Intestinal absorption of octreotide: N-trimethyl chitosan chloride (TMC) ameliorates the permeability and absorption properties of the somatostatin analogue in vitro and in vivo

Acromegaly: Pathophysiological Considerations and Treatment Options Including the Evolving Role of Oral Somatostatin Analogs

Acromegaly is a condition most commonly diagnosed in the fifth decade of life and has numerous treatment options. In this regard, Mycapssa® is the first FDA-approved oral octreotide capsule for treating acromegaly, combining the efficacy of the somatostatin receptor ligand, octreotide, with the ease of a twice-daily oral capsule. Where surgical treatment is not an option, somatostatin analogs, including octreotide, are the first line of medical treatment for acromegaly, requiring regular subcutaneous or intramuscular injections administered by a patient's healthcare provider. Octreotide capsules (Mycapssa®) provide an alternative to these somatostatin receptor ligand injections by combining octreotide with other excipients to produce a transient permeability enhancer technology that improves paracellular transport of octreotide across the gastrointestinal wall into the small intestine. Across multiple trials, including open-label (CH-ACM-01), double-blind placebo-controlled (CHIASMA OPTIMAL), and open-label extension of the trial period (CHIASMA OPTIMAL OLE), Mycapssa® octreotide capsules maintained a consistent biochemical normalization of IGF-1 and GH levels, safety profiles similar to injected somatostatin receptor ligands, and patient preference to continued treatment with octreotide capsules. While clinical trial data supports the use of octreotide capsules (Mycapssa®) in the pharmacological management of GH and IGF-1 levels, very little data exist regarding the drug's efficacy, tolerability, and use in female or pediatric-specific populations. A better understanding of the efficacy, application, and role of oral octreotide capsules in the long-term medical management of acromegaly in a diversity of populations is imperative to best determine the risks/benefits for the clinician.

Surveying the Oral Drug Delivery Avenues of Novel Chitosan Derivatives

Chitosan has come a long way in biomedical applications: drug delivery is one of its core areas of imminent application. Chitosan derivatives are the new generation variants of chitosan. These modified chitosans have overcome limitations and progressed in the area of drug delivery. This review briefly surveys the current chitosan derivatives available for biomedical applications. The biomedical applications of chitosan derivatives are revisited and their key inputs for oral drug delivery have been discussed. The limited use of the vast chitosan resources for oral drug delivery applications, speculated to be probably due to the interdisciplinary nature of this research, is pointed out in the discussion. Chitosan-derivative synthesis and practical implementation for oral drug delivery require distinct expertise from chemists and pharmacists. The lack of enthusiasm could be related to the inadequacy in the smooth transfer of the synthesized derivatives to the actual implementers. With thiolated chitosan derivatives predominating the oral delivery of drugs, the need for representation from the vast array of ready-to-use chitosan derivatives is emphasized. There is plenty to explore in this direction.

Novel Chitosan Derivatives and Their Multifaceted Biological Applications

Chitosan is a rather attractive material, especially because of its bio-origins as well as generation from exoskeletal waste. As the mantle has been effectively transferred from chitin to chitosan, so has it been extrapolated to in-house synthesized novel chitosan derivatives. This review comprehensively lists the available novel chitosan derivatives (ChDs) and summarizes their biological applications. The fact that chitosan derivatives do comprise multifaceted biological applications is attested by the voluminous reports on their varied contributions. However, this review points out to the fact that there has been selective focus on bio functions such as antifungal, antioxidant, antibacterial, whereas other biomedical applications and antiviral applications remain relatively less explored. With their current functionality record, there is definitely no doubt that the plethora of synthesized ChDs will have a profound impact on the unexplored biological aspects. This review points out this lacuna as room for future exploration.

Versatile Oral Insulin Delivery Nanosystems: From Materials to Nanostructures

Diabetes is a chronic metabolic disease characterized by lack of insulin in the body leading to failure of blood glucose regulation. Diabetes patients usually need frequent insulin injections to maintain normal blood glucose levels, which is a painful administration manner. Long-term drug injection brings great physical and psychological burden to diabetic patients. In order to improve the adaptability of patients to use insulin and reduce the pain caused by injection, the development of oral insulin formulations is currently a hot and difficult topic in the field of medicine and pharmacy. Thus, oral insulin delivery is a promising and convenient administration method to relieve the patients. However, insulin as a peptide drug is prone to be degraded by digestive enzymes. In addition, insulin has strong hydrophilicity and large molecular weight and extremely low oral bioavailability. To solve these problems in clinical practice, the oral insulin delivery nanosystems were designed and constructed by rational combination of various nanomaterials and nanotechnology. Such oral nanosystems have the advantages of strong adaptability, small size, convenient processing, long-lasting pharmaceutical activity, and drug controlled-release, so it can effectively improve the oral bioavailability and efficacy of insulin. This review summarizes the basic principles and recent progress in oral delivery nanosystems for insulin, including physiological absorption barrier of oral insulin and the development of materials to nanostructures for oral insulin delivery nanosystems.

Lipophilic Salts and Lipid-Based Formulations: Enhancing the Oral Delivery of Octreotide

PURPOSE

Successful oral peptide delivery faces two major hurdles: low enzymatic stability in the gastro-intestinal lumen and poor intestinal membrane permeability. While lipid-based formulations (LBF) have the potential to overcome these barriers, effective formulation of peptides remains challenging. Lipophilic salt (LS) technology can increase the apparent lipophilicity of peptides, making them more suitable for LBF.

METHODS

As a model therapeutic peptide, octreotide (OCT) was converted to the docusate LS (OCT.DoS₂), and compared to the commercial acetate salt (OCT.OAc₂) in oral absorption studies and related in vitro studies, including parallel artificial membrane permeability assay (PAMPA), Caco-2, in situ intestine perfusion, and simulated digestion in vitro models. The in vivo oral absorption of OCT.DoS₂ and OCT.OAc₂ formulated in self-emulsifying drug delivery systems (SEDDS) was studied in rats.

RESULTS

LS formulation improved the solubility and loading of OCT in LBF excipients and OCT.DoS₂ in combination with SEDDS showed higher OCT absorption than the acetate comparator in the in vivo studies in rats. The Caco-2 and in situ intestine perfusion models indicated no increases in permeability for OCT.DoS₂. However, the in vitro digestion studies showed reduced enzymatic degradation of OCT.DoS₂ when formulated in the SEDDS formulations. Further in vitro dissociation and release studies suggest that the enhanced bioavailability of OCT from SEDDS-incorporating OCT.DoS₂ is likely a result of higher partitioning into and prolonged retention within lipid colloid structures.

CONCLUSION

The combination of LS and LBF enhanced the in vivo oral absorption of OCT primarily via the protective effect of LBF sheltering the peptide from gastrointestinal degradation.

Computational avenues in oral protein and peptide therapeutics

Proteins and peptides are amongst the most sought-after biomolecules because of their exceptional potential to cater to a vast range of diseases. Although widely studied and researched, the oral delivery of these biomolecules remains a challenge. Alongside formulation strategies, approaches to overcome the inherent barriers for peptide absorption are being designed at the molecular level to establish a sound rationale and to achieve higher bioavailability. Computer-aided drug design (CADD) is a modern in silico approach for developing successful bio-formulations. CADD enables intricate study of the biomolecules in conjunction with their target sites or receptors at the molecular level. Knowledge of the molecular interactions of proteins and peptides makes way for the pre-screening of suitable formulation components and facilitates their delivery.

Overexpression of P-glycoprotein, MRP2, and CYP3A4 impairs intestinal absorption of octreotide in rats with portal hypertension

Background

Portal hypertension (PH) is the main cause of complications and death in liver cirrhosis. The effect of oral administration of octreotide (OCT), a drug that reduces PH by the constriction of mesenteric arteries, is limited by a remarkable intestinal first-pass elimination.

Methods

The bile duct ligation (BDL) was used in rats to induce liver cirrhosis with PH to examine the kinetics and molecular factors such as P-glycoprotein (P-gp), multidrug resistance-associated protein 2 (MRP2) and cytochrome P450 3A4 (CYP3A4) influencing the intestinal OCT absorption via in situ and in vitro experiments on jejunal segments, transportation experiments on Caco-2 cells and experiments using intestinal microsomes and recombinant human CYP3A4. Moreover, RT-PCR, western blot, and immunohistochemistry were performed.

Results

Both in situ and in vitro experiments in jejunal segments showed that intestinal OCT absorption in both control and PH rats was largely controlled by P-gp and, to a lesser extent, by MRP2. OCT transport mediated by P-gp and MRP2 was demonstrated on Caco-2 cells. The results of RT-PCR, western blot, and immunohistochemistry suggested that impaired OCT absorption in PH was in part due to the jejunal upregulation of these two transporters. The use of intestinal microsomes and recombinant human CYP3A4 revealed that CYP3A4 metabolized OCT, and its upregulation in PH likely contributed to impaired drug absorption.

Conclusions

Inhibition of P-gp, MRP2, and CYP3A4 might represent a valid option for decreasing intestinal first-pass effects on orally administered OCT, thereby increasing its bioavailability to alleviate PH in patients with cirrhosis.

PEGylated trimethylchitosan emulsomes conjugated to octreotide for targeted delivery of sorafenib to hepatocellular carcinoma cells of HepG2

The current study aimed to develop PEGylated trimethyl chitosan (TMC) coated emulsomes (EMs) conjugated with octreotide for targeted delivery of sorafenib to hepatocellular carcinoma cells (HCC) of HepG2. Sorafenib loaded TMC coated EMs were prepared by the emulsion evaporation method and characterized concerning particle size, zeta potential, drug encapsulation efficiency, and in vitro drug release. Synthesized EMs were then conjugated to octreotide. The cytotoxicity of the targeted and non-targeted EMs was determined by cellular uptake and MTT assay on HepG2 cell. Cell cycle assay was also studied using flow cytometry. The results showed the optimized EMs had the particle size of 127 nm, zeta potential of -5.41 mV, loading efficiency of 95%, and drug release efficiency of 62% within 52 h. Octreotide was attached efficiently to the surface of EMs as much as 71%. MTT assay and cellular uptake studies showed that targeted EMs had more cytotoxicity than free sorafenib and non-targeted EMs. Cell cycle analyses revealed that there was a significant more accumulation of targeted EMs treated HepG2 cells in the G1 phase than free sorafenib and non-targeted EMs. The results indicate that designed EMs may be promising for the treatment of hepatocellular carcinoma.

Polyglutamic acid-trimethyl chitosan-based intranasal peptide nano-vaccine induces potent immune responses against group A streptococcus

Peptide-based vaccines have the potential to overcome the limitations of classical vaccines; however, their use is hampered by a lack of carriers and adjuvants suitable for human use. In this study, an efficient self-adjuvanting peptide vaccine delivery system was developed based on the ionic interactions between cationic trimethyl chitosan (TMC) and a peptide antigen coupled with synthetically defined anionic α-poly-(l-glutamic acid) (PGA). The antigen, possessing a conserved B-cell epitope derived from the group A streptococcus (GAS) pathogen and a universal T-helper epitope, was conjugated to PGA using cycloaddition reaction. The produced anionic conjugate formed nanoparticles (NP-1) through interaction with cationic TMC. These NP-1 induced higher systemic and mucosal antibody titers compared to antigen adjuvanted with standard mucosal adjuvant cholera toxin B subunit or antigen mixed with TMC. The produced serum antibodies were also opsonic against clinically isolated GAS strains. Further, a reduction in bacterial burden was observed in nasal secretions, pharyngeal surface and nasopharyngeal-associated lymphoid tissue of mice immunized with NP-1 in GAS challenge studies. Thus, conjugation of defined-length anionic polymer to peptide antigen as a means of formulating ionic interaction-based nanoparticles with cationic polymer is a promising strategy for peptide antigen delivery. STATEMENT OF SIGNIFICANCE: A self-adjuvanting delivery system is required for peptide vaccines to enhance antigen delivery to immune cells and generate systemic and mucosal immunity. Herein, we developed a novel self-adjuvanting nanoparticulate delivery system for peptide antigens by combining polymer-conjugation and complexation strategies. We conjugated peptide antigen with anionic α-poly-(l-glutamic acid) that in turn, formed nanoparticles with cationic trimethyl chitosan by ionic interactions, without using external crosslinker. On intranasal administration to mice, these nanoparticles induced systemic and mucosal immunity, at low dose. Additionally, nanoparticles provided protection to vaccinated mice against group A streptococcus infection. Thus, this concept should be particularly useful in developing nanoparticles for the delivery of peptide antigens.

A novel pH-responsive quaternary ammonium chitosan-liposome nanoparticles for periodontal treatment

The aim of this study was to evaluate the antibacterial activity and cytocompatibility of novel pH-activated nanoparticles (NPs) in vitro and in vivo. The NPs were synthesized from a quaternary ammonium chitosan, i.e., N,N,N-trimethyl chitosan, a liposome, and doxycycline (TMC-Lip-DOX NPs). The cytocompatibility of the NPs was evaluated. The TMC-Lip-DOX NPs achieved superb inhibition of free mixed bacteria and biofilm formation. They also showed excellent biocompatibility with human periodontal ligament fibroblasts. Animal experiments showed that the NPs strongly inhibited biofilm formation and prevented alveolar bone absorption in vivo. All the results indicate that the TMC-Lip-DOX NPs have good potential for use in the treatment of periodontal and other inflammatory diseases.

Chitosan-based nanoparticles as drug delivery systems: a review on two decades of research

Chitosan (CS) is one of the most functional natural biopolymer widely used in the pharmaceutical field due to its biocompatibility and biodegradability. These privileges lead to its application in the synthesis of nanoparticles for the drug during the last two decades. This article gives rise to a general review of the different chitosan nanoparticles (CSNPs) preparation techniques: Ionic gelation, emulsion cross-linking, spray-drying, emulsion-droplet coalescence method, nanoprecipitation, reverse micellar method, desolvation method, modified ionic gelation with radial polymerisation and emulsion solvent diffusion, from the point of view of the methodological and mechanistic aspects involved. The physicochemical behaviour of CSNPs including drug loading, drug release, particles size, zeta potential and stability are briefly discussed. This review also directs to bring an outline of the major applications of CSNPs in drug delivery according to drug and route of administration. Finally, derivatives of CSNPs and CS nano-complexes are also discussed.

Inhibition of P-glycoprotein, multidrug resistance-associated protein 2 and cytochrome P450 3A4 improves the oral absorption of octreotide in rats with portal hypertension

The aim of the present study was to increase the intestinal transport of octreotide (OCT) by targeting the first-pass impact to identify a potential method for decreasing portal vein pressure (PVP) using oral OCT. Thus, the bioavailability of intestinally absorbed OCT was evaluated in normal rats and rats with portal hypertension (PH) that had been administered P-glycoprotein/multidrug resistance-associated protein 2/cytochrome P450 3A4 (P-gp/MRP2/CYP3A4) inhibitors. The mRNA and protein expression levels of P-gp, MRP2 and CYP3A4 were evaluated in normal and PH rats with or without OCT and the inhibitors using RT-PCR, western blot and immunohistochemical analyses. The potential effects of the inhibitor administration on PVP were also examined. The results suggest that P-gp, MRP2 and CYP3A4 play important roles in prohibiting the enteral absorption of OCT, particularly under a PH environment. Moreover, inhibitors of P-gp, MRP2 and CYP3A4 decrease the first-pass effects of OCT and effectively reduce PVP under PH conditions. Therefore, the present results suggest P-gp, MRP2 and CYP3A4 are key factors in the intestinal absorption of OCT. The inhibition of P-gp, MRP2 and CYP3A4 can markedly decrease the first-pass effects of OCT, and their use may facilitate the use of orally administered OCT.

Optimized Synthesis and Characterization of N-Triethyl Chitosan

Chitosan exhibits poor solubility at pH values above 6 which prevents its enhancing effects at drugs absorption of sites. In the present work, N-triethylated chitosan (TEC) was prepared based on a modified one-step process via a 22 factorial design to optimize the preparative conditions. TEC polymer with different degree of quaternization for pharmacological and pharmaceutical experiments was achieved. Ethyl iodide and sodium hydroxide concentrations were chosen as independent variables. The degree of deacetylation of the starting chitosan was predetermined by pH-metric titration, infrared, and NMR methods. TEC chloride was fully characterized using FTIR and 1H-NMR spectroscopies. Based on NMR calculations, a high degree of quaternization was achieved through the optimized one-step process. These highly N-triethylated chitosan chlorides were soluble in water at room temperature.

Update on the use of oral octreotide therapy for acromegaly

Somatostatin analogs are most commonly used in pharmacological treatment of acromegaly. Pegvisomant and dopamine agonists are alternatives, which are used to a lesser extent. Dopamine agonists are the only orally applicable medication but are less effective than the other options. For a large number of patients, life-long pharmacotherapy has to be applied and frequent injections represent a reduction of quality of life for many of them. Areas covered: Recently published evidence for the use of oral octreotide therapy for acromegaly. Expert commentary: Oral octreotide is a novel and effective treatment for acromegaly and the side effects have been shown to be comparable to the injectable SSAs. The combination with a transient permeability enhancer allows intestinal permeation but also enables molecules with a size <70 kDa to pass transiently. This does not seem to have an acute or subacute consequence, but the long-term effect is still elusive. Therefore, more long-term trials are desirable.

Oral delivery of macromolecular drugs: Where we are after almost 100years of attempts

Since the first attempt to administer insulin orally in humans more than 90years ago, the oral delivery of macromolecular drugs (>1000g/mol) has been rather disappointing. Although several clinical pilot studies have demonstrated that the oral absorption of macromolecules is possible, the bioavailability remains generally low and variable. This article reviews the formulations and biopharmaceutical aspects of orally administered biomacromolecules on the market and in clinical development for local and systemic delivery. The most successful approaches for systemic delivery often involve a combination of enteric coating, protease inhibitors and permeation enhancers in relatively high amounts. However, some of these excipients have induced local or systemic adverse reactions in preclinical and clinical studies, and long-term studies are often missing. Therefore, strategies aimed at increasing the oral absorption of macromolecular drugs should carefully take into account the benefit-risk ratio. In the absence of specific uptake pathways, small and potent peptides that are resistant to degradation and that present a large therapeutic window certainly represent the best candidates for systemic absorption. While we acknowledge the need for systemically delivering biomacromolecules, it is our opinion that the oral delivery to local gastrointestinal targets is currently more promising because of their accessibility and the lacking requirement for intestinal permeability enhancement.

Effect of permeability enhancers on paracellular permeability of acyclovir

Objectives

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

Methods

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

Key findings

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

Conclusions

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

Preparation, characterization, and potential application of chitosan, chitosan derivatives, and chitosan metal nanoparticles in pharmaceutical drug delivery

Naturally occurring polymers, particularly of the polysaccharide type, have been used pharmaceutically for the delivery of a wide variety of therapeutic agents. Chitosan, the second abundant naturally occurring polysaccharide next to cellulose, is a biocompatible and biodegradable mucoadhesive polymer that has been extensively used in the preparation of micro-as well as nanoparticles. The prepared particles have been exploited as a potential carrier for different therapeutic agents such as peptides, proteins, vaccines, DNA, and drugs for parenteral and nonparenteral administration. Therapeutic agent-loaded chitosan micro- or nanoparticles were found to be more stable, permeable, and bioactive. In this review, we are highlighting the different methods of preparation and characterization of chitosan micro- and nanoparticles, while reviewing the pharmaceutical applications of these particles in drug delivery. Moreover, the roles of chitosan derivatives and chitosan metal nanoparticles in drug delivery have been illustrated.

A novel suspension formulation enhances intestinal absorption of macromolecules via transient and reversible transport mechanisms

PURPOSE

Medium chain fatty acid salts promote absorption by increasing paracellular permeability of the intestinal epithelium. Novel oily suspension (OS) formulation disperses a powder containing sodium caprylate and macromolecules such as octreotide or fluorescent dextran (FD). Formulation safety, macromolecule absorption and pharmacokinetic (PK)/pharmacodynamic (PD) were evaluated.

METHODS

Octreotide/OS toxicity was evaluated in monkeys following 9 months of daily oral enteric-coated capsule administration. The OS permeation effect was also assessed in rats, using FD/OS and octreotide/OS preparations. Octreotide/OS effects on circulating growth hormone (GH) levels were also measured.

RESULTS

Safety assessment of octreotide/OS in monkeys after 9 months showed minor drug-related findings, comparable to the injectable octreotide. Octreotide exposure levels were similar across the treatment periods. In rats, OS facilitated FD permeation up to 70 kDa in a reversible, spatial and dose-dependent manner, independent of the intestinal dosing site. Following OS administration, the staining pattern of the tight-junction protein, ZO-1, changed transiently, and a paracellular penetration marker, LC-biotin, permeated between adjacent epithelial cells. Enteral octreotide/OS absorption was dose-dependent and suppressed rat GH levels.

CONCLUSIONS

Oral octreotide/OS dosing was shown to be safe in monkeys. OS enhances intestinal absorption of active octreotide, likely by transient alteration of the tight junction protein complex.

Preparation and characterization of laminated thiolated chitosan-based freeze-dried wafers for potential buccal delivery of macromolecules

This study involves the development and functional characterization of a thiolated chitosan (CS) system for potential buccal delivery of proteins. Thiolated CS was synthesized by conjugating pure CS with thioglycolic acid and dialyzed to remove excess acid. Amount of thiol groups immobilized on CS was determined using L-cysteine calibration curve. The weight average molecular weights of CS and thiolated CS were monitored using gel permeation chromatography. Laminated wafers were obtained by pouring gels (containing bovine serum albumin; BSA, different amounts of glutathione as enzyme inhibitor and mucin to mimic salivary conditions) of the thiolated CS into moulds previously lined with impervious ethylcellulose (EC) films and freeze-dried. The resulting formulations were analyzed using attenuated total reflectance Fourier transform infrared (FTIR) spectroscopy, circular dichroism (CD) and scanning electron microscopy (SEM). The formulations were further characterized for functional buccal mucosa performance using hydration, swelling, mucoadhesion and in vitro drug dissolution studies. FTIR showed successful thiolation of CS's amine functionality, CD confirmed that BSA conformation remained unchanged throughout the gel formulation and freeze-drying process, whilst SEM showed a porous microstructure of the wafers and a uniform EC film laminate with no visible pores or cracks. The functional characterization studies showed that glutathione had significant effects on hydration, mucoadhesion and subsequently drug dissolution and release characteristics, whilst mucin affected the mucoadhesive properties of the wafers. It was concluded that BSA-loaded wafers containing 10% w/w glutathione as enzyme inhibitor was the formulation choice for potential buccal delivery and should be selected for further investigations.

Oral drug delivery systems using chemical conjugates or physical complexes

Oral delivery of therapeutics is extremely challenging. The digestive system is designed in a way that naturally allows the degradation of proteins or peptides into small molecules prior to absorption. For systemic absorption, the intact drug molecules must traverse the impending harsh gastrointestinal environment. Technologies, such as enteric coating, with oral dosage formulation strategies have successfully provided the protection of non-peptide based therapeutics against the harsh, acidic condition of the stomach. However, these technologies showed limited success on the protection of therapeutic proteins and peptides. Importantly, inherent permeability coefficient of the therapeutics is still a major problem that has remained unresolved for decades. Addressing this issue in the context, we summarize the strategies that are developed in enhancing the intestinal permeability of a drug molecule either by modifying the intestinal epithelium or by modifying the drug itself. These modifications have been pursued by using a group of molecules that can be conjugated to the drug molecule to alter the cell permeability of the drug or mixed with the drug molecule to alter the epithelial barrier function, in order to achieve the effective drug permeation. This article will address the current trends and future perspectives of the oral delivery strategies.

Nanomedicine in cardiovascular therapy: recent advancements

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

A review on mucoadhesive polymer used in nasal drug delivery system

This update review is on mucoadhesive polymers used in nasal dosage forms. The nasal mucosa provides a potentially good route for systemic drug delivery. One of the most important features of the nasal route is that it avoids first-pass hepatic metabolism, thereby reducing metabolism. The application of mucoadhesive polymers in nasal drug delivery systems has gained to promote dosage form residence time in the nasal cavity as well as improving intimacy of contact with absorptive membranes of the biological system. The various new technology uses in development of nasal drug delivery dosage forms are discussed. The various dosage forms are vesicular carriers (liposome, noisome), nanostructured particles, prodrugs, in situ gelling system with special attention to in vivo studies.

N-trimethyl chitosan nanoparticle-encapsulated lactosyl-norcantharidin for liver cancer therapy with high targeting efficacy

N-Trimethyl chitosan (TMC) was synthesized and used to prepare lactosyl-norcantharidin TMC nanoparticles (Lac-NCTD-TMC-NPs) using an ionic cross-linkage process. Lac-NCTD-TMC-NPs with an average particle size of 120.6 ± 1.7 nm were obtained, with an entrapment efficiency of 69.29% ± 0.76%, and a drug-loading amount of 9.1% ± 0.07%. The release of Lac-NCTD-TMC-NPs in vitro was investigated through a dialysis method, and its sustained effect was evident. In the human liver cancer cell line HepG2, the half-maximum inhibiting concentration (IC(50)) of TMC-encapsulated Lac-NCTD (Lac-NCTD-TMC-NPs) was only 24.2% that of free Lac-NCTD at 24 hours. Lac-NCTD induced HepG2 cell death by triggering apoptosis. In vitro cellular uptake and in vivo NIR fluorescence real-time imaging both indicated a high targeting efficacy. In comparison with Lac-NCTD and Lac-NCTD chitosan NPs (Lac-NCTD-CS-NPs ), Lac-NCTD-TMC-NPs had the strongest antitumor activity on the murine hepatocarcinoma 22 subcutaneous model.

FROM THE CLINICAL EDITOR

In this article the preparation of N-trimethyl chitosan-encapsulated lactosyl-norcantharidin nanoparticles is described that displayed efficient targeting and sustained release in a hepatocarcinoma SC murine model.

Chitosan-based nanoparticles as delivery systems of therapeutic proteins

Therapeutic proteins represent a significant part of the new pharmaceuticals coming on the market every year and are now widely spread in therapy to treat or relief symptoms related to many metabolic and oncologic diseases. The parenteral route remains as a primary strategy for protein administration essentially due to its specific physicochemical properties. However, the research on alternative nonparenteral delivery routes continues. The high molecular weight (MW), hydrophilicity, and charged nature of therapeutically valued proteins render transport through membranes very difficult. In this regard, chitosan arises as a promising candidate for the development of protein-containing drug formulations, due to its exceptional biological properties. Chitosan-based delivery systems have been proposed as valid approaches to provide protective conditions to proteins from denaturation and loss of activity, during preparation and delivery, as well as during long-term storage of the prepared formulation. In this chapter, one production method of a chitosan-based nanoparticle formulation is presented, as well as several characterization techniques to assess both nanoparticles and proteins characteristics and stability.

Transport across Caco-2 cell monolayer and sensitivity to hydrolysis of two anxiolytic peptides from αs1-casein, α-casozepine, and αs1-casein-f91-97: effect of bile salts

α-Casozepine and f91-97, peptides from α(s1)-casein, display anxiolytic activity in rats and may have to cross the intestinal epithelium to exert this central effect. We evaluated their resistance to hydrolysis by the peptidases of Caco-2 cells and their ability to cross the cell monolayer. To mimic physiological conditions, two preparations of bile salts were used in noncytotoxic concentrations: porcine bile extract and an equimolar mixture of taurocholate, cholate, and deoxycholate. The presence and composition of bile salts appeared to modulate the peptidase activities of the Caco-2 cells involved (i) in the hydrolysis of α-casozepine, leading to much higher formation of fragments f91-99, f91-98, and f91-97, and (ii) in the hydrolysis of f91-97, leading to lower degradation of this peptide. Transport of α-casozepine across Caco-2 monolayer increased significantly, in the presence of bile extract, and of fragment f91-97, in the presence of bile salts.

Absorption enhancers: applications and advances

Absorption enhancers are functional excipients included in formulations to improve the absorption of a pharmacologically active drug. The term absorption enhancer usually refers to an agent whose function is to increase absorption by enhancing membrane permeation, rather than increasing solubility, so such agents are sometimes more specifically termed permeation enhancers. Absorption enhancers have been investigated for at least two decades, particularly in efforts to develop non-injection formulations for peptides, proteins, and other pharmacologically active compounds that have poor membrane permeability. While at least one product utilizing an absorption enhancer for transdermal use has reached the market, quite a few more appear to be at the threshold of becoming products, and these include oral and transmucosal applications. This paper will review some of the most advanced absorption enhancers currently in development and the formulation technologies employed that have led to their success. In addition, a more basic review of the barriers to absorption and the mechanisms by which those barriers can be surmounted is presented. Factors influencing the success of absorption-enhancing formulations are discussed. If ultimately successful, the products now in development should offer non-injection alternatives for several peptide or protein drugs currently only administered by injection. The introduction of new absorption enhancers as accepted pharmaceutical excipients, and the development of formulation technologies that afford the greatest benefit/risk ratio for their use, may create opportunities to apply these enabling technologies more broadly to existing drugs with non-optimal delivery properties.

Chitosan microspheres in novel drug delivery systems

The main aim in the drug therapy of any disease is to attain the desired therapeutic concentration of the drug in plasma or at the site of action and maintain it for the entire duration of treatment. A drug on being used in conventional dosage forms leads to unavoidable fluctuations in the drug concentration leading to under medication or overmedication and increased frequency of dose administration as well as poor patient compliance. To minimize drug degradation and loss, to prevent harmful side effects and to increase drug bioavailability various drug delivery and drug targeting systems are currently under development. Handling the treatment of severe disease conditions has necessitated the development of innovative ideas to modify drug delivery techniques. Drug targeting means delivery of the drug-loaded system to the site of interest. Drug carrier systems include polymers, micelles, microcapsules, liposomes and lipoproteins to name some. Different polymer carriers exert different effects on drug delivery. Synthetic polymers are usually non-biocompatible, non-biodegradable and expensive. Natural polymers such as chitin and chitosan are devoid of such problems. Chitosan comes from the deacetylation of chitin, a natural biopolymer originating from crustacean shells. Chitosan is a biocompatible, biodegradable, and nontoxic natural polymer with excellent film-forming ability. Being of cationic character, chitosan is able to react with polyanions giving rise to polyelectrolyte complexes. Hence chitosan has become a promising natural polymer for the preparation of microspheres/nanospheres and microcapsules. The techniques employed to microencapsulate with chitosan include ionotropic gelation, spray drying, emulsion phase separation, simple and complex coacervation. This review focuses on the preparation, characterization of chitosan microspheres and their role in novel drug delivery systems.

Nasal absorption and local tissue reaction of insulin nanocomplexes of trimethyl chitosan derivatives in rats

OBJECTIVES

The objective of this work was to explore the potential and safety of trimethyl chitosan (TMC) and PEGylated TMC for improved absorption of insulin after nasal administration.

METHODS

The nasal absorption of insulin nanocomplexes of TMC or PEGylated TMC was evaluated in anaesthetized rats. Concomitantly, the histopathological effects of these nanocomplexes on rat nasal mucosa were studied using a perfusion fixation technique.

KEY FINDINGS

All insulin nanocomplexes containing TMC or PEGylated TMC showed a 34-47% reduction in the blood glucose concentration, when the insulin absorption through the rat nasal mucosa was measured indirectly. In addition, the relative pharmacodynamic bioavailability (F(dyn)) of the formulations was found to be dependent upon the charge ratio of insulin and polymer, regardless of polymer structure. The F(dyn) apparently decreased with increasing charge ratio of insulin : polymer. Although acute alterations in nasal morphology by the formulations were affected by the charge ratio of insulin and polymer, the formulation of insulin/PEGylated TMC nanocomplexes was shown to be less toxic to the nasal epithelial membrane than insulin/TMC nanocomplexes.

CONCLUSIONS

PEGylated TMC nanocomplexes were a suitable absorption enhancer for nasal delivery of insulin.

Anti-tumor activity of N-trimethyl chitosan-encapsulated camptothecin in a mouse melanoma model

Background

Camptothecin (CPT) has recently attracted increasing attention as a promising anticancer agent for a variety of tumors. But the clinical application is largely hampered by its extreme water insolubility and unpredictable side effect. It is essential to establish an efficient and safe protocol for the administration of CPT versus melanoma.

Methods

Camptothecin was encapsulated with N-trimethyl chitosan (CPT-TMC) through microprecipitation and sonication. Its inhibition effect on B16-F10 cell proliferation and induction of apoptosis was evaluated by MTT assay and flow cytometric analysis in vitro. The anti-tumor activity of CPT-TMC was evaluated in C57BL/6 mice bearing B16-F10 melanoma. Tumor volume, tumor weight and survival time were recorded. Assessment of apoptotic cells within tumor tissue was performed by TUNEL assay. Antiangiogenesis and antiproliferation effects of CPT-TMC in vivo were conducted via CD31 and PCNA immunohistochemistry, respectively.

Results

CPT-TMC efficiently inhibited B16-F10 cells proliferation and increased apoptosis in vitro. Experiment group showed significant inhibition compared with free CPT-treated group (81.3% vs. 56.9%) in the growth of B16-F10 melanoma xenografts and prolonged the survival time of the treated mice (P < 0.05). Decreased cell proliferation, increased tumor apoptosis as well as a reduction in angiogenesis were observed.

Conclusions

Our data suggest that N-trimethyl chitosan-encapsulated camptothecin is superior to free CPT by overcoming its insolubility and finally raises the potential of its application in melanoma therapy.

In vivo antitumor and antimetastatic activities of camptothecin encapsulated with N-trimethyl chitosan in a preclinical mouse model of liver cancer

Application of camptothecin (CPT) is hampered due to its extreme water insolubility and unpredictable side effects. Therefore, it is essential to establish an efficient and safe protocol for the administration of camptothecin against tumor growth and metastasis. Here, we encapsulated camptothecin with N-trimethyl chitosan (CPT-TMC) and tested it on BALB/c mice subcutaneously injected with murine hepatocellular carcinoma cells at the hindlimb feet pad. CPT-TMC effectively inhibited tumor growth and lymphatic metastasis, prolonged survival time, yet without apparent toxic effects. Thus, CPT-TMC may provide a novel and effective therapeutic strategy against human advanced hepatic cancer without conspicuous systemic toxic effects.

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

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

Chitosan-based delivery systems for protein therapeutics and antigens

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

Fasting increases tobramycin oral absorption in mice

The pharmacokinetics of the aminoglycoside tobramycin was evaluated after oral administration to fed or fasting (15 h) mice. As expected, under normal feeding conditions, oral absorption was negligible; however, fasting induced a dramatic increase in tobramycin bioavailability. The dual-sugar test with lactulose and l-rhamnose confirmed increased small bowel permeability via the paracellular route in fasting animals. When experiments aimed at increasing the oral bioavailability of hydrophilic compounds are performed, timing of fasting should be extremely accurate.