Screening of cationic compounds as an absorption enhancer for nasal drug delivery

Brain drug delivery from the nasal olfactory region is enhanced using lauroylcholine chloride: An estimation using in vivo PET imaging

INTRODUCTION

Intranasal (IN) administration, often referred to as nose-to-brain (N2B) drug delivery, is an attractive approach for delivering drugs to the central nervous system. However, the efficacy of this method is limited because of the small size of the nasal olfactory region, which limits the drug dosage. Using permeation enhancers could improve drug delivery from this region to the brain, though their effects are not fully understood. We therefore investigated the effects of co-administration of permeation enhancers on N2B drug delivery of a model drug domperidone, a peripherally acting dopamine D2 receptor (D2R) blocker.

METHODS

We conducted in vitro permeability assays to evaluate the effects of sodium lauryl sulfate (SLS), a classical permeation enhancer, and lauroylcholine chloride (LCC) on domperidone permeation in human nasal mucosa-derived cells. We also used the D2R ligand [11C]raclopride to assess the in vivo effects of LCC on domperidone delivery in the rat brain using a positron emission tomography (PET) competition paradigm. In comparative PET experiments, we tested the effects of intravenously administered domperidone without LCC co-administration.

RESULTS

LCC effectively improved nasal mucosal permeation of domperidone in vitro compared to SLS. In rat IN administration experiments, striatal [11C]raclopride uptake was significantly decreased by the addition of LCC to domperidone. On the other hand, intravenously administered domperidone with or without intranasally administered LCC did not decrease [11C]raclopride brain uptake, suggesting a lesser influence of peripheral domperidone on [11C]raclopride brain uptake. PET studies showed that striatal D2R occupancy of domperidone was increased 2.4-fold by co-administration of LCC.

CONCLUSION

LCC effectively enhances the domperidone delivery from the rat olfactory region to the brain, probably not via a circulating blood. The combination of permeation enhancers and olfactory region-selective drug administration could be effective for N2B drug delivery.

Factors affecting nasal drug delivery and design strategies for intranasal drug delivery

Intranasal drug delivery system is a non-invasive drug delivery route with the advantages of no first-pass effect, rapid effect and brain targeting. It is a feasible alternative to drug delivery via injection, and a potential drug delivery route for the central nervous system. However, the nasal physiological environment is complex, and the nasal delivery system requires "integration of medicine and device". Its delivery efficiency is affected by many factors such as the features and formulations of drug, delivery devices and nasal cavity physiology. Some strategies have been designed to improve the solubility, stability, membrane permeability and nasal retention time of drugs. These include the use of prodrugs, adding enzyme inhibitors and absorption enhancers to preparations, and new drug carriers, which can eventually improve the efficiency of intranasal drug delivery. This article reviews recent publications and describes the above mentioned aspects and design strategies for nasal intranasal drug delivery systems to provide insights for the development of intranasal drug delivery systems.

Arginine-Coated Nanoglobules for the Nasal Delivery of Insulin

Multiple daily injections via subcutaneous route are the primary modes of insulin delivery for patients with Diabetes Mellitus. While this process is invasive, painful and may cause patients to develop lipohypertrophy at injection site, the perception of fear surrounding this process causes patients to delay in initiation and remain persistent with insulin therapy over time. Moreover, poor glycemic control may often lead to acute complications, such as severe hypoglycemia and nocturnal hypoglycemia, especially in older patients with diabetes. To address the imperative need for a patient-convenient non-invasive insulin therapy, an insulin-loaded arginine-coated self-emulsifying nanoglobule system (INS-LANano) was developed for nasal delivery of insulin with a biodegradable cationic surfactant-Lauroyl Ethyl Arginate (LAE). Incorporation of LAE resulted in formation of positively charged nanoglobules with L-arginine oriented on the surface. LANano enabled binding of insulin molecules on the surface of nanoglobules via an electrostatic interaction between negatively charged α-helix and LAE molecules at physiological pH. INS-LANano showed a hydrodynamic diameter of 23.38 nm with a surface charge of +0.118 mV. The binding efficiency of insulin on LANano globules was confirmed by zeta potential, circular dichroism (CD) spectroscopy and centrifugal ultrafiltration studies. The attachment of insulin with permeation-enhancing nanoglobules demonstrated significantly higher in vitro permeability of insulin of 15.2% compared to insulin solution across human airway epithelial cell (Calu-3) monolayer. Upon intranasal administration of INS-LANano to diabetic rats at 2 IU/kg insulin dose, a rapid absorption of insulin with significantly higher Cmax of 14.3 mU/L and relative bioavailability (BA) of 23.3% was observed. Therefore, the INS-LANano formulation significant translational potential for intranasal delivery of insulin.

Nose-to-brain delivery: exploring newer domains for glioblastoma multiforme management

Glioblastoma multiforme (GBM) is the most common and aggressive form of the primary brain tumors in humans. The intricate pathophysiology, the development of resistance by tumor cells, and the inability of the drugs to effectively cross the blood-brain and blood-tumor barriers result in poor prognosis for GBM patients, with a median survival time of only 1 to 2 years. Nose-to-brain delivery offers an attractive, noninvasive strategy to enhance drug penetration or transport novel drug/gene carriers into the brain. Although the exact mechanism of intranasal delivery remains elusive, the olfactory and trigeminal nerve pathways have been found to play a vital role in circumventing the traditional barriers of brain targeting. This review discusses the intranasal pathway as a novel domain for delivering drugs and nanocarriers encapsulating drugs/genes, as well as stem cell carriers specifically to the glioma cells. Considering the fact that most of these studies are still in preclinical stage, translating such intranasal delivery strategies from bench to bedside would be a critical step for better management and prognosis of GBM. Graphical abstract.

Cetylpyridinium chloride blocks herpes simplex virus replication in gingival fibroblasts

Infections with herpes simplex viruses are lifelong and highly prevalent worldwide. Individuals with clinical symptoms elicited by HSVs may suffer from occasional or recurrent herpetic lesions in the orofacial and genital areas. Despite the existence of nucleoside analogues that interfere with HSV replication, such as acyclovir, these drugs are somewhat ineffective in treating skin lesions as topical formulations only reduce in one or few days the duration of the herpetic ulcers. Cetylpyridinium chloride (CPC) is a quaternary ammonium compound present in numerous hygiene products, such as mouthwashes, deodorants, aphtae-treating formulations and oral tablets as an anti-septic to limit bacterial growth. Some reports indicate that CPC can also modulate host signaling pathways, namely NF-κB signaling. Because HSV infection is modulated by NF-κB, we sought to assess whether CPC has antiviral effects against HSVs. Using wild-type HSV-1 and HSV-2, as well as viruses that are acyclovir-resistant or encode GFP reporter genes, we assessed the antiviral capacity of CPC in epithelial cells and human gingival fibroblasts expanded from the oral cavity and its mechanism of action. We found that a short, 10-min exposure to CPC added after HSV entry into the cells, significantly limited viral replication in both cell types by impairing viral gene expression. Interestingly, our results suggest that CPC blocks HSV replication by interfering with the translocation of NF-κB into the nucleus of HSV-infected cells. Taken together, these findings suggest that formulations containing CPC may help limit HSV replication in infected tissues and consequently reduce viral shedding.

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.

Recent advances in carrier mediated nose-to-brain delivery of pharmaceutics

Central nervous system (CNS) disorders (e.g., multiple sclerosis, Alzheimer's disease, etc.) represent a growing public health issue, primarily due to the increased life expectancy and the aging population. The treatment of such disorders is notably elaborate and requires the delivery of therapeutics to the brain in appropriate amounts to elicit a pharmacological response. However, despite the major advances both in neuroscience and drug delivery research, the administration of drugs to the CNS still remains elusive. It is commonly accepted that effectiveness-related issues arise due to the inability of parenterally administered macromolecules to cross the Blood-Brain Barrier (BBB) in order to access the CNS, thus impeding their successful delivery to brain tissues. As a result, the direct Nose-to-Brain delivery has emerged as a powerful strategy to circumvent the BBB and deliver drugs to the brain. The present review article attempts to highlight the different experimental and computational approaches pursued so far to attain and enhance the direct delivery of therapeutic agents to the brain and shed some light on the underlying mechanisms involved in the pathogenesis and treatment of neurological disorders.

Improved Intranasal Retentivity and Transnasal Absorption Enhancement by PEGylated Poly-l-ornithine

We reported that the introduction of polyethylene glycol (PEG) to poly-l-ornithine (PLO), which is an homopolymeric basic amino acid having absorption-enhancement ability, prolonged retention time in an in vitro inclined plate test, probably due to an increase in viscosity caused by PEGylation. The aim of the present study is to investigate whether the introduction of PEG chains to PLO improves intranasal retention and transnasal absorption in vivo. We performed intranasal administration experiments using PLO and PEG-PLO with a model drug, fluorescein isothiocyanate dextran (FD-4), in rats under closed and open systems. In the open system, transition of plasma FD-4 concentration after co-administration with unmodified PLO was low, and the area under the plasma concentration-time curve (AUC) decreased to about 60% of that in the closed system. In contrast, the AUC after co-administration with PEG-PLO in the open system was about 90% of that in the closed system, and the transition of plasma FD-4 concentration and FD-4 absorption profile were similar to those of the closed system. These findings indicate that introducing PEG chains to homopolymeric basic amino acids (HPBAAs) is a very useful method for developing a functional absorption enhancer that can exhibit an efficient in vivo absorption-enhancing effect.

Nanogel-based nasal vaccines for infectious and lifestyle-related diseases

Because the mucosa is the major entry route for most pathogens, the development of mucosal vaccines is a rational approach for protecting against these undesired agents. Mucosal administration of vaccine antigen is useful for non-infectious chronic diseases as well, because of its advantages over injection routes, including comparable efficacy in the induction of systemic immune responses, less pain, and no risk of adverse events at the injection site. However, because it is difficult to effectively induce and regulate antigen-specific mucosal and systemic immune responses when antigen alone is mucosally administered, an appropriate form of mucosal delivery vehicle must be used. Antigen delivery systems involving nanogels, which act as artificial chaperones and mucosal adhesives, are a promising approach to overcoming this problem. Here, we introduce current perspectives regarding the development of nanogel-based nasal vaccines for both infectious and lifestyle-related diseases.

Polyarginine nanocapsules: A versatile nanocarrier with potential in transmucosal drug delivery

The objective of this work was to investigate the potential utility of nanocapsules composed of an oily core decorated with a single polyarginine (PARG), or double PARG/polyacrylic acid (PAA) layer as oral peptide delivery carrier. A step-by-step formulation optimization process was designed, which involved the study of the influence of the surfactants, oils and polymer shells (PARG of different molecular weight and PAA) on the nanocapsules physicochemical properties, peptide loading efficiency, stability in simulated intestinal fluids (SIF) and capacity to enhance the permeability of the intestinal epithelium. Despite the lipophilic nature of the nanocapsules, it was possible to achieve a moderate loading of the hydrophilic model peptide salmon calcitonin and control its release in SIF, by adjusting the formulation conditions. Finally, studies in the Caco-2 epithelial cell line showed the capacity of the nanocapsules to reduce the transepithelial electric resistance of the monolayer, without compromising their viability. Overall, these properties suggest the capacity of polyarginine nanocapsules for enhancing the transport of peptides across epithelia.

Preparation and Evaluation of PEGylated Poly-L-ornithine Complex as a Novel Absorption Enhancer

Polycationic compounds, such as poly-L-arginine and poly-L-ornithine (PLO), enhance the nasal absorption of hydrophilic macromolecular drugs. However, the bio availability corresponding to the dose of these enhancers has not been obtained in an open system study, where an administered solution is transferred to the pharynx because they do not exhibit mucoadhesion/retention in the nasal cavity. In this study, we prepared PEGylated-poly-L-ornithine (PEG-PLO) and investigated the effects of PEGylation on in vitro adhesion/retention properties, permeation enhancement efficiency, and cytotoxicity. PEG-PLO bearing 3-4 polyethylene glycol (PEG) chains per PLO molecule was more retentive than unmodified PLO on an inclined plate. The permeability of a model drug, FD-4, across Caco-2 cell sheets was enhanced by PEG-PLO as well as by PLO. PLO showed cytotoxicity at high concentrations, whereas PEG-PLO did not decrease cell viability, even above the concentration giving a sufficient enhancement effect. These findings suggest that PEGylation of polycationic absorption enhancers improves their adhesion/retention and decreases their cytotoxicity, which may lead to enhancers with greater utility.

Stearylated cycloarginine nanosystems for intracellular delivery – simulations, formulation and proof of concept

Novel cationic agent liposomes performed better in silico translating in higher cellular uptake with reduced toxicity.

Development of a Transnasal Delivery System for Recombinant Human Growth Hormone (rhGH): Effects of the Concentration and Molecular Weight of Poly-L-arginine on the Nasal Absorption of rhGH in Rats

A novel system for delivering recombinant human growth hormone (rhGH) that is noninvasive and has a simple method of administration is strongly desired to improve the compliance of children. The aim of this study was to investigate the potential for the intranasal (i.n.) co-administration of rhGH with poly-L-arginine (PLA) as a novel delivery system by evaluating the effects of the concentration and molecular weight of PLA on the nasal absorption of rhGH. The influence of the formation of insoluble aggregates and a soluble complex in the dosage formulation on nasal rhGH absorption was also evaluated by size-exclusion chromatography and ultrafiltration. PLA enhanced the nasal absorption of rhGH at each concentration and molecular weight examined. Nasal rhGH absorption increased dramatically when the PLA concentration was 1.0 % (w/v) due to the improved solubility of rhGH in the formulation. A delay in rhGH absorption was observed when the molecular weight of PLA was increased. This appeared to be because the increase in molecular weight caused the formation of a soluble complex. It seems that the PLA concentration affects the absorption-enhancing effect on rhGH, while the molecular weight of PLA affects the time when the maximum plasma rhGH concentration was reached (Tmax) of rhGH after i.n. administration, mainly because of the interactions among rhGH, PLA, and additives. Therefore, the transnasal rhGH delivery system using PLA is considered to be a promising alternative to subcutaneous (s.c.) injection if these interactions are sufficiently controlled.

How to overcome the limitations of current insulin administration with new non-invasive delivery systems

Non-invasive insulin delivery systems have potential to overcome the most pressing problem regarding effective treatment of diabetic patients: therapy compliance. To overcome this disadvantage, non-invasive routes such as oral, buccal, pulmonary, nasal and transdermal have been proposed. These new routes of insulin administration may help to suppress hypoglycemia episodes and aid to control weight gain and post-meal glucose. Despite all efforts the invasive route remains preferential, since studies on insulin administration by non-invasive routes conducted to date have not demonstrated clinical efficacy and safety, including some products introduced in the market. Therefore, the aim of this review is to make an update of the current state of administration of insulin by non-invasive routes as alternatives to the conventional invasive route.

Novel designed polyoxyethylene nonionic surfactant with improved safety and efficiency for anticancer drug delivery

In order to limit the adverse reactions caused by polysorbate 80 in Taxotere^®, a widely used formulation of docetaxel, a safe and effective nanocarrier for this drug has been developed based on micelles formed by a new class of well-defined polyoxyethylene sorbitol oleate (PSO) with sorbitol as the matrix in aqueous solution. The physicochemical properties of the amphiphilic surfactant and the resulting micelles can be easily fine-tuned by the homogeneous sorbitol matrix and pure oleic acid. Composition, critical micelle concentration, and entrapment efficiency were investigated by ultraviolet visible spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, fluorospectrophotometry, and high-performance liquid chromatography. In vitro and in vivo evaluation revealed that PSO had exceptionally low hemolysis and histamine release rates compared with commercial polysorbate 80. Moreover, the tumor targeting delivery of PSO was investigated by in vivo imaging in S180 tumor-bearing mice. The results suggest that this novel delivery system, PSO, provides an acceptable alternative to polysorbate 80 for delivery of docetaxel. Further, due to the hypoallergenic nature of PSO, the mechanism of pseudoallergy caused by the polyoxyethylene nonionic surfactant was investigated. Based on in vitro cell analysis, it was assumed that the initial contact of polyoxyethylene nonionic surfactant with mast cells provoked pseudoallergy via polyamine receptor-mediated endocytosis.

A mechanism enhancing macromolecule transport through paracellular spaces induced by Poly-L-Arginine: Poly-L-Arginine induces the internalization of tight junction proteins via clathrin-mediated endocytosis

PURPOSE

Poly-L-arginine (PLA) enhances the paracellular permeability of the Caco-2 cell monolayer to hydrophilic macromolecules by disappearance of tight junction (TJ) proteins from cell-cell junctions. However, the mechanism of the disappearance of TJ proteins in response to PLA has been unclear. In this study, we investigated the mechanism of disappearance of TJ proteins from cell-cell junctions after the application of PLA to Caco-2 cell monolayers.

METHODS

The membrane conductance (Gt), FITC-dextran (FD-4) permeability, and localization of TJ proteins were examined after the treatment of Caco-2 cell monolayers with PLA in the presence of various endocytosis inhibitors. In addition, the localization of endosome marker proteins was also observed.

RESULTS

Clathrin-mediated endocytosis inhibitors suppressed the increase in Gt and Papp of FD-4 induced by PLA, and also significantly suppressed the disappearance of TJ proteins induced by PLA. Furthermore, occludin, one of the TJ proteins, colocalized with early endosome and recycling endosomes after the internalization of occludin induced by PLA, and then was recycled to the cell-cell junctions.

CONCLUSION

PLA induced the transient internalization of TJ proteins in cell-cell junctions via clathrin-mediated endocytosis, subsequently increasing the permeability of the Caco-2 cell monolayer to FD-4 via a paracellular route.

Bioavailability enhancement of verapamil HCl via intranasal chitosan microspheres

Chitosan microspheres are potential drug carriers for maximizing nasal residence time, circumventing rapid mucociliary clearance and enhancing nasal absorption. The aim of the present study was to develop and characterize chitosan mucoadhesive microspheres of verapamil hydrochloride (VRP) for intranasal delivery as an alternative to oral VRP which suffers low bioavailability (20%) due to extensive first pass effect. The microspheres were produced using a spray-drying and precipitation techniques and characterized for morphology (scanning electron microscopy), particle size (laser diffraction method), drug entrapment efficiency, thermal behavior (differential scanning calorimetry) and crystallinity (X-ray diffractometric studies) as well as in vitro drug release. Bioavailability of nasal VRP microspheres was studied in rabbits and the results were compared to those obtained after nasal, oral and intravenous administration of VRP solution. Results demonstrated that the microspheres were spherical with size 21-53 μm suitable for nasal deposition. The spray-drying technique was superior over precipitation technique in providing higher VRP entrapment efficiency and smaller burst release followed by a more sustained one over 6h. The bioavailability study demonstrated that the nasal microspheres exhibited a significantly higher bioavailability (58.6%) than nasal solution of VRP (47.8%) and oral VRP solution (13%). In conclusion, the chitosan-based nasal VRP microspheres are promising for enhancing VRP bioavailability by increasing the nasal residence time and avoiding the first-pass metabolism of the drug substance.

Enhanced nasal mucosal delivery and immunogenicity of anti-caries DNA vaccine through incorporation of anionic liposomes in chitosan/DNA complexes

The design of optimized nanoparticles offers a promising strategy to enable DNA vaccines to cross various physiological barriers for eliciting a specific and protective mucosal immunity via intranasal administration. Here, we reported a new designed nanoparticle system through incorporating anionic liposomes (AL) into chitosan/DNA (CS/DNA) complexes. With enhanced cellular uptake, the constructed AL/CS/DNA nanoparticles can deliver the anti-caries DNA vaccine pGJA-P/VAX into nasal mucosa. TEM results showed the AL/CS/DNA had a spherical structure. High DNA loading ability and effective DNA protection against nuclease were proved by gel electrophoresis. The surface charge of the AL/CS/DNA depended strongly on pH environment, enabling the intracellular release of loaded DNA via a pH-mediated manner. In comparison to the traditional CS/DNA system, our new design rendered a higher transfection efficiency and longer residence time of the AL/CS/DNA at nasal mucosal surface. These outstanding features enable the AL/CS/DNA to induce a significantly (p<0.01) higher level of secretory IgA (SIgA) than the CS/DNA in animal study, and a longer-term mucosal immunity. On the other hand, the AL/CS/DNA exhibited minimal cytotoxicity. These results suggest that the developed nanoparticles offer a potential platform for DNA vaccine packaging and delivery for more efficient elicitation of mucosal immunity.

Thermal-sensitive hydrogel as adjuvant-free vaccine delivery system for H5N1 intranasal immunization

For H5N1 influenza immunization, we developed a thermal-sensitive hydrogel as intranasal vaccine delivery system, which was formulated with N-[(2-hydroxy-3-trimethylammonium) propyl] chitosan chloride (HTCC) and α, β-glycerophosphate (α, β-GP). The flowing solution of HTCC/GP under room temperature could gelate rapidly at body temperature, which significantly prolonged the H5N1 split antigen residence time in nasal cavity. This system also enhanced the transepithelial transport via the paracellular routes due to the disorganization of ZO-1 protein in nasal epithelial tissue. In comparison to naked H5N1 split antigen and MF59 adjuvanted antigen, as designed hydrogel/H5N1 vaccine induced greater antigen-specific systemic immune responses and mucosal IgA immunity without adjuvants. Furthermore, a boosted cellular and humoral response was also obtained by examination of IFN-γ and IL-4 cytokines, respectively. In addition, hydrogel based formulation promoted the antigen-specific CD8(+) T cell immune memory as determined by the proportion of central and effector memory CD8(+) T cells in nasal associated lymphoid tissue (NALT). These results demonstrate that the HTCC hydrogel has potential as an adjuvant-free platform for H5N1 split antigen intranasal vaccination.

[Effects of sperminated pullulans on the pulmonary absorption of insulin]

Sperminated pullulans (SP) having different molecular weights (MWs) were prepared, and the enhancing effect on the pulmonary absorption of insulin in rats was examined. SP acted as enhancers of insulin absorption when a 0.1% solution was applied with insulin simultaneously and their enhancing effects depended on the MW of the SP; the same solutions exhibited low toxicity in the in vivo LDH leaching test. In the in vitro experiments using Calu-3 cells, tight junction-opening effects and a toxic effect of SP in the MTT assay were observed at lower concentrations compared with the in vivo experiments. A mucus layer might interfere with the interaction between SP and the cell surface and might suppress both these effects and toxicity. SP having a high MW will be useful for preparing safe and efficient formulations of peptide and protein drugs. The change in the localization of the tight junction proteins may be related to the permeation-enhancing mechanism of SP.

[Enhancement of insulin absorption through mucosal membranes using cationic polymers]

Cationic polymers (e.g., cationated gelatins, cationated pullulans and poly-L-arginines) have potential to promote transmucosal delivery of peptide and protein drugs without producing any toxic effects on epithelial cells. These cationic polymers could interact with the mucosal membranes and increase the number of pathways for water-soluble macromolecules in the tight junctions. In the case of insulin having negative charges in neutral solutions, interaction between the cationic polymers and insulin is also important to promote suitable delivery. An appropriate interaction can help insulin to access to cell surface, but too strong interaction suppresses insulin absorption. When the absorption-enhancing effects of sperminated pullulans and gelatin having different numbers of amino groups on the pulmonary absorption of insulin in rats were evaluated, their enhancing effects correlated with the amino group content. Cationic polymers having suitable charge density will be useful for pulmonary delivery systems of insulin.

Drug transporter expression and localization in rat nasal respiratory and olfactory mucosa and olfactory bulb

Uptake of drugs and other xenobiotics from the nasal cavity and into either the brain or systemic circulation can occur through several different mechanisms, including paracellular transport and movement along primary olfactory nerve axons, which extend from the nasal cavity to the olfactory bulb of the brain. The present study was conducted to expand knowledge on a third means of uptake, namely the expression of drug transporters in the rat nasal epithelium. We used branched DNA technology to compare the level of expression of nine transporters [(equilibrative nucleoside transporters (ENT)1 and ENT2; organic cation transporter (OCT)1, 2, and 3; OCTN1; organic anion-transporting polypeptide (OATP)3; and multidrug resistance (MRP)1 and MRP4] in nasal respiratory mucosa, olfactory mucosa, and olfactory bulb to the level of expression of these transporters in the liver and kidney. Transporters with high expression in the nasal respiratory mucosa or olfactory tissues were immunolocalized by immunohistochemistry. ENT1 and ENT2 expression was relatively high in nasal epithelia and olfactory bulb, which may explain the uptake of intranasally administered nucleoside derivatives observed by other investigators. OATP3 immunoreactivity was high in olfactory epithelium and olfactory nerve bundles, which suggests that substrates transported by OATP3 may be candidates for intranasal administration.

Effect of sperminated pullulans on drug permeation through isolated rabbit cornea and determination of ocular irritation

The aim of this study was to investigate the effect of two sperminated pullulans (SP) with a different number of amino groups (SP-L, amino group content 0.124 mmol/g polymer; and SP-H, amino group content 0.578 mmol/g polymer) on the permeation of drugs through isolated rabbit corneas. Determination of corneal hydration levels and Draize eye tests were performed to assess the safety of SP both in vitro and in vivo. For 0.2% (w/v) SP-L and 0.2% (w/v) SP-H, the enhancement ratios (ERs) with dexamethasone of 1.34 and 1.42, respectively, were not statistically significant. For ofloxacin, tobramycin and sodium fluorescein, the ERs with 0.2% SP-L were 1.37, 2.02 and 2.12, respectively, and with 0.2% SP-H the ERs were 1.84, 4.69 and 6.87, respectively; these ERs were all statistically significant. Enhancement increased with increasing amino group content of the SP. The improved transcorneal drug absorption via the paracellular route indicated opening of the tight junctions in the corneal epithelium. Irritation tests indicated that 0.2% SP-L and 0.2% SP-H did not damage the corneal tissues.

Chitosan salts as nasal sustained delivery systems for peptidic drugs

The aim of this study was to describe a sustained drug release system based on chitosan salts for vancomycin hydrochloride delivery. Chitosan lactate, chitosan aspartate, chitosan glutamate and chitosan hydrochloride were prepared by spray-drying technique. Vancomycin hydrochloride was used as a model peptidic drug, the nasal sustained release of which should avoid first-pass metabolism in the liver. This in-vitro study evaluated the influence of chitosan salts on the release behaviour of vancomycin hydrochloride from the physical mixtures at pH 5.5 and 7.4. In-vitro release of vancomycin was retarded by chitosan salts and, in particular, chitosan hydrochloride provided the lowest release of vancomycin.

Rat nasal lavage biomarkers to assess preclinical irritation potential of nasal drug formulations and excipients

The goal of this study was to evaluate biomarkers of nasal mucosal damage for rapid assessment of irritancy potential of formulations in the rat nasal lavage model, a tool to facilitate nasal formulation development prior to histopathology studies. The nasal cavity of anesthetized rats was lavaged with normal saline 20 min pos-tdose. The collected fluid was analyzed for secreted total protein and biomarkers. Solutions tested include: normal saline, buffers, benzalkonium chloride (BAC), lysophosphatidylcholine (LPC), and four marketed nasal products. Total protein, lactate dehydrogenase and interleukin-1alpha biomarkers were secreted to varying degrees. BAC (0.2%) and LPC (0.5%) exhibiting the strongest response with a signal window ranging from 3.4- to 87-fold greater levels than normal saline. Buffer treatments, excipients, and most marketed nasal products yielded levels similar to normal saline. There was a weak correlation between formulation osmolarity and surface tension with any of the biomarkers. Each nasal formulation elicited a unique protein and biomarker profile with total protein secretion correlated with IL-1alpha secretion suggesting the potential for an inflammatory response. Taken together, rapid and potentially mechanistic information on the preclinical acute irritancy potential of formulations was assessed in the rat nasal lavage model by benchmarking treatments relative to controls and marketed nasal products.

Polymeric Enhancers of Mucosal Epithelia Permeability: Synthesis, Transepithelial Penetration-Enhancing Properties, Mechanism of Action, Safety Issues

Transmucosal drug administration across nasal, buccal, and ocular mucosae is noninvasive, eliminates hepatic first-pass metabolism and harsh environmental conditions, allows rapid onset, and further, mucosal surfaces are readily accessible. Generally, however, hydrophilic drugs, such as peptides and proteins, are poorly permeable across the epithelium, which results in insufficient bioavailability. Therefore, reversible modifications of epithelial barrier structure by permeation enhancers are required. Low molecular weight enhancers generally have physicochemical characteristics favoring their own absorption, whereas polymeric enhancers are not absorbed, and this minimizes the risk of systemic toxicity. The above considerations have warranted the present survey of the studies on polymeric transmucosal penetration-enhancers that have appeared in the literature during the last decade. Studies on intestinal permeation enhancers are also reviewed as they give information on the mechanism of action and safety of polymers. The synthesis and characterization of polymers, their effectiveness in enhancing the absorption of different drugs across different epithelium types, their mechanism of action and structure-efficacy relationship, and the relevant safety issues are reviewed. The active polymers are classified into: polycations (chitosan and its quaternary ammonium derivatives, poly-L-arginine (poly-L-Arg), aminated gelatin), polyanions (N-carboxymethyl chitosan, poly(acrylic acid)), and thiolated polymers (carboxymethyl cellulose-cysteine, polycarbophil (PCP)-cysteine, chitosan-thiobutylamidine, chitosan-thioglycolic acid, chitosan-glutathione conjugates).

Thermodynamic studies and binding mechanisms of cell-penetrating peptides with lipids and glycosaminoglycans

Cell-penetrating peptides (CPPs) traverse the membrane of biological cells at low micromolar concentrations and are able to take various cargo molecules along with. Despite large differences in their chemical structure, CPPs share the structural similarity of a high cationic charge density. This property confers to them the ability to bind electrostatically membrane constituents such as anionic lipids and glycosaminoglycans (GAGs). Controversies exist, however, about the biological response after the interaction of CPPs with such membrane constituents. Present review compares thermodynamic binding studies with conditions of the biological CPP uptake. It becomes evident that CPPs enter biological cells by different and probably competing mechanisms. For example, some amphipathic CPPs traverse pure lipid model membranes at low micromolar concentrations--at least in the absence of cargos. In contrast, no direct translocation at these conditions is observed for non-amphipathic CPPs. Finally, CPPs bind GAGs at low micromolar concentrations with potential consequences for endocytotic pathways.

Dendrimers as a Carrier for Pulmonary Delivery of Enoxaparin, a Low-Molecular Weight Heparin

This study was designed to test the hypothesis that positively charged dendrimers form a complex with enoxaparin, a low-molecular weight heparin (LMWH), and that the resulting drug-dendrimer complex is effective in preventing deep vein thrombosis after pulmonary administration. Fourier Transform Infrared (FTIR) spectroscopy and the azure A assay were used to evaluate interactions between dendrimers and enoxaparin. The efficacy of polyamidoamine (PAMAM) dendrimers in enhancing pulmonary absorption of enoxaparin was studied by administering enoxaparin-dendrimer formulations into the lungs of anesthetized rats and monitoring drug absorption by measuring plasma anti-factor Xa activity. The optimized formulations were evaluated for their efficacy in preventing deep vein thrombosis in a rodent model. The safety of the formulations was tested by studying their effects on mucociliary transport rate (MTR) in a frog palate model and by measuring injury markers in rat bronchoalveolar fluid. The FTIR data and azure A assay revealed ionic interactions between the amino groups of cationic dendrimers and the carboxylic and sulfate groups of enoxaparin. Positively charged dendrimers increased the relative bioavailability of enoxaparin by 40%, while a negatively charged dendrimer had no effect. Formulations containing 1% G2 or 0.5% G3 PAMAM dendrimer plus enoxaparin were as efficacious in preventing deep vein thrombosis in a rat model as subcutaneously administered enoxaparin. The formulations did not adversely affect the MTR or produce extensive damage to the lungs. Positively charged dendrimers are a suitable carrier for pulmonary delivery of enoxaparin. They enhance pulmonary absorption of LMWH probably by reducing negative surface charge density of the drug molecule.

Transport characteristics of a beta sheet breaker peptide across excised bovine nasal mucosa

The purpose of the present study was to investigate the permeation characteristics of the beta sheet breaker peptide AS 602704 (BSB) on excised bovine nasal mucosa using an Ussing chamber model. The influence of various absorption enhancers such as sodium cholate, sodium dodecyl sulfate (SDS), cetrimidum, sodium caprate, Na(2)EDTA, polycarbophil (PCP), the thiomer conjugate polycarbophil-cysteine (PCP-Cys), and poly-l-arginine (poly-l-arg; 100 kDa) was evaluated. Additionally, the influence of temperature and pH on the transport rate as well as the stability of the peptide drug against enzymatic degradation were investigated in vitro. The effective permeability coefficient (P(eff)) of BSB in Krebs-Ringer-buffer (KRB) pH 7.4 was (1.89 +/- 0.44)* 10-5, while in the presence of sodium caprate (0.5%) a P(eff) of (9.58 +/- 1.82)*10-5 was achieved. Rank order of enhancement ratio was sodium caprate > SDS > sodium cholate > Na(2)EDTA > poly-L-arg = PCP-Cys. In case of cetrimidum and PCP even a decrease in the absorption of BSB was determined. Na2EDTA reduced the enzymatic degradation of BSB when exposed to a nasal tissue homogenate by more than the half. An increased lipophilicity of BSB because of a more acidic milieu (pH 5.5) did not lead to an increased transcellular transport. Permeation studies carried out at 4 degrees C compared to 37 degrees C demonstrated a temperature dependent permeation behaviour suggesting an additional active carrier mediated transport. The results obtained within these studies should facilitate the development of a nasal delivery system for AS 602704 for the treatment of Alzheimer's disease.

Nasal residence of insulin containing lyophilised nasal insert formulations, using gamma scintigraphy

Bioadhesive dosage forms are a potential method for overcoming rapid mucociliary transport in the nose. A lyophilised nasal insert formulation previously investigated in sheep demonstrated prolonged absorption of nicotine hydrogen tartrate suggestive of extended nasal residence, and increased bioavailability. The current study was performed to quantify nasal residence of the formulations using gamma scintigraphy, and to investigate the absorption of a larger molecule, namely insulin. A four-way crossover study was conducted in six healthy male volunteers, comparing a conventional nasal spray solution with three lyophilised nasal insert formulations (1-3% hydroxypropylmethylcellulose (HPMC)). The conventional nasal spray deposited in the posterior nasal cavity in only one instance, with a rapid clearance half-life of 9.2 min. The nasal insert formulations did not enhance nasal absorption of insulin, however an extended nasal residence time of 4-5 h was observed for the 2% HPMC formulation. The 1% HPMC insert initially showed good spreading behaviour; however, clearance was faster than for the 2% formulation. The 3% HPMC nasal insert showed no spreading, and was usually cleared intact from the nasal cavity within 90 min. In conclusion, the 2% HPMC lyophilised insert formulation achieved extended nasal residence, demonstrating an optimum combination of rapid adhesion without over hydration.

Effects of a sperminated gelatin on the nasal absorption of insulin

The effects of a sperminated gelatin (SG), which was prepared as a candidate absorption enhancer by the addition of spermine to gelatin, on the nasal absorption of insulin, were examined in rats. The AUC of immuno-reactive insulin levels in the plasma after nasal administration of insulin were increased 5.3-fold by addition of 0.2% SG, and the plasma glucose levels fell in a manner dependent on the insulin levels. In Calu-3 cell monolayer permeation experiments, SG showed significant enhancing effects on 5(6)-carboxyfluorescein (CF), FITC-dextran (MW 4400, FD4) and insulin. Evaluation of the tight junctions in the Calu-3 cell monolayers based on the Renkin molecular sieving function suggests that the pore occupancy/length ratio of the permeation pathways for water-soluble molecules in the tight junctions increases, while the equivalent cylindrical pore radius is not changed by SG treatment. SG may transform the true tight junctions, which act as a barrier for water-soluble molecules, into pathways for CF and FD4 to increase their number. SG is a good candidate for a safe absorption enhancer to produce a slight modification of the permeability of the paracellular pathway of mucosal membranes, while retaining the sieving property of the epithelial membranes.

Ability of Poly-L-arginine to Enhance Drug Absorption into Aqueous Humor and Vitreous Body after Instillation in Rabbits

The effect of poly-L-arginine with a molecular weight of 35.5 kDa (PLA) on the ocular absorption of hydrophilic molecules after instillation was examined in rabbits in vivo. FITC-labeled dextran (3.8 kDa, FD-4) and pyridoxamine were used as model hyprophilic molecules for absorption. The potential toxicity of PLA was evaluated by microscopic observation of the cornea, production of TNF-alpha, and the thickness of the corneal epithelia and stroma. The concentration of pyridoxamine and FD-4 in aqueous humor 30 min after a single instillation of a solution of PLA was 29- and 16-fold higher than that without PLA, respectively, but the drug concentrations were not determined in the vitreous body. Repetitive instillation of PLA every 30 min for 150 min achieved 31.1- and 13.3-fold increases in pyridoxamine and FD-4 in aqueous humor, respectively. Furthermore, significant amounts of pyridoxamine and FD-4 were detected in the vitreous body after the repetitive instillation of PLA, even although very little of these drugs was detected in the vitreous body in the control eye without PLA. On the other hand, repetitive instillation of PLA did not induce any alteration of corneal epithelial and stromal thickness, production of TNF-alpha, and disruption of the epithelial and stromal morphologies and neutrophil infiltration. Our findings suggest that PLA may be useful in promoting drug delivery of hydrophilic drugs to the ocular tissues without producing any significant corneal damage and inflammation.

In vitro formulation optimization of intranasal galantamine leading to enhanced bioavailability and reduced emetic response in vivo

The purpose of the current investigation was to optimize an intranasal (IN) galantamine (an acetylcholinesterase inhibitor used for treatment of Alzheimer's disease) formulation using an in vitro tissue model, to correlate those results to in vivo bioavailability, and to compare emetic response to oral dosing. A design-of-experiments (DOE) based formulation screening employing an in vitro tissue model of human nasal epithelium was used to assess drug permeability, tight junction modulation, and cellular toxicity. In vivo studies in rats compared pharmacokinetic (PK) profiles of different formulations dosed intranasally. Finally, studies in ferrets evaluated PK and gastrointestinal (GI) related side effects of oral compared to nasal dosage forms. Galantamine permeation was enhanced without increasing cytotoxicity. Pharmacokinetic testing in rats confirmed the improved drug bioavailability and demonstrated an in vitro-in vivo correlation. Compared to oral dosing, IN galantamine resulted in a dramatically lowered incidence of GI-related side effects, e.g., retching and emesis. These findings illustrate that IN delivery represents an attractive alternative to oral dosing for this important Alzheimer's disease therapeutic. To our knowledge, the data herein represent the first direct confirmation of reducing GI-related side effects for IN galantamine compared to oral dosing.

Effect of cationized gelatins on the paracellular transport of drugs through caco-2 cell monolayers

Cationized gelatins, candidate absorption enhancers, were prepared by addition of ethylenediamine or spermine to gelatin and the effects of the resulting ethylenediaminated gelatin (EG) and sperminated gelatin (SG) on the paracellular transport of 5(6)-carboxyfluorescein (CF), FITC-dextran-4 (FD4), and insulin through caco-2 cell monolayers were examined. The Renkin function was used for characterization of the paracellular pathway and changes in the pore radius (R) and pore occupancy/length ratio (epsilon/L) calculated from the apparent permeability coefficients (P(app)) of CF and FD4 are discussed. Ethylenediaminetetraacetic acid (EDTA) increased the R of the caco-2 cell monolayer and the P(app) of all compounds examined was markedly increased by the addition of EDTA. On the other hand, EG and SG did not increase R and their enhancing effects were not as strong as those of EDTA. The increase in epsilon/L could be the enhancing mechanism for the cationized gelatins. The number of pathways for water-soluble drugs, such as CF and FD4, in the caco-2 monolayers could be increased by the addition of the cationized gelatins. The ratios of the permeability coefficients of insulin (observed/calculated based on the Renkin function) suggest that insulin undergoes enzymatic degradation during transport which is not inhibited by enhancers.

Rapid-onset intranasal delivery of metoclopramide hydrochloride. Part I. Influence of formulation variables on drug absorption in anesthetized rats

Intranasal (IN) administration is a promising approach for rapid-onset delivery of medications and to circumvent their first-pass elimination when taken orally. Metoclopramide (MCP) is a potent antiemetic, effective even for preventing emesis induced by cancer chemotherapy. The feasibility of developing an efficacious intranasal formulation of metoclopramide has been undertaken in this study. The nasal absorption of MCP was studied in anesthetized rats over 60min using the in vivo in situ technique. The influence of several formulation variables, vis., pH and the addition of preservative, viscosity and absorption enhancing agents on the nasal MCP absorption was examined. The data obtained showed that MCP was well absorbed nasally where almost 90% of the drug was absorbed after 60min from the rat nasal cavity. The MCP absorption was pH-dependant such that the apparent first-order rate constant of absorption (K(app)) was almost tripled when the pH of the solution was increased from 5 to 8. However, deviation from the classical pH-partition theory was observed pointing to the role of aqueous pore pathway in MCP nasal absorption. The K(app) was significantly increased (P<0.05) by incorporation of 0.01% of the preservative benzalkonium chloride. Conversely, increasing the solution viscosity by the use of hydroxylpropyl methylcellulose adversely affected the rate of absorption. The use of enhancers namely sodium deoxycholate, sodium cholate, chitosan low and high molecular weight, protamine sulphate and poly-l-arginine resulted in significant increase in MCP absorption. The highest promoting effect was observed with the bile salt sodium deoxycholate where about 92% of the drug was absorbed in 25min from the rat nasal cavity and the K(app) showed more than two-fold increase as compared to control (from 0.0452 to 0.1017min(-1)).