Reduced and oxidized rice straw biochar for hexavalent chromium adsorption: Revisiting the mechanism of adsorption

Surface oxygen functional groups of biochar were tuned by oxidation and reduction of biochar for establishing Cr(VI) adsorption mechanism. Oxygen functional groups (OFGs) on the surface of leached rice straw biochar (LBC4-6) obtained from pyrolysis at 400, 500 and 600 °C, were oxidized to furnish OBC4-6 using modified Hummer's method. Reduced biochar RBC4-6 were obtained by esterification and NaBH4/I2 reduction of oxidized biochar (OBC4-6). The modified biochar were characterized by increase in O/C and H/C ratio, respectively, in case of OBC4-6 and RBC4-6. The Cr(VI) adsorption by modified biochar LBC4-6, OBC4-6, and RBC4-6 showed optimum conditions of pH 3 and dose 0.1 g/L with a good non-linear fit for Langmuir & Freundlich isotherm. The maximum adsorption (Qm) followed the trend: OBC4 (17.47 mg/g) > RBC4 (15.23) > OBC5 (13.23) > LBC4 (10.23) > RBC5 (9.83) > OBC6 (9.60) > RBC6 (7.24) > LBC5 (6.32) > LBC6 (5.98). The adsorption kinetics for adsorption of Cr(VI) on to modified biochar fits pseudo second order (PSO), Elovich and intraparticle diffusion kinetics, showing a chemisorptions in case of biochar L/O/RBC4-6. The lower temperature modified biochar O/RBC4 show better Cr(VI) adsorption. X-ray Photoelectron Spectroscopy (XPS) studies establish optimum OFGs for reduction of Cr(VI) and chelation of the reduced Cr(III). Adsorption and stripping cycles show the oxidized and reduced biochar as better adsorbents with excellent stripping of Cr up to >98 % upon desorption with 1 M NaOH.

Valine conjugated polymeric nanocarriers for targeted co-delivery of rivastigmine and quercetin in rat model of Alzheimer disease

Multifunctional nanocarriers are increasingly promising for disease treatment aimed at finding effective therapy and overcoming barriers in drug delivery. Herein, valine conjugated chitosan (VLCS) was used for surface modification of nanocarriers (NCs) based on Poly (ε-caprolactone)-Poly (ethylene glycol)-Poly (ε-caprolactone) (PCL-PEG-PCL) triblock copolymers (NCs@VLCS). The nanocarriers were co-loaded with rivastigmine (RV) and quercetin (QT) to yield the final RV/QT-NCs@VLCS as a multifunctional nanocarrier for Alzheimer's disease (AD) treatment. The large amino acid transporter 1 (LAT-1) was selected for the direction of the NCs to the brain. The biocompatibility of the nanocarrier was studied in HEK-293 and SH-SY5Y cells and rats. The Morris water maze test demonstrated a faster regain of memory loss with RV/QT-NCs@VLCS compared to the other groups. Furthermore, RV/QT-NCs@VLCS and RV/QT-NCs improved GSH depletion induced by scopolamine (SCO), with RV/QT-NCs@VLCS having a superior effect. The real-time PCR analysis revealed that co-delivery of RV and QT by NCs@VLCS showed significantly higher efficacy than sole delivery of RV. RV/QT-NCs@VLCS treatment also modulated the expression of BDNF, ACHE, and TNF-α. The findings revealed that NCs@VLCS co-loaded with RV and QT, significantly increased efficacy relative to the single use of RV and could be considered a potent multifunctional drug delivery system for Alzheimer's treatment.

Novel strategies to oral delivery of insulin: Current progress of nanocarriers for diabetes management

Diabetes mellitus is one of the most serious public health problems in the world. Repeated daily injections of subcutaneous insulin is the standard treatment for patients with type 1 diabetes mellitus; however, subcutaneous insulin injections can potentially cause local discomfort, patient noncompliance, hypoglycemia, failure to regulate glucose homeostasis, infections, and fat deposits at the injection sites. In recent years, numerous attempts have been made to produce safe and efficient nanoparticles for oral insulin delivery. Oral administration is considered the most effective alternative route to insulin injection, but it is accompanied by several challenges related to enzymatic proteolysis, digestive breakdown, and absorption barriers. A number of natural and synthetic polymeric, lipid-based, and inorganic nanoparticles have been investigated for use. Although improvements have recently been made in potential oral insulin delivery systems, these require further investigation before clinical trials are conducted. In this review, new approaches to oral insulin delivery for diabetes treatment are discussed, including polymeric, lipid-based, and inorganic nanoparticles, as well as the clinical trials performed for this purpose.

In vitro evaluation of curcumin-loaded chitosan-coated hydroxyapatite nanocarriers as a potential system for effective treatment of cancer

Nanotechnology has many potential applications in cancer treatment. For example, nano-drug delivery systems (NDDS) with high bioavailability, biodegradability, and biocompatibility have been developed, in order to increase the therapeutic effects of anticancer drugs. Among these NDDS, high-performance hydroxyapatite (HA) nanoparticles are rapidly advancing in the targeted cancer treatment due to their numerous benefits. Curcumin is an herbal metabolite that acts as a chemical inhibitor through the inhibition of tumor cells and the progression of many cancers. However, the poor bioavailability of curcumin is the most important challenge in using this substance. In this study, HA nanoparticles coated by chitosan were used as a pH-sensitive biopolymer to improve the efficiency and bioavailability of curcumin. For this purpose, HA nanoparticles were first synthesized by the sol-gel method. Then, a layer of chitosan was coated on it, and the curcumin drug was encapsulated in the nanocarrier, under controlled conditions. Techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were used to characterize the nanocarriers. In the second part, nano-drugs prepared by various bioassays were examined. For this purpose, the rate of cytotoxicity by the methyl-thiazol-tetrazolium (MTT) assay and the rate of apoptosis induction by the acridine orange and ethidium bromide (AO/EB) staining method on the brain carcinoma U87MG cell line were investigated.

Preparation and characterization of polylactic-co-glycolic acid/insulin nanoparticles encapsulated in methacrylate coated gelatin with sustained release for specific medical applications

This study aimed to examine the possibility of using insulin orally with gelatin encapsulation to enhance the usefulness of the drug and increase the lifespan of insulin in the body using polylactic-co-glycolic acid (PLGA) nanoparticles alongside gelatin encapsulation. In this regard, PLGA was synthesized via ring opening polymerization, and PLGA/insulin nanoparticles were prepared by a modified emulsification-diffusion process. The resulting nanoparticles with various amounts of insulin were fully characterized using FTIR, DSC, DLS, zeta potential, SEM, and glucose uptake methods, with results indicating the interaction between the insulin and PLGA. The process efficiency of encapsulation was higher than 92%, while the encapsulation efficiency of nanoparticles, based on an insulin content of 20 to 40%, was optimized at 93%. According to the thermal studies, the PLGA encapsulation increases the thermal stability of the insulin. The morphological studies showed the fine dispersion of insulin in the PLGA matrix, which we further confirmed by the Kjeldahl method. According to the release studies and kinetics, in-vitro degradation, and particle size analysis, the sample loaded with 30% insulin showed optimum overall properties, and thus it was encapsulated with gelatin followed by coating with aqueous methacrylate coating. Release studies at pH values of 3 and 7.4, alongside the Kjeldahl method and standard dissolution test at pH 5.5, and glucose uptake assay tests clearly showed the capsules featured 3-4 h biodegradation resistance at a lower pH along with the sustained release, making these gelatin-encapsulated nanoparticles promising alternatives for oral applications.[Figure: see text].

Collagen/Chitosan Complexes: Preparation, Antioxidant Activity, Tyrosinase Inhibition Activity, and Melanin Synthesis

Bioactive collagen/chitosan complexes were prepared by an ion crosslinking method using fish skin collagen and chitosan solution as raw materials. Scanning electron microscopy observation confirmed that the collagen/chitosan complexes were of a uniform spherical shape and uniform particle size. The complexes were stable at different pH values for a certain period of time through swelling experiments. Differential scanning calorimetry (DSC) showed the collagen/ chitosan complexes were more stable than collagen. X-ray diffraction (XRD) showed that the complexes had a strong crystal structure, and Fourier transform infrared spectroscopy (FTIR) data revealed the changes in the secondary structure of the protein due to chitosan and TPP crosslinking. The content of malondialdehyde (MDA) in the complex treatment group was considerably lower, but the content of SOD was significantly higher than that of the collagen group or chitosan group. In addition, the collagen/chitosan complexes could considerably reduce melanin content, inhibit tyrosinase activity, and down-regulate tyrosinase mRNA expression. In conclusion, the collagen/chitosan complexes were potential oral protein preparation for antioxidant enhancement and inhibiting melanin synthesis.

Nanoparticles: Oral Delivery for Protein and Peptide Drugs

Protein and peptide drugs have many advantages, such as high bioactivity and specificity, strong solubility, and low toxicity. Therefore, the strategies for improving the bioavailability of protein peptides are reviewed, including chemical modification of nanocarriers, absorption enhancers, and mucous adhesion systems. The status, advantages, and disadvantages of various strategies are systematically analyzed. The systematic and personalized design of various factors affecting the release and absorption of drugs based on nanoparticles is pointed out. It is expected to design a protein peptide oral delivery system that can be applied in the clinic.

Targeted folate-conjugated pluronic P85/poly(lactide-co-glycolide) polymersome for the oral delivery of insulin

Aim: To explore the better efficacy of targeted folic acid (FA)-Pluronic 85-poly(lactide-co-glycolide) (FA–P85–PLGA) polymersome in oral insulin delivery. Materials & methods: The cytotoxicity of the polymers, in vitro qualitative and quantitative cellular uptake and the internalization mechanism of insulin-loaded FA–P85–PLGA and PLGA–P85–PLGA polymersomes were studied with the human colon adenocarcinoma cells (Caco-2 cells). Their pharmacodynamics and pharmacokinetics properties were also studied with diabetic rats. Results & conclusion: Polymersomes have shown good biocompatibility. Polymersomes are mainly localized within the cytoplasm of Caco-2 cells from fluorescence microscopy images. FA–P85–PLGA exhibited higher cellular uptake than PLGA–P85–PLGA polymersomes and free fluorescein isothiocyanate-labeled insulin (FITC–insulin) did. The uptake process of targeted polymersomes included clathrin- and caveolae-mediated endocytosis, macropinocytosis and the folate receptor-mediated endocytosis. Insulin-loaded FA–P85–PLGA showed better hypoglycemic effects than insulin-loaded PLGA–P85–PLGA.

Stimuli-Responsive Delivery of Therapeutics for Diabetes Treatment

Diabetic therapeutics, including insulin and glucagon-like peptide 1 (GLP-1), are essential for diabetic patients to regulate blood glucose levels. However, conventional treatments that are based on subcutaneous injections are often associated with poor glucose control and a lack of patient compliance. In this review, we focus on the different stimuli-responsive systems to deliver therapeutics for diabetes treatment to improve patient comfort and prevent complications. Specifically, the pH-responsive systems for oral drug delivery are introduced first. Then, the closed-loop glucose-responsive systems are summarized based on different glucose-responsive moieties, including glucose oxidase (GOx), glucose binding protein (GBP), and phenylboronic acid (PBA). Finally, the on-demand delivery systems activated by external remote triggers are also discussed. We conclude by discussing advantages and limitations of current strategies, as well as future opportunities and challenges in this area.