Macromolecules as safe penetration enhancers for hydrophilic drugs—a fiction?

Reproductive Performance of Female Rabbits Inseminated with Extenders Supplemented with GnRH Analogue Entrapped in Chitosan-Based Nanoparticles

Rabbit is a reflexively ovulating species. Accordingly, in the practice of artificial insemination (AI) ovulation must be induced via exogenous GnRH (Gonadotropin-Releasing Hormone) administration, which may be performed intramuscularly, subcutaneously, or intravaginally. Unfortunately, the bioavailability of the GnRH analogue when added to the extender is lower due to the proteolytic activity in the seminal plasma and the poor permeability of the vaginal mucosa. The aim of the study was to refine the practice of AI practice in rabbits by replacing parenteral GnRH analogue administration (subcutaneous, intravenous, or intramuscular injection) with intravaginal application, while reducing its concentration in the diluent. Extenders containing the buserelin acetate in chitosan-dextran sulphate and chitosan-alginate nanoparticles were designed and 356 females were inseminated. Reproductive performance of females inseminated with the two experimental extenders, receiving 4 μg of buserelin acetate intravaginally per doe, was compared with that in the control group, the does of which were inseminated with the extender without the GnRH analogue and induced to ovulate with 1 μg of buserelin acetate administered intramuscularly. The entrapment efficiency of the chitosan-dextran sulphate complex was higher than that of chitosan-alginate. However, females inseminated with both systems showed similar reproductive performance. We conclude that both nanoencapsulation systems are an efficient way of intravaginal ovulation induction, allowing a reduction in the level of the GnRH analogue normally used in seminal doses from 15-25 μg to 4 μg.

Influence of permeability enhancers on the paracellular permeability of metformin hydrochloride and furosemide across Caco-2 cells

Permeability enhancers can affect absorption of paracellularly transported drugs. This study aims to evaluate effects of permeability enhancers (chitosan, methyl-β -cyclodextrin, sodium caprate, sodium lauryl sulfate, etc.) on the permeability of paracellularly absorbed furosemide and metformin hydrochloride. Methyl thiazole tetrazolium bromide test was carried out to determine the drug concentrations in permeability study. Trans-epithelial electrical resistance (TEER) values determined to assess the integrity of tight junctions. Permeability enhancers were applied at different concentrations alone, in dual/triple combinations. Permeability was determined using human colorectal adenocarcinoma (Caco-2) cells (TEER > 400 Ω·cm²). Permeability enhancers have no significant effect (<2-fold; p > 0.05) on the permeability of furosemide (1.80 × 10^-5 ± 4.55 × 10^-7 cm/s); however, metformin permeability (1.36 × 10^-5 ± 1.25 × 10^-6 cm/s) increased significantly (p < 0.05) with 0.3% and 0.5% (w/v) chitosan (2.0- and 2.7-fold, respectively), 1% methyl-β -cyclodextrin (w/v) (3.5-fold), 10 and 20 µmol/L sodium caprate (2.2- and 2.8-fold, respectively), and 0.012% sodium lauryl sulfate (w/v) (1.9-fold). Furosemide permeability increased significantly (p < 0.05) with chitosan-sodium lauryl sulfate combination (1.7-fold), and all triple combinations (1.4- to 1.9-fold). Chitosan containing dual/triple combinations resulted in significant increase (p < 0.05) in metformin permeability (1.7 to 2.8-fold). All results indicated that absorption of furosemide and metformin can be improved by the combination of permeability enhancers. Therefore, it can be evaluated for the formulation of development strategies containing furosemide and metformin by the pharmaceutical industry.

Fabrication and Characterization of Clozapine Nanoemulsion Sol-Gel for Intranasal Administration

Clozapine is the most effective antipsychotic for treatment-resistant schizophrenia. However, it causes many adverse drug reactions (ADRs), which lead to poor treatment outcomes. Nose-to-brain (N2B) drug delivery offers a promising approach to reduce peripheral ADRs by minimizing systemic drug exposure. The aim of the present study was to develop and characterize clozapine-loaded nanoemulsion sol-gel (CLZ-NESG) for intranasal administration using high energy sonication method. A range of oils, surfactants, and cosurfactants were screened with the highest clozapine solubility selected for the development of nanoemulsion. Pseudoternary phase diagrams were constructed using a low-energy (spontaneous) method to identify the microemulsion regions (i.e., where mixtures were transparent). The final formulation, CLZ-NESG (pH 5.5 ± 0.2), comprising 1% w/w clozapine, 1% w/w oleic acid, 10% w/w polysorbate 80/propylene glycol (3:1), and 20% w/w poloxamer 407 (P407) solution, had an average globule size of ≤30 nm with PDI 0.2 and zeta potential of -39.7 ± 1.5 mV. The in vitro cumulative drug release of clozapine from the nanoemulsion gel at 34 °C (temperature of nasal cavity) after 72 h was 38.9 ± 4.6% compared to 84.2 ± 3.9% with the control solution. The permeation study using sheep nasal mucosa as diffusion barriers confirmed a sustained release of clozapine with 56.2 ± 2.3% cumulative drug permeated after 8 h. Additionally, the histopathological examination found no severe nasal ciliotoxicity on the mucosal tissues. The thermodynamic stability studies showed that the gel strength and viscosity of CLZ-NESG decreased after temperature cycling but was still seen to be in "gel" form at nasal temperature. However, the accelerated storage stability study showed a decrease in drug concentration after 3 months, which can be expected at elevated stress conditions. The formulation developed in this study showed desirable physicochemical properties for intranasal administration, highlighting the potential value of a nanoemulsion gel for improving drug bioavailability of clozapine for N2B delivery.

Rapid Ultratough Topological Tissue Adhesives

Tissue adhesives capable of achieving strong and tough adhesion in permeable wet environments are useful in many biomedical applications. However, adhesion generated through covalent bond formation directly with the functional groups of tissues (i.e., COOH and NH2  groups in collagen), or using non-covalent interactions can both be limited by weak, unstable, or slow adhesion. Here, it is shown that by combining pH-responsive bridging chitosan polymer chains and a tough hydrogel dissipative matrix one can achieve unprecedented ultratough adhesion to tissues (>2000 J m-2 ) in 5-10 min without covalent bond formation. The strong non-covalent adhesion is shown to be stable under physiologically relevant conditions and strongly influenced by chitosan molecular weight, molecular weight of polymers in the matrix, and pH. The adhesion mechanism relies primarily on the topological entanglement between the chitosan chains and the permeable adherends. To further expand the applicability of the adhesives, adhesion time can be decreased by dehydrating the hydrogel matrix to facilitate rapid chitosan interpenetration and entanglement (>1000 J m-2  in ≤1 min). The unprecedented adhesive properties presented in this study open opportunities for new strategies in the development of non-covalent tissue adhesives and numerous bioapplications.

Effect of Penetration Enhancers and Safety on the Transdermal Delivery of Apremilast in Skin

The poor water solubility of apremilast (APR) is the main impediment to the penetration of the drug through the skin barrier. The objective of this study was to evaluate the permeability of APR in different solutions enriched with penetration promoters in ex vivo samples of human skin, and additionally assess its tolerance in vivo. To this end, APR solutions with 5% promoter were developed, and the drug's ability to penetrate human abdominal skin samples was evaluated; the coefficients of permeability, cumulated amounts permeated, and flow were some of the parameters evaluated; likewise, the in vitro and in vivo tolerance of the solutions was evaluated. The results obtained showed that the solutions containing squalene as a promoter improved the penetration of APR compared to the other promoters evaluated; in the same way, on an in vitro scale in HaCaT cells, the promoters were not toxic, finding a cell viability greater than 80% at the different dilutions evaluated. In the in vivo tests carried out with the solution that presented the best results (APR-Squalene solution), it was observed that it does not cause irritation or erythema on the skin after its colorimetric and histological evaluation of the dorsal region of rats after its application. Squalene becomes an excellent candidate to improve the permeability of the drug in the case of the development of a topical formulation; in addition, it was confirmed that this penetration enhancer is neither toxic nor irritating when in contact with the skin in in vivo tests.

The Use of Chitosan, Alginate, and Pectin in the Biomedical and Food Sector-Biocompatibility, Bioadhesiveness, and Biodegradability

Nowadays, biopolymers as intelligent and active biopolymer systems in the food and pharmaceutical industry are of considerable interest in their use. With this association in view, biopolymers such as chitosan, alginate, pectin, cellulose, agarose, guar gum, agar, carrageenan, gelatin, dextran, xanthan, and other polymers have received significant attention in recent years due to their abundance and natural availability. Furthermore, their versatile properties such as non-toxicity, biocompatibility, biodegradability, and flexibility offer significant functionalities with multifunctional applications. The purpose of this review is to summarize the most compatible biopolymers such as chitosan, alginate, and pectin, which are used for application in food, biotechnological processes, and biomedical applications. Therefore, chitosan, alginate, and pectin are biopolymers (used in the food industry as a stabilizing, thickening, capsular agent, and packaging) with great potential for future developments. Moreover, this review highlights their characteristics, with a particular focus on their potential for biocompatibility, biodegradability, bioadhesiveness, and their limitations on certain factors in the human gastrointestinal tract.

Penetration Enhancers in Ocular Drug Delivery

There are more than 100 recognized disorders of the eye. This makes the development of advanced ocular formulations an important topic in pharmaceutical science. One of the ways to improve drug delivery to the eye is the use of penetration enhancers. These are defined as compounds capable of enhancing drug permeability across ocular membranes. This review paper provides an overview of anatomical and physiological features of the eye and discusses some common ophthalmological conditions and permeability of ocular membranes. The review also presents the analysis of literature on the use of penetration-enhancing compounds (cyclodextrins, chelating agents, crown ethers, bile acids and bile salts, cell-penetrating peptides, and other amphiphilic compounds) in ocular drug delivery, describing their properties and modes of action.

The importance of microfluidics for the preparation of nanoparticles as advanced drug delivery systems

INTRODUCTION

Nanoparticles are anticipated to overcome persistent challenges in efficient drug delivery, but the limitations associated with conventional methods of preparation are resulting in slow translation from research to clinical applications. Due to their enormous potential, microfluidic technologies have emerged as an advanced approach for the development of drug delivery systems with well-defined physicochemical characteristics and in a reproducible manner.

AREAS COVERED

This review provides an overview of microfluidic devices and materials used for their manufacturing, together with the flow patterns and regimes commonly used for nanoparticle preparation. Additionally, the different geometries used in droplet microfluidics are reviewed, with particular attention to the co-flow geometry used for the production of nanoparticles. Finally, this review summarizes the main and most recent nanoparticulate systems prepared using microfluidics, including drug nanosuspensions, polymeric, lipid, structured, and theranostic nanoparticles.

EXPERT OPINION

The production of nanoparticles at industrial scale is still a challenge, but the microfluidic technologies bring exciting opportunities to develop drug delivery systems that can be engineered in an easy, cost-effective and reproducible manner. As a highly interdisciplinary research field, more efforts and general acceptance are needed to allow for the translation of nanoparticulate drug delivery systems from academic research to the clinical practice.

Enhanced nasal drug delivery efficiency by increasing mechanical loading using hypergravity

Nasal route drug administration for local and systemic delivery of many therapeutics has received attention because the nasal cavity is highly vascularized and provides a large surface area for drug absorption. However, nasal mucosa exhibits limited permeability to polar molecules. In this study, we developed a novel method for improving absorption efficiency of polar drugs by applying hypergravity. RPMI 2650 cells and primary human nasal epithelial cells were exposed three times to a 20 min hypergravitational condition (10 × g) with a 20 min rest period after each exposure. The applied hypergravity induced a decrease in transepithelial electrical resistance without significant loss of cellular metabolic activity, and cellular permeability of fluorescein sodium salt (MW 376 Da; NaFI) and FITC-labeled dextran (average MW 4,000 Da; FD-4) increased by 19% and 16%, respectively. Immunostaining and RT-qPCR results demonstrated that hypergravity conditions affected cytoskeletal structures and tight junctions, leading to weakening of the cell barrier function and increasing the cellular permeability of polar molecules. Our results indicate that hypergravity could be used as a new strategy for enhancing the efficiency of drug absorption via the nasal route.

Gamma sterilization of diclofenac sodium loaded- N-trimethyl chitosan nanoparticles for ophthalmic use

This study was conducted to investigate the effect of gamma irradiation on physicochemical properties of N-trimethyl chitosan (TMC), diclofenac sodium (DC) and diclofenac sodium loaded N-trimethylchitosan nanoparticles (DC-TMCNs), and to determine suitable doses of gamma rays for sterilization of DC-TMCNs. Physicochemical properties of TMC, DC and DC-TMCNs before and after exposure to gamma rays at various doses were investigated. It was found that gamma irradiation at doses of 5-25kGy did not cause any significant changes in physical and chemical properties of TMC, DC and DC-TMCNs. The bioburden of DC-TMCNs was 1.5×10⁶ CFU/vial. The initial contaminating bacteria were radiosensitive bacteria. A number of microorganisms was reduced to 10^-6 after exposure to 9.9kGy of gamma rays. Therefore, DC-TMCNs could be sterilized by gamma irradiation at a dose of 10kGy, which did not alter their physicochemical properties and did not produce any substances toxic to the eye.

Effect of permeability enhancers on paracellular permeability of acyclovir

Objectives

According to Biopharmaceutics Classification System (BCS), acyclovir is a class III (high solubility, low permeability) compound, and it is transported through paracellular route by passive diffusion. The aim of this study was to investigate the effect of various pharmaceutical excipients on the intestinal permeability of acyclovir.

Methods

The single-pass in-situ intestinal perfusion (SPIP) method was used to estimate the permeability values of acyclovir and metoprolol across different intestinal segments (jejunum, ileum and colon). Permeability coefficient (Peff) of acyclovir was determined in the absence and presence of a permeation enhancer such as dimethyl β-cyclodextrin (DM-β-CD), sodium lauryl sulfate (SLS), sodium caprate (Cap-Na) and chitosan chloride.

Key findings

All enhancers increased the permeability of paracellularly transported acyclovir. Although Cap-Na has the highest permeability-enhancing effect in all segments, permeation-enhancing effect of chitosan and SLS was only significant in ileum. On the other hand, DM-β-CD slightly decreased the permeability in all intestinal segments.

Conclusions

These findings have potential implication concerning the enhancement of absorption of paracellularly transported compounds with limited oral bioavailability. In the case of acyclovir, Cap-Na either alone or in combination with SLS or chitosan has the potential to improve its absorption and bioavailability and has yet to be explored.

Photochemical tissue penetration via photosensitizer for effective drug penetration in a non-vascular tumor

To improve the tissue penetration efficiency (PE%) of hydrophilic-drugs in non-vascular drug eluting stents (DES), we designed photochemical tissue penetration (PTP) invested DES (PTP-DES). The PTP technology was applied to the stent as a covering membrane to generate singlet oxygen. Singlet oxygen damages the epithelial layer, so the PE% of released drugs could be improved. To prepare the PTP-DES membrane, chlorin e6 (Ce6, photosensitizer) was incorporated in a gemcitabine (GEM) eluting polyurethane (PU) membrane (Ce6-GEM-PU). Ce6-GEM-PU has smooth surface that is ∼40 μm thick. The photoactivity of Ce6 was maintained for 2 weeks (in vitro GEM releasing period). In a separate cell culture system, both 1.5 folds higher PE% and an improved tumor cell growth inhibition effect were shown after light exposure. Additionally, in tissue penetration experimental system, 2 folds increased in the PE% of GEM was induced by laser exposure at 80 J/cm2. Additionally, improved PE% of hydrophilic molecules (Fluorescein and GEM) was confirmed in colon tumor bearing mice. Consequentially, tumor growth, when implanted with Ce6-GEM-PU, was effectively inhibited without significant side effects. Based on these results, we believe that the PTP-DES system has great potential for improving the therapeutic effect of conventional DES.

Heparin-derived supersulfated disaccharide inhibits allergic airway responses in sheep

The tetrasaccharide sequence of heparin oligosaccharides is the minimum chain length possessing anti-allergic activity, as the disaccharide fraction is inactive. Since sulfation pattern can modify the biological actions of heparin, we hypothesized that "supersulfation" of the inactive heparin disaccharide could confer anti-allergic activity to this molecule. To test this, we produced a supersulfated heparin disaccharide (Hep-SSD) and evaluated its anti-allergic activity in sheep with documented antigen-induced early and late airway responses (EAR and LAR) and airway hyperresponsiveness (AHR). Porcine intestinal heparin was depolymerized with nitrous acid, the disaccharide fraction separated by size exclusion chromatography, and then treated with pyridine-sulfur trioxide complex to yield Hep-SSD. Its chemical structure [IdoU2',3',4'S (1→4) AMan1,3,6S] was confirmed by HPLC, Mass Spectrometry and NMR analysis. Inhaled doses of 5 mg, 10 mg and 20 mg Hep-SSD produced inhibition of EAR (8%, 35% and 35%), LAR (50%, 80%, and 77%) and AHR (67%, 100% and 75%), respectively. A single oral dose of 2 mg/kg Hep-SSD given 90 min before challenge significantly inhibited EAR, LAR and AHR, but 1 mg/kg was ineffective. Multi dose oral treatment with Hep-SSD had a cumulative effect, as a once daily dose of 2 mg/kg for 3 days (last dose, 16 h before antigen) inhibited EAR, LAR and AHR by 30%, 75% and 74%, respectively. Finally, the oral activity of Hep-SSD could be enhanced 4 fold by formulating it with Carbopol(®)934P, in an enteric coated capsule. These data demonstrate that "supersulfation" can confer biological activity to the inactive heparin disaccharide. Both inhaled and oral Hep-SSD demonstrate significant anti-allergic activity and, therefore, may have therapeutic potential.

Nanomedicine in cardiovascular therapy: recent advancements

Cardiovascular disease (CVD) is comprised of a group of disorders affecting the heart and blood vessels of the human body and is one of the leading causes of death worldwide. Current therapy for CVD is limited to the treatment of already established disease, and it includes pharmacological and/or surgical procedures, such as percutaneous coronary intervention with stenting and coronary artery bypass grafting. However, lots of complications have been raised with these modalities of treatment, including systemic toxicity with medication, stent thrombosis with percutaneous coronary intervention and nonsurgical candidate patients for coronary artery bypass grafting. Nanomedicine has emerged as a potential strategy in dealing with these obstacles. Applications of nanotechnology in medicine are already underway and offer tremendous promise. This review explores the recent developments of nanotechnology in the field of CVD and gives an insight into its potential for diagnostics and therapeutics applications. The authors also explore the characteristics of the widely used biocompatible nanomaterials for this purpose and evaluate their opportunities and challenges for developing novel nanobiotechnological tools with high efficacy for biomedical applications, such as radiological imaging, vascular implants, gene therapy, myocardial infarction and targeted delivery systems.

Oral colon delivery of insulin with the aid of functional adjuvants

Oral colon delivery is currently considered of importance not only for the treatment of local pathologies, such as primarily inflammatory bowel disease (IBD), but also as a means of accomplishing systemic therapeutic goals. Although the large bowel fails to be ideally suited for absorption processes, it may indeed offer a number of advantages over the small intestine, including a long transit time, lower levels of peptidases and higher responsiveness to permeation enhancers. Accordingly, it has been under extensive investigation as a possible strategy to improve the oral bioavailability of peptide and protein drugs. Because of a strong underlying rationale, most of these studies have focused on insulin. In the present review, the impact of key anatomical and physiological characteristics of the colon on its viability as a protein release site is discussed. Moreover, the main formulation approaches to oral colon targeting are outlined along with the design features and performance of insulin-based devices.

Structural features and bioactivities of the chitosan

Fourier transform infrared (FT-IR) spectroscopic studies (3500-600 cm(-1)) showed some different bands of chitosan. The absorption at 3439 cm(-1) is stretching vibration of -OH and -NH(2) bonds, indicating the association of the hydrogen-bond between them. The bands at 1659, 1599 and 1321 cm(-1) are attributable to the peaks of stretching vibrations of amide I (ν((C=O))), II (δ((N-H))), and the peak of stretching and bending vibrations of III (ν((C-N))) (δ((N-H))). The chitosan showed strong free radical scavenging activities. Pretreatment with chitosan significantly prevented the decrease of antioxidant enzymes activities and the increase of p-JNK at 3 h after renal ischemia and reduced renal tubular epithelial cell apoptosis.

A review on composite liposomal technologies for specialized drug delivery

The combination of liposomes with polymeric scaffolds could revolutionize the current state of drug delivery technology. Although liposomes have been extensively studied as a promising drug delivery model for bioactive compounds, there still remain major drawbacks for widespread pharmaceutical application. Two approaches for overcoming the factors related to the suboptimal efficacy of liposomes in drug delivery have been suggested. The first entails modifying the liposome surface with functional moieties, while the second involves integration of pre-encapsulated drug-loaded liposomes within depot polymeric scaffolds. This attempts to provide ingenious solutions to the limitations of conventional liposomes such as short plasma half-lives, toxicity, stability, and poor control of drug release over prolonged periods. This review delineates the key advances in composite technologies that merge the concepts of depot polymeric scaffolds with liposome technology to overcome the limitations of conventional liposomes for pharmaceutical applications.

Potential prospects of chitosan derivative trimethyl chitosan chloride (TMC) as a polymeric absorption enhancer: synthesis, characterization and applications

In recent years, researchers have been working extensively on various novel properties of polymers to develop increased efficiency of drug delivery and improve bioavailability of various drug molecules, especially macromolecules. Chitosan, a naturally occurring polysaccharide, because of its protonated/polymeric nature, provides effective and safe absorption of peptide and protein drugs. Its transmucosal absorption is, however, limited to acidic media because of its strong intermolecular hydrogen bonds. A new partially quaternized chitosan derivative, N-trimethyl chitosan chloride (TMC), has been synthesized with improved solubility, safety and effectiveness as an absorption enhancer at neutral pH and in aqueous environment. It enhances the absorption, especially of peptide drugs, by reversible opening of tight junctions in between epithelial cells, thereby facilitating the paracellular diffusion of peptide drugs. This derivative thus opens new perspectives as a biomaterial for various pharmaceutical applications/drug delivery systems. This review deals with the potential use of the quaternized chitosan derivative as a permeation enhancer for the mucosal delivery of macromolecular drugs along with its other biomedical applications.

A mucoadhesive nanoparticulate system for the simultaneous delivery of macromolecules and permeation enhancers to the intestinal mucosa

The feasibility of combining safe permeation enhancers in a mucoadhesive particulate system for the oral delivery of peptide drugs was investigated in this study. Polyelectrolyte complex nanoparticles (NPs) were prepared by ionic interaction of spermine (SPM) with polyacrylic acid (PAA) polymer. Cytotoxicity studies in Caco-2 monolayers revealed the safety of the delivery system in the concentration range used for permeation enhancement. The cellular transport of fluorescein isothiocyanate dextran (FD4) showed higher permeation enhancing profiles of SPM-PAA NPs, as compared to SPM solution or PAA NPs prepared by ionic gelation with MgCl(2) (Mg-PAA NPs). These permeation enhancing effects were associated with a reversible decrease in TEER values, suggesting a paracellular permeation pathway by reversible opening of the tight junctions. Furthermore, confocal microscopy results revealed strong association of the NPs prepared using fluorescence labeled PAA to Caco-2 cells. The permeation enhancing properties of SPM-PAA NPs were further evaluated in vivo after oral administration to rats, using FD4 and calcitonin as models of poorly permeating drugs. Confocal microscopy images of rats' small intestine confirmed previous findings in Caco-2 cells and revealed a strong and prolonged penetration of FD4 from the mucosal to the basolateral side of the intestinal wall. In addition, the proposed NPs were efficient in improving the oral absorption of calcitonin, as evidenced by the significant and prolonged reduction of the blood calcemia in rats.

Chitosan-based delivery systems for protein therapeutics and antigens

Therapeutic peptides/proteins and protein-based antigens are chemically and structurally labile compounds, which are almost exclusively administered by parenteral injections. Recently, non-invasive mucosal routes have attracted interest for administration of these biotherapeutics. Chitosan-based delivery systems enhance the absorption and/or cellular uptake of peptides/proteins across mucosal sites and have immunoadjuvant properties. Chitosan is a mucoadhesive polysaccharide capable of opening the tight junctions between epithelial cells and it has functional groups for chemical modifications, which has resulted in a large variety of chitosan derivatives with tunable properties for the aimed applications. This review provides an overview of chitosan-based polymers for preparation of both therapeutic peptides/protein and antigen formulations. The physicochemical properties of these carrier systems as well as their applications in protein and antigen delivery through parenteral and mucosal (particularly nasal and pulmonary) administrations are summarized and discussed.

Effect of chitosan glutamate, carbomer 974P, and EDTA on the in vitro Caco-2 permeability and oral pharmacokinetic profile of acyclovir in rats

BACKGROUND

Chitosan glutamate and polyacrylic acid (e.g., carbomer 974P) are known to modulate the tight junctions in the intestinal wall and increase permeability and blood exposure of drugs absorbed orally by the paracellular route.

AIM

To assess the impact of chitosan glutamate and carbomer 974P on the absorption of paracellularly absorbed model drug, acyclovir, in vitro and in rat in vivo.

METHODS

The influence of chitosan glutamate and carbomer 974P (alone and in combination with EDTA-Na2) on the in vitro Caco-2 permeability and oral pharmacokinetic profile in the rat of acyclovir was investigated.

RESULTS

In the presence of chitosan glutamate, the apparent permeability of acyclovir across Caco2 monolayer increased 4.1 times relative to control. This increase was accompanied by a significant ( approximately 60%) decrease in transepithelial electrical resistance values indicating opening of the tight junctions in the cell monolayer. In rat, chitosan glutamate doubled oral bioavailability of acyclovir and tripled the amount of acyclovir excreted unchanged into urine. In contrast, the effect of carbomer 974P was not statistically significant at 5% level.

CONCLUSIONS

In conclusion, chitosan glutamate (1-3%) and chitosan glutamate (1%)/EDTA-Na2 (0.01%) are effective excipients to increase permeability of acyclovir across Caco-2 cell monolayers and the oral absorption in the rat in vivo.

Efficient mucosal delivery of optical contrast agents using imidazole-modified chitosan

The clinical applicability of antibodies and plasmonic nanosensors as topically applied, molecule-specific optical diagnostic agents for noninvasive early detection of cancer and precancer is severely limited by our inability to efficiently deliver macromolecules and nanoparticles through mucosal tissues. We have developed an imidazole-functionalized conjugate of the polysaccharide chitosan (chitosan-IAA) to enhance topical delivery of contrast agents, ranging from small molecules and antibodies to gold nanoparticles up to 44 nm in average diameter. Contrast agent uptake and localization in freshly resected mucosal tissues was monitored using confocal microscopy. Chitosan-IAA was found to reversibly enhance mucosal permeability in a rapid, reproducible manner, facilitating transepithelial delivery of optical contrast agents. Permeation enhancement occurred through an active process, resulting in the delivery of contrast agents via a paracellular or a combined paracellular/transcellular route depending on size. Coadministration of epidermal growth factor receptor-targeted antibodies with chitosan-IAA facilitated specific labeling and discrimination between paired normal and malignant human oral biopsies. Together, these data suggest that chitosan-IAA is a promising topical permeation enhancer for mucosal delivery of optical contrast agents.

Methylated N-(4-N,N-dimethylaminobenzyl) chitosan, a novel chitosan derivative, enhances paracellular permeability across intestinal epithelial cells (Caco-2)

The aim of this study was to investigate the effect of methylated N-(4-N,N-dimethylaminobenzyl) chitosan, TM-Bz-CS, on the paracellular permeability of Caco-2 cell monolayers and its toxicity towards the cell lines. The factors affecting epithelial permeability, e.g., degree of quaternization (DQ) and extent of dimethylaminobenzyl substitution (ES), were evaluated in intestinal cell monolayers of Caco-2 cells using the transepithelial electrical resistance and permeability of Caco-2 cell monolayers, with fluorescein isothiocyanate dextran 4,400 (FD-4) as a model compound for paracellular tight-junction transport. Cytotoxicity was evaluated with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide viability assay. The results revealed that, at pH 7.4, TM-Bz-CS appeared to increase cell permeability in a concentration-dependent manner, and this effect was relatively reversible at lower doses of 0.05-0.5 mM. Higher DQ and the ES caused the permeability of FD-4 to be higher. The cytotoxicity of TM-Bz-CS depended on concentration, %DQ, and %ES. These studies demonstrated that this novel modified chitosan has potential as an absorption enhancer.

Development of a Gas Empowered Drug Delivery system for peptide delivery in the small intestine

The aim of this investigation was to design a novel Gas Empowered Drug Delivery (GEDD) system for CO(2) forced transport of peptide drugs together with mucoadhesive polymers to the surface of the small intestine. The GEDD effect of the core tablet was achieved using CO(2) gas to push insulin together with the mucoadhesive excipients poly(ethyleneoxide) (PEO) and the permeation enhancer trimethyl chitosan (TMC) to the surface of the small intestine. The in-vitro insulin release showed that almost 100% of the insulin was released from enterically coated tablets within 30 min at pH 6.8. The designed GEDD system was shown to increase the insulin transport by approximately 7 times in comparison with the free insulin across sheep's intestine ex-vivo. Three different peroral formulations were administered to male rabbits: F1 containing no TMC or PEO, F2 containing PEO but no TMC and F3 containing both PEO and TMC. The administrations of insulin using the formulation F1 resulted in a low FR value of 0.2%+/-0.1%, while the formulations F2 and F3 resulted in a much higher FR values of 0.6+/-0.2% and 1.1%+/-0.4%, respectively. Hence, the insulin permeation achieved by the GEDD system is primarily due to the enhancing effect of TMC and the mucoadhesive properties of PEO both of which synergistically increase the bioavailability of insulin.

Composition and applications of Aloe vera leaf gel

Many of the health benefits associated with Aloe vera have been attributed to the polysaccharides contained in the gel of the leaves. These biological activities include promotion of wound healing, antifungal activity, hypoglycemic or antidiabetic effects antiinflammatory, anticancer, immunomodulatory and gastroprotective properties. While the known biological activities of A. vera will be briefly discussed, it is the aim of this review to further highlight recently discovered effects and applications of the leaf gel. These effects include the potential of whole leaf or inner fillet gel liquid preparations of A. vera to enhance the intestinal absorption and bioavailability of co-administered compounds as well as enhancement of skin permeation. In addition, important pharmaceutical applications such as the use of the dried A. vera gel powder as an excipient in sustained release pharmaceutical dosage forms will be outlined.