Mucus-penetrating nanoparticles for drug and gene delivery to mucosal tissues

Nanoparticle mediated non-covalent drug delivery

The use of nanoparticles (NPs) for enhanced drug delivery has been heavily explored during the last decade. Within the field, it is has become increasingly apparent that the physical properties of the particles themselves dictate their efficacy, and the relevant non-covalent chemistry at the NP interface also influences how drugs are immobilized and delivered. In this review, we reflect on the physical chemistry of NP mediated drug delivery (and more specifically, non-covalent drug delivery) at the three main experimental stages of drug loading, NP-drug conjugate transport, and the resulting cellular drug delivery. Through a critical evaluation of advances in drug delivery within the last decade, an outlook for biomedical applications of nanoscale transport vectors will be presented.

How do polymeric micelles cross epithelial barriers?

Non-parenteral delivery of drugs using nanotechnology-based delivery systems is a promising non-invasive way to achieve effective local or systemic drug delivery. The efficacy of drugs administered non-parenterally is limited by their ability to cross biological barriers, and epithelial tissues particularly present challenges. Polymeric micelles can achieve transepithelial drug delivery because of their ability to be internalized into cells and/or cross epithelial barriers, thereby delivering drugs either locally or systematically following non-parenteral administration. This review discusses the particular characteristics of various epithelial barriers and assesses their potential as non-parenteral routes of delivery. The material characteristics of polymeric micelles (e.g., size, surface charge, and surface decoration) and of unimers dissociated from polymeric micelles determine their interactions (non-specific and/or specific) with mucus and epithelial cells as well as their intracellular fate. This paper outlines the mechanisms governing the major modes of internalization of polymeric micelles into epithelial cells, with an emphasis on specific recent examples of the transport of drug-loaded polymeric micelles across epithelial barriers.

Comparative study of Pluronic(®) F127-modified liposomes and chitosan-modified liposomes for mucus penetration and oral absorption of cyclosporine A in rats

Liposomes modified using cationic and hydrophilic nonionic polymers are 2 popular carriers for improving oral drug absorption. Cationic polymer-modified liposomes can adhere to the intestinal wall mucus (mucoadhesive type), while liposomes modified using hydrophilic nonionic polymers can penetrate across the mucus barrier (mucus-penetrating type). Chitosan-modified liposomes (CS-Lip, mucoadhesive type) and Pluronic(®) F127-modified liposomes (PF127-Lip, mucus-penetrating type) were engineered to investigate the differences between these mucoadhesive and mucus-penetrating systems in oral absorption of a poorly soluble drug, cyclosporine A (CyA). Stability of CS-Lip and PF127-Lip was studied in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). The intestinal mucus adhesion or penetration of liposomes was studied by confocal laser scanning microcopy and fluorophotometry using coumarin 6 as the fluorescent probe. The oral absorption of CyA-loaded liposomes was also studied in Sprague-Dawley rats. In vitro and in vivo studies revealed that CS-Lip tended to aggregate in SIF, to be trapped by mucus, to remain mainly in the upper portion of the intestinal tract, and to show limited penetration ability. In contrast, PF127-Lip were more stable in the SIF and SGF, were found throughout the intestinal tract, and were able to penetrate the mucus layers to reach the epithelial surface. Pharmacokinetic analysis in rats showed that the Cmax and AUC0-t of PF127-Lip were 1.73- and 1.84-fold higher than those of CS-Lip, respectively (P<0.05). In conclusion, the stability and mucus-penetrating ability of PF127-Lip in the gastrointestinal tract rendered it more suitable than the mucoadhesive CS-Lip for oral delivery CyA.

Exosome-like nanoparticles from intestinal mucosal cells carry prostaglandin E2 and suppress activation of liver NKT cells

Regulation and induction of anergy in NKT cells of the liver can inhibit autoimmune and antitumor responses by mechanisms that are poorly understood. We investigated the effects of PGE2, delivered by intestinal, mucus-derived, exosome-like nanoparticles (IDENs), on NKT cells in mice. In this study, we demonstrate that IDENs migrate to the liver where they induce NKT cell anergy. These effects were mediated by an IDENs' PGE2. Blocking PGE2 synthesis attenuated IDENs inhibition of induction of IFN-γ and IL-4 by α-galactosylceramide (α-GalCer)-stimulated liver NKT cells in a PGE2 E-type prostanoid 2/E-type prostanoid 4 receptor-mediated manner. Proinflammatory conditions enhanced the migration of IDENs to the liver where α-GalCer and PGE2 induced NKT anergy in response to subsequent α-GalCer stimulation. These findings demonstrate that IDENs carrying PGE2 can be transferred from the intestine to the liver, where they act as immune modulators, inducing an anergic-like state of NKT cells. These reagents might be developed as therapeutics for autoimmune liver diseases.

Nanoparticle diffusion in respiratory mucus from humans without lung disease

A major role of respiratory mucus is to trap inhaled particles, including pathogens and environmental particulates, to limit body exposure. Despite the tremendous health implications, how particle size and surface chemistry affect mobility in respiratory mucus from humans without lung disease is not known. We prepared polymeric nanoparticles densely coated with low molecular weight polyethylene glycol (PEG) to minimize muco-adhesion, and compared their transport to that of uncoated particles in human respiratory mucus, which we collected from the endotracheal tubes of surgical patients with no respiratory comorbidities. We found that 100 and 200 nm diameter PEG-coated particles rapidly penetrated respiratory mucus, at rates exceeding their uncoated counterparts by approximately 15- and 35-fold, respectively. In contrast, PEG-coated particles ≥500 nm in diameter were sterically immobilized by the mucus mesh. Thus, even though respiratory mucus is a viscoelastic solid at the macroscopic level (as measured using a bulk rheometer), nanoparticles that are sufficiently small and muco-inert can penetrate the mucus as if it were primarily a viscous liquid. These findings help elucidate the barrier properties of respiratory mucus and provide design criteria for therapeutic nanoparticles capable of penetrating mucus to approach the underlying airway epithelium.

Method for quantitative study of airway functional microanatomy using micro-optical coherence tomography

We demonstrate the use of a high resolution form of optical coherence tomography, termed micro-OCT (μOCT), for investigating the functional microanatomy of airway epithelia. μOCT captures several key parameters governing the function of the airway surface (airway surface liquid depth, periciliary liquid depth, ciliary function including beat frequency, and mucociliary transport rate) from the same series of images and without exogenous particles or labels, enabling non-invasive study of dynamic phenomena. Additionally, the high resolution of μOCT reveals distinguishable phases of the ciliary stroke pattern and glandular extrusion. Images and functional measurements from primary human bronchial epithelial cell cultures and excised tissue are presented and compared with measurements using existing gold standard methods. Active secretion from mucus glands in tissue, a key parameter of epithelial function, was also observed and quantified.

Advancements in the field of intravaginal siRNA delivery

The vaginal tract is a suitable site for the administration of both local and systemic acting drugs. There are numerous vaginal products on the market such as those approved for contraception, treatment of yeast infection, hormonal replacement therapy, and feminine hygiene. Despite the potential in drug delivery, the vagina is a complex and dynamic organ that requires greater understanding. The recent discovery that injections of double stranded RNA (dsRNA) in Caenorhabditis elegans (C. elegans) results in potent gene specific silencing, was a major scientific revolution. This phenomenon known as RNA interference (RNAi), is believed to protect host genome against invasion by mobile genetic elements such as transposons and viruses. Gene silencing or RNAi has opened new potential opportunities to study the function of a gene in an organism. Furthermore, its therapeutic potential is being investigated in the field of sexually transmitted infections such as human immunodeficiency virus (HIV) and other diseases such as age-related macular degeneration (AMD), diabetes, hypercholesterolemia, respiratory disease, and cancer. This review will focus on the therapeutic potential of siRNA for the treatment and/or prevention of infectious diseases such as HIV, HPV, and HSV within the vaginal tract. Specifically, formulation design parameters to improve siRNA stability and therapeutic efficacy in the vaginal tract will be discussed along with challenges, advancements, and future directions of the field.

Self-assembled nanoparticles based on amphiphilic chitosan derivative and hyaluronic acid for gene delivery

The present work described nanoparticles (NPs) made of oleoyl-carboxymethy-chitosan (OCMCS)/hyaluronic acid (HA) using coacervation process as novel potential carriers for gene delivery. An N/P ratio of 5 and OCMCS/HA weight ratio of 4 were the optimal conditions leading to the smallest (164.94 nm), positive charged (+14.2 mV) and monodispersed NPs. OCMCS-HA/DNA (OHD) NPs showed higher in vitro DNA release rates and increased cellular uptake by Caco-2 cells due to the HA involved in NPs. The MTT survival assay indicated no significant cytotoxicity. The transfection efficiency of OHD NPs was 5-fold higher than OCMCS/DNA (OD) NPs; however, it decreased significantly in the presence of excess free HA. The results indicated that OHD NPs internalized in Caco-2 cells were mediated by the hyaluronan receptor CD44. The data obtained in the present research gave evidence of the potential of OHD NPs for the targeting and further transfer of genes to the epithelial cells.

Mucosal Delivery of RNAi Therapeutics

The effectiveness of RNA interference-based drugs is dependent on accumulation at the target site in therapeutically relevant amounts. Local administration to the mucosal surfaces lining the respiratory, gastrointestinal and genitourinary tracts allows access into diseased areas without the necessity to overcome serum nuclease degradation, rapid renal and hepatic clearance and non-specific tissue accumulation associated with systemic delivery. This work describes RNAi therapeutics focused on pulmonary, oral, rectal and intravaginal routes of administration. Mucosal barrier components including site variations and delivery considerations are addressed in order to design an effective mucosal delivery strategy.

Targeting receptor-mediated endocytotic pathways with nanoparticles: rationale and advances

Targeting of drugs and their carrier systems by using receptor-mediated endocytotic pathways was in its nascent stages 25 years ago. In the intervening years, an explosion of knowledge focused on design and synthesis of nanoparticulate delivery systems as well as elucidation of the cellular complexity of what was previously-termed receptor-mediated endocytosis has now created a situation when it has become possible to design and test the feasibility of delivery of highly specific nanoparticle drug carriers to specific cells and tissue. This review outlines the mechanisms governing the major modes of receptor-mediated endocytosis used in drug delivery and highlights recent approaches using these as targets for in vivo drug delivery of nanoparticles. The review also discusses some of the inherent complexity associated with the simple shift from a ligand-drug conjugate versus a ligand-nanoparticle conjugate, in terms of ligand valency and its relationship to the mode of receptor-mediated internalization.

Intestinal absorption and bioavailability of traditional Chinese medicines: a review of recent experimental progress and implication for quality control

Objectives

Experimental studies on the pharmacokinetics of traditional Chinese medicines (TCMs) have achieved great progress in recent years. This review aims to summarize the progress made on intestinal absorption and bioavailability of TCMs, and proposes the application of intestinal absorption assays as new tools for the quality and safety control of these medicines.

Key findings

Since only the absorbed constituents may produce possible therapeutic effect (except those that directly target the digestive tract), intestinal absorption is of utmost importance for the drug action of TCMs, which are usually taken orally. Meanwhile, complicated drug interactions may occur among the multiple ingredients in a herbal mixture. In this regard, the intestinal permeability assays not only provide useful pharmacokinetic data of TCMs, but have potential applications for quality and safety control. Moreover, knockout animals, 2/4/A1 in-vitro cell model and physiologically-based in-silico models based on the online TCM database can be quite useful for the prediction of absorption and bioavailability of TCMs.

Summary

A variety of in-vivo, in-vitro, in-situ and in-silico models for predicting the intestinal absorption and bioavailability can be applied to study the herbal interactions and screen appropriate biomarkers for the quality and safety control of TCMs.

Multifunctional dendrimer-entrapped gold nanoparticles for dual mode CT/MR imaging applications

We report the synthesis, characterization, and utilization of gadolium-loaded dendrimer-entrapped gold nanoparticles (Gd-Au DENPs) for dual mode computed tomography (CT)/magnetic resonance (MR) imaging applications. In this study, amine-terminated generation five poly(amidoamine) dendrimers (G5.NH₂) modified with gadolinium (Gd) chelator and polyethylene glycol (PEG) monomethyl ether were used as templates to synthesize gold nanoparticles (AuNPs). Followed by sequential chelation of Gd(III) and acetylation of the remaining dendrimer terminal amine groups, multifunctional Gd-Au DENPs were formed. The formed Gd-Au DENPs were characterized via different techniques. We show that the formed Gd-Au DENPs are colloidally stable and non-cytotoxic at an Au concentration up to 50 μM. With the coexistence of two radiodense imaging elements of AuNPs and Gd(III) within one NP system, the formed Gd-Au DENPs display both r₁ relaxivity for MR imaging mode and X-ray attenuation property for CT imaging mode, which enables CT/MR dual mode imaging of the heart, liver, kidney, and bladder of rat or mouse within a time frame of 45 min. Furthermore, in vivo biodistribution studies reveal that the Gd-Au DENPs have an extended blood circulation time and can be cleared from the major organs within 24 h. The strategy to use facile dendrimer technology to design dual mode contrast agents may be extended to prepare multifunctional platforms for targeted multimode molecular imaging of various biological systems.

Pharmaceutical nanoparticles and the mucin biopolymer barrier

Mucus in the gastrointestinal tract remains a tenacious barrier that restricts the passage of many orally administered compounds into the GIT's epithelial layer and consequently into the systemic circulation. This results in significant decreases in the oral bioavailability of many therapeutic molecules. Nanoparticles offer an avenue to surpass this mucus barrier. They can be used as drug carriers to improve the bioavailability of many compounds that are restricted by mucus. Nanoparticles achieve penetration of the mucus barrier through a multitude of properties that they possess as their size, charge density, and surface functional groups which can all be tailored to achieve optimal penetration of the thick and fibrous mucus barrier. This article offers a quick review about the use of nanoparticles as drug carriers to increase mucus penetration in the gastro intestinal tract.

Oral delivery of glucagon-like peptide-1 and analogs: alternatives for diabetes control?

Type 2 diabetes mellitus (T2DM) is one of the most prevalent diseases worldwide. Current treatments are often associated with off-target effects and do not significantly impact disease progression. New therapies are therefore urgently needed to overcome this social burden. Glucagon-like peptide-1 (GLP-1), an incretin hormone, has been used to control T2DM symptomatology. However, the administration of peptide or proteins drugs is still a huge challenge in the pharmaceutical field, requiring administration by parenteral routes. This article reviews the main hurdles in oral administration of GLP-1 and focuses on the strategies utilized to overcome them.

Mucus-penetrating nanoparticles for vaginal drug delivery protect against herpes simplex virus

Incomplete coverage and short duration of action limit the effectiveness of vaginally administered drugs, including microbicides, for preventing sexually transmitted infections. We investigated vaginal distribution, retention, and safety of nanoparticles with surfaces modified to enhance transport through mucus. We show that mucus-penetrating particles (MPPs) provide uniform distribution over the vaginal epithelium, whereas conventional nanoparticles (CPs) that are mucoadhesive are aggregated by mouse vaginal mucus, leading to poor distribution. Moreover, when delivered hypotonically, MPPs were transported advectively (versus diffusively) through mucus deep into vaginal folds (rugae) within minutes. By penetrating into the deepest mucus layers, more MPPs were retained in the vaginal tract after 6 hours compared to CPs. After 24 hours, when delivered in a conventional vaginal gel, patches of a model drug remained on the vaginal epithelium, whereas the epithelium was coated with drug delivered by MPPs. We then developed MPPs composed of acyclovir monophosphate (ACVp). When administered before vaginal herpes simplex virus 2 challenge, ACVp-MPPs protected 53% of mice compared to only 16% protected by soluble drug. Overall, MPPs improved vaginal drug distribution and retention, provided more effective protection against vaginal viral challenge than soluble drug, and were nontoxic when administered daily for 1 week.

Oral colon-specific therapeutic approaches toward treatment of inflammatory bowel disease

INTRODUCTION

Inflammatory bowel disease (IBD) is a chronic relapsing idiopathic disease. In clinical terms, most patients require lifelong medication associated with possible unpleasant adverse effects. Oral colon-specific drug delivery systems are designed to deliver therapeutic drugs to the inflamed colon to target pathophysiological manifestations of IBD. The aim is to maintain the drug with proper concentration in the inflamed colon, to enhance drug residence time and to minimize drug absorption by healthy tissues.

AREAS COVERED

This review addresses the main barriers for colon-specific drug delivery from organism, tissue and cell levels, respectively. It also summarizes novel colon-specific therapeutic strategies using microparticles and nanoparticles.

EXPERT OPINION

Oral colon-specific drug delivery represents a possible approach toward efficient treatment of IBD. As the environment of the gastrointestinal tract is harsh and intricate, this approach requires that drug carriers can respond to specific environmental factors of the inflamed colon, permitting stimulus-responsive release of loaded drugs to specific cells or even into specific organelles within cells.

Chitosan-alginate microcapsules of amoxicillin for gastric stability and mucoadhesion

Amoxicillin-loaded microcapsules were prepared by ionotropic gelation of sodium alginate (ALG) with chitosan (CS) in presence of calcium chloride as gastroretentive delivery system. The effect of pH, concentration of ALG, CS and calcium chloride, and drug : ALG ratio were optimized in this study for minimizing the degradation of drug in acidic environment and increasing the loading efficacy and mucoadhesive efficiency of microcapsules. The optimum condition for prepared CS-ALG microcapsules was 2%w/v ALG, 0.75%w/v CS (pH5.0), and 1.0% w/v calcium chloride. The resulting microcapsules had drug entrapment efficiency of 84% and average size of 840 mm. CS concentration significantly influenced particle size and encapsulation efficiency of CS–ALG microcapsules (P<0.05). Decrease in the drug: ALG ratio resulted in an increased release of amoxicillin in acidic media. The relative decomposition of drug after encapsulation in CS-ALG microcapsules was decreased to 20.7%, 41.9%, and 83.3% in 2, 4, and 8 hours, respectively.

Advances in biomimetic regeneration of elastic matrix structures

Elastin is a vital component of the extracellular matrix, providing soft connective tissues with the property of elastic recoil following deformation and regulating the cellular response via biomechanical transduction to maintain tissue homeostasis. The limited ability of most adult cells to synthesize elastin precursors and assemble them into mature crosslinked structures has hindered the development of functional tissue-engineered constructs that exhibit the structure and biomechanics of normal native elastic tissues in the body. In diseased tissues, the chronic overexpression of proteolytic enzymes can cause significant matrix degradation, to further limit the accumulation and quality (e.g., fiber formation) of newly deposited elastic matrix. This review provides an overview of the role and importance of elastin and elastic matrix in soft tissues, the challenges to elastic matrix generation in vitro and to regenerative elastic matrix repair in vivo, current biomolecular strategies to enhance elastin deposition and matrix assembly, and the need to concurrently inhibit proteolytic matrix disruption for improving the quantity and quality of elastogenesis. The review further presents biomaterial-based options using scaffolds and nanocarriers for spatio-temporal control over the presentation and release of these biomolecules, to enable biomimetic assembly of clinically relevant native elastic matrix-like superstructures. Finally, this review provides an overview of recent advances and prospects for the application of these strategies to regenerating tissue-type specific elastic matrix structures and superstructures.

An orally administered redox nanoparticle that accumulates in the colonic mucosa and reduces colitis in mice

BACKGROUND & AIMS

Drugs used to treat patients with ulcerative colitis are not always effective because of nonspecific distribution, metabolism in the gastrointestinal tract, and side effects. We designed a nitroxide radical-containing nanoparticle (RNP(O)) that accumulates specifically in the colon to suppress inflammation and reduce the undesirable side effects of nitroxide radicals.

METHODS

RNP(O) was synthesized by assembly of an amphiphilic block copolymer that contains stable nitroxide radicals in an ether-linked hydrophobic side chain. Biodistribution of RNP(O) in mice was determined from radioisotope and electron spin resonance measurements. The effects of RNP(O) were determined in mice with dextran sodium sulfate (DSS)-induced colitis and compared with those of low-molecular-weight drugs (4-hydroxyl-2,2,6,6-tetramethylpiperidine-1-oxyl [TEMPOL] or mesalamine).

RESULTS

RNP(O), with a diameter of 40 nm and a shell of poly(ethylene glycol), had a significantly greater level of accumulation in the colonic mucosa than low-molecular-weight TEMPOL or polystyrene latex particles. RNP(O) was not absorbed into the bloodstream through the intestinal wall, despite its long-term retention in the colon, which prevented its distribution to other parts of the body. Mice with DSS-induced colitis had significantly lower disease activity index and less inflammation following 7 days of oral administration of RNP(O) compared with mice with DSS-induced colitis or mice given low-molecular-weight TEMPOL or mesalamine.

CONCLUSIONS

We designed an orally administered RNP(O) that accumulates specifically in the colons of mice with colitis and is more effective in reducing inflammation than low-molecular-weight TEMPOL or mesalamine. RNP(O) might be developed for treatment of patients with ulcerative colitis.

Near IR fluorescent polystyrene/albumin core/shell nanoparticles for specific targeting of colonic neoplasms

Previous studies have shown that albumin has a high affinity towards tumours, and, as a result, many drug/albumin conjugates, as well as albumin nanoparticles, have been studied as antineoplastic drug carriers. Numerous studies have also shown the high affinity of cyanine dyes for albumin. This work combines the former and the latter for the preparation of NIR fluorescent and photostable nanoparticles as diagnostic biomaterials. Tumour-specific labelling by NIR fluorescent polystyrene/albumin core/shell nanoparticles is demonstrated, without the presence of additional targeting moieties, and they possess great potential for clinical applications.

Production of Inhalable Submicrometer Aerosols from Conventional Mesh Nebulizers for Improved Respiratory Drug Delivery

Submicrometer and nanoparticle aerosols may significantly improve the delivery efficiency, dissolution characteristics, and bioavailability of inhaled pharmaceuticals. The objective of this study was to explore the formation of submicrometer and nanometer aerosols from mesh nebulizers suitable for respiratory drug delivery using experiments and computational fluid dynamics (CFD) modeling. Mesh nebulizers were coupled with add-on devices to promote aerosol drying and the formation of submicrometer particles, as well as to control the inhaled aerosol temperature and relative humidity. Cascade impaction experiments were used to determine the initial mass median aerodynamic diameters of 0.1% albuterol aerosols produced by the AeroNeb commercial (4.69 μm) and lab (3.90 μm) nebulizers and to validate the CFD model in terms of droplet evaporation. Through an appropriate selection of flow rates, nebulizers, and model drug concentrations, submicrometer and nanometer aerosols could be formed with the three devices considered. Based on CFD simulations, a wire heated design was shown to overheat the airstream producing unsafe conditions for inhalation if the aerosol was not uniformly distributed in the tube cross-section or if the nebulizer stopped producing droplets. In comparison, a counter-flow heated design provided sufficient thermal energy to produce submicrometer particles, but also automatically limited the maximum aerosol outlet temperature based on the physics of heat transfer. With the counter-flow design, submicrometer aerosols were produced at flow rates of 5, 15, and 30 LPM, which may be suitable for various forms of oral and nasal aerosol delivery. Thermodynamic conditions of the aerosol stream exiting the counter-flow design were found be in a range of 21-45 °C with relative humidity greater than 40% in some cases, which was considered safe for direct inhalation and advantageous for condensational growth delivery.

A periciliary brush promotes the lung health by separating the mucus layer from airway epithelia

Mucus clearance is the primary defense mechanism that protects airways from inhaled infectious and toxic agents. In the current gel-on-liquid mucus clearance model, a mucus gel is propelled on top of a "watery" periciliary layer surrounding the cilia. However, this model fails to explain the formation of a distinct mucus layer in health or why mucus clearance fails in disease. We propose a gel-on-brush model in which the periciliary layer is occupied by membrane-spanning mucins and mucopolysaccharides densely tethered to the airway surface. This brush prevents mucus penetration into the periciliary space and causes mucus to form a distinct layer. The relative osmotic moduli of the mucus and periciliary brush layers explain both the stability of mucus clearance in health and its failure in airway disease.

The importance of the vaginal delivery route for antiretrovirals in HIV prevention

The HIV/AIDS pandemic continues to be a global health priority, with high rates of new HIV-I infections persisting in young women. One HIV prevention strategy is topical pre-exposure prophylactics or microbicides, which are applied vaginally or rectally to protect the user from HIV and possibly other sexually transmitted infections. Vaginal microbicide delivery will be the focus of this review. Multiple nonspecific and specific antiretroviral microbicide products have been clinically evaluated, and many are in preclinical development, The events of HIV mucosal transmission and dynamics of the cervicovaginal environment should be considered for successful vaginal microbicide delivery. Beyond conventional vaginal formulations, intravaginal rings, tablets and films are employed as platforms in the hope to increase the likelihood of microbicide use. Furthermore, combining multiple antiretrovirals within a given formulation, combining a microbicide product with a vaginal device and integrating novel drug-delivery strategies within a microbicide product are approaches to successful vaginal-microbicide delivery.

Oral delivery of peptides and proteins using lipid-based drug delivery systems

INTRODUCTION

In order to successfully develop lipid-based drug delivery systems (DDS) for oral administration of peptides and proteins, it is important to gain an understanding of the colloid structures formed by these DDS, the mode of peptide and protein incorporation as well as the mechanism by which intestinal absorption of peptides and proteins is promoted.

AREAS COVERED

The present paper reviews the literature on lipid-based DDS, employed for oral delivery of peptides and proteins and highlights the mechanisms by which the different lipid-based carriers are expected to overcome the two most important barriers (extensive enzymatic degradation and poor transmucosal permeability). This paper also gives a clear-cut idea about advantages and drawbacks of using different lipidic colloidal carriers ((micro)emulsions, solid lipid core particles and liposomes) for oral delivery of peptides and proteins.

EXPERT OPINION

Lipid-based DDS are safe and suitable for oral delivery of peptides and proteins. Significant progress has been made in this area with several technologies on clinical trials. However, a better understanding of the mechanism of action in vivo is needed in order to improve the design and development of lipid-based DDS with the desired bioavailability and therapeutic profile.

Antibacterial activities of liposomal linolenic acids against antibiotic-resistant Helicobacter pylori

Helicobacter pylori (H. pylori) infection with its vast prevalence is responsible for various gastric diseases including gastritis, peptic ulcers, and gastric malignancy. While effective, current treatment regimens are challenged by a fast-declining eradication rate due to the increasing emergence of H. pylori strains resistant to existing antibiotics. Therefore, there is an urgent need to develop novel antibacterial strategies against H. pylori. In this study, we developed a liposomal nanoformulation of linolenic acid (LipoLLA) and evaluated its bactericidal activity against resistant strains of H. pylori. Using a laboratory strain of H. pylori, we found that LipoLLA was effective in killing both spiral and coccoid forms of the bacteria via disrupting bacterial membranes. Using a metronidazole-resistant strain of H. pylori and seven clinically isolated strains, we further demonstrated that LipoLLA eradicated all strains of the bacteria regardless of their antibiotic resistance status. Furthermore, under our experimental conditions, the bacteria did not develop drug resistance when cultured with LipoLLA at various sub-bactericidal concentrations, whereas they rapidly acquired resistance to both metronidazole and free linolenic acid (LLA). Our findings suggest that LipoLLA is a promising antibacterial nanotherapeutic to treat antibiotic-resistant H. pylori infection.

Targeted delivery of transferrin-conjugated liposomes to an orthotopic model of lung cancer in nude rats

BACKGROUND

Lung cancer is the leading cause of cancer death worldwide. Pulmonary anticancer therapy might offer several advantages over systemic delivery, leading to an increased exposure of the lung tumor to the drug, while minimizing side effects, due to regional containment. Here, we studied if a combination of inhalation therapy and drug targeting holds potential as an even more efficient lung cancer therapy.

METHODS

Transferrin (Tf )-conjugated PEG liposomes loaded with doxorubicin (DOX) were administered using an intracorporeal nebulizing catheter to an orthotopic lung cancer model established in athymic Rowett nude rats. Different DOX formulations and doses (0.2 and 0.4 mg/kg) were tested and the influence on tumor progression and life span of rats was evaluated in comparison with the i.v. administration of Tf-PEG-liposomes loaded with DOX at a therapeutic dose of 2 mg/kg.

RESULTS

Rats in the untreated control group showed significant weight loss 2 weeks after tumor induction and died between days 19 and 29. Lungs of these animals showed multiple foci of neoplastic deposits, ranging up to 20 mm replacing the entire lobe. Empty Tf-liposomes showed a significant effect on survival time. This might be caused by the secondary cytotoxicity via stimulation of pulmonary macrophages. All animal treated intravenously also perished before the end of the study. No significant (p<0.05) improvement in survival was observed between the groups treated with aerosols of free drug, DOX encapsulated in plain and in Tf-modified liposomes. However, more animals survived in the Tf-liposome groups than in the other treatment regimes, and their lung tissue generally had fewer and smaller tumors. Nevertheless, the size of the groups, and the duration of the trial render it impossible to come to a definite conclusion.

CONCLUSIONS

Drug targeting demonstrated potential for improving the aerosol treatment of lung cancer.

Biodistribution and endocytosis of ICAM-1-targeting antibodies versus nanocarriers in the gastrointestinal tract in mice

Drug delivery to the gastrointestinal (GI) tract is key for improving treatment of GI maladies, developing oral vaccines, and facilitating drug transport into circulation. However, delivery of formulations to the GI tract is hindered by pH changes, degradative enzymes, mucus, and peristalsis, leading to poor GI retention. Targeting may prolong residence of therapeutics in the GI tract and enhance their interaction with this tissue, improving such aspects. We evaluated nanocarrier (NC) and ligand-mediated targeting in the GI tract following gastric gavage in mice. We compared GI biodistribution, degradation, and endocytosis between control antibodies and antibodies targeting the cell surface determinant intercellular adhesion molecule 1 (ICAM-1), expressed on GI epithelium and other cell types. These antibodies were administered either as free entities or coated onto polymer NCs. Fluorescence and radioisotope tracing showed proximal accumulation, with preferential retention in the stomach, jejunum, and ileum; and minimal presence in the duodenum, cecum, and colon by 1 hour after administration. Upstream (gastric) retention was enhanced in NC formulations, with decreased downstream (jejunal) accumulation. Of the total dose delivered to the GI tract, ∼60% was susceptible to enzymatic (but not pH-mediated) degradation, verified both in vitro and in vivo. Attenuation of peristalsis by sedation increased upstream retention (stomach, duodenum, and jejunum). Conversely, alkaline NaHCO(3), which enhances GI transit by decreasing mucosal viscosity, favored downstream (ileal) passage. This suggests passive transit through the GI tract, governed by mucoadhesion and peristalsis. In contrast, both free anti-ICAM and anti-ICAM NCs demonstrated significantly enhanced upstream (stomach and duodenum) retention when compared to control IgG counterparts, suggesting GI targeting. This was validated by transmission electron microscopy and energy dispersive X-ray spectroscopy, which revealed anti-ICAM NCs in vesicular compartments within duodenal epithelial cells. These results will guide future work aimed at improving intraoral delivery of targeted therapeutics for the treatment of GI pathologies.