Improved paracellular uptake by the combination of different types of permeation enhancers

Enzymatic absorption promoters for non-invasive peptide delivery

Peptide drugs offer considerable potential for treating a diverse range of diseases. Yet, their clinical application is generally restricted to injectable therapies. The main challenge hindering their broader use through globally accessible, patient-friendly, and non-invasive delivery routes such as oral or buccal, lies in their poor ability to cross biological barriers effectively. Here, we demonstrate that enzymes can be harnessed to transiently reduce these barriers and improve absorption. As a proof of concept, we employ a mucin-specific protease (mucinase) and a phospholipase to increase mucus diffusivity and epithelial cell membrane permeability, respectively. In a canine model, we show that enteric capsules containing both enzymes, and the peptide drug desmopressin achieved a relative bioavailability of 155 % compared to the drug alone. Additionally, a buccal patch loaded with phospholipase and semaglutide displayed a 5-fold higher bioavailability and lower variability (71.5 % reduction in the coefficient of variation) compared to the commercially available oral tablet. These results suggest that enzymatic modulation of biological barriers holds promise as a strategy to improve non-invasive delivery of peptides and potentially other macromolecular drugs.

Papain Suppresses Atopic Skin Inflammation through Anti-Inflammatory Activities Using In Vitro and In Vivo Models

Papain (PN) is a proteolytic enzyme derived from Carica Papaya L. While the pharmacological effects of PN have not been extensively studied compared to its enzymatic activity, PN also holds potential benefits beyond protein digestion. This study aimed to investigate the potential effects of PN against skin inflammation in house dust mite Dermatophagoides farinae body (Dfb)-exposed NC/Nga atopic dermatitis (AD) mice and human HaCaT keratinocytes and their underlying mechanisms. The effects of PN on the skin were assessed via histological examination, measurements of transepidermal water loss (TEWL), quantitative reverse transcription-polymerase chain reaction, Western blotting, and enzyme-linked immunosorbent assay. Our findings indicated that the oral intake of PN decreased the severity scores of lesions resembling AD, TEWL, and the levels of inflammatory cytokines and serum immunoglobulin E in Dfb-induced AD mice, along with a reduction in epidermal thickness and mast cell infiltration. Additionally, PN inhibited the activation of the mitogen-activated protein kinases (MAPKs) and the signal transducer and activator of transcription (STAT) pathways in Dfb-induced AD mice and HaCaT keratinocytes. Moreover, PN improved survival and reduced ROS production in H2O2-damaged HaCaT keratinocytes and enhanced the expression of antioxidant enzymes in Dfb-induced AD mice. Concludingly, the oral administration of PN suppressed inflammatory mediators and downregulated the MAPKs/STAT pathway, suggesting its potential role in AD pathogenesis.

Nose-to-Brain (N2B) Delivery: An Alternative Route for the Delivery of Biologics in the Management and Treatment of Central Nervous System Disorders

In recent years, there have been a growing number of small and large molecules that could be used to treat diseases of the central nervous system (CNS). Nose-to-brain delivery can be a potential option for the direct transport of molecules from the nasal cavity to different brain areas. This review aims to provide a compilation of current approaches regarding drug delivery to the CNS via the nose, with a focus on biologics. The review also includes a discussion on the key benefits of nasal delivery as a promising alternative route for drug administration and the involved pathways or mechanisms. This article reviews how the application of various auxiliary agents, such as permeation enhancers, mucolytics, in situ gelling/mucoadhesive agents, enzyme inhibitors, and polymeric and lipid-based systems, can promote the delivery of large molecules in the CNS. The article also includes a discussion on the current state of intranasal formulation development and summarizes the biologics currently in clinical trials. It was noted that significant progress has been made in this field, and these are currently being applied to successfully transport large molecules to the CNS via the nose. However, a deep mechanistic understanding of this route, along with the intimate knowledge of various excipients and their interactions with the drug and nasal physiology, is still necessary to bring us one step closer to developing effective formulations for nasal-brain drug delivery.

Effects of Proteases from Pineapple and Papaya on Protein Digestive Capacity and Gut Microbiota in Healthy C57BL/6 Mice and Dose-Manner Response on Mucosal Permeability in Human Reconstructed Intestinal 3D Tissue Model

Cysteine proteases obtained from the stem of pineapple or papaya latex, bromelain and papain, respectively, exhibit a broad spectrum of beneficial effects on human health. However, their effects on gut microbiota composition or dose-manner effects on the intestinal integrity of healthy tissue have not been evaluated. In this study, C57BL/6 young, healthy mice were fed bromelain or papain in a dose of 1 mg per animal/day for three consecutive days, followed by the assessment of digestive protein capacity, intestinal morphology and gut microbiota composition. Furthermore, a human reconstructed 3D tissue model EpiIntestinal (SMI-100) was used to study the effects of 1, 0.1 and 10 mg/mL doses of each enzyme on tissue integrity and mucosal permeability using TEER measurements and passage of Lucifer Yellow marker from the apical to the basolateral side of the mucosa. The results indicated that fruit proteases have the potential to modulate gut microbiota with decreasing abundance of Proteobacteria and increasing beneficial Akkermansia muciniphila. The enhancement of pancreatic trypsin was observed in bromelain and papain supplementation, while bromelain also increased the thickness of the ileal mucosa. Furthermore, an in vitro study showed a dose-dependent interruption in epithelial integrity, which resulted in increased paracellular permeability by the highest doses of enzymes. These findings define bromelain and papain as promising enzymatic supplementation for controlled enhancement of paracellular uptake when needed, together with beneficial effects on the gut microbiota.

Convolutions in the rendition of nose to brain therapeutics from bench to bedside: Feats & fallacies

Brain, a subtle organ of multifarious nature presents plethora of physiological, metabolic and bio-chemical convolutions that impede the delivery of biomolecules and thereby resulting in truncated therapeutic outcome in pathological conditions of central nervous system (CNS). The absolute bottleneck in the therapeutic management of such devastating CNS ailments is the BBB. Another pitfall is the lack of efficient technological platforms (due to high cost and low approval rates) as well as limited clinical trials (due to failures of neuro‑leads in late-stage pipelines) for CNS disorders which has become a literal brain drain with poorest success rates compared to other therapeutic areas, owing to time consuming processes, tremendous convolutions and conceivable adverse effects. With the advent of intranasal delivery (via direct N2B or indirect nose to blood to brain), several novel drug delivery carriers viz. unmodified or surface modified nanoparticle based carriers, lipid based colloidal nanocarriers and drysolid/liquid/semisolid nanoformulations or delivery platforms have been designed as a means to deliver therapeutic agents (small and large molecules, peptides and proteins, genes) to brain, bypassing BBB for disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), epilepsy, schizophrenia and CNS malignancies primarily glioblastomas. Intranasal application offers drug delivery through both direct and indirect pathways for the peripherally administered psychopharmacological agents to CNS. This route could also be exploited for the repurposing of conventional drugs for new therapeutic uses. The limited clinical translation of intranasal formulations has been primarily due to existence of barriers of mucociliary clearance in the nasal cavity, enzyme degradation and low permeability of the nasal epithelium. The present review literature aims to decipher the new paradigms of nano therapeutic systems employed for specific N2B drug delivery of CNS drugs through in silico complexation studies using rationally chosen mucoadhesive polymers (exhibiting unique physicochemical properties of nanocarrier's i.e. surface modification, prolonging retention time in the nasal cavity, improving penetration ability, and promoting brain specific delivery with biorecognitive ligands) via molecular docking simulations. Further, the review intends to delineate the feats and fallacies associated with N2B delivery approaches by understanding the physiological/anatomical considerations via decoding the intranasal drug delivery pathways or critical factors such as rationale and mechanism of excipients, affecting the permeability of CNS drugs through nasal mucosa as well as better efficacy in terms of brain targeting, brain bioavailability and time to reach the brain. Additionally, extensive emphasis has also been laid on the innovative formulations under preclinical investigation along with their assessment by means of in vitro /ex vivo/in vivo N2B models and current characterization techniques predisposing an efficient intranasal delivery of therapeutics. A critical appraisal of novel technologies, intranasal products or medical devices available commercially has also been presented. Finally, it could be warranted that more reminiscent pharmacokinetic/pharmacodynamic relationships or validated computational models are mandated to obtain effective screening of molecular architecture of drug-polymer-mucin complexes for clinical translation of N2B therapeutic systems from bench to bedside.

Thiolated Chitosans: A Multi-talented Class of Polymers for Various Applications

Various properties of chitosan can be customized by thiolation for very specific needs in a wide range of application areas. Since the discovery of thiolated chitosans, many studies have proven their advantageous characteristics, such as adhesion to biological surfaces, adjustable cross-linking and swelling behavior, controllable drug release, permeation as well as cellular uptake enhancement, inhibition of efflux pumps and enzymes, complexation of metal ions, antioxidative properties, and radical scavenging activity. Simultaneously, these polymers remain biodegradable without increased toxicity. Within this Review, an overview about the different possibilities to covalently attach sulfhydryl ligands to the polymeric backbone of chitosan is given, and the resulting versatile physiochemical properties are discussed in detail. Furthermore, the broad spectrum of applications for thiolated chitosans in science and industry, ranging from their most advanced use in pharmaceutical and medical science over wastewater treatment to the impregnation of textiles, is addressed.

Advanced formulations for intranasal delivery of biologics

INTRODUCTION

The global biologics market has been ever increasing over the last decades and is predicted to top Euro 350 by 2020. Facing this scenario, the parenteral route of biologics administration as hitherto standard route is inconvenient for the future. Among the alternatives, the intranasal delivery of therapeutic biologicals seems to be most promising but researchers are still facing challenges as indicated by the scarce number of successfully marketed peptide drugs.

AREAS COVERED

This review article is a compilation of current research focusing on achievements in the field of auxiliary agents for biologics delivery. First, the key benefits of the nose as most promising alternative route of drug administration are highlighted. Then, the potential of the different auxiliary agents in preclinical research is in detail discussed. Moreover, the most used permeation enhancing agents, mucolytic agents, mucoadhesive agents, in situ gelling agents and enzyme inhibiting agents in the formulation of nasal drug delivery systems are described. Thus, the overall purpose of this review is to highlight recent achievements in nasal delivery of biologics and to encourage researchers to work in the direction of needle-free nasal administration of biologics.

EXPERT OPINION

The nasal epithelium is a promising route for biologics administration, which is reflected in a number of well-established products on the market treating chronic diseases as well as a large number of clinical trials currently in progress. The nasal route of drug administration might be a chance to improve therapy of biologics however break-through advances, especially for very complex molecules, such as antibodies, are still needed.

Chemical modification of drug molecules as strategy to reduce interactions with mucus

Many drug molecules possess inadequate physical-chemical characteristics that prevent to surpass the viscous mucus layer present in the surface of mucosal tissues. Due to mucus protective role and its fast turnover, these drug molecules end up being removed from the body before being absorbed and, thus, before exerting any physiologic affect. Envisaging a better pharmacokinetics profile, chemical modifications, to render drug a more mucopenetrating character, have been introduced to drug molecules backbone towards more effective therapies. Mucus penetration increases when drug molecules are provided with net-neutral charge, when they are conjugated with mucolytic agents and through modifications that makes them resistant to enzymes present in mucus, with the overall increase of their hydrophilicity and the decrease of their molecular weight. All of these characteristics act as a whole and influence each other so they must be well thought when drug molecules are being designed for mucosal delivery.

Potential advantages of a novel chitosan-N-acetylcysteine surface modified nanostructured lipid carrier on the performance of ophthalmic delivery of curcumin

The transient precorneal retention time and low penetration capacity into intraocular tissues are the key obstacles that hinder the ophthalmic drug delivery of many therapeutic compounds, especially for drugs with poor solubility and permeability. To break the stalemate, N-acetyl-L-cysteine functionalized chitosan copolymer (CS-NAC), which exhibit marked bioadhesion and permeation enhancing effect, was synthesized. The curcumin encapsulated NLC (CUR-NLC) was produced and optimized followed by surface absorption of CS-NAC. After coating, changed particle size from 50.76 ± 2.21 nm to 88.64 ± 1.25 nm and reversed zeta potential from −20.38 ± 0.39 mV to 22.51 ± 0.34 mV was observed. The in vitro CUR release from NLC was slower than that of CUR-NLC and chitosan hydrochlorides (CH) coated NLC due to the inter and/or intramolecular disulfide formation of thiomers on the surface of nanocarriers. The modification also significantly enhanced transcorneal penetration compared with CH-NLC and the uncoated ones. The effect on bioadhesion and precorneal retention were evaluated by in vivo imaging technique and ocular pharmacokinetics studies revealing that the clearance of the formulations was significantly delayed in the presence of CS-NAC and the effect was positively related to the degree of thiolation. In summary, CS-NAC-NLC presented a series of notable advantages for ophthalmic drug application.

A comparative study on the efficiency of chitosan-N-acetylcysteine, chitosan oligosaccharides or carboxymethyl chitosan surface modified nanostructured lipid carrier for ophthalmic delivery of curcumin

To develop a potential nanocarrier for the topical ocular administration of curcumin (CUR), a novel thiolated chitosan was synthesized by the covalent binding between N-acetyl-l-cysteine (NAC) and chitosan (CS) to surface modify the nanostructured lipid carrier loaded CUR (CUR-NLC). And the superiorities of the CS-NAC co polymer coated CUR-NLC over chitosan oligosaccharides (COS) or carboxymethyl chitosan (CMCS) modification were also verified in detail. As expected, the increment in particle size and the reversal of zeta potential occurred after surface decorating, and the most prominent electropositivity was obtained for the CS-NAC-CUR-NLC group. Additionally, the utilization of the CS-NAC coating demonstrated an effectively controlled release over 72h and attained a 6.4 and 18.8 fold increase in apparent permeability coefficients (Papp) compared with the CUR-NLC and the self-made eye drops, respectively. Meanwhile, the clearance rate of the NLC labeled with Rhodamine B was significantly delayed in the presence of CS-NAC. By contrast, CS-NAC-CUR-NLC was superior to the COS and CMCS coated ones in view of in vitro release, drug permeability and corneal retention. Moreover, the results of the in-vivo and in-vitro characteristics demonstrated that the promoting effect of CMCS coating was relatively weaker than COS coated ones. Ocular irritation test was executed on the CS-NAC-CUR-NLC, neither a sign of toxicity nor irritation to the external ocular tissues was observed. In conclusion, CS-NAC-CUR-NLC possesses a greater potential as an ocular drug-delivery system comparing with the COS-CUR-NLC and CMCS-CUR-NLC.

Permeation enhancement via thiolation: in vitro and ex vivo evaluation of hyaluronic acid-cysteine ethyl ester

It was the aim of this study to evaluate the permeation-enhancing effect of synthesized thiolated hyaluronic acid (HA). HA, a naturally found polysaccharide, was chemically modified with l-cysteine ethyl ether (C) via amide bond formation. In vitro permeation enhancement was tested on Caco-2 cells with two compounds, sulforhodamine (SR) and fluorescein isothiocyanate-dextran (FD4). Cytotoxicity assays as lactate dehydrogenase and thiazolyl blue tetrazolium bromide (MTT) were performed on colon carcinoma cell line. Transepithelial electrical resistance (TEER) measurements were conducted. Ex vivo evaluation was accomplished on rat intestinal mucosa in order to predict the permeation enhancing effect with SR, sodium fluorescein (SF), and FD4, respectively. The MTT as well as lactate dehydrogenase revealed no toxicity over time periods of 3 and 12 h, respectively. The bioconjugate is biocompatible and safe to use. Furthermore, TEER measurements showed the integrity of tight junctions. The in vitro permeation studies on cell studies exhibit 1.28-fold enhancement for SR and 1.47-fold enhancement for FD4 with hyaluronic acid-cysteine ethyl ester (HAC) in comparison to unmodified one. The ex vivo transport studies exhibit 1.9-fold enhancement for SF, 1.31-fold enhancement for Rhodamine123, and 1.3-fold enhancement for FD4 with HAC in comparison to unmodified one, respectively. Thus, the promising results encourage further investigations and exploitation of this versatile polysaccharide.

Effect of P-glycoprotein on the rat intestinal permeability and metabolism of the BDDCS class 1 drug verapamil

The Biopharmaceutics Drug Disposition Classification System (BDDCS) predicts intestinal transporter effects to be clinically insignificant following oral dosing for highly soluble and highly permeable/metabolized drugs (class 1 drugs). We investigated the effect of inhibiting P-glycoprotein (P-gp) on the in vitro rat intestinal permeability (Papp) and metabolism of the class 1 drug verapamil. Jejunal segments from Sprague-Dawley rats fasted overnight were mounted in Ussing chambers filled with 10 mL of Krebs-Ringer buffer (KRB). For P-gp inhibition studies, GG918 0.5 μM was added to the KRB solution. The experiment started by the addition of verapamil (1 or 10 μM) to either apical or basolateral sides. Samples from verapamil donor and receiver compartments were collected at 30 s and 0.166, 0.5, 1, 1.83 and 3 h after the start of the experiment. Analysis of verapamil and its major metabolite, norverapamil, in the samples and intracellularly at 3 h was performed by HPLC. The same experiment was repeated with norverapamil 10 μM (verapamil metabolite), digoxin 100 nM (positive control for P-gp activity) and atorvastatin 1 and 10 μM (example of a class 2 drug). For 1 μM verapamil, efflux ratio (B to A Papp/A to B Papp) was 4.6 and markedly decreased by GG918 (efflux ratio = 1.1). For 10 μM verapamil efflux ratio was 4.1 (control) vs 1.8 (GG918), comparable to the change seen for digoxin 100 nM with an efflux ratio of 3.6 (control) vs 1.6 (with GG918) and atorvastatin (efflux ratio of 5.2 and 3.0 for atorvastatin 1.0 and 10 μM, respectively, changed to 1.0 and 0.65 with GG918). The changes observed in the norverapamil 10 μM experiment were also significant, where efflux ratio decreased from 13.5 (control) to 1.5 (GG918). The extraction ratio (ER) of 10 μM verapamil to norverapamil decreased from 0.41 after an apical dose to 0.21 after a basolateral dose, but was unaffected by the incubation with GG918. The results suggest that P-gp inhibition has an effect on class 1 drug verapamil and class 2 drug atorvastatin Papp in the rat intestine. Moreover, a stronger P-gp effect on the Papp of the more polar norverapamil metabolite was observed. Papp changes caused by the P-gp inhibitor GG918 do not affect the extent of verapamil metabolism.

Oral Bromelain Attenuates Inflammation in an Ovalbumin-induced Murine Model of Asthma

Bromelain, a widely used pineapple extract with cysteine protease activity, has been shown to have immunomodulatory effects in a variety of immune system models. The purpose of the present study was to determine the effects of orally administered bromelain in an ovalbumin (OVA)-induced murine model of acute allergic airway disease (AAD). To establish AAD, female C57BL/6J mice were sensitized with intraperitoneal (i.p.) OVA/alum and then challenged with OVA aerosols for 3 days. Mice were gavaged with either (phosphate buffered saline)PBS or 200 mg/kg bromelain in PBS, twice daily for four consecutive days, beginning 1 day prior to OVA aerosol challenge. Airway reactivity and methacholine sensitivity, bronchoalveolar lavage (BAL) cellular differential, Th2 cytokines IL-5 and IL-13, and lung histology were compared between treatment groups. Oral bromelain-treatment of AAD mice demonstrated therapeutic efficacy as evidenced by decreased methacholine sensitivity (P ≤ 0.01), reduction in BAL eosinophils (P ≤ 0.02) and IL-13 concentrations (P ≤ 0.04) as compared with PBS controls. In addition, oral bromelain significantly reduced BAL CD19+ B cells (P ≤ 0.0001) and CD8+ T cells (P ≤ 0.0001) in AAD mice when compared with controls. These results suggest that oral treatment with bromelain had a beneficial therapeutic effect in this murine model of asthma and bromelain may also be effective in human conditions.

Thiolated chitosan nanoparticles for enhancing oral absorption of docetaxel: preparation, in vitro and ex vivo evaluation

The aim of this study was to prepare and evaluate mucoadhesive core-shell nanoparticles based on copolymerization of thiolated chitosan coated on poly methyl methacrylate cores as a carrier for oral delivery of docetaxel. Docetaxel-loaded nanoparticles with various concentrations were prepared via a radical emulsion polymerization method using cerium ammonium nitrate as an initiator. The physicochemical properties of the obtained nanoparticles were characterized by: dynamic light-scattering analysis for their mean size, size distribution, and zeta potential; scanning electron microscopy and transmission electron microscopy for surface morphology; and differential scanning calorimetry analysis for confirmation of molecular dispersity of docetaxel in the nanoparticles. Nanoparticles were spherical with mean diameter below 200 nm, polydispersity of below 0.15, and positive zeta potential values. The entrapment efficiency of the nanoparticles was approximately 90%. In vitro release studies showed a sustained release characteristic for 10 days after a burst release at the beginning. Ex vivo studies showed a significant increase in the transportation of docetaxel from intestinal membrane of rat when formulated as nanoparticles. Cellular uptake of nanoparticles was investigated using fluoresceinamine-loaded nanoparticles. Docetaxel nanoparticles showed a high cytotoxicity effect in the Caco-2 and MCF-7 cell lines after 72 hours. It can be concluded that by combining the advantages of both thiolated polymers and colloidal particles, these nanoparticles can be proposed as a drug carrier system for mucosal delivery of hydrophobic drugs.

Effect of milk formula protein content on intestinal barrier function in a porcine model of LBW neonates

Our study aimed at investigating the impact of the level of protein in milk formula on intestinal structure, barrier function, and its nervous regulation in normal and LBW neonates using a porcine model. Normal birth weight (NBW) or LBW piglets were fed from d7 to d28 of age either with a high protein (HP) or with an adequate protein (AP) formula or stayed with their mother [mother fed (MF)]. The proximal jejunum and distal ileum were sampled at d28 for morphometry analysis and ex vivo permeability measurement in Ussing chambers. Formula feeding induced a trophic effect on the jejunum and ileum of both NBW and LBW piglets, which exhibited longer villi than MF animals, irrespective of the type of formula. In NBW piglets, intestinal permeability was not altered by formula feeding. On the contrary, LBW piglets fed with HP formula, but not AP, exhibited a greater ileal permeability than MF piglets. Feeding the HP formula also disturbed jejunal and ileal regulation of permeability by acetylcholine and vasoactive intestinal peptide (VIP) in LBW compared with MF LBW piglets. In conclusion, the level of protein in formulas did not modify intestinal structure and function in NBW individuals but dramatically modified intestinal barrier function physiology in LBW individuals.

Possible Association between Th1 Immune Polarization and Epithelial Permeability with Toll-Like Receptors 2 Dysfunction in the Pathogenesis of the Recurrent Aphthous Ulceration

Recurrent Aphthous Ulceration (RAU) is a chronic oral inflammatory disease that affects approximately 25% of the general population. The etiology of the disease is unknown; however, factors that favor the onset of RAU have been correlated with a Th1 immune polarization, while factors that reduce RAU episodes have been associated with down regulation of immune reaction or stimulation of the peripheral tolerance. In this context, the integrity of the epithelial barrier is also fundamental for the prevention of the disease and conditions that augment its permeability or produce disruption are considered potential triggers. The key factor responsible for increased susceptibility is unclear, though a deficiency of Toll-like receptor (TLR) activity seems to be a good candidate. TLRs are a group of membrane proteins that recognize conserved molecules derived from bacterial, virus, fungal, or host tissues. Particularly, the TLR2 is involved in both immune regulation and control of epithelial barrier integrity. Thus, based on literature review, we showed evidences that correlate the TLR2 dysfunction and the diverse predisposing factors with the elements considered critical for disease pathogenesis: the Th1 immune reaction and the increased epithelial permeability.

Preparation and in vitro evaluation of mucoadhesion and permeation enhancement of thiolated chitosan-pHEMA core-shell nanoparticles

The aim of the present work was to evaluate the in vitro mucoadhesion and permeation enhancement properties of thiolated chitosan (chitosan-glutathione) coated poly(hydroxyl ethyl methacrylate) nanoparticles. Core-shell nanoparticles were prepared by radical emulsion polymerization method initiated by cerium(IV) ammonium nitrate. Different molecular weights of chitosan were utilized for nanoparticles preparation. The physicochemical properties of nanoparticles were characterized by size, zeta potential, and thiol content. Incorporation of fluorescein isothiocyanate dextran (FD4, MW 4400 Da), which was used as the model macromolecule, was achieved by incubation method. The intestinal mucoadhesion and penetration enhancement properties of nanoparticles were investigated using excised rat jejunum. All nanoparticle systems showed mucoadhesion and improved apparent permeation coefficient (P(app)) of FD4. Nanoparticles prepared by thiolated chitosan with medium molecular weight revealed the most mucoadhesion and penetration enhancement properties.

Chitosan-N-acetyl cysteine conjugates: in vitro evaluation of permeation enhancing and P-glycoprotein inhibiting properties

This study evaluated three chitosan-N-acetyl cysteine (CAC) conjugates of increasing molecular mass as a valuable tool to improve the absorption of drugs by assessing its permeation enhancing effect regarding the active P-gp substrate rhodamine-123 in comparison to the trans- and paracellular marker FD 4 both in rat intestine and Caco 2 monolayers. Additional LDH and MTT cytotoxicity tests have attested a non-toxic profile to CAC, which can consequently be seen as a safe and promising novel drug carrier with the ability to enhance drug absorption and to inhibit P-gp efflux transporters.

Papain: An Effective Permeation Enhancer for Orally Administered Low Molecular Weight Heparin

PURPOSE

The purpose of this study was to evaluate an effect of the proteolytic enzyme papain on permeation of low molecular weight heparin (LMWH) in vitro and in vivo.

MATERIALS AND METHODS

In vitro permeation studies were performed using rat small intestine as permeation barrier. In order to determine the ratio of papain to heparin resulting in the highest heparin permeation rate, molar ratios 1:1, 1:2 and 2:1 of papain to heparin were tested. Interactions of heparin with papain were investigated spectro-photometrically. For in vivo studies, 15 mg tablets containing heparin (13%), papain (64%) and hydroxyethylcellulose (22%) were orally administered to rats.

RESULTS

Since molar ratio papain to heparin 1:1 resulted in the highest permeation rate, it was used for in vivo studies. The results of binding studies of papain with heparin indicated a strong interaction between papain and heparin. Oral administration of tablets containing LMWH/papain/HEC resulted in sevenfold improvement of plasma anti-Xa activity in comparison to control. For tablets based on heparin/papain/HEC, a relative bioavailability of 9.1% vs. subcutaneous injection was obtained, whereas the relative bioavailability of control was 2.4%.

CONCLUSION

The co-administration of papain with heparin represents a new approach in improvement of absorption and bioavailability of orally administered heparin.

Improvement of the intestinal membrane permeability of low molecular weight heparin by complexation with stem bromelain

The aim of this study was to investigate the influence of the proteolytic enzyme bromelain on the permeation of heparin across the gastrointestinal epithelial barrier. Stability of the complex and effect of heparin on the enzymatic activity of bromelain was analysed photometrically by measuring bromelain enzymatic activity in complex with the heparin. In vitro permeation studies were performed with Caco-2 cell monolayer and rat small intestinal mucosa in Ussing-type chambers, respectively. Results revealed that enzymatic activity of bromelain remained uninfluenced by the immobilization of heparin on it. Transport studies across Caco-2 cell monolayer and rat small intestine showed that the permeation of heparin could be significantly increased in presence of bromelain. In the study with Caco-2 cells, the most effective molar ratio of bromelain to heparin was 2:1, leading to 6.7-fold improvement in uptake, whereas the molar ratio 1:1 showed the highest permeation enhancing effect in the study on intestinal mucosa. This study provides evidence that heparin and bromelain form stable complexes leading to a significantly improved uptake of heparin.

Elaboration and characterization of thiolated chitosan-coated acrylic nanoparticles

The aim of the present work was to investigate the use of thiolated chitosan in the development of polysaccharide-coated nanoparticles in order to confer specific functionality to the system. After chemical modification of commercial and hydrolysed chitosan (400,000 and 9400 g/mol respectively), thiolated chitosans were used to elaborate particles in the nano-range. They were characterized in terms of size and surface charge measurement. Both analysis showed nanoparticles of mean hydrodynamic diameter around 200 nm and positive zeta potential values, indicating the presence of the cationic polysaccharide at the nanoparticle surface. Moreover, the Ellman's reaction was used to demonstrate the presence of thiol groups at the particle surface. The observation of nanoparticles by scanning electronic microscopy (SEM) showed spherical nanoparticles for all formulations. This new system, combining both the advantages of thiolated polymers and colloidal particles can be proposed as an original drug carrier system for mucosal delivery of biotechnology products.

Synthesis and in Vitro Evaluation of a Novel Chitosan–Glutathione Conjugate

PURPOSE

It was the aim of this study to synthesize and characterize a novel chitosan-glutathione (GSH) conjugate providing improved mucoadhesive and permeation-enhancing properties.

METHODS

Mediated by carbodiimide and N-hydroxysuccinimide, glutathione was covalently attached to chitosan via the formation of an amide bond. The adhesive properties of chitosan-GSH conjugate were evaluated in vitro on freshly excised porcine mucosa via tensile studies and the rotating cylinder method. The cohesive properties and stability of the resulting conjugate were evaluated by disintegration test and by oxidation experiments, respectively. The permeation-enhancing effect of the chitosan-GSH/GSH system was evaluated in Ussing chambers by using rhodamine 123 as model compound.

RESULTS

The obtained conjugate displayed 265.5 mumol immobilized free thiol groups and 397.9 micromol disulfide bonds per gram polymer. Because of the formation of disulfide bonds within the polymer, the stability of matrix tablets could be strongly improved. In tensile studies, the total work of adhesion of the conjugate was determined to be 9.9-fold increased in comparison to unmodified chitosan. Results from the rotating cylinder method showed more than 55-fold increase in the adhesion time of thiolated chitosan vs. unmodified chitosan. In addition, the conjugate in combination with GSH displayed a 4.9-fold higher permeation-enhancing effect compared with unmodified chitosan.

CONCLUSIONS

Because of the improved mucoadhesive and cohesive properties, and the strong permeation-enhancing effect of the chitosan-GSH conjugate/GSH system, the novel thiolated chitosan seems to represent a promising multifunctional excipient for various drug delivery systems.

Gastrointestinal patch systems for oral drug delivery

Gastrointestinal patch systems with integrated multifunctions could surmount the challenges associated with conventional drug delivery. Several gastrointestinal patch systems provide bioadhesion, drug protection and unidirectional release. This combination of function could improve the overall oral bioavailability of large molecules that can currently be delivered only by injection, for example, epoetin-alpha and granulocyte-colony-stimulating factor, which are commonly used to treat chemotherapy-associated anemia and leukopenia, respectively. Furthermore, self-regulated release and cell-specific targeting provide additional 'smart' characteristics to this innovative therapeutic platform.