Lectin-mediated drug delivery: the second generation of bioadhesives

Biomedical microelectromechanical systems (BioMEMS): Revolution in drug delivery and analytical techniques

Advancement in microelectromechanical system has facilitated the microfabrication of polymeric substrates and the development of the novel class of controlled drug delivery devices. These vehicles have specifically tailored three dimensional physical and chemical features which together, provide the capacity to target cell, stimulate unidirectional controlled release of therapeutics and augment permeation across the barriers. Apart from drug delivery devices microfabrication technology’s offer exciting prospects to generate biomimetic gastrointestinal tract models. BioMEMS are capable of analysing biochemical liquid sample like solution of metabolites, macromolecules, proteins, nucleic acid, cells and viruses. This review summarized multidisciplinary application of biomedical microelectromechanical systems in drug delivery and its potential in analytical procedures.

Medibots: Dual-Action Biogenic Microdaggers for Single-Cell Surgery and Drug Release

An innovative concept for the fabrication of dual-action microrobots capable of performing single-cell microsurgery along with a site-directed drug-delivery feature is presented. These multi-action plant-derived biocompatible "medibots" can play a pivotal role in understanding micromotor interactions at the cellular level, aiming toward the destruction of harmful cells (like cancer) among others in living systems.

Polymeric nanoparticles for colon cancer therapy: overview and perspectives

Colorectal cancer (CRC) is the third-most common malignant tumour and is associated with high morbidity and mortality worldwide.

Recent progresses in bioadhesive microspheres via transmucosal administration

Based on the advantages of adhesion preparations and the application status of microspheres (MSs) in mucous delivery, this paper primarily reviews the bioadhesive MSs via transmucosal administration routes, including the mucosa in alimentary tract and other lumens. Particularly, the detailed researches about of celladhesive MSs and some new-style bioadhesive MSs are mentioned. Furthermore, this review attempts to reveal the advances of bioadhesive MSs as cell-selective bioadhesion systems and the stimuli-responsive MSs as location-specific drug delivery systems. Although these MSs show powerful strength, some far-sighted ideas should be brought on agendas. In the future, mechanisms should be put under tight scrutiny and more attention should be focused on the excellent bioadhesive materials and the 'second generation mucoadhesives'. Meaningful clinical applications of these novel MSs are also of current concerns and need more detailed researches.

Respiratory nanoparticle-based vaccines and challenges associated with animal models and translation

Vaccine development has had a huge impact on human health. However, there is a significant need to develop efficacious vaccines for several existing as well as emerging respiratory infectious diseases. Several challenges need to be overcome to develop efficacious vaccines with translational potential. This review focuses on two aspects to overcome some barriers - 1) the development of nanoparticle-based vaccines, and 2) the choice of suitable animal models for respiratory infectious diseases that will allow for translation. Nanoparticle-based vaccines, including subunit vaccines involving synthetic and/or natural polymeric adjuvants and carriers, as well as those based on virus-like particles offer several key advantages to help overcome the barriers to effective vaccine development. These include the ability to deliver combinations of antigens, target the vaccine formulation to specific immune cells, enable cross-protection against divergent strains, act as adjuvants or immunomodulators, allow for sustained release of antigen, enable single dose delivery, and potentially obviate the cold chain. While mouse models have provided several important insights into the mechanisms of infectious diseases, they are often a limiting step in translation of new vaccines to the clinic. An overview of different animal models involved in vaccine research for respiratory infections, with advantages and disadvantages of each model, is discussed. Taken together, advances in nanotechnology, combined with the right animal models for evaluating vaccine efficacy, has the potential to revolutionize vaccine development for respiratory infections.

The Potential of Silk and Silk-Like Proteins as Natural Mucoadhesive Biopolymers for Controlled Drug Delivery

Drug delivery across mucus membranes is a particularly effective route of administration due to the large surface area. However, the unique environment present at the mucosa necessitates altered drug formulations designed to (1) deliver sensitive biologic molecules, (2) promote intimate contact between the mucosa and the drug, and (3) prolong the drug's local residence time. Thus, the pharmaceutical industry has an interest in drug delivery systems formulated around the use of mucoadhesive polymers. Mucoadhesive polymers, both synthetic and biological, have a history of use in local drug delivery. Prominently featured in the literature are chitosan, alginate, and cellulose derivatives. More recently, silk and silk-like derivatives have been explored for their potential as mucoadhesive polymers. Both silkworms and spiders produce sticky silk-like glue substances, sericin and aggregate silk respectively, that may prove an effective, natural matrix for drug delivery to the mucosa. This mini review will explore the potential of silk and silk-like derivatives as a biocompatible mucoadhesive polymer matrix for local controlled drug delivery.

Toxic proteins in plants

Plants have evolved to synthesize a variety of noxious compounds to cope with unfavorable circumstances, among which a large group of toxic proteins that play a critical role in plant defense against predators and microbes. Up to now, a wide range of harmful proteins have been discovered in different plants, including lectins, ribosome-inactivating proteins, protease inhibitors, ureases, arcelins, antimicrobial peptides and pore-forming toxins. To fulfill their role in plant defense, these proteins exhibit various degrees of toxicity towards animals, insects, bacteria or fungi. Numerous studies have been carried out to investigate the toxic effects and mode of action of these plant proteins in order to explore their possible applications. Indeed, because of their biological activities, toxic plant proteins are also considered as potentially useful tools in crop protection and in biomedical applications, such as cancer treatment. Genes encoding toxic plant proteins have been introduced into crop genomes using genetic engineering technology in order to increase the plant's resistance against pathogens and diseases. Despite the availability of ample information on toxic plant proteins, very few publications have attempted to summarize the research progress made during the last decades. This review focuses on the diversity of toxic plant proteins in view of their toxicity as well as their mode of action. Furthermore, an outlook towards the biological role(s) of these proteins and their potential applications is discussed.

Micro/nanofabricated platforms for oral drug delivery

The oral route of drug administration is most preferred due to its ease of use, low cost, and high patient compliance. However, the oral uptake of many small molecule drugs and biotherapeutics is limited by various physiological barriers, and, as a result, drugs suffer from issues with low solubility, low permeability, and degradation following oral administration. The flexibility of micro- and nanofabrication techniques has been used to create drug delivery platforms designed to address these barriers to oral drug uptake. Specifically, micro/nanofabricated devices have been designed with planar, asymmetric geometries to promote device adhesion and unidirectional drug release toward epithelial tissue, thereby prolonging drug exposure and increasing drug permeation. Furthermore, surface functionalization, nanotopography, responsive drug release, motion-based responses, and permeation enhancers have been incorporated into such platforms to further enhance drug uptake. This review will outline the application of micro/nanotechnology to specifically address the physiological barriers to oral drug delivery and highlight technologies that may be incorporated into these oral drug delivery systems to further enhance drug uptake.

Functional recombinants designed from a fetuin/asialofetuin-specific marine algal lectin, rhodobindin

Plant lectins have attracted much attention for biomedical applications including targeted drug delivery system and therapy against tumors and microbial infections. The main problem of using lectins as a biomedical tool is a batch-to-batch variation in isoforms content. The production of lectins using recombination tools has the advantage of obtaining high amounts of proteins with more precise properties, but there are only a handful of functional recombinant lectins presently available. A fetuin/asialo-fetuin specific lectin, Rhodobindin, has unique tandem repeats structure which makes it useful in exploiting for recombinant lectin. We developed three functional recombinant lectins using E. coli expression system: one from full cDNA sequence and two from fragmentary sequences of Rhodobindin. Hemagglutinating activity and solubility of the recombinant lectins were highest at OD 0.7 cell concentration at 20 °C. The optimized process developed in this study was suitable for the quality-controlled production of high amounts of soluble recombinant lectins.

Surface engineered and ligand anchored nanobioconjugate: an effective therapeutic approach for oral insulin delivery in experimental diabetic rats

The present study was designed to enhance intestinal absorption of insulin by nanobioconjugate formulated with PEGylation and Concanavalin A based targeted synergistic approach. The attempts were aimed at maximizing bioavailability and therapeutic efficacy of insulin by incorporating it in Concanavalin A anchored PEGylated nanoconstructs. The Con A anchored PEGylated PLGA diblock copolymer was synthesized by modified surface functionalization method, and was then characterized by FTIR and 1H NMR spectrum analysis. The nanoparticles from synthesized polymers were prepared and characterized for mean size and distribution by laser diffraction spectroscopy. The physicochemically characterized (by SEM and TEM) formulations were evaluated for optimum particle size, polydispersity index, zeta potential and entrapment efficiency 196.3±4.5 nm, 0.15±0.04, -25.6±1.68 and 44.6±3.5% respectively. The insulin encapsulation efficiency and in vitro release were assessed by bicinchoninic protein assay (BCA). The in vitro results corroborated in vivo studies carried out in experimentally created diabetic albino rats. The nano-encapsulated insulin was discovered to meet the requirements by achieving better stability, improved absorption and enhanced oral bioavailability elucidated by in vivo and in vitro bioassays.

Cationic Polymers for Intracellular Delivery of Proteins

Many therapeutic proteins exert their pharmaceutical action inside the cytoplasm or onto individual organelles inside the cell. Intracellular protein delivery is considered to be the most direct, fastest and safest approach for curing gene-deficiency diseases, enhancing vaccination and triggering cell transdifferentiation processes, within other curative applications. However, several hurdles have to be overcome. For this purpose the use of polymers, with their ease of modification in physical and chemical properties, is attractive in protein drug carriers. They can protect their therapeutic protein cargo from degradation and enhance their bioavailability at targeted sites. In this chapter, potential and currently used polymers for fabrication of protein delivery systems and their applications for intracellular administration are discussed. Special attention is given to the use of cationic polymers for their ability to promote the cellular uptake of therapeutic proteins.

Planar microdevices for enhanced in vivo retention and oral bioavailability of poorly permeable drugs

The development of novel oral drug delivery platforms for administering therapeutics in a safe and effective manner through the harsh gastrointestinal environment is of great importance. Here, the use of engineered thin planar poly(methyl methacrylate) (PMMA) microdevices is tested to enhance oral bioavailability of acyclovir, a poorly permeable drug. Acyclovir is loaded into the unidirectional drug releasing microdevice reservoirs using a drug entrapping photocross-linkable hydrogel matrix. An increase in acyclovir permeation across in vitro caco-2 monolayer is seen in the presence of microdevices as compared with acyclovir-entrapped hydrogels or free acyclovir solution. Cell proliferation studies show that microdevices are relatively nontoxic in nature for use in in vivo studies. Enhanced in vivo retention of microdevices is observed as their thin side walls experience minimal peristaltic shear stress as compared with spherical microparticles. Unidirectional acyclovir release and enhanced retention of microdevices achieve a 4.5-fold increase in bioavailability in vivo as compared with an oral gavage of acyclovir solution with the same drug mass. The enhanced oral bioavailability results suggest that thin, planar, bioadhesive, and unidirectional drug releasing microdevices will significantly improve the systemic and localized delivery of a broad range of oral therapeutics in the near future.

Ionic liquids and cellulose: dissolution, chemical modification and preparation of new cellulosic materials

Due to its abundance and a wide range of beneficial physical and chemical properties, cellulose has become very popular in order to produce materials for various applications. This review summarizes the recent advances in the development of new cellulose materials and technologies using ionic liquids. Dissolution of cellulose in ionic liquids has been used to develop new processing technologies, cellulose functionalization methods and new cellulose materials including blends, composites, fibers and ion gels.

Clinical efficacy of a spray containing hyaluronic Acid and dexpanthenol after surgery in the nasal cavity (septoplasty, simple ethmoid sinus surgery, and turbinate surgery)

Background. This prospective, controlled, parallel-group observational study investigated the efficacy of a spray containing hyaluronic acid and dexpanthenol to optimise regular treatment after nasal cavity surgery in 49 patients with chronic rhinosinusitis. Methods. The control group received standard therapy. Mucosal regeneration was determined using rhinoscopy sum score (RSS). Pre- and postoperative nasal patency was tested using anterior rhinomanometry. The participants were questioned about their symptoms. Results. Regarding all RSS parameters (dryness, dried nasal mucus, fibrin deposition, and obstruction), mucosal regeneration achieved good final results in both groups, tending to a better improvement through the spray application, without statistically significant differences during the whole assessment period, the mean values being 7.04, 5.00, 3.66, and 3.00 (intervention group) and 7.09, 5.14, 4.36, and 3.33 (control group). No statistically significant benefit was identified for nasal breathing, foreign body sensation, and average rhinomanometric volume flow, which improved by 12.31% (control group) and 11.24% (nasal spray group). Conclusion. The investigational product may have additional benefit on postoperative mucosal regeneration compared to standard cleaning procedures alone. However, no statistically significant advantage could be observed in this observational study. Double-blind, controlled studies with larger populations will be necessary to evaluate the efficacy of this treatment modality.

Poly(lactic acid) nanoparticles coated with combined WGA and water-soluble chitosan for mucosal delivery of β-galactosidase

A combinatorial design, physical adsorption of water-soluble chitosan (WSC) to particle surface and covalent conjugation of wheat germ agglutinin (WGA) to WSC, was applied to surface modification of poly(lactic acid) nanoparticles (NPs) for targeted delivery of β-galactosidase to the intestinal mucosa. All the surface-engineered NPs in the size range of 500-600 nm were prepared by a w/o/w solvent diffusion/evaporation technique. β-Galactosidase encapsulated in these NPs was well protected from external proteolysis and exerted high hydrolytic activity on the permeable lactose. The presence of WSC coating, whether alone or with WGA, highly improved the suspension stability of NPs and tailored the particle surface positively charged. In comparison to NPs modified with WGA or WSC alone, the synergistic action of WGA and WSC greatly enhanced the NP-mucin interactions in vitro. The highest amount of NPs was found in the small intestine at 24 h after oral administration in rats. Notably, calculated half-life of WGA-WSC-NPs in the small intestine was 6.72 h, resulting in 2.1- and 4.3-fold increase when compared to WGA-polyvinylalcohol (PVA)-NPs and WSC-NPs, much longer than that of control PVA-NPs (6.9-fold). These results suggest that NPs with the combined WGA and WSC coating represent promising candidates for efficient mucosal drug delivery as well as biomimetic treatment of lactose intolerance.

Drug delivery strategies in the therapy of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a frequently occurring disease in young people, which is characterized by a chronic inflammation of the gastrointestinal tract. The therapy of IBD is dominated by the administration of anti-inflammatory and immunosuppressive drugs, which suppress the intestinal inflammatory burden and improve the disease-related symptoms. Established treatment strategies are characterized by a limited therapeutical efficacy and the occurrence of adverse drug reactions. Thus, the development of novel disease-targeted drug delivery strategies is intended for a more effective therapy and demonstrates the potential to address unmet medical needs. This review gives an overview about the established as well as future-oriented drug targeting strategies, including intestine targeting by conventional drug delivery systems (DDS), disease targeted drug delivery by synthetic DDS and disease targeted drug delivery by biological DDS. Furthermore, this review analyses the targeting mechanisms of the respective DDS and discusses the possible field of utilization in IBD.

Glycan-targeted drug delivery for intravesical therapy: in the footsteps of uropathogenic bacteria

The human urothelium belongs to the most efficient biobarriers, and represents a highly rewarding but challenging target for local drug administration. Inadequate urothelial bioavailability is a major obstacle for successful treatment of bladder cancer and other diseases, yet little research has addressed the development of advanced delivery concepts for the intravesical route. A prominent example of how to overcome the urothelial barrier by means of specific biorecognition is the efficient cytoinvasion of UPEC bacteria, mediated by the mannose-targeted lectin domain FimH. Similar mechanisms of non-bacterial origin may be exploited for enhancing drug uptake from the bladder cavity. This review covers the current status in the development of lectin-based delivery strategies for the urinary tract. Different concepts for preparing and optimizing carbohydrate-targeted delivery systems are presented, along with important design parameters, benefits and shortcomings. Bioconjugate- and nano-/microparticle-based systems are discussed in further detail with regard to their performance in preclinical testing.

Role of mucoadhesive polymers in enhancing delivery of nimodipine microemulsion to brain via intranasal route

Intranasal drug administration is receiving increased attention as a delivery method for bypassing the blood–brain barrier and rapidly targeting therapeutics to the CNS. However, rapid mucociliary clearance in the nasal cavity is a major hurdle. The purpose of this study was to evaluate the effect of mucoadhesive polymers in enhancing the delivery of nimodipine microemulsion to the brain via the intranasal route. The optimized mucoadhesive microemulsion was characterized, and the in vitro drug release and in vivo nasal absorption of drug from the new formulation were evaluated in rats. The optimized formulation consisted of Capmul MCM as oil, Labrasol as surfactant, and Transcutol P as co-surfactant, with a particle size of 250 nm and zeta potential value of −15 mV. In vitro and ex vivo permeation studies showed an initial burst of drug release at 30 min and sustained release up to 6 h, attributable to the presence of free drug entrapped in the mucoadhesive layer. In vivo pharmacokinetic studies in rats showed that the use of the mucoadhesive microemulsion enhanced brain and plasma concentrations of nimodipine. These results suggest that incorporation of a mucoadhesive agent in a microemulsion intranasal delivery system can increase the retention time of the formulation and enhance brain delivery of drugs.

Development of an advanced intestinal in vitro triple culture permeability model to study transport of nanoparticles

Intestinal epithelial cell culture models, such as Caco-2 cells, are commonly used to assess absorption of drug molecules and transcytosis of nanoparticles across the intestinal mucosa. However, it is known that mucus strongly impacts nanoparticle mobility and that specialized M cells are involved in particulate uptake. Thus, to get a clear understanding of how nanoparticles interact with the intestinal mucosa, in vitro models are necessary that integrate the main cell types. This work aimed at developing an alternative in vitro permeability model based on a triple culture: Caco-2 cells, mucus-secreting goblet cells and M cells. Therefore, Caco-2 cells and mucus-secreting goblet cells were cocultured on Transwells and Raji B cells were added to stimulate differentiation of M cells. The in vitro triple culture model was characterized regarding confluence, integrity, differentiation/expression of M cells and cell surface architecture. Permeability of model drugs and of 50 and 200 nm polystyrene nanoparticles was studied. Data from the in vitro model were compared with ex vivo permeability results (Ussing chambers and porcine intestine) and correlated well. Nanoparticle uptake was size-dependent and strongly impacted by the mucus layer. Moreover, nanoparticle permeability studies clearly demonstrated that particles were capable of penetrating the intestinal barrier mainly via specialized M cells. It can be concluded that goblet cells and M cells strongly impact nanoparticle uptake in the intestine and should thus be integrated in an in vitro permeability model. The presented model will be an efficient tool to study intestinal transcellular uptake of particulate systems.

Liposomal antibiotics for the treatment of infectious diseases

INTRODUCTION

Liposomal delivery systems have been utilized in developing effective therapeutics against cancer and targeting microorganisms in and out of host cells and within biofilm community. The most attractive feature of liposome-based drugs are enhancing therapeutic index of the new or existing drugs while minimizing their adverse effects.

AREAS COVERED

This communication provides an overview on several aspects of liposomal antibiotics including the most widely used preparation techniques for encapsulating different agents and the most important characteristic parameters applied for examining shape, size and stability of the spherical vesicles. In addition, the routes of administration, liposome-cell interactions and host parameters affecting the biodistribution of liposomes are highlighted.

EXPERT OPINION

Liposomes are safe and suitable for delivery of variety of molecules and drugs in biomedical research and medicine. They are known to improve the therapeutic index of encapsulated agents and reduce drug toxicity. Recent studies on liposomal formulation of chemotherapeutic and bioactive agents and their targeted delivery show liposomal antibiotics potential in the treatment of microbial infections.

Polymeric micelles, a promising drug delivery system to enhance bioavailability of poorly water-soluble drugs

Oral administration is the most commonly used and readily accepted form of drug delivery; however, it is find that many drugs are difficult to attain enough bioavailability when administered via this route. Polymeric micelles (PMs) can overcome some limitations of the oral delivery acting as carriers able to enhance drug absorption, by providing (1) protection of the loaded drug from the harsh environment of the GI tract, (2) release of the drug in a controlled manner at target sites, (3) prolongation of the residence time in the gut by mucoadhesion, and (4) inhibition of efflux pumps to improve the drug accumulation. To explain the mechanisms for enhancement of oral bioavailability, we discussed the special stability of PMs, the controlled release properties of pH-sensitive PMs, the prolongation of residence time with mucoadhesive PMs, and the P-gp inhibitors commonly used in PMs, respectively. The primary purpose of this paper is to illustrate the potential of PMs for delivery of poorly water-soluble drugs with bioavailability being well maintained.

Synergistic targeting/prodrug strategies for intravesical drug delivery--lectin-modified PLGA microparticles enhance cytotoxicity of stearoyl gemcitabine by contact-dependent transfer

The direct access to the urothelial tissue via intravesical therapy has emerged as a promising means for reducing the high recurrence rate of bladder cancer. However, few advanced delivery concepts have so far been evaluated to overcome critical inherent efficacy limitations imposed by short exposure times, low tissue permeability, and extensive washout. This study reports on a novel strategy to enhance gemcitabine treatment impact on urothelial cells by combining a pharmacologically advantageous prodrug approach with the pharmacokinetic benefits of a glycan-targeted carrier system. The conversion of gemcitabine to its 4-(N)-stearoyl derivative (GEM-C₁₈) allowed for stable, homogeneous incorporation into PLGA microparticles (MP) without compromising intracellular drug activation. Fluorescence-labeled GEM-C₁₈-PLGA-MP were surface-functionalized with wheat germ agglutinin (WGA) or human serum albumin (HSA) to assess in direct comparison the impact of biorecognitive interaction on binding rate and anchoring stability. MP adhesion on urothelial cells of non-malignant origin (SV-HUC-1), and low- (5637) or high-grade (HT-1376) carcinoma was correlated to the resultant antiproliferative and antimetabolic effect in BrdU and XTT assays. More extensive and durable binding of the WGA-GEM-C₁₈-PLGA-MP induced a change in the pharmacological profile and substantially higher cytotoxicity, allowing for maximum response within the temporal restrictions of instillative administration (120 min). Mechanistically, a direct, contact-dependent transfer of stearoyl derivatives from the particle matrix to the urothelial membrane was found to account for this effect. With versatile options for future application, our results highlight the potential offered by the synergistic implementation of targeting/prodrug strategies in delivery systems tailored to the intravesical route.

Surface modification of liposomes using polymer-wheat germ agglutinin conjugates to improve the absorption of peptide drugs by pulmonary administration

In this study, we investigated the feasibility of a system based on liposomal surface modification with a novel mucoadhesive polymer-lectin conjugate for the pulmonary delivery of therapeutic peptides and proteins. We covalently attached wheat germ agglutinin (WGA), a ligand that specifically interacts with alveolar epithelial cells, to carbopol (CP), a mucoadhesive polymer, using the carbodiimide method and then evaluated the efficacy and potential toxicity of CP-WGA surface-modified liposomes in vivo and in vitro. In association studies, CP-WGA modification enhanced the interaction with A549 lung epithelial cells compared with unmodified or CP-modified liposomes. This increased association was dependent on temperature and the surface concentration of free WGA. These results suggested synergy of WGA and CP, and retention of the biological cell binding activity of WGA, leading to improved liposome-cell interactions. Moreover, improvement of liposomal bioadhesion to lung epithelia significantly enhanced and prolonged the therapeutic efficacy of calcitonin, a model peptide drug, without any evidence of toxicity, following administration of calcitonin-loaded CP-WGA-modified liposomes. Hence, surface modification of liposomes with CP-WGA has potential for effective pulmonary administration of peptides.

Multi-reservoir bioadhesive microdevices for independent rate-controlled delivery of multiple drugs

A variety of oral administrative systems such as enterically coated tablets, capsules, particles, and liposomes have been developed to improve oral bioavailability of drugs. However, they suffer from poor intestinal localization and therapeutic efficacy due to the various physiological conditions and high shear fluid flow. Fabrication of novel microdevices combined with the introduction of controlled release, improved adhesion, selective targeting, and tissue permeation may overcome these issues and potentially diminish the toxicity and high frequency of conventional oral administration. Herein, thin, asymmetric, poly(methyl methacrylate) (PMMA) microdevices are fabricated with multiple reservoirs using photolithography and reactive ion etching. They are loaded with different individual model drug in each reservoir. Enhanced bioadhesion of the microdevices is observed in the presence of a conjugated of targeting protein (tomato lectin) to the PMMA surface. As compared to drug encompassing hydrogels, an increase in drug permeation across the caco-2 monolayer is noticed in the presence of a microdevice loaded with the same drug-hydrogel system. Also, the release of multiple drugs from their respective reservoirs is found to be independent from each other. The use of different hydrogel systems in each reservoir shows differences in the controlled release of the respective drugs over the same release period. These results suggest that, in the future, microfabricated unidirectional multi-drug releasing devices will have an impact on the oral administration of a broad range of therapeutics.

Medicinal Applications of Plant Lectins

Plant lectins are a unique group of proteins and glycoproteins with potent biological activity and have received widespread attention for many years. They can be found in wheat, corn, tomatoes, peanuts, kidney beans, bananas, peas, lentils, soybeans, mushrooms, tubers, seeds, mistletoe and potatoes among many others. Due to their ability to bind reversibly with specific carbohydrate structures and their abundant availability, plant lectins have commonly been used as a molecular tool in various disciplines of biology and medicine. Whilst once thought of being a dietary toxin, the focus on plant lectins has since shifted to understanding the useful properties of these lectins and utilizing them in medicinal applications to advance human health. This chapter reviews the current and potential applications of plant lectins in various areas of medically related research.

Emerging microtechnologies for the development of oral drug delivery devices

The development of oral drug delivery platforms for administering therapeutics in a safe and effective manner across the gastrointestinal epithelium is of much importance. A variety of delivery systems such as enterically coated tablets, capsules, particles, and liposomes have been developed to improve oral bioavailability of drugs. However, orally administered drugs suffer from poor localization and therapeutic efficacy due to various physiological conditions such as low pH, and high shear intestinal fluid flow. Novel platforms combining controlled release, improved adhesion, tissue penetration, and selective intestinal targeting may overcome these issues and potentially diminish the toxicity and high frequency of administration associated with conventional oral delivery. Microfabrication along with appropriate surface chemistry, provide a means to fabricate these platforms en masse with flexibility in tailoring the shape, size, reservoir volume, and surface characteristics of microdevices. Moreover, the same technology can be used to include integrated circuit technology and sensors for designing sophisticated autonomous drug delivery devices that promise to significantly improve point of care diagnostic and therapeutic medical applications. This review sheds light on some of the fabrication techniques and addresses a few of the microfabricated devices that can be effectively used for controlled oral drug delivery applications.

Airway delivery of peptides and proteins using nanoparticles

Delivery of peptides and proteins via the airways is one of the most exciting potential applications of nanomedicine. These macromolecules could be used for many therapeutic applications, however due to their poor stability in physiological medium and difficulties in delivering them across biological barriers, they are very difficult to use in therapy. Nanoparticulate drug delivery systems have emerged as one of the most promising technologies to overcome these limitations, owing mainly to their proven capacity to cross biological barriers and to enter cells in high yields, thus improving delivery of macromolecules. In this review, we summarize the current advances in nanoparticle designed for transmucosal delivery of peptides and proteins. Challenges that must be overcome in order to derive clinical benefits are also discussed.

Mucin multilayers assembled through sugar-lectin interactions

Multilayer films of biopolymers are attractive tools to exploit the extraordinary properties of certain biomacromolecules and introduce new functionalities to surfaces. Mucins, the gel-forming constituents of mucus, are versatile glycoproteins that have potential as new building blocks for biomaterial surface coatings. Multilayer films have mostly been assembled through the electrostatic pairing of polyelectrolytes, which results in limited pH and salt stability and screens charges otherwise available for useful payload binding. Here, we aim at assembling mucin multilayer films that differ from conventional paired polyelectrolyte assemblies to obtain highly stable and functional surface modifications. Using the lectin wheat germ agglutinin (WGA) to cross-link mucin-bound sugar residues, we show that (Mucin/WGA) films can grow into hydrated films and sustain exceptional resistance to extreme salt conditions and a large range of pH. Furthermore, we show that the addition of soluble N-acetyl-d-glucosamine can induce the controlled release of WGA from (Mucin/WGA) films. Last, we show that (Mucin/WGA) films can repeatedly incorporate and release a positively charged model cargo. The lubricating, hydration, barrier, and antimicrobial properties of mucins open multiple applicative perspectives for these highly stable mucin-based multilayer films.

Strategies for non-invasive delivery of biologics

Macromolecular therapeutics, in particular, many biologics, is the most advancing category of drugs over conventional chemical drugs. The potency and specificity of the biologics for curing certain disease made them to be a leading compound in the pharmaceutical industry. However, due to their intrinsic nature, including high molecular weight, hydrophilicity and instability, they are difficult to be administered via non-invasive route. This is a major quest especially in biologics, as they are frequently used clinically for chronic disorders, which requires long-term administration. Therefore, many efforts have been made to develop formulation for non-invasive administration, in attempt to improve patient compliance and convenience. In this review, strategies for non-invasive delivery, in particular, oral, pulmonary and nasal delivery, that are recently adopted for delivery of biologics are discussed. Insulin, calcitonin and heparin were mainly focused for the discussion as they could represent protein, polypeptide and polysaccharide drugs, respectively. Many recent attempts for non-invasive delivery of biologics are compared to provide an insight of developing successful delivery system.

Bioadhesion: a review of concepts and applications

Bioadhesion refers to the phenomenon where natural and synthetic materials adhere to biological surfaces. An understanding of the fundamental mechanisms that govern bioadhesion is of great interest for various researchers who aim to develop new biomaterials, therapies and technological applications such as biosensors. This review paper will first describe various examples of the manifestation of bioadhesion along with the underlying mechanisms. This will be followed by a discussion of some of the methods for the optimization of bioadhesion. Finally, nanoscale and macroscale characterization techniques for the efficacy of bioadhesion and the analysis of failure surfaces are described.

Oral biodrug delivery using cell-penetrating peptide

During the past few decades, the novel biotherapeutic agents such as peptides and proteins have been contributed to the treatment of several diseases. However, their oral absorption is significantly limited due to their poor delivery through the intestinal mucosa. Therefore, the feasible approaches are needed for improving the oral bioavailability of biodrugs. Recently, cell-penetrating peptides (CPPs) such as HIV-1 Tat, penetratin and oligoarginine are considered as a useful tool for the intracellular delivery of therapeutic macromolecules. Hence, it was expected that the ability of CPPs may be applicable to enhance the absorption of biodrugs through intestinal epithelial membrane. CPPs are likely to become powerful tools for overcoming the low permeability of therapeutic peptides and proteins through the intestinal membrane, the major barrier to their oral delivery. Further advantage of this promising strategy is that this successful intestinal absorption could be achieved by more convenient methodology, coadministration of CPP with drugs via intermolecular interaction among them. Hereafter, the further establishment of delivery system based on CPPs is required to realize the development of the oral forms of therapeutic peptides and proteins. The aim here is to introduce our vision focusing on oral biodrug delivery by the use of CPPs as potential peptide carrier in order to provide new information in the design and development of new oral delivery systems for novel biotherapeutics.

Microfabrication technologies for oral drug delivery

Micro-/nanoscale technologies such as lithographic techniques and microfluidics offer promising avenues to revolutionalize the fields of tissue engineering, drug discovery, diagnostics and personalized medicine. Microfabrication techniques are being explored for drug delivery applications due to their ability to combine several features such as precise shape and size into a single drug delivery vehicle. They also offer to create unique asymmetrical features incorporated into single or multiple reservoir systems maximizing contact area with the intestinal lining. Combined with intelligent materials, such microfabricated platforms can be designed to be bioadhesive and stimuli-responsive. Apart from drug delivery devices, microfabrication technologies offer exciting opportunities to create biomimetic gastrointestinal tract models incorporating physiological cell types, flow patterns and brush-border like structures. Here we review the recent developments in this field with a focus on the applications of microfabrication in the development of oral drug delivery devices and biomimetic gastrointestinal tract models that can be used to evaluate the drug delivery efficacy.

Recent trends in oral transmucosal drug delivery systems: an emphasis on the soft palatal route

INTRODUCTION

The oral mucosa is an appropriate route for drug delivery systems, as it evades first-pass metabolism, enhances drug bioavailability and provides the means for rapid drug transport to the systematic circulation. This delivery system offers a more comfortable and convenient delivery route compared with the intravenous route. Although numerous drugs have been evaluated for oral mucosal delivery, few of them are available commercially. This is due to limitations such as the high costs associated with developing such drug delivery systems.

AREAS COVERED

The present review covers recent developments and applications of oral transmucosal drug delivery systems. More specifically, the review focuses on the suitability of the oral soft palatal site as a new route for drug delivery systems.

EXPERT OPINION

The novelistic oral soft palatal platform is a promising mucoadhesive site for delivering active pharmaceuticals, both systemically and locally, and it can also serve as a smart route for the targeting of drugs to the brain.

Comparison of in vitro methods of measuring mucoadhesion: ellipsometry, tensile strength and rheological measurements

In this work three in vitro methods for the measurement of mucoadhesion have been compared: ellipsometry, tensile strength and rheology. The conditions used for the three methods have been as similar as possible. Six different polymers were investigated: sodium carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), chitosan, polyvinyl pyrrolidone (PVP) and two cross-linked polyacrylic acids, Noveon (hydrophobically modified) and Carbopol. The results showed that PVP did not exhibit mucoadhesion according to any of the methods used. Chitosan, Noveon, Carbopol, CMC and HEC showed good mucoadhesion in the tensile strength and the rheological measurements, but not in the ellipsometry investigation. Chitosan was the only polymer showing good mucoadhesion with the ellipsometry method. No two methods gave the same ranking of mucoadhesive strength of the polymers. The conflicting results obtained with the different methods underline the need for further improvements in existing experimental techniques and theoretical concepts for the correct assessment of mucoadhesive properties.