The influence of multivalent phosphate structure on the properties of ionically cross-linked chitosan films for controlled drug release

Increased Cytotoxic Efficacy of Protocatechuic Acid in A549 Human Lung Cancer Delivered via Hydrophobically Modified-Chitosan Nanoparticles As an Anticancer Modality

The growing incidence of global lung cancer cases against successful treatment modalities has increased the demand for the development of innovative strategies to complement conventional chemotherapy, radiation, and surgery. The substitution of chemotherapeutics by naturally occurring phenolic compounds has been touted as a promising research endeavor, as they sideline the side effects of current chemotherapy drugs. However, the therapeutic efficacy of these compounds is conventionally lower than that of chemotherapeutic agents due to their lower solubility and consequently poor intracellular uptake. Therefore, we report herein a hydrophobically modified chitosan nanoparticle (pCNP) system for the encapsulation of protocatechuic acid (PCA), a naturally occurring but poorly soluble phenolic compound, for increased efficacy and improved intracellular uptake in A549 lung cancer cells. The pCNP system was modified by the inclusion of a palmitoyl group and physico-chemically characterized to assess its particle size, Polydispersity Index (PDI) value, amine group quantification, functional group profiling, and morphological properties. The inclusion of hydrophobic palmitoyl in pCNP-PCA was found to increase the encapsulation of PCA by 54.5% compared to unmodified CNP-PCA samples whilst it only conferred a 23.4% larger particle size. The single-spherical like particles with uniformed dispersity pCNP-PCA exhibited IR bands, suggesting the successful incorporation of PCA within its core, and a hydrophobic layer was elucidated via electron micrographs. The cytotoxic efficacy was then assessed by using an MTT cytotoxicity assay towards A549 human lung cancer cell line and was compared with traditional chitosan nanoparticle system. Fascinatingly, a controlled release delivery and enhanced therapeutic efficacy were observed in pCNP-PCA compared to CNP, which is ascribed to lower IC50 values in the 72-h treatment in the pCNP system. Using the hydrophobic system, efficacy of PCA was significantly increased in 24-, 48-, and 72-h treatments compared to a single administration of the compound, and via the unmodified CNP system. Findings arising from this study exhibit the potential of using such modified nanoparticulate systems in increasing the efficacy of natural phenolic compounds by augmenting their delivery potential for better anti-cancer responses.

Thermo- and pH-sensitive glycosaminoglycans derivatives obtained by controlled grafting of poly(N-isopropylacrylamide)

Poly(N-isopropyl acrylamide) grafted heparin and chondroitin sulfate were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The copolymers were characterized by NMR, IR, SEC, DLS, SLS and NTA methods. High grafting densities were reached for both glycosaminoglycans. The temperature, pH and polymer concentration affected the low critical solution temperatures values. The increased pNIPAAm chain length, grafting density and concentration led to the sharp phase transition at 35 °C. Spherical nanogels were formed around this temperature. Terminal dodecyl trithiocarbonate groups of the copolymers were reduced to thiols that allowed formation of sensitive nanogels with sharp phase transitions induced by pNIPAAm chains. The copolymers showed no toxicity to the ocular cells and they provided the prolonged release of dexamethasone phosphate at 37 °C. These copolymers are interesting alternatives for ocular drug delivery.

Controlled Release of 5-FU from Chi-DHA Nanoparticles Synthetized with Ionic Gelation Technique: Evaluation of Release Profile Kinetics and Cytotoxicity Effect

The ionic gelation technique allows us to obtain nanoparticles able to function as carriers for hydrophobic anticancer drugs, such as 5-fluoruracil (5-FU). In this study, reticulated chitosan– docosahexaenoic acid (Chi–DHAr) nanoparticles were synthesized by using a chemical reaction between amine groups of chitosan (Chi) and carboxylic acids of docosahexaenoic acid (DHA) and the presence of a link between Chi and DHA was confirmed by FT-IR, while the size and morphology of the obtained Chi-DHAr nanoparticles was evaluated with dynamic light scattering (DLS) and scanning electron microscopy (SEM), respectively. Drug-loading content (DLC) and drug-loading efficiency (DLE) of 5-FU in Chi-DHAr nanoparticles were 33.74 ± 0.19% and 7.9 ± 0.26%, respectively, while in the non-functionalized nanoparticles (Chir + 5FU), DLC, and DLE were in the ranges of 23.73 ± 0.14%, 5.62%, and 0.23%, respectively. The in vitro release profile, performed in phosphate buffer saline (PBS, pH 7.4) at 37 °C, indicated that the synthetized Chi–DHAr nanoparticles provided a sustained release of 5-FU. Based on the obtained regression coefficient value (R²), the first order kinetic model provided the best fit for both Chir and Chi-DHAr nanoparticles. Finally, cytotoxicity studies of chitosan, 5-FU, Chir, Chir + 5-FU, Chi-DHAr, and Chi-DHAr + 5-FU nanoparticles were conducted. Overall, Chi-DHAr nanoparticles proved to be much more biocompatible than Chir nanoparticles while retaining the ability to release the drug with high efficiency, especially towards specific types of cancerous cells.

Formulation, characterization and in vitro release study of 5-fluorouracil loaded chitosan nanoparticles

The main objective of this study was to evaluate the most suitable conditions to prepare 5-fluorouracil (5-FU) loaded chitosan nanoparticles (CSNPs). 5-FU loaded CSNPs were prepared employing the ionic gelation technique using three different molecular weights of CS with the polyanion sodium tripolyphosphate (STPP) as cross-linking agent. The preparation was based on the ionic interaction of positively charged CS and negatively charged STPP. The entrapment efficiency (EE%) of CSNPs was in the range of 3.86-21.82% EE% exhibited a clear increase with increasing CS concentration. The averge particles size was in the nanosize range and monodisperse in nature whereas transmission electron microscope micrographs showed that the prepared nanoparticles have a spherical shape. Fourier transform infrared (FTIR), X- ray differaction (XRD) and differential scanning calorimetry (DSC) confirmed successful incorporation of 5-FU in prepared CSNPs. In vitro release of 5-FU from selected formulations exhibited sustained release from the nanoparticles where slower release was observed when higher molecular weight CS was used. The study of drug release kinetics revealed that the release of 5-FU from CSNPs followed a diffusion controlled pattern.

Toxicity evaluation of 6-mercaptopurine-Chitosan nanoparticles in rats

Background

The 6-mercaptopurine (6-MP) is an effective immunosuppressant and anti-cancer drug. However, the usage of 6-MP is limited due to its well-known side effects, such as myelotoxicity and hepato-renal toxicity. To curtail the potential toxic effects, we have used chitosan as a natural biodegradable and biocompatible polysaccharide to synthesize 6-Mercaptopurine-Chitosan Nanoparticles (6-MP-CNPs).

Methods

The 6-MP-CNPssize, morphology, physicochemical interactions, and thermal stability were characterized using Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Differential Scanning Calorimetry (DSC), respectively. The loading efficiency of the 6-MP in CNPs was estimated using LCMS/MS. Then, the 6-MP-CNPs were subjected to in vivo acute and sub-acute oral toxicity evaluations.

Results

The DLS and SEM analysis respectively indicated size (70.0 nm to 400.0 nm), polydispersity index (0.462), and zeta potential (54.9 mV) with improved morphology of 6-MP-CNPs. The FTIR and DSC results showed the efficient interactive and stable nature of the 6-MP-CNPs, which sustained the drug-delivery process. The loading efficiency of 6-MP-CNPs was found to be 25.23%. The chitosan improved the lethal dose (LD50 cut off) of 6-MP-CNPs (1000 mg/kg b.w) against 6-MP (500 mg/kg b.w) and also significantly (p ≤ 0.05) reduces the toxic adverse effect (28-day repeated oral dose) on hemato-biochemical and hepato-renal histological profiles.

Conclusion

The findings suggest that chitosan, as a prime drug-delivery carrier, significantly alleviates the acute and sub-acute toxic effects of 6-MP.

Chitosan Encapsulation of FerrateVI for Controlled Release to Water:Mechanistic Insights and Degradation of Organic Contaminant

Tetraoxy-anion of iron in +6 oxidation state (Fe^VIO₄²⁻, Fe^VI), commonly called ferrate, has shown tremendous potential as a green oxidative agent for decontaminating water and air. Encapsulation of solid potassium salt of ferrate (K₂FeO₄) circumvents the inherent drawbacks of the instability of ferrate under humid conditions. In the encapsulated strategy, controlled release without exposing the solid ferrate to the humid environment avoids self-decomposition of the oxidant by water in the air, and the ferrate is mostly used to decontaminate water efficiently. This study demonstrated the formulation of oxidative microcapsules with natural materials present in chitosan, whose release rate of the core material can be controlled by the type of intermediate hydrocarbon layer and the pH-dependent swelling of chitosan shell. The pH played a pivotal role in swelling chitosan shell and releasing the core oxidant. In a strong acidic solution, chitosan tended to swell quickly and release Fe^VI at a faster rate than under neutral conditions. Additionally, among the several long-chain hydrocarbon compounds, oleic acid exhibited the strongest “locking” effect when applied as the intermediate layer, giving rise to the slow release of Fe^VI. Coconut oil and mineral oil, in comparison, allowed Fe^VI to penetrate the layer within shorter lengths of time and showed comparable degrees of degradation of target contaminant, methylene orange, under ambient temperature and near-neutral conditions. These findings have practical ramifications for remediating environmental and industrial processes.

Novel purine thioglycoside analogs: synthesis, nanoformulation and biological evaluation in in vitro human liver and breast cancer models

Background: A series of novel pyrazolopyrimidine and pyrazololpyridine thioglycosides were synthesized and confirmed via their spectral analyses. Purpose: To evaluate the effect of these anti-metabolic compounds against proliferation of Huh-7 and Mcf-7 as in vitro models of human liver and breast cancers, respectively. Vero cells were used as an example of normal green monkey kidney cells. Methods: The most promising compound was subjected to a nanoformulation by its encapsulation into chitosan nanoparticles to increase its anti-cancerous activity. Nanoformulation was confirmed by TEM and FT-IR to ensure encapsulation and screened for their cytotoxicity against Huh-7 and Mcf-7 cells using MTT colorimetric assay and morphological examination. Genotoxic effect was performed by cellular DNA fragmentation assay. Simulated CompuSyn software (linear interaction effect) was conducted to predict the possible synergistic effect of nanocomposite as anticancerous activity. Apoptotic effect was further analyzed by detection of apoptotic proteins using ELISA assay. Results: The nano preparation was successfully prepared by encapsulation of compound 14 into chitosan nanoparticles, controlled to a size at 105 nm and zeta charges at 40.2 mV. Treatment of Huh-7 and Mcf-7 showed that compound 14 was the most cytotoxic compound on both cancer cell lines where IC50 was 24.59 (9.836 μg/mL) and 12.203 (4.8812 μg/mL) on Huh-7 and Mcf-7 respectively. But IC50 of the nano preparation was 37.19 and 30.68 μg/mL on Huh-7 and Mcf-7, respectively, indicating its aggressiveness on human breast cancer cells as confirmed by DNA fragmentation assay and theoretically by CompuSyn tool. Conclusion: A novel series of pyrazolopyrimidine thioglycosides and pyrazolopyridine thioglycosides were synthesized. Nanoformulation of compound 14 into chitosan nanoparticles demonstrated anticancer activity and can be used as a drug delivery system, but further studies are still required.

Multifunctional prosthetic polyester-based hybrid mesh for repairing of abdominal wall hernias and defects

This study involves the design, development and evaluation of a new multifunctional prosthetic mesh for treatment of abdominal wall defects without complications. The developed prosthetic mesh is a hybrid platform of both synthetic and natural materials with its backbone consisting of a synthetic commercial polyester fabric (CPF) to provide the required mechanical integrity. The CPF mesh was coated by a natural biodegradable, biocompatible and antimicrobial layer of chitosan (CS) incorporating phenytoin (PH)-loaded pluronic nanomicelles for healing promotion, and ciprofloxacin (CPX)-alginate polyelectrolyte complex-based microparticles as antibacterial agent. The prosthetic mesh was optimized and evaluated in-vitro and in-vivo. The optimum PH-loaded micelles had particle size of 95.42 nm, polydispersity index of 0.41, zeta potential of -18 and entrapment efficiency of 89.4%, while the optimum CPX microcomplexes had particle size of 1292.0 nm, polydispersity index of 0.8, zeta potential of -20.1, complexation efficiency of 81.1%, and minimum inhibitory concentration of 0.25 μg/ml and 0.125 μg/ml against Staphylococcus aureus and Pseudomonas aeruginosa, respectively. In-vivo study on abdominal wall defect dog model was conducted, followed by implantation of the proposed prosthetic meshes. The developed mesh depicted an efficient healing with excellent biocompatibility, and could be an ideal and feasible alternative prosthesis with many advantages such as low cost, inertness, mechanical stability, pliability, low infection rate, limited modification by body tissues, sterilizability, non-carcinogenicity, limited inflammatory reaction, hypoallergenic as well as minimal complications.

Development of CS-TPP-dsRNA nanoparticles to enhance RNAi efficiency in the yellow fever mosquito, Aedes aegypti

Mosquito-borne diseases are a major threat to human health and are responsible for millions of deaths globally each year. Vector control is one of the most important approaches used in reducing the incidence of these diseases. However, increasing mosquito resistance to chemical insecticides presents challenges to this approach. Therefore, new strategies are necessary to develop the next generation vector control methods. Because of the target specificity of dsRNA, RNAi-based control measures are an attractive alternative to current insecticides used to control disease vectors. In this study, Chitosan (CS) was cross-linked to sodium tripolyphosphate (TPP) to produce nano-sized polyelectrolyte complexes with dsRNA. CS-TPP-dsRNA nanoparticles were prepared by ionic gelation method. The encapsulation efficiency, protection of dsRNA from nucleases, cellular uptake, in vivo biodistribution, larval mortality and gene knockdown efficiency of CS-TPP-dsRNA nanoparticles were determined. The results showed that at a 5:1 weight ratio of CS-TPP to dsRNA, nanoparticles of less than 200 nm mean diameter and a positive surface charge were formed. Confocal microscopy revealed the distribution of the fed CS-TPP-dsRNA nanoparticles in midgut, fat body and epidermis of yellow fever mosquito, Aedes aegypti larvae. Bioassays showed significant mortality of larvae fed on CS-TPP-dsRNA nanoparticles. These assays also showed knockdown of a target gene in CS-TPP-dsRNA nanoparticle fed larvae. These data suggest that CS-TPP nanoparticles may be used for delivery of dsRNA to mosquito larvae.

Supramolecular Strategy Effects on Chitosan Bead Stability in Acidic Media: A Comparative Study

Chitosan beads attract interest in diverse applications, including drug delivery, biocatalysis and water treatment. They can be formed through several supramolecular pathways, ranging from phase inversion in alkaline solutions, to the ionic crosslinking of chitosan with multivalent anions, to polyelectrolyte or surfactant/polyelectrolyte complexation. Many chitosan bead uses require control over their stability to dissolution. To help elucidate how this stability depends on the choice of supramolecular gelation chemistry, we present a comparative study of chitosan bead stability in acidic aqueous media using three common classes of supramolecular chitosan beads: (1) alkaline solution-derived beads, prepared through simple precipitation in NaOH solution; (2) ionically-crosslinked beads, prepared using tripolyphosphate (TPP); and (3) surfactant-crosslinked beads prepared via surfactant/polyelectrolyte complexation using sodium salts of dodecyl sulfate (SDS), caprate (NaC10) and laurate (NaC12). Highly variable bead stabilities with dissimilar sensitivities to pH were achieved using these methods. At low pH levels (e.g., pH 1.2), chitosan/SDS beads were the most stable, requiring roughly 2 days to dissolve. In weakly acidic media (at pH 3.0⁻5.0), however, chitosan/TPP beads exhibited the highest stability, remaining intact throughout the entire experiment. Beads prepared using only NaOH solution (i.e., without ionic crosslinking or surfactant complexation) were the least stable, except at pH 5.0, where the NaC10 and NaC12-derived beads dissolved slightly faster. Collectively, these findings provide further guidelines for tailoring supramolecular chitosan bead stability in acidic media.

Continuous assembly of supramolecular polyamine-phosphate networks on surfaces: preparation and permeability properties of nanofilms

Supramolecular self-assembly of molecular building blocks represents a powerful "nanoarchitectonic" tool to create new functional materials with molecular-level feature control. Here, we propose a simple method to create tunable phosphate/polyamine-based films on surfaces by successive assembly of poly(allylamine hydrochloride) (PAH)/phosphate anions (Pi) supramolecular networks. The growth of the films showed a great linearity and regularity with the number of steps. The coating thickness can be easily modulated by the bulk concentration of PAH and the deposition cycles. The PAH/Pi networks showed chemical stability between pH 4 and 10. The transport properties of the surface assemblies formed from different deposition cycles were evaluated electrochemically by using different redox probes in aqueous solution. The results revealed that either highly permeable films or efficient anion transport selectivity can be created by simply varying the concentration of PAH. This experimental evidence indicates that this new strategy of supramolecular self-assembly can be useful for the rational construction of single polyelectrolyte nanoarchitectures with multiple functionalities.

An Evaluation of Curcumin-Encapsulated Chitosan Nanoparticles for Transdermal Delivery

Curcumin-loaded chitosan nanoparticles were synthesised and evaluated in vitro for enhanced transdermal delivery. Zetasizer® characterisation of three different formulations of curcumin nanoparticles (Cu-NPs) showed the size ranged from 167.3 ± 3.8 nm to 251.5 ± 5.8 nm, the polydispersity index (PDI) values were between 0.26 and 0.46 and the zeta potential values were positive (+ 18.1 to + 20.2 mV). Scanning electron microscopy (SEM) images supported this size data and confirmed the spherical shape of the nanoparticles. All the formulations showed excellent entrapment efficiency above 80%. FTIR results demonstrate the interaction between chitosan and sodium tripolyphosphate (TPP) and confirm the presence of curcumin in the nanoparticle. Differential scanning calorimetry (DSC) studies of Cu-NPs indicate the presence of curcumin in a disordered crystalline or amorphous state, suggesting the interaction between the drug and the polymer. Drug release studies showed an improved drug release at pH 5.0 than in pH 7.4 and followed a zero order kinetics. The in vitro permeation studies through Strat-M® membrane demonstrated an enhanced permeation of Cu-NPs compared to aqueous curcumin solution (p ˂ 0.05) having a flux of 0.54 ± 0.03 μg cm^-2 h^-1 and 0.44 ± 0.03 μg cm^-2 h^-1 corresponding to formulations 5:1 and 3:1, respectively. The cytotoxicity assay on human keratinocyte (HaCat) cells showed enhanced percentage cell viability of Cu-NPs compared to curcumin solution. Cu-NPs developed in this study exhibit superior drug release and enhanced transdermal permeation of curcumin and superior percentage cell viability. Further ex vivo and in vivo evaluations will be conducted to support these findings.

Ionically Crosslinked Chitosan Membranes Used as Drug Carriers for Cancer Therapy Application

The aim of this paper was to prepare, by the freeze-drying method, ionically crosslinked chitosan membranes with different contents of pentasodium tripolyphosphate (TPP) and loaded with 1,4-naphthoquinone (NQ14) drug, in order to evaluate how the physical crosslinking affects NQ14 release from chitosan membranes for cancer therapy application. The membranes were characterized by Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), swelling degree, and through in vitro drug release and cytotoxicity studies. According to the results, the molecular structure, porosity and hydrophilicity of the chitosan membranes were affected by TPP concentration and, consequently, the NQ14 drug release behavior from the membranes was also affected. The release of NQ14 from crosslinked chitosan membranes decreased when the cross-linker TPP quantity increased. Thus, depending on the TPP amount, the crosslinked chitosan membranes would be a potential delivery system to control the release of NQ14 for cancer therapy application. Lastly, the inhibitory potential of chitosan membranes ionically crosslinked with TPP and loaded with NQ14 against the B16F10 melanoma cell line was confirmed through in vitro cytotoxicity studies assessed via MTT assay. The anti-proliferative effect of prepared membranes was directly related to the amount of cross-linker and among all membranes prepared, such that one crosslinked with 0.3% of TPP may become a potential delivery system for releasing NQ14 drug for cancer therapy.

Hyaluronic Acid-Decorated Chitosan Nanoparticles for CD44-Targeted Delivery of Everolimus

Bronchiolitis obliterans syndrome (BOS), caused by lung allograft-derived mesenchymal cells' abnormal proliferation and extracellular matrix deposition, is the main cause of lung allograft rejection. In this study, a mild one-step ionotropic gelation method was set up to nanoencapsulate the everolimus, a key molecule in allograft organ rejection prevention, into hyaluronic acid-decorated chitosan-based nanoparticles. Rationale was the selective delivery of everolimus into lung allograft-derived mesenchymal cells; these cells are characterized by the CD44-overexpressing feature, and hyaluronic acid has proven to be a natural selective CD44-targeting moiety. The optimal process conditions were established by a design of experiment approach (full factorial design) aiming at the control of the nanoparticle size (≤200 nm), minimizing the size polydispersity (PDI 0.171 ± 0.04), and at the negative ζ potential maximization (-30.9 mV). The everolimus was successfully loaded into hyaluronic acid-decorated chitosan-based nanoparticles (95.94 ± 13.68 μg/100 mg nanoparticles) and in vitro released in 24 h. The hyaluronic acid decoration on the nanoparticles provided targetability to CD44-overexpressing mesenchymal cells isolated from bronchoalveolar lavage of BOS-affected patients. The mesenchymal cells' growth tests along with the nanoparticles uptake studies, at 37 °C and 4 °C, respectively, demonstrated a clear improvement of everolimus inhibitory activity when it is encapsulated in hyaluronic acid-decorated chitosan-based nanoparticles, ascribable to their active uptake mechanism.

Preparation and Characterization of Doripenem-Loaded Microparticles for Pulmonary Delivery

Background: Pneumonia is a bacterial lower respiratory tract infection that has a high morbidity rate. The gram-negative pathogen Pseudomonas aeruginosa is a significant cause of nosocomial infections and ventilator-associated pneumonias and is mainly treated by carbapenems. Doripenem is a carbapenem drug, which has a broad-spectrum antibacterial activity. The aim of this study was to develop doripenem-loaded chitosan microparticles for pulmonary administration to provide more efficient treatment for pneumonia. Methods: Ionotropic gelation and the spray-drying method were used to obtain doripenem-loaded chitosan microparticles with different lactose, trehalose, and L-leucine concentrations. Physicochemical characteristics, in vitro drug release properties, and aerodynamics properties were investigated and in vitro antimicrobial susceptibility tests of the formulations were performed. Assessment of aerodynamic properties of the powders, including Mass Median Aerodynamic Diameter, size distribution, and fine particle fraction (FPF), were performed using a Next Generation Impactor. Cytotoxicity of the fabricated microparticles was assessed using the Calu-3 cell airway epithelial cell line. Results: Optimum microparticles were produced using a combination of ionotropic gelation and spray-drying methods. Spray-dried microparticle production yield was relatively high (74.03% ± 3.88% to 98.23% ± 1.70%). Lactose, trehalose, and L-leucine were added to the formulation to prevent aggregation produced by the ionotropic gelation spray-drying method. Each formulation's encapsulation efficiency was above 78.98% ± 2.37%. The doripenem-loaded microparticle mean diameter ranged from 3.8 ± 0.110 to 6.9 ± 0.090 μm. Microparticles with 20% (w/w) L-leucine had the highest FPF ratio indicating the best aerosolization properties of the formulations. The efficacy of the formulations as an antibacterial agent was increased by forming doripenem-loaded microparticles compared to blank microparticles. P. aeruginosa showed the same susceptibility to all doripenem-loaded microparticle formulations. Cell viability of microparticles was between 70% ± 0.08% and 90% ± 0.04% at 0.5 and 10 mg/mL concentration, respectively. Conclusions: Doripenem-loaded microparticles, produced using a combination of ionotropic gelation and spray-drying methods, are suitable for pulmonary drug delivery based on their particles size, zeta potential, cytotoxicity and high production yield. To our knowledge, this is the first study that microparticles containing doripenem were produced and characterized.

Biopolymer-based strategies in the design of smart medical devices and artificial organs

Advances in regenerative medicine and in modern biomedical therapies are fast evolving and set goals causing an upheaval in the field of materials science. This review discusses recent developments involving the use of biopolymers as smart materials, in terms of material properties and stimulus-responsive behavior, in the presence of environmental physico-chemical changes. An overview on the transformations that can be triggered in natural-based polymeric systems (sol-gel transition, polymer relaxation, cross-linking, and swelling) is presented, with specific focus on the benefits these materials can provide in biomedical applications.

siRNA: an alternative treatment for diabetes and associated conditions

Diabetes is a condition that is not completely treatable but life of a diabetic patient can be smoothed by preventing or delaying the associate conditions like diabetic retinopathy, nephropathy, impaired wound healing process, etc. Apart from conventional methods to regulate diabetic condition, new techniques using siRNA have been emerged to prevent the associated conditions. This paper focuses on how siRNA used as a tool to silence the expression of genes which plays critical role in pathogenesis of these conditions. A marked improvement in wound-healing process of diabetic patients has been observed with siRNA treatment by silencing of Keap1 gene. Glucagon plays critical role in glucose homoeostasis and increases blood glucose level during hypoglycaemia. Glucose homoeostasis is impaired in diabetic patient and suppressing the expression of glucagon secretion with siRNA is used to suppress the progress of diabetes. Similarly, silencing expression of several factors has demonstrated improvement of treatment of diabetic nephropathy, retinopathy and inflammation by the use of siRNA.

Thermoresponsive curcumin/DsiRNA nanoparticle gels for the treatment of diabetic wounds: synthesis and drug release

AIM

Chitosan (CS) has been extensively studied as drug delivery systems for wound healing. Results/methodology: CS nanoparticles were loaded with curcumin (Cur) and DsiRNA against prostaglandin transporter gene and they were incorporated into 20 and 25% w/v Pluronic F-127. The gels were later analyzed for their rheology, gelation temperature (T_gel), morphology, drug incorporation and in vitro drug release. The particle size was in the range of 231 ± 17-320 ± 20 nm, depending on CS concentration. The gels had T_gel of 23-28°C and exhibited sustained drug release with high accumulated amount of drugs over 48 h.

CONCLUSION

A thermo-sensitive gel containing Cur/DsiRNA CS nanoparticles was successfully developed and has a great potential to be further developed.

Starch-Chitosan Polyplexes: A Versatile Carrier System for Anti-Infectives and Gene Delivery

Despite the enormous potential of nanomedicine, the search for materials from renewable resources that balance bio-medical requirements and engineering aspects is still challenging. This study proposes an easy method to make nanoparticles composed of oxidized starch and chitosan, both isolated from natural biopolymers. The careful adjustment of C/N ratio, polymer concentration and molecular weight allowed for tuning of particle characteristics. The system's carrier capability was assessed both for anti-infectives and for nucleic acid. Higher starch content polyplexes were found to be suitable for high encapsulation efficiency of cationic anti-infectives and preserving their bactericidal function. A cationic carrier was obtained by coating the anionic polyplex with chitosan. Coating allowed for a minimal amount of cationic polymer to be employed and facilitated plasmid DNA loading both within the particle core and on the surface. Transfection studies showed encouraging result, approximately 5% of A549 cells with reporter gene expression. In summary, starch-chitosan complexes are suitable carriers with promising perspectives for pharmaceutical use.

Development of Yam Dioscorin-Loaded Nanoparticles for Paracellular Transport Across Human Intestinal Caco-2 Cell Monolayers

Dioscorins, the major storage proteins of yam tubers, exert immunomodulatory activities. To improve oral bioavailability of dioscorins in the intestine, recombinant dioscorin (rDioscorin) was coated with N,N,N-trimethyl chitosan (TMC) and tripolyphosphate (TPP), resulting in the formation of TMC-rDio-TPP nanoparticles (NPs). The loading capacity and entrapment efficiency of rDioscorin in the NPs were 26 ± 0.7% and 61 ± 1.4%, respectively. The NPs demonstrated a substantial release profile in the pH environment of the jejunum. The rDioscorin released from the NPs stimulated proliferation and phagocytosis of the macrophage RAW264.7 and activated the gene expression of IL-1β and IL-6. Incubation of the NPs in the Caco-2 cell monolayer led to a 5.2-fold increase of P_app compared with rDioscorin alone, suggesting that rDioscorin, with the assistance of TMC, can be promptly transported across the intestinal epithelia. These results demonstrate that the TMC-rDio-TPP NPs can be utilized for elucidating the immunopharmacological effects of dioscorins through oral delivery.

The chitosan hydrogels: from structure to function

This review places an emphasis on chitosan intelligent hydrogels. The fabrication methods and mechanisms are introduced in this review and the interactions of the formation of hydrogels with both physical and chemical bonds are also introduced. The relationship between the structural characteristics and the corresponding functions of stimuli-responsive characteristics, self-healing functions and high mechanical strength properties of the chitosan hydrogels are discussed in detail.

Increased Loading, Efficacy and Sustained Release of Silibinin, a Poorly Soluble Drug Using Hydrophobically-Modified Chitosan Nanoparticles for Enhanced Delivery of Anticancer Drug Delivery Systems

Conventional delivery of anticancer drugs is less effective due to pharmacological drawbacks such as lack of aqueous solubility and poor cellular accumulation. This study reports the increased drug loading, therapeutic delivery, and cellular accumulation of silibinin (SLB), a poorly water-soluble phenolic compound using a hydrophobically-modified chitosan nanoparticle (pCNP) system. In this study, chitosan nanoparticles were hydrophobically-modified to confer a palmitoyl group as confirmed by 2,4,6-Trinitrobenzenesulfonic acid (TNBS) assay. Physicochemical features of the nanoparticles were studied using the TNBS assay, and Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) analyses. The FTIR profile and electron microscopy correlated the successful formation of pCNP and pCNP-SLB as nano-sized particles, while Dynamic Light Scattering (DLS) and Field Emission-Scanning Electron Microscopy (FESEM) results exhibited an expansion in size between pCNP and pCNP-SLB to accommodate the drug within its particle core. To evaluate the cytotoxicity of the nanoparticles, a Methylthiazolyldiphenyl-tetrazolium bromide (MTT) cytotoxicity assay was subsequently performed using the A549 lung cancer cell line. Cytotoxicity assays exhibited an enhanced efficacy of SLB when delivered by CNP and pCNP. Interestingly, controlled release delivery of SLB was achieved using the pCNP-SLB system, conferring higher cytotoxic effects and lower IC₅₀ values in 72-h treatments compared to CNP-SLB, which was attributed to the hydrophobic modification of the CNP system.

Molecular dynamics study on the mechanism of polynucleotide encapsulation by chitosan

The safe and effective delivery of therapeutic genes into target cell interiors is of great importance in gene therapy. Chitosan has been extensively studied as a gene delivery carrier due to its good biocompatibility and biodegradability. Understanding the atomic interaction mechanism between chitosan and DNA is important in the design and application of chitosan-based drug and gene delivery systems. In this work, the interactions between single-stranded polynucleotides and different types of chitosan were systematically investigated by using molecular dynamics (MD) simulation. Our results demonstrate that the functional groups of chitosan, the types of base and length of polynucleotides regulate the interaction behavior between chitosan and polynucleotides. The encapsulation capacity of polynucleotide by chitosan is mainly balanced by two factors: the strength of polynucleotide binding to chitosan and the tendency of self-aggregation of polynucleotide in the solution. For -NH3+ chitosan, due to the strong electrostatic interaction, especially the H-bond between -NH3+ groups in chitosan and phosphate groups in polynucleotide, the aggregation effect could be partially eliminated. The good dispersal capacity of polynucleotides may improve the encapsulation of polynucleotides by chitosan, and hence increase the delivery and transfection efficiency of chitosan-based gene carrier.

Preparation of chitosan/tripolyphosphate nanoparticles with highly tunable size and low polydispersity

Nanoparticles prepared through the ionotropic gelation of chitosan with tripolyphosphate (TPP) have been extensively studied as vehicles for drug and gene delivery. Though a number of these works have focused on preparing particles with narrow size distributions, the monodisperse particles produced by these methods have been limited to narrow size ranges (where the average particle size was not varied by more than twofold). Here we show how, by tuning the NaCl concentration in the parent chitosan and TPP solutions, low-polydispersity particles with z-average diameters ranging between roughly 100 and 900nm can be prepared. Further, we explore how the size of these particles depends on the method by which the TPP is mixed into the chitosan solution, specifically comparing: (1) single-shot mixing; (2) dropwise addition; and (3) a dilution technique, where chitosan and TPP are codissolved at a high (gelation-inhibiting) ionic strength and then diluted to lower ionic strengths to trigger gelation. Though the particle size increases sigmoidally with the NaCl concentration for all three mixing methods, the dilution method delivers the most uniform/gradual size increase - i.e., it provides the most precise control. Also investigated are the effects of mixture composition and mixing procedure on the particle yield. These reveal the particle yield to increase with the chitosan/TPP concentration, decrease with the NaCl concentration, and vary only weakly with the mixing protocol; thus, at elevated NaCl concentrations, it may be beneficial to increase chitosan and TPP concentrations to ensure high particle yields. Finally, possible pitfalls of the salt-assisted size control strategy (and their solutions) are discussed. Taken together, these findings provide a simple and reliable method for extensively tuning chitosan/TPP particle size while maintaining narrow size distributions.

Dehydroascorbate-derivatized chitosan particles for targeting antimalarial agents to infected erythrocytes

The mammalian glucose transporter GLUT-1 and Plasmodium falciparum hexose transporter PfHT1 are overexpressed on human RBC infected with the parasite (iRBC), presumably for enhanced glucose uptake. Dehydroascorbic acid (DHA) competes out glucose in GLUT-1 binding. We prepared particles containing chloroquine phosphate using novel derivatives of chitosan (CSN). CSN was either pre-derivatized with DHA (PRE) or particles made of CSN were derivatized by surface-grafting DHA (POST). The optimized formulations were analyzed for size (170-200nm) drug content (about 40%) entrapment efficiency (50-57%), in vitro drug release (80% in 72h, Higuchi's model), hemolysis on exposure to whole blood or RBC at 5% hematocrit, cytotoxicity towards cultured HEK 293T (kidney) and HepG2 (hepatic) cells, targeting iRBC and in vitro efficacy against P. falciparum. PRE particles were superior to POST CSN particles in terms of uptake and extent of preferential targeting to iRBCs than RBCs. Unlike starch particles reported earlier, dextrose did not competitively inhibit uptake of DHA-derivatized CSN particles. Both formulations significantly induced parasite inhibition at 1nM while free drug showed comparable activity at 100nM. Both PRE and POST particles were superior to free drug in efficacy. Targeting with high efficiency promises dose reduction and possibility of overcoming efflux-based drug resistance.