Rhodamine B isothiocyanate-(3 aminopropyl) triethoxysilane functionalized ⁶⁵CuO nanoprobes (RBITC-APTES@⁶⁵CuO) (size = 7.41 ± 1 nm) within the range of Predicted Environmental Concentration (PEC) of CuO nanoparticles in soil and sediments. Fluorescence emission (570 nm) was detected in the lumen of the intestine and the pharynx of C. elegans with no impact of nanoparticle exposure on the brood size and life span of worms. The ingested fluorescent labelled RBITC-APTES@⁶⁵CuO nanoprobes did not enter the reproductive system and were distributed in the alimentary canal of C. elegans. Strong fluorescent signals from the ingested RBITC-APTES@⁶⁵CuO nanoprobes were achieved even after 24 h of exposure demonstrating the high stability of these nanoprobes in vivo. The net accumulation measured of ⁶⁵Cu in C. elegans after background subtraction was 0.001 μg mg^-1 (3.52 %), 0.005 μg mg^-1 (1.76 %) and 0.024 μg mg^-1 (1.69 %) for an exposure concentration of 0.0284 μg mg^-1, 0.284 μg mg^-1, and 1.42 μg mg^-1 of ⁶⁵Cu, respectively. Using C. elegans as a model organism, we demonstrated that RBITC-APTES tagged ⁶⁵CuO nanoparticles acted as novel nanoprobes for measuring the uptake, accumulation, and biodistribution through quantification and imaging the nanoprobes at a very low exposure concentration (⁶⁵CuO concentration: 0.033 μg mg^-1).

Water-soluble pillar[5]arene sulfo-derivatives self-assemble into biocompatible nanosystems to stabilize therapeutic proteins

Pillar[5]arenes containing sulfonate fragments have been shown to form supramolecular complexes with therapeutic proteins to facilitate targeted transport with an increased duration of action and enhanced bioavailability. Regioselective synthesis was used to obtain a water-soluble pillar[5]arene containing the fluorescent label FITC and nine sulfoethoxy fragments. The pillar[5]arene formed complexes with the therapeutic proteins binase, bleomycin, and lysozyme in a 1:2 ratio as demonstrated by UV-vis and fluorescence spectroscopy. The formation of stable spherical nanosized macrocycle/binase complexes with an average particle size of 200 nm was established by dynamic light scattering and transmission electron microscopy. Flow cytometry demonstrated the ability of macrocycle/binase complexes to penetrate into tumor cells where they exhibited significant cytotoxicity towards A549 cells at 10^-5-10^-6 M while maintaining the enzymatic activity of binase.

Supramolecular ultra-short carboxybenzyl-protected dehydropeptide-based hydrogels for drug delivery

Self-assembled peptide-based hydrogels are promising materials for biomedical research owing to biocompatibility and similarity to the extracellular matrix, amenable synthesis and functionalization and structural tailoring of the rheological properties. Wider developments of self-assembled peptide-based hydrogels in biomedical research and clinical translation are hampered by limited commercial availability allied to prohibitive costs. In this work a focused library of Cbz-protected dehydrodipeptides Cbz-L-Xaa-Z-ΔPhe-OH (Xaa= Met, Phe, Tyr, Ala, Gly) was synthesised and evaluated as minimalist hydrogels. The Cbz-L-Met-Z-ΔPhe-OH and Cbz-L-Phe-Z-ΔPhe-OH hydrogelators were comprehensively evaluated regarding molecular aggregation and self-assembly, gelation, biocompatibility and as drug carriers for delivery of the natural compound curcumin and the clinically important antitumor drug doxorubicin. Drug release profiles and FRET studies of drug transport into small unilamellar vesicles (as biomembrane models) demonstrated that the Cbz-protected dehydropeptide hydrogels are effective nanocarriers for drug delivery. The expedite and scalable synthesis (in 3 steps), using commercially available reagents and amenable reaction conditions, makes Cbz-protected dehydrodipeptide hydrogels, widely available at affordable cost to the research community.

Detection Methods and Research Progress of Human Serum Albumin

Human serum albumin (HSA) is a biological macromolecule with important physiological functions; abnormal HSA levels are associated with coronary heart disease, multiple myeloma, diabetes, nephropathy, neurometabolic disorders, liver cirrhosis and other diseases. Therefore, accurate and quantitative detection of HAS have extremely important research and application value in biological science, molecular biology, clinical medicine and other fields. As for the detection method of HSA, dye-binding method and immune method are the first to be used, and have been applied in clinical detection. In recent years, many new detection technologies have emerged, such as fluorescent probe detection method, nano-materials for HSA detection, biosensor and so on. Although there are many methods developed recently to detect HSA, comprehensive reviews for HSA detection methods are still rare. Thus, writing this review to fill in the blank is in need. In order to highlight the recent progress in the field of HSA detection, in this review, the methods used to detect HSA are summarized and sorted, the advantages and disadvantages of these detection methods are also listed, then the research progress of small molecular fluorescence probe method is emphatically introduced in this paper. Then, we briefly discussed the challenges and future development directions in this field.