Novel pH responsive polymethacrylic acid-chitosan-polyethylene glycol nanoparticles for oral peptide delivery

Polyelectrolytes for Environmental, Agricultural, and Medical Applications

In recent decades, polyelectrolytes (PELs) have attracted significant interest owing to a surge in research dedicated to the development of new technologies and applications at the biological level. Polyelectrolytes are macromolecules of which a substantial portion of the constituent units contains ionizable or ionic groups. These macromolecules demonstrate varied behaviors across different pH ranges, ionic strengths, and concentrations, making them fascinating subjects within the scientific community. The aim of this review is to present a comprehensive survey of the progress in the application studies of polyelectrolytes and their derivatives in various fields that are vital for the advancement, conservation, and technological progress of the planet, including agriculture, environmental science, and medicine. Through this bibliographic review, we seek to highlight the significance of these materials and their extensive range of applications in modern times.

Oral nanotherapeutic formulation of insulin with reduced episodes of hypoglycaemia

Injectable insulin is an extensively used medication with potential life-threatening hypoglycaemic events. Here we report on insulin-conjugated silver sulfide quantum dots coated with a chitosan/glucose polymer to produce a responsive oral insulin nanoformulation. This formulation is pH responsive, is insoluble in acidic environments and shows increased absorption in human duodenum explants and Caenorhabditis elegans at neutral pH. The formulation is sensitive to glucosidase enzymes to trigger insulin release. It is found that the formulation distributes to the liver in mice and rats after oral administration and promotes a dose-dependent reduction in blood glucose without promoting hypoglycaemia or weight gain in diabetic rodents. Non-diabetic baboons also show a dose-dependent reduction in blood glucose. No biochemical or haematological toxicity or adverse events were observed in mice, rats and non-human primates. The formulation demonstrates the potential to orally control blood glucose without hypoglycaemic episodes.

Chitosan Nanoparticle Encapsulation of Antibacterial Essential Oils

Chitosan is the most suitable encapsulation polymer because of its natural abundance, biodegradability, and surface functional groups in the form of free NH₂ groups. The presence of NH₂ groups allows for the facile grafting of functionalized molecules onto the chitosan surface, resulting in multifunctional materialistic applications. Quaternization of chitosan's free amino is one of the typical chemical modifications commonly achieved under acidic conditions. This quaternization improves its ionic character, making it ready for ionic-ionic surface modification. Although the cationic nature of chitosan alone exhibits antibacterial activity because of its interaction with negatively-charged bacterial membranes, the nanoscale size of chitosan further amplifies its antibiofilm activity. Additionally, the researcher used chitosan nanoparticles as polymeric materials to encapsulate antibiofilm agents (such as antibiotics and natural phytochemicals), serving as an excellent strategy to combat biofilm-based secondary infections. This paper provided a summary of available carbohydrate-based biopolymers as antibiofilm materials. Furthermore, the paper focuses on chitosan nanoparticle-based encapsulation of basil essential oil (Ocimum basilicum), mandarin essential oil (Citrus reticulata), Carum copticum essential oil ("Ajwain"), dill plant seed essential oil (Anethum graveolens), peppermint oil (Mentha piperita), green tea oil (Camellia sinensis), cardamom essential oil, clove essential oil (Eugenia caryophyllata), cumin seed essential oil (Cuminum cyminum), lemongrass essential oil (Cymbopogon commutatus), summer savory essential oil (Satureja hortensis), thyme essential oil, cinnamomum essential oil (Cinnamomum zeylanicum), and nettle essential oil (Urtica dioica). Additionally, chitosan nanoparticles are used for the encapsulation of the major essential components carvacrol and cinnamaldehyde, the encapsulation of an oil-in-water nanoemulsion of eucalyptus oil (Eucalyptus globulus), the encapsulation of a mandarin essential oil nanoemulsion, and the electrospinning nanofiber of collagen hydrolysate-chitosan with lemon balm (Melissa officinalis) and dill (Anethum graveolens) essential oil.

Nanochitosan: Commemorating the Metamorphosis of an ExoSkeletal Waste to a Versatile Nutraceutical

Chitin (poly-N-acetyl-D-glucosamine) is the second (after cellulose) most abundant organic polymer. In its deacetylated form-chitosan-becomes a very interesting material for medical use. The chitosan nano-structures whose preparation is described in this article shows unique biomedical value. The preparation of nanochitosan, as well as the most vital biomedical applications (antitumor, drug delivery and other medical uses), have been discussed in this review. The challenges confronting the progress of nanochitosan from benchtop to bedside clinical settings have been evaluated. The need for inclusion of nano aspects into chitosan research, with improvisation from nanotechnological inputs has been prescribed for breaking down the limitations. Future perspectives of nanochitosan and the challenges facing nanochitosan applications and the areas needing research focus have been highlighted.

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-based nanoparticles as drug delivery systems: a review on two decades of research

Chitosan (CS) is one of the most functional natural biopolymer widely used in the pharmaceutical field due to its biocompatibility and biodegradability. These privileges lead to its application in the synthesis of nanoparticles for the drug during the last two decades. This article gives rise to a general review of the different chitosan nanoparticles (CSNPs) preparation techniques: Ionic gelation, emulsion cross-linking, spray-drying, emulsion-droplet coalescence method, nanoprecipitation, reverse micellar method, desolvation method, modified ionic gelation with radial polymerisation and emulsion solvent diffusion, from the point of view of the methodological and mechanistic aspects involved. The physicochemical behaviour of CSNPs including drug loading, drug release, particles size, zeta potential and stability are briefly discussed. This review also directs to bring an outline of the major applications of CSNPs in drug delivery according to drug and route of administration. Finally, derivatives of CSNPs and CS nano-complexes are also discussed.

Reappearance of slow mode in mixtures of polyethylene glycol and poly(sodium methacrylate)

Mixtures of an anionic polyelectrolyte, poly(sodium methacrylate), NaPMA, and a neutral polymer, polyethylene glycol, PEG, were investigated by dynamic and static light scattering techniques at different concentrations and chain-lengths of PEG. The NaPMA standard with a narrow molecular weight distribution was chosen for the study. The so called slow-mode behaviour, characteristic of salt-free NaPMA solutions, vanishes as the simple salt, NaCl in this case, is added in a sufficient amount. However, in NaPMA-NaCl-PEG mixtures, the slow-mode signal is observed again. We assume that the dielectric constant of the mixture with PEG, which is substantially lower than that of pure water, causes the reappearance of the slow-mode signal through reinforced electrostatic interactions between NaPMA polyions. Monte Carlo simulations of a coarse-grained model of the system confirm stronger correlations between NaPMA molecules and thus qualitatively agree with experimental results.

Development of a Gastric Absorptive, Immediate Responsive, Oral Protein-Loaded Versatile Polymeric Delivery System

A multifunctional platform to deliver three diverse proteins of insulin, interferon beta (INF-β) and erythropoietin (EPO), using a novel copolymeric microparticulate system of TMC-PEGDMA-MAA, was synthesised as an intelligent pH-responsive 2-fold gastric and intestinal absorptive system. Physiochemical and physicomechanical studies proved the degree of crystallinity that supported the controlled protein delivery of the microparticulate system. The copolymer was tableted before undertaking in vitro and in vivo analysis. After 2.5 h in simulated gastric fluid (SGF), insulin showed a fractional release of 3.2% in comparison to simulated intestinal fluid (SIF), in which a maximum of 83% of insulin was released. Similarly, INF-β and EPO released 3 and 9.7% in SGF and a maximum of 74 and 81.3% in SIF, respectively. In vivo studies demonstrated a significant decrease in blood glucose by 54.19% within 4 h post-dosing, and the comparator formulation provided 74.6% decrease in blood glucose within the same time period. INF-β peak bioavailable dose in serum was calculated to be 1.3% in comparison to an SC formulation having a peak concentration of 0.9%, demonstrating steady-state release for 24 h. EPO-loaded copolymeric microparticles had a 1.6% peak bioavailable concentration, in comparison to the 6.34% peak concentration after 8 h from the SC comparator formulation.

Intelligent semi-IPN chitosan–PEG–PAAm hydrogel for closed-loop insulin delivery and kinetic modeling

Design of an intelligent semi-IPN chitosan–PEG–PAAm hydrogel using glucose oxidase (GOx) and catalase (CAT) to improve closed-loop insulin delivery systems.

A hybrid modeling approach for optimization of PMAA–chitosan–PEG nanoparticles for oral insulin delivery

This study aimed to develop pH sensitive polymethacrylic acid–chitosan–polyethylene glycol (PCP) nanoparticles for oral insulin delivery.

Nanolayer encapsulation of insulin-chitosan complexes improves efficiency of oral insulin delivery

Current oral insulin formulations reported in the literature are often associated with an unpredictable burst release of insulin in the intestine, which may increase the risk for problematic hypoglycemia. The aim of the study was to develop a solution based on a nanolayer encapsulation of insulin-chitosan complexes to afford sustained release after oral administration. Chitosan/heparin multilayer coatings were deposited onto insulin-chitosan microparticulate cores in the presence of poly(ethylene) glycol (PEG) in the precipitating and coating solutions. The addition of PEG improved insulin loading and minimized an undesirable loss of the protein resulting from redissolution. Nanolayer encapsulation and the formation of complexes enabled a superior loading capacity of insulin (>90%), as well as enhanced stability and 74% decreased solubility at acid pH in vitro, compared with nonencapsulated insulin. The capsulated insulin administered by oral gavage lowered fasting blood glucose levels by up to 50% in a sustained and dose-dependent manner and reduced postprandial glycemia in streptozotocin-induced diabetic mice without causing hypoglycemia. Nanolayer encapsulation reduced the possibility of rapid and erratic falls of blood glucose levels in animals. This technique represents a promising strategy to promote the intestinal absorption efficiency and release behavior of the hormone, potentially enabling an efficient and safe route for oral insulin delivery of insulin in diabetes management.

Recent advances in oral vaccine development: yeast-derived β-glucan particles

Oral vaccination is the most challenging vaccination method due to the administration route. However, oral vaccination has socio-economic benefits and provides the possibility of stimulating both humoral and cellular immune responses at systemic and mucosal sites. Despite the advantages of oral vaccination, only a limited number of oral vaccines are currently approved for human use. During the last decade, extensive research regarding antigen-based oral vaccination methods have improved immunogenicity and induced desired immunological outcomes. Nevertheless, several factors such as the harsh gastro-intestinal environment and oral tolerance impede the clinical application of oral delivery systems. To date, human clinical trials investigating the efficacy of these systems are still lacking. This review addresses the rationale and key biological and physicochemical aspects of oral vaccine design and highlights the use of yeast-derived β-glucan microparticles as an oral vaccine delivery platform.

Drug transport mechanism of oral antidiabetic nanomedicines

CONTEXT

Over the last few decades, extensive efforts have been made worldwide to develop nanomedicine delivery systems, especially via oral route for antidiabetic drugs. Absorption of insulin is hindered by epithelial cells of gastrointestinal tract, acidic gastric pH and digestive enzymes.

EVIDENCE ACQUISITION

Recent reports have identified and explained the beneficial role of several structural molecules like mucoadhesive polymers (polyacrylic acid, sodium alginate, chitosan) and other copolymers for the efficient transport and release of insulin to its receptors.

RESULTS

Insulin nanomedicines based on alginate-dextran sulfate core with a chitosan-polyethylene glycol-albumin shell reduced glycaemia in a dose dependent manner. Orally available exendin-4 formulations exerted their effects in a time dependent manner. Insulin nanoparticles formed by using alginate and dextran sulfate nucleating around calcium and binding to poloxamer, stabilized by chitosan, and subsequently coated with albumin showed a threefold increase of the hypoglycemic effect in comparison to free insulin in animal models. Solid lipid nanoparticles showed an enhancement of the bioavailability of repaglinide (RG) within optimized solid lipid nanoparticle formulations when compared with RG alone.

CONCLUSIONS

Nanoparticles represent multiparticulate delivery systems designed to obtain prolonged or controlled drug delivery and to improve bioavailability as well as stability. Nanoparticles can also offer advantages like limiting fluctuations within therapeutic range, reducing side effects, protecting drugs from degradation, decreasing dosing frequency, and improving patient compliance and convenience.

Design and engineering of disulfide crosslinked nanocomplexes of polyamide polyelectrolytes: stability under biorelevant conditions and potent cellular internalization of entrapped model peptide

Counter polyelectrolytes (PEs) having a degradable polyamide backbone and controlled thiolation are prepared. Their nanosized polyelectrolyte complexes (PECs) spontaneously crosslink under ambient conditions via bioreducible disulfide bonds. These PECs are regenerable after centrifugation, and resist degradation by proteases. They are stable to variations of pH and electrolyte concentration, similar to those encountered in biological milieu. However, they are unraveled in reductive conditions. These PECs act as efficient vectors for delivering entrapped cargo. They entrap with high efficiency, and controllably release, fluorescein isothiocyanate (FITC)-insulin (a model peptide) in vitro. Potent cellular internalization of FITC-insulin within human lung cancer cells with high cell viability is demonstrated.

Polymeric hydrogels for oral insulin delivery

The search for an effective and reliable oral insulin delivery system has been a major challenge facing pharmaceutical scientists for over many decades. Even though innumerable carrier systems that protect insulin from degradation in the GIT with improved membrane permeability and biological activity have been developed, yet a clinically acceptable device is not available for human application. Efforts in this direction are continuing at an accelerated speed. One of the preferred systems widely explored is based on polymeric hydrogels that protect insulin from enzymatic degradation in acidic stomach and delivers effectively in the intestine. Swelling and deswelling mechanisms of the hydrogel under varying pH conditions of the body control the release of insulin. The micro and nanoparticle (NP) hydrogel devices based on biopolymers have been widely explored, but their applications in human insulin therapy are still far from satisfactory. The present review highlights the recent findings on hydrogel-based devices for oral delivery of insulin. Literature data are critically assessed and results from different laboratories are compared.

Chitosan-zinc-insulin complex incorporated thermosensitive polymer for controlled delivery of basal insulin in vivo

Thermosensitive polymeric delivery system (PLA-PEG-PLA) loaded with chitosan-zinc-insulin complex was designed for continuous in vivo insulin delivery at basal level for prolonged period after a single subcutaneous injection. Chitosan-zinc-insulin complex was optimized to restrict the diffusion of insulin from the delivery system by forming large complexes and thereby reducing the initial burst release. The in vivo absorption and bioactivity of insulin released from the delivery systems were studied in streptozotocin-induced diabetic rat model. The amount of insulin released in vivo was quantified using the Enzyme Linked Immunosorbent Assay (ELISA), and its bioactivity was determined by its ability to reduce the blood glucose levels in diabetic rats. An indirect ELISA was performed to determine the immunogenic potential of insulin released from the formulations. Furthermore, the in vitro and in vivo biocompatibility of the delivery system was studied using an MTT assay, and by studying the histology of skin samples, respectively. Chitosan-zinc-insulin complex significantly (P<0.05) reduced the initial burst release of insulin from the polymeric delivery system in comparison to zinc-insulin or insulin alone. The delivery system released insulin for ~3 months in biologically active form with corresponding reduction in blood glucose levels in diabetic rats. The insulin released from the delivery systems did not provoke any immune response. The delivery systems demonstrated excellent biocompatibility both in vitro and in vivo and were non-toxic. The results indicate that the chitosan-zinc-insulin complex incorporated in the thermosensitive polymeric delivery system can be used as an alternative to the conventional daily basal insulin therapy.

Copolymer nanoparticles composed of sulfobetaine and poly(ε-caprolactone) as novel anticancer drug carriers

Novel ABA type amphiphilic copolymers (PCL-APS-PCL) consisting of polycaprolactone (PCL) (A) as hydrophobic block and N,N'-bis (2-hydroxyethyl) methylamine ammonium propane sulfonate (APS) (B) as hydrophilic segment, self-assembled into nanoparticles (NPs) with solvent evaporation method. The sizes and size distributions of NPs were characterized by dynamic light scattering. The morphology of NPs was observed by scanning electron microscopy (SEM). The critical micelle concentration (CMC) was determined by fluorescent probe. The drug loading content (DLC) and the drug release amount were characterized by UV-visible spectrophotometer. The cytotoxicity of the NPs was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylte-trazoliumbromide (MTT) assay. It was found that the NPs were spherical in shape with sizes around 100 nm. The CMCs of the copolymers were quite low (×10(-4) mg/mL). The DLC decreased with lengthening of hydrophobic PCL block. In vitro drug release experiment demonstrated that the release rate of paclitaxel sped with the decrease of PCL length. MTT results showed that NPs were nontoxic to osteoblast and human epithelial carcinoma (hela) cells. After drug loading, NPs could restrain the growth of hela or even kill hela cells. Therefore, these preliminary studies suggest that the novel PCL-APS-PCL NPs have a great potential application as anticancer drug-delivery carriers.

Oral delivery of therapeutic protein/peptide for diabetes--future perspectives

Diabetes is a metabolic disease and is a major cause of mortality and morbidity in epidemic proportions. A type I diabetic patient is dependent on daily injections of insulin, for survival and also to maintain a normal life, which is uncomfortable, painful and also has deleterious effects. Extensive efforts are being made worldwide for developing noninvasive drug delivery systems, especially via oral route. Oral route is the most widely accepted means of administration. However it is not feasible for direct delivery of peptide and protein drugs. To overcome the gastro-intestinal barriers various types of formulations such as polymeric micro/nanoparticles, liposomes, etc. are investigated. In the recent years lot of advances have taken place in developing and understanding the oral peptide delivery systems. Simultaneously, the development and usage of other peptides having anti-diabetic potentials are also considered for diabetes therapy. In this review we are focusing on the advances reported during the past decade in the field of oral insulin delivery along with the possibility of other peptidic incretin hormones such as GLP-1, exendin-4, for diabetes therapy.

HP55-coated capsule containing PLGA/RS nanoparticles for oral delivery of insulin

In this work, we designed and developed a two-stage delivery system composed of enteric capsule and cationic nanoparticles for oral delivery of insulin. The enteric capsule was coated with pH-sensitive hydroxypropyl methylcellulose phthalate (HP55), which could selectively release insulin from nanoparticles in the intestinal tract, instead of stomach. The biodegradable poly(lactic-co-glycolic acid) (PLGA) was selected as the matrix for loading insulin. Eurdragit(®) RS (RS) was also introduced to the nanoparticles for enhancing the penetration of insulin across the mucosal surface in the intestine. The nanoparticles were prepared with the multiple emulsions solvent evaporation method via ultrasonic emulsification. The optimized nanoparticles have a mean size of 285nm, a positive zeta potential of 42mV. The encapsulation efficiency was up to 73.9%. In vitro results revealed that the initial burst release of insulin from nanoparticles was markedly reduced at pH 1.2, which mimics the stomach environment. In vivo effects of the capsule containing insulin PLGA/RS nanoparticles were also investigated in diabetic rat models. The oral delivered capsules induced a prolonged reduction in blood glucose levels. The pharmacological availability was found to be approximately 9.2%. All the results indicated that the integration of HP55-coated capsule with cationic nanoparticles may be a promising platform for oral delivery of insulin with high bioavailability.

The oral delivery of proteins using interpolymer polyelectrolyte complexes

In spite of the numerous barriers inherent in the oral delivery of therapeutically active proteins, research into the development of functional protein-delivery systems is still intense. The effectiveness of such oral protein-delivery systems depend on their ability to protect the incorporated protein from proteolytic degradation in the GI tract and enhance its intestinal absorption without significantly compromising the bioactivity of the protein. Among these delivery systems are polyelectrolyte complexes (PECs) which are composed of polyelectrolyte polymers complexed with a protein via coulombic and other interactions. This review will focus on the current status of PECs with a particular emphasis on the potential and limitations of multi- or inter-polymer PECs used to facilitate oral protein delivery.

pH-Responsive nanoparticles for drug delivery

First-generation nanoparticles (NPs) have been clinically translated as pharmaceutical drug delivery carriers for their ability to improve on drug tolerability, circulation half-life, and efficacy. Toward the development of the next-generation NPs, researchers have designed novel multifunctional platforms for sustained release, molecular targeting, and environmental responsiveness. This review focuses on environmentally responsive mechanisms used in NP designs, and highlights the use of pH-responsive NPs in drug delivery. Different organs, tissues, and subcellular compartments, as well as their pathophysiological states, can be characterized by their pH levels and gradients. When exposed to these pH stimuli, pH-responsive NPs respond with physicochemical changes to their material structure and surface characteristics. These include swelling, dissociating or surface charge switching, in a manner that favors drug release at the target site over surrounding tissues. The novel developments described here may revise the classical outlook that NPs are passive delivery vehicles, in favor of responsive, sensing vehicles that use environmental cues to achieve maximal drug potency.

Thiol functionalized polymethacrylic acid-based hydrogel microparticles for oral insulin delivery

In the present study thiol functionalized polymethacrylic acid-polyethylene glycol-chitosan (PCP)-based hydrogel microparticles were utilized to develop an oral insulin delivery system. Thiol modification was achieved by grafting cysteine to the activated surface carboxyl groups of PCP hydrogels (Cys-PCP). Swelling and insulin loading/release experiments were conducted on these particles. The ability of these particles to inhibit protease enzymes was evaluated under in vitro experimental conditions. Insulin transport experiments were performed on Caco-2 cell monolayers and excised intestinal tissue with an Ussing chamber set-up. Finally, the efficacy of insulin-loaded particles in reducing the blood glucose level in streptozotocin-induced diabetic rats was investigated. Thiolated hydrogel microparticles showed less swelling and had a lower insulin encapsulation efficiency as compared with unmodified PCP particles. PCP and Cys-PCP microparticles were able to inhibit protease enzymes under in vitro conditions. Thiolation was an effective strategy to improve insulin absorption across Caco-2 cell monolayers, however, the effect was reduced in the experiments using excised rat intestinal tissue. Nevertheless, functionalized microparticles were more effective in eliciting a pharmacological response in diabetic animal, as compared with unmodified PCP microparticles. From these studies thiolation of hydrogel microparticles seems to be a promising approach to improve oral delivery of proteins/peptides.

Engineering strategies to enhance nanoparticle-mediated oral delivery

Oral delivery is the most preferred route of drug administration due to convenience, patient compliance and cost-effectiveness. Despite these advantages it remains difficult to achieve satisfactory bioavailability levels via oral administration due to the harsh environment of the gastrointestinal (GI) tract, particularly for biomacromolecules. One promising method to increase the bioavailability of macromolecular drugs such as proteins and nucleic acids is to encapsulate them in nanoparticles before oral administration. This review describes innovative strategies for increasing the efficacy of nanoparticle-mediated delivery to the GI tract. Approaches to optimize nanoparticle formulation by exploiting mucoadhesion, environmental responsiveness and external delivery control mechanisms are discussed. The application of recent advances in nanoparticle synthesis using supercritical fluids, microfluidics and imprint lithography to oral delivery are also presented, as well as possible strategies for incorporating nanoparticles into micro- and macroscale oral delivery devices.

Polysaccharides-based nanoparticles as drug delivery systems

Natural polysaccharides, due to their outstanding merits, have received more and more attention in the field of drug delivery systems. In particular, polysaccharides seem to be the most promising materials in the preparation of nanometeric carriers. This review relates to the newest developments in the preparation of polysaccharides-based nanoparticles. In this review, four mechanisms are introduced to prepare polysaccharides-based nanoparticles, that is, covalent crosslinking, ionic crosslinking, polyelectrolyte complex, and the self-assembly of hydrophobically modified polysaccharides.

PEG-grafted chitosan nanoparticles as an injectable carrier for sustained protein release

The development of injectable nanoparticulate "stealth" carriers for protein delivery is a major challenge. The objective of this work was to investigate the possibility of achieving the controlled release of a model protein, insulin, from PEG-grafted chitosan (PEG-g-chitosan) nanoparticles (mean diameter 150-300 nm) prepared by the ion gelation method. Insulin was efficiently incorporated into the nanoparticles, and reached as high as 38%. In vitro release showed that it could control the insulin release by choosing the composition, loading and release temperature. We observed that the composition of the nanoparticle surface (C/O ratio) increased from 2.40 to 3.23, with an increase in the incubation time. Therefore, we concluded that during this time, insulin release from PEG-g-chitosan nanoparticles followed a diffusion mechanism in which erosion was negligible. The experiments also demonstrated that PEG-g-chitosan helped to maintain the natural structure of the protein entrapped in the nanoparticles.

Recent developments in nanoparticle-based drug delivery and targeting systems with emphasis on protein-based nanoparticles

BACKGROUND

Drug delivery systems with nm dimensions (nanoparticles [NPs]) are attracting increasing attention because they can sequester drugs in systemic circulation, prevent non-specific biodistribution, and target to specific tissues.

OBJECTIVE

We reviewed the recent literature pertinent to NP-based drug delivery, primarily emphasizing NPs fabricated from proteins.

METHODS

A summary of common NP fabrication techniques is provided along with the range of sizes and functional properties obtained. The NP properties critical for injectable drug delivery are reviewed, as well as the attempts to design 'tissue-specific' NPs.

RESULTS/CONCLUSIONS

It has been possible to design > 100 nm NPs from different biomaterials, and further understanding of in vivo stability and interactions with physiologic systems will lead to improved drug delivery systems.

Complexation Hydrogels for Oral Insulin Delivery: Effects of Polymer Dosing on in Vivo Efficacy

Hydrogels comprised of poly(methacrylic acid) grafted with poly(ethylene glycol) (P(MAA-g-EG)) were characterized and examined for their potential as oral insulin carriers. Insulin loaded polymer (ILP) samples were made using two different polymer formulations. The values for the effective molecular weight between crosslinks, M _e , and the network mesh size, xi, were characterized and increased with increasing pH levels for both formulations. Insulin uptake studies indicated a high insulin loading efficiency for all samples tested, however release was dependent on the amount of insulin loaded. The effect of total polymer dosing was investigated by in situ administration in isolated ileal segments in rats. All ILP samples induced a hypoglycemic effect and an increase in insulin levels, proving that insulin was still biologically active. Insulin dosing amounts were varied by (i) maintaining a constant insulin fraction within an ILP sample while changing the amount of ILP and (ii) by varying the insulin fraction while dosing with the same amount of ILP. The total insulin absorption was dependent on both the amount of the polymer present and the concentration of insulin within an ILP sample, with a maximum relative bioavailability of 8.0%.

Polymers and nanoparticles: Intelligent tools for intracellular targeting?

In recent years, a new generation of drugs has entered the pharmaceutical market. Some are more potent, but some are also more toxic and thus, therapeutical efficacy may be hindered, and severe side effects may be observed, unless they are delivered to their assigned place of effect. Those targets are not only certain cell types, moreover, in cancer therapy for example, some drugs even have to be targeted to a specific cell organelle. Those targets in eukaryotic cells include among others endo- and lysosomes, mitochondria, the so-called power plants of the cells, and the biggest compartment with almost all the genetic information, the nucleus. In this review, we describe how the drugs can be directed to specific subcellular organelles and focus especially on synthetic polymers and nanoparticles as their carriers. Furthermore, we portray the progress that has been accomplished in recent years in the field of designing the carriers for efficient delivery into these target structures. Yet, we do not fail to mention the obstacles that still exist and are preventing polymeric and nanoparticular drug carrier systems from their broad application in humans.

Characterization of hydrogels prepared from copolymerization of the different degrees of methacrylate-grafted chondroitin sulfate macromers and acrylic acid

Different degrees (between 20 and 75%) of methacrylate-grafted chondroitin sulfate (CS-MA) were synthesized. These CS-MA macromers were further copolymerized with acrylic acid (AA) at the molar ratio of 1 to 5 to form hydrogels. The sol percents of these CS-MA-AA hydrogels decreased and the cross-linking densities were studied with respect to the degrees of MA substitution onto CS-MA. The cytotoxicity with the increase in degree of MA substitution (DS) onto CS-MA as well as their hydrogels prepared from the corresponding macromers was tested using 293T cells. The cell viability of human dermal fibroblast and mescenchymal stem cells was further tested upon exposure to 75% CS-MA for 1-, 3-, and 7-day incubation period. The hydrogels maintained degradability for long periods of time as evidenced by SEM. A model protein, BSA, demonstrated the prolong-release behaviors of these hydrogels in simulated gastric fluids and pH 7.4 phosphate buffer solutions and a faster release rate in the presence of chondroitinase and esterase at pH 7.4.