Synthesis and characterization of modified chitosan microspheres: Effect of the grafting ratio on the controlled release of nifedipine through microspheres

Chitosan and chito-oligosaccharide: a versatile biopolymer with endless grafting possibilities for multifarious applications

Chito-oligosaccharides (COS), derived from chitosan (CH), are attracting increasing attention as drug delivery carriers due to their biocompatibility, biodegradability, and mucoadhesive properties. Grafting, the process of chemically modifying CH/COS by adding side chains, has been used to improve their drug delivery performance by enhancing their stability, targeted delivery, and controlled release. In this review, we aim to provide an in-depth study on the recent advances in the grafting of CH/COS for multifarious applications. Moreover, the various strategies and techniques used for grafting, including chemical modification, enzymatic modification, and physical modification, are elaborated. The properties of grafted CH/COS, such as stability, solubility, and biocompatibility, were reported. Additionally, the review detailed the various applications of grafted CH/COS in drug delivery, including the delivery of small drug molecule, proteins, and RNA interference therapeutics. Furthermore, the effectiveness of grafted CH/COS in improving the pharmacokinetics and pharmacodynamics of drugs was included. Finally, the challenges and limitations associated with the use of grafted CH/COS for drug delivery and outline directions for future research are addressed. The insights provided in this review will be valuable for researchers and drug development professionals interested in the application of grafted CH/COS for multifarious applications.

Nanoparticles in sustainable agriculture: An emerging opportunity

Conventional agriculture often relies on bulky doses of fertilizers and pesticides that have adversely affected the living beings as well as the ecosystems. As a basic tenet of sustainable agriculture, minimum agrochemicals should be used so that the environment can be protected and various species can be conserved. Further, sustainable agriculture should be a low input system, where the production costs are lower and net returns are higher. The application of nanotechnology in agriculture can significantly enhance the efficiency of agricultural inputs and thus it offers a significant way to maintain sustainable development of agroecosystems via nanoparticles. In this regard, nano-plant growth promoters, nanopesticides, nanofertilizers, nano-herbicides, agrochemical encapsulated nanocarrier systems etc. have been developed for the potential applications in agriculture. These can have great benefits for agriculture, including higher production of crops, inhibition of plant pathogens, removal of unwanted weeds and insects with lesser cost, energy and waste production. However, there are several concerns related to the use of nanoparticles in agriculture. These include the approaches for synthesis, their mechanisms of penetration to applied surfaces and the risks involved. Though, advent of new technologies has significantly improved the synthesis and application of nanomaterials in agriculture, there are many uncertainties regarding nano-synthesis, their way of utilization, uptake and internalization inside the crop cells. Therefore, an elaborate investigation is required for deciphering the engineered nanomaterials, assessing their mechanistic application and agroecological toxicity. Hence, this review is aimed to critically highlight the NPs material application and points towards the vital gaps in the use of nanotechnology for sustainable agriculture.

Injectable RANKL sustained release formulations to accelerate orthodontic tooth movement

BACKGROUND

Accelerating orthodontic tooth movement (OTM) through biologically effective methods, such as increasing osteoclast-mediated alveolar resorption, could effectively shorten treatment time.

OBJECTIVE

To evaluate an injectable formulation containing receptor activator of nuclear factor kappa-B ligand (RANKL) on the OTM.

MATERIALS AND METHODS

We fabricated a RANKL formulation from 100 µl of 100 µg/ml RANKL adsorbed on 10 mg of poly(lactic acid-co-glycolic acid) microspheres embedded in a 10 wt% aqueous hydroxyethyl cellulose carrier gel. We characterized these formulations for the rate of RANKL release, and then tested for bioactivity using in vitro cell culture. In vivo OTM studies were conducted using 15 week old male Wistar rats for 14 days. We injected the RANKL formulations palatal to the left maxillary first molar and accomplished OTM with a nickel-titanium (NiTi) coil spring applying 5-8 g force. Control groups involved the application of NiTi coil spring with and without placebo formulation. The outcome measure included the distance of tooth movement, bone volume fraction, tissue density, and root volume determined with micro-computed tomography. We determined the amount of osteoclast activity using tartrate-resistant acid phosphatase (TRAP) staining.

RESULTS

These formulations were able to sustain the release of RANKL for more than 30 days, and the released RANKL showed a positive effect on mice osteoclast precursor cells (RAW 264.7). Reported injectable RANKL formulations were effective in accelerating OTM compared with other control groups, with 129.2 per cent more tooth movement than no formulation and 71.8 per cent more than placebo formulation, corresponding with a significant increase in the amount of TRAP activity. We did not observe any significant differences in root resorption between the groups.

CONCLUSION

Our study shows a significant increase in OTM with injectable formulations containing RANKL.

PCL–DOX microdroplets: an evaluation of the enhanced intracellular delivery of doxorubicin in metastatic cancer cells via in silico and in vitro approaches

A schematic diagram of HCC & TACE; injections of HepaSphere with DOX are made into the femoral artery, abdominal aorta, and hepatic artery to make the tumor shrink to a resectable size due to a shortage of nutrients and drug treatment.

Bioactive polymeric formulations for wound healing

Ricinoleic acid (RA) has potential to promote wound healing because of its analgesic and anti-inflammatory properties. This study investigates the synthesis and characterization of RA liposomes infused in a hydrogel for topical application. Lecithin liposomes containing RA were prepared and incorporated into a chitosan solution and were subsequently cross-linked with dialdehyde β-cyclodextrin (Di-β-CD). Chitosan/Di-β-CD concentrations and reaction temperatures were varied to alter gelation time, water content, and mechanical properties of the hydrogel in an effort to obtain a wide range of RA release profiles. Hydrogel cross-linking was confirmed by spectroscopy, and liposome and carrier hydrogel morphology via microscopy. Chitosan, Di-β-CD, and liposome concentrations within the formulation affected the extent of matrix swelling, mechanical strength, and pore and overall morphology. Higher cross-linking density of the hydrogel led to lower water uptake and slower release rate of RA. Optimized formulations resulted in a burst release of RA followed by a steady release pattern accounting for 80% of the encapsulated RA over a period of 48 hours. However, RA concentrations above 0.1 mg/mL were found to be cytotoxic to fibroblast cultures in vitro because of the oily nature of RA. These formulations promoted wound healing when used to treat full thickness skin wounds (2 cm²) in Wister male rats. The wound contraction rates were significantly higher compared to a commercially available topical cream after a time period of 21 days. Histopathological analysis of the RA-liposomal chitosan hydrogel group showed that the epidermis, dermis, and subcutaneous skin layers displayed an accelerated yet normal healing compared to control group.

Synthesis of xanthan gum graft copolymer and its application for controlled release of highly water soluble Levofloxacin drug in aqueous medium

Graft copolymers (XG-g-PNVP-1 to XG-g-PNVP-5) of xanthan gum (XG) and poly(N-vinyl-2-pyrrolidone) (PNVP) was synthesized by free radical polymerization using peroxymonosulphate/thiourea redox pair. The synthesized graft copolymers were well characterized by ¹H NMR, FTIR, XRD, SEM, TGA/DTA and AFM analyses. The optimum conditions for maximum grafting were determined by varying the concentrations of N-vinyl-2-pyrrolidone (NVP) from 10×10^-2 to 18×10^-2moldm^-3; the grafting ratios increases up to 14×10^-2moldm^-3, while thereafter decreased. Graft copolymer (XG-g-PNVP-D) hybrid was prepared to load levofloxacin drug, about 15mg drug was loaded; and its release was studied in phosphate buffer solution (PBS) at pH 7.4 on 37±0.1°C; About 80% drug was released in 36h.

New Biofunctional Loading of Natural Antimicrobial Agent in Biodegradable Polymeric Films for Biomedical Applications

The study focuses on the development of novel Aloe vera based polymeric composite films and antimicrobial suture coatings. Polyvinyl alcohol (PVA), a synthetic biocompatible and biodegradable polymer, was combined with Aloe vera, a natural herb used for soothing burning effects and cosmetic purposes. The properties of these two materials were combined together to get additional benefits such as wound healing and prevention of surgical site infections. PVA and Aloe vera were mixed in a fixed quantity to produce polymer based films. The films were screened for antibacterial and antifungal activity against bacterial (E. coli, P. aeruginosa) and fungal strains (Aspergillus flavus and Aspergillus tubingensis) screened. Aloe vera based PVA films showed antimicrobial activity against all the strains; the lowest Aloe vera concentration (5%) showed the highest activity against all the strains. In vitro degradation and release profile of these films was also evaluated. The coating for sutures was prepared, in vitro antibacterial tests of these coated sutures were carried out, and later on in vivo studies of these coated sutures were also performed. The results showed that sutures coated with Aloe vera/PVA coating solution have antibacterial effects and thus have the potential to be used in the prevention of surgical site infections and Aloe vera/PVA based films have the potential to be used for wound healing purposes.

Supramolecular Complexation of Carbohydrates for the Bioavailability Enhancement of Poorly Soluble Drugs

In this review, a comprehensive overview of advances in the supramolecular complexes of carbohydrates and poorly soluble drugs is presented. Through the complexation process, poorly soluble drugs could be efficiently delivered to their desired destinations. Carbohydrates, the most abundant biomolecules, have diverse physicochemical properties owing to their inherent three-dimensional structures, hydrogen bonding, and molecular recognition abilities. In this regard, oligosaccharides and their derivatives have been utilized for the bioavailability enhancement of hydrophobic drugs via increasing the solubility or stability. By extension, polysaccharides and their derivatives can form self-assembled architectures with poorly soluble drugs and have shown increased bioavailability in terms of the sustained or controlled drug release. These supramolecular systems using carbohydrate will be developed consistently in the field of pharmaceutical and medical application.

Controlled delivery of the popular nonsteroidal anti-inflammatory drug, paracetamol, from chitosan-g-polyacrylamide microspheres prepared by the emulsion crosslinking technique

In this paper, chitosan-graft-polyacrylamide (CS-g-PAAm) microspheres as drug delivery matrices of paracetamol were prepared by the emulsion crosslinking technique, using glutaraldehyde (GA) as a crosslinker. Graft copolymer of chitosan with acrylamide was synthesized using cerium (IV) ammonium nitrate (CAN). The microspheres formed had average particle sizes in the range of 78-252 μm. Paracetamol entrapment efficiency was found to vary between 31.89% and 72.61%, as determined by UV spectroscopy. Drug release in acidic and phosphate buffer solutions (pH 1.2 and 7.4) of the CS-g-PAAm microspheres was influenced by formulation factors such as the concentration of CS-g-PAAm, the paracetamol/polymer ratio (w/w), and the amount of crosslinker.

Ibuprofen microencapsulation within acrylamide-grafted chitosan and methylcellulose interpenetrating polymer network microspheres: Synthesis, characterization, and release studies

This study deals with the development of interpenetrating polymer network (IPN) microspheres of acrylamide (AAm) grafted onto a chitosan (CS) backbone and methylcellulose (MC). Chitosan-graft-polyacrylamide (CS-g-PAAm) was synthesized by cerium (IV) ammonium nitrate-induced free radical graft polymerization. The grafting percentage was found to be 50.58%. The synthesized graft copolymer and MC were used to prepare microspheres by the water-in-oil (w/o) emulsion-crosslinking method, and crosslinked with glutaraldehyde (GA) as drug delivery matrices of ibuprofen (IBU). The release of IBU from microspheres decreased when the amount of CS-g-PAAm in the polymer matrix and amount of crosslinker added were increased, while it increased with the increase of the IBU/polymer ratio.

Preparation of magnetite-chitosan/methylcellulose nanospheres by entrapment and adsorption techniques for targeting the anti-cancer drug 5-fluorouracil

In this work, we have formulated novel nanospheres that could be used in the controlled release of the anticancer drug, 5-fluorouracil (5-FU). The nanospheres are composed of magnetite, containing chitosan (CS) and methylcellulose (MC). The drug entrapment was achieved through the encapsulation and adsorption processes. The effects of the preparation conditions, such as magnetite content, CS/MC ratio, crosslinking concentration, exposure time to glutaraldehyde (GA), and the drug/polymer ratio were investigated for both processes. The 5-FU release was found to follow the Fickian mechanism, and the Langmuir isotherm for the nanospheres was achieved through encapsulation and adsorption processes, respectively.

pH-sensitive interpenetrating polymer network microspheres of poly(vinyl alcohol) and carboxymethyl cellulose for controlled release of the nonsteroidal anti-inflammatory drug ketorolac tromethamine

In this study, we aimed to produce pH-sensitive microspheres for the controlled release of the nonsteroidal anti-inflammatory drug, ketorolac tromethamine (KT). For this purpose, an interpenetrating polymer network (IPN) of microspheres of poly(vinyl alcohol) (PVA)/sodium carboxymethyl cellulose (NaCMC) were prepared, based on different formulations using glutaraldehyde (GA) (0.66 M) and hydrochloric acid (HCl) (3%, v/v). The preparation conditions of the microspheres were optimized by considering the percentage of entrapment efficiency and swelling capacity of the microspheres, and their release data. The effects of PVA and NaCMC ratio on the release of KT for over a period of 6 h, at three pH values (1.2, 6.8, and 7.4), have been discussed.

Preparation of Polysaccharide-Based Microspheres by a Water-in-Oil Emulsion Solvent Diffusion Method for Drug Carriers

Polysaccharide-based microspheres of chitosan, starch, and alginate were prepared by the water-in-oil emulsion solvent diffusion method for use as drug carriers. Blue dextran was used as a water-soluble biomacromolecular drug model. Scanning electron microscopy showed sizes of the resultant microspheres that were approximately 100 μm or less. They were spherical in shape with a rough surface and good dispersibility. Microsphere matrices were shown as a sponge. Drug loading efficiencies of all the microspheres were higher than 80%, which suggested that this method has potential to prepare polysaccharide-based microspheres containing a biomacromolecular drug model for drug delivery applications.

Synthesis and evaluation of chitosan-graft-poly (2-hydroxyethyl methacrylate-co-itaconic acid) as a drug carrier for controlled release of tramadol hydrochloride

Chitosan-graft-poly (2-hydroxyethyl methacrylate-co-itaconic acid) has been synthesized for different feed ratios of 2-hydroxyethyl methacrylate and itaconic acid and characterized by FT-IR, thermogravimetry and swelling in simulated biological fluids (SBF) and evaluated as a drug carrier with model drug, tramadol hydrochloride (TRM). Grafting decreased the thermal stability of chitosan. FT-IR spectra of tablet did not reveal any molecular level (i.e. at <10 nm scale) drug-polymer interaction. But differential scanning calorimetric studies indicated a probable drug-polymer interaction at a scale >100 nm level. The observed Korsmeyer-Peppas's power law exponents (0.19-1.21) for the in vitro release profiles of TRM in SBF and other drugs such as 5-fluorouracil (FU), paracetamol (PCM) and vanlafaxine hydrochloride (VNF) with the copolymer carriers revealed an anomalous drug release mechanism. The decreased release rates for the grafted chitosan and the enhanced release rate for the grafts with increasing itaconic acid content in the feed were more likely attributed to the enhanced drug-matrix interaction and polymer-SBF interactions, respectively. The different release profiles of FU, PCM, TRM and VNF with the copolymer matrix are attributed to the different chemical structures of drugs. The above features suggest the graft copolymer's candidature for use as a promising oral drug delivery system.

Evaluation of a matrix tablet prepared with polyacrylamide-g-sodium alginate co-polymers and their partially hydrolyzed co-polymers for sustained release of diltiazem hydrochloride

Diltiazem hydrochloride (DTZ) matrix tablets were prepared using polyacrylamide-grafted sodium alginate (PAam-g-SA) co-polymers having different percentages of grafting and their partially hydrolyzed products with a view to achieve sustained release of the highly water-soluble drug. PAam-g-SA co-polymers having different percentages of grafting were synthesized by free radical polymerization using acrylamide (Aam) as monomer and ammonium persulphate (APS) as initiator, and the resulting co-polymers were subjected to alkaline hydrolysis to produce their corresponding partially hydrolyzed co-polymers. Matrix tablets of DTZ were prepared by wet granulation using either PAam-g-SA co-polymers or partially hydrolyzed PAam-g-SA co-polymers. The effect of percentage grafting, drug load and calcium gluconate (CG), used as excipient, was studied in simulated gastrointestinal fluid. While the tablets prepared using the co-polymer having higher percentages of grafting provided faster drug release (100% in 5.5 h), the tablets prepared with the corresponding hydrolyzed co-polymer released the drug slowly (71% in 12 h). This behaviour in release appeared to be controlled by the relative magnitude of the viscosity and the swelling capacity of the copolymers. Moreover, increase in drug load tended to decrease the drug release from all types of tablets and increase in the amount of CG increased the drug release. FT-IR and DSC studies revealed the absence of any interaction between the drug and the co-polymers. The matrix tablet made of partially hydrolyzed graft co-polymer having the highest percentage of grafting provided the most sustained release of the drug.

A pH-sensitive nanocomposite microsphere based on chitosan and montmorillonite with in vitro reduction of the burst release effect

OBJECTIVE

The aim of this study was to prepare pH-sensitive ofloxacin (OFL)/montmorillonite (MMT)/chitosan (CTS) nanocomposite microspheres that improve the burst release effect of the drug by the solution intercalation technique and emulsification cross-linking techniques.

METHODS

First, OFL/MMT hybrids were prepared through the solution intercalation technique. Then, OFL/MMT-intercalated OFL/MMT/CTS nanocomposite microspheres were obtained through emulsification cross-linking technology. The intercalated nanocomposite was confirmed by Fourier-transform infrared spectroscopy and X-ray diffraction. Finally, in vitro release of OFL from the microspheres was performed in simulated gastric fluids and simulated intestinal fluids. The effect of MMT content on drug encapsulation efficiency and the drug release of the nanocomposite microspheres were investigated.

RESULTS

The results showed that the release rate of OFL from the nanocomposite microspheres at pH 7.4 was higher than that at pH 1.2. Compared with pure CTS microspheres, the incorporation of certain amount of MMT in the nanocomposite microspheres can enhance the drug encapsulation efficiency and reduce the burst release.

CONCLUSION

A sustained release particulate system can be obtained by incorporating MMT into the nanocomposite microspheres and can improve the burst release effect of the drug.

Review Paper: Chitosan Derivatives as Promising Materials for Controlled Drug Delivery

Chitosan, a natural based-polymer obtained by alkaline deacetylation of chitin, is nontoxic, biocompatible, and biodegradable. These properties make chitosan a good candidate for the development of conventional and novel drug delivery systems. Chitosan has been found to be used as a support material for gene delivery, cell culture, and tissue engineering. However, practical use of chitosan has been mainly confined to the unmodified forms. For a breakthrough in utilization, especially in the field of controlled drug delivery, graft copolymerization onto chitosan will be a key point, which will introduce desired properties and enlarge the field of the potential applications of chitosan by choosing various types of side chains. Chemical modification of chitosan is useful for the association of bioactive molecules to polymer and controlling the drug release profile. This paper reviews the various methods of preparation of chitosan derivatives intended for controlled drug delivery. From the studies reviewed it is concluded that chitosan derivatives are promising materials for controlled drug and nonviral gene delivery.

Release characteristics of diclofenac sodium from poly(vinyl alcohol)/sodium alginate and poly(vinyl alcohol)-grafted-poly(acrylamide)/sodium alginate blend beads

In this study, acrylamide (AAm) was grafted onto poly(vinyl alcohol) (PVA) with UV radiation at ambient temperature. The graft copolymer (PVA-g-PAAm) was characterized by using Fourier transform infrared spectroscopy (FTIR), elemental analysis and differential scanning calorimetry (DSC). Polymeric blend beads of PVA-g-PAAm and PVA with sodium alginate (NaAlg) were prepared by cross-linking with glutaraldehyde (GA) and used to deliver a model anti-inflammatory drug, diclofenac sodium (DS). Preparation condition of the beads was optimized by considering the percentage entrapment efficiency, particle size, swelling capacity of beads and their release data. Effects of variables such as PVA/NaAlg ratio, acrylamide content, exposure time to GA and drug/polymer ratio on the release of DS were discussed at three different pH values (1.2, 6.8, 7.4). It was observed that, DS release from the beads decreased with increasing PVA/NaAlg (m/m) ratio, drug/polymer ratio (d/p) and extent of cross-linking. However, DS release increased with increasing acrylamide content of the PVA-g-PAAm polymer. The highest DS release was obtained to be 92% for 1/1 PVA-g-PAAm/NaAlg ratio beads. It was also observed from release results that DS release from the beads through the external medium is much higher at high pH (6.8 and 7.4) than that at low pH (1.2). The drug release from the beads mostly followed Case II transport.

Recent advances on chitosan-based micro- and nanoparticles in drug delivery

Considerable research efforts have been directed towards developing safe and efficient chitosan-based particulate drug delivery systems. The present review outlines the major new findings on the pharmaceutical applications of chitosan-based micro/nanoparticulate drug delivery systems published over the past decade. Methods of their preparation, drug loading, release characteristics, and applications are covered. Chemically modified chitosan or its derivatives used in drug delivery research are discussed critically to evaluate the usefulness of these systems in delivering the bioactive molecules. From a literature survey, it is realized that research activities on chitosan micro/nanoparticulate systems containing various drugs for different therapeutic applications have increased at the rapid rate. Hence, the present review is timely.