Oral Delivery Of Protein Drugs Research Articles

Recent Progress in the Oral Delivery of Therapeutic Peptides and Proteins: Overview of Pharmaceutical Strategies to Overcome Absorption Hurdles.

Proteins and peptides have secured a place as excellent therapeutic moieties on account of their high selectivity and efficacy. However due to oral absorption limitations, current formulations are mostly delivered parenterally. Oral delivery of peptides and proteins (PPs) can be considered the need of the hour due to the immense benefits of this route. This review aims to critically examine and summarize the innovations and mechanisms involved in oral delivery of peptide and protein drugs. Comprehensive literature search was undertaken, spanning the early development to the current state of the art, using online search tools (PubMed, Google Scholar, ScienceDirect and Scopus). Research in oral delivery of proteins and peptides has a rich history and the development of biologics has encouraged additional research effort in recent decades. Enzyme hydrolysis and inadequate permeation into intestinal mucosa are the major causes that result in limited oral absorption of biologics. Pharmaceutical and technological strategies including use of absorption enhancers, enzyme inhibition, chemical modification (PEGylation, pro-drug approach, peptidomimetics, glycosylation), particulate delivery (polymeric nanoparticles, liposomes, micelles, microspheres), site-specific delivery in the gastrointestinal tract (GIT), membrane transporters, novel approaches (self-nanoemulsifying drug delivery systems, Eligen technology, Peptelligence, self-assembling bubble carrier approach, luminal unfolding microneedle injector, microneedles) and lymphatic targeting, are discussed. Limitations of these strategies and possible innovations for improving oral bioavailability of protein and peptide drugs are discussed. This review underlines the application of oral route for peptide and protein delivery, which can direct the formulation scientist for better exploitation of this route.

Oral Delivery of Protein Drugs via Lysine Polymer-Based Nanoparticle Platforms.

Oral delivery of proteins has opened a new perspective for the treatment of different diseases. However, advances of oral protein formulation are usually hindered by protein susceptibility and suboptimal absorption in the gastrointestinal tract (GIT). Polymeric nano drug delivery systems are considered revolutionary candidates to solve these issues, which can be preferably tunable against specific delivery challenges. Herein, a tailored family of lysine-based poly(ester amide)s (Lys-aaPEAs) is designed as a general oral protein delivery platform for efficient protein loading and protection from degradation. Insulin, as a model protein, can achieve effective internalization by epithelial cells and efficient transport across the intestinal epithelium layer into the systemic circulation, followed by controlled release in physiological environments. After the oral administration of insulin carried by Lys-aaPEAs with ornamental hyaluronic acid (HA), mice with type 1 diabetes mellitus showed an acceptable hypoglycemic effect with alleviated complications. A successful oral insulin delivery is associated with patient comfort and convenience and simultaneously avoids the risk of hypoglycemia compared with injections, which is of great feasibility for daily diabetes therapy. More importantly, this versatile Lys-aaPEAs polymeric library can be recognized as a universal vehicle for oral biomacromolecule delivery, providing more possibilities for treating various diseases.

In Situ Polymerization of Zwitterions on Therapeutic Proteins to Enable Their Effective Oral Delivery.

Oral administration of protein drugs has always been challenging owing to various intestinal barriers. Herein, we developed an efficient oral protein delivery strategy by using in situ polymerization of zwitterions to encapsulate proteins, which were then loaded into enteric coated capsules for oral feeding. After oral administration of such capsules, the enteric coating would be degraded once the capsule enters the intestine, releasing polyzwitterion/protein nanocomplexes. With the help of polyzwitterion modification, such nanocomplexes were able to pass through the mucus and cellular barriers, likely by the proton-assisted amino acid transporter 1 (PAT1) pathway. Such a polyzwitterion-based protein encapsulation strategy could allow for effective oral delivery of different proteins, including bovine serum albumin (BSA), insulin, and antibodies. Using this strategy, the oral bioavailabilities of insulin and immunoglobin G (IgG) were measured to be as high as 16.9% and 12.5%, respectively. Notably, oral feeding of polyzwitterion/insulin capsules could effectively lower the blood glucose level of diabetic animals (mice, rats, and pigs). Moreover, polyzwitterion/antiprogramed death-1 (αPD-1) capsules were able to induce efficient antitumor immune responses, showing significant tumor inhibition effects toward B16F10- and 4T1-tumor bearing mouse models after oral administration. No significant toxic effect was observed for such oral protein formulations in the treated animals. Our work presents a strategy for the efficient oral delivery of protein drugs, including those with large molecular weights (e.g., antibodies) that can hardly be orally delivered using existing technologies.

Herbal Bioenhancers with Nanocarriers: A Promising Approach for Oral Peptide Delivery

The oral delivery of protein and peptide drugs faces immense challenges due to the harsh gastrointestinal (GI) environment, large molecular size, and low stability. Even though different approaches are employed to deliver peptide drugs efficiently, they have limited success. Recently, the use of nanoparticles as carriers for peptides as a means of surmounting the gastrointestinal barrier and as an effective alternative to parenteral administration has gained much attention. It is often necessary to supplement this mode of delivery by using strategies such as permeation enhancers. Bio-enhancers play a significant role in reducing the dose, drug resistance, toxicity, and treatment expenses. The potential of herbal bio-enhancers as a safe and effective substitute to non-herbal permeation enhancers in improving oral absorption of peptides from nanoparticulate systems has been explored recently. Piperine is counted first in the list of bio-enhancers and can improve the bioavailability of peptides and other drugs. Other molecules like naringin, glycyrrhizin, quercetin have great significance either alone or in combination in improving the oral bioavailability of drug molecules. Bioenhancers are beneficial for drugs with poor lipid solubility and large molecular size, causing poor absorption and low bioavailability. Herbal bioenhancers can decrease the dose, drug resistance, toxicity, adverse effects, and overall treatment cost as they are inert, easily procured and economical. This review article focuses on the significance of nanoparticles in the oral delivery of peptide drugs and the vital role played by herbal bioenhancers in their absorption from the GI tract.

Oral delivery of protein and peptide drugs: from non-specific formulation approaches to intestinal cell targeting strategies.

The past few years has witnessed a booming market of protein and peptide drugs, owing to their superior efficiency and biocompatibility. Parenteral route is the most commonly employed method for protein and peptide drugs administration. However, short plasma half-life protein and peptide drugs requires repetitive injections and results in poor patient compliance. Oral delivery is a promising alternative but hindered by harsh gastrointestinal environment and defensive intestinal epithelial barriers. Therefore, designing suitable oral delivery systems for peptide and protein drugs has been a persistent challenge. This review summarizes the main challenges for oral protein and peptide drugs delivery and highlights the advanced formulation strategies to improve their oral bioavailability. More importantly, major intestinal cell types and available targeting receptors are introduced along with the potential strategies to target these cell types. We also described the multifunctional biomaterials which can be used to prepare oral carrier systems as well as to modulate the mucosal immune response. Understanding the emerging delivery strategies and challenges for protein and peptide drugs will surely inspire the production of promising oral delivery systems that serves therapeutic needs in clinical settings.

Oral insulin delivery by epithelium microenvironment-adaptive nanoparticles

Oral protein drug delivery using nano-based systems remains challenging, as contradictory surface properties are required for efficient navigation through the intestinal mucus and epithelium barriers. Therefore, new nanoplatforms with tunable surface properties in vivo are urgently needed. Inspired by the slightly acidic microclimate of the jejunal epithelial surface, we report a novel epithelium microenvironment-adaptive nanoplatform that undergoes a hydrophilicity-hydrophobicity transition at the epithelial surface. First, we synthesized and characterized a biodegradable copolymer consisting of PEG and PLGA building blocks linked by a hydrazone bond (PLGA-Hyd-PEG) to fabricate the pH-sensitive core-shell architecture of an oral insulin system. Then we loaded the system as a freeze-dried powder into enteric-coated capsules. PLGA-Hyd-PEG nanoparticles showed excellent drug protection and rapid mucus penetration owing to the high stability of the PEG coating in jejunal fluid. In the acidic microenvironment of the jejunal epithelial surface (pH ~5.5), PEG was rapidly cleaved and the hydrazone bond was hydrolyzed, converting the nanoparticle surface from hydrophilic to hydrophobic, thereby facilitating internalization into cells. Pharmacodynamic studies showed that PLGA-Hyd-PEG nanoparticles resulted in significant decrease in blood glucose level after intrajejunal administration in both normal and diabetic rats relative to control nanoparticles. In addition, enteric-coated capsules containing PLGA-Hyd-PEG nanoparticles reduced blood glucose by 35% for up to 10 h after oral administration to diabetic rats. Our findings provide a new strategy for regulating the surface properties of nanoparticles for efficient oral drug delivery.

Current Status and Perspectives of Oral Therapeutic Protein and Peptide Formulations: A Review

Medicinal formulations have evolved from the use of small molecules that act by blocking various receptors. On the contrary, therapeutic proteins are a class of medicines that have gained increased popularity owing to its low toxicity, high stability and exquisite specificity. Oral delivery of protein drugs is a very interesting but a highly challenging area of medicine that requires advancements in terms of bioavailability of oral drugs. The main objective of the present review is to provide a systematic overview of the various physiological barriers of delivery of therapeutic proteins and novel approaches available in this field in order to counter these physiological barriers. Advances in terms of inhibitors of proteases, permeation enhancers, mucoadhesives, short peptide conjugates, particulate delivery system including nanoparticles. Oral therapeutic proteins face challenges with regard to oral bioavailability, stability of the protein and reproducibility. Among the various strategies, a co-administration of permeation enhancers with protease inhibitors have proven most effective, while particulate delivery system is still under clinical studies in order to be establishes as a method. Overall, a thorough and focused research with sufficient knowledge on the structure-function relationship, substrate specificity and physiological parameters can deliver a potent therapeutic protein with high efficiency.

Cellulose nanocrystals as support nanomaterials for dual droplet-based freeform 3D printing

The selection of sacrificial support materials is important in the fabrication of complex freeform structures. In this study, a dual droplet-based, freeform 3D printing method for pseudoplastic alginate biomaterial inks was developed using Bingham plastic cellulose nanocrystals (CNCs) as support nanomaterials. CNCs-CaCl2 mixture compositions and alginate concentrations were varied to enhance printability with rheological properties of shape fidelity and structural stability. The mixtures supported the shape of alginate and allowed CaCl2 diffusion-based cross-linking during 3D printing. The hydrogels showed rheological and physicochemical properties similar to those of pure alginate hydrogel, as CNCs were removed during post-printing processing. BSA-loaded multi-layered spheres, freeform 3D-printed for oral protein drug delivery, protected BSA in the gastric environment and provided controlled and sustained release of BSA into the intestinal environment as layer width and alginate concentration increased. This method can facilitate freeform 3D printing of diverse pseudoplastic biomaterial inks for biomedical applications.

Virus-Mimicking Mesoporous Silica Nanoparticles with an Electrically Neutral and Hydrophilic Surface to Improve the Oral Absorption of Insulin by Breaking Through Dual Barriers of the Mucus Layer and the Intestinal Epithelium.

Protein and peptide drugs orally suffer from extremely low bioavailability principally for the complicated gastrointestinal environment along with the difficulty of passing through the mucus layer and the underlying epithelium. In our work, we fabricated mesoporous silica nanoparticles with modification groups (MSN-NH2@COOH/CPP5) that effectively penetrated the mucus layer and passed through the intestinal epithelium by mimicking the virus surface. Naked nanoparticles were prepared with inner pores of 6 nm diameter to allow efficient insulin loading and coated with the cationic cell-penetrating KLPVM peptide and the anionic glutaric anhydride to yield hydrophilic MSN-NH2@COOH/CPP5 with a ζ-potential of -0.49 mV. The apparent permeability coefficient of virus-mimicking nanoparticles was 14.61 × 10-5 cm/s. The virus-mimicking nanoparticles showed dramatically lower binding to mucin and faster penetration of the mucus layer than positively charged nanoparticles (MSN@NH2) with a ζ-potential of +35.00 mV. The KLPVM peptide enhanced the uptake of MSN-NH2@COOH/CPP5 by coculturing Caco-2 and E12 cells as an intestinal epithelium model. MSN-NH2@COOH/CPP5 enhanced apical-to-basal transcytosis for being internalized primarily through caveolae-mediated endocytosis. Indeed, for MSN-NH2@COOH/CPP5, the transepithelial transport of the Caco-2 cell monolayer was 2.4-fold higher than MSN@NH2 and 2.0-fold higher than MSN-NH2@COOH. In vitro, loading insulin into nanoparticles maintained the bioactivity of the protein under simulated intestinal conditions. Insulin loaded into MSN-NH2@COOH/CPP5 reduced the diabetic rats' blood glucose level by nearly 50%. The bioavailability of insulin encapsulated in the MSN-NH2@COOH/CPP5 nanoparticles was 2.1-fold more than insulin when administered directly into the jejunum. Nanoparticles with modifications indicated no significant toxicity in in vitro or in vivo preliminary studies. The obstacles of the mucus layer and intestinal epithelium may be effectively conquered by these virus-mimicking nanoparticles for oral delivery of protein and peptide drugs.

Poly(vinyl alcohol)/poly(hydroxypropyl methacrylate-co-methacrylic acid) as pH-sensitive semi-IPN hydrogels for oral insulin delivery: preparation and characterization

A series of pH-sensitive semi-interpenetrating polymer network (semi-IPN) hydrogels poly(vinyl alcohol)/poly(hydroxypropyl methacrylate-co-methacrylic acid) (PVA/P(HPMA-co-MAA)) were synthesized by free-radical polymerization of HPMA and MAA in the presence of PVA. The physicochemical property of the obtained hydrogels was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analyses and scanning electron microscopy (SEM) measurements. The SEM photograph revealed the network formation with uniform pore distribution. The swelling behavior of each hydrogel in buffer solution showed a simultaneous sensitivity to pH and ionic strength: the swelling ratio of all hydrogels was higher in neutral environment than in acidic medium; besides, equilibrium swelling ratio of the hydrogels decreases as the ionic strength increases. Insulin was loaded into the PVA/P(HPMA-co-MAA) semi-IPN hydrogel. The in vitro insulin release experiment was carried out in buffer solutions at pHs 1.2 and 6.8. Results showed that the release of entrapped insulin was inhibited at pH 1.2 but obviously increased at pH 6.8. Cell viability revealed that the hydrogels were biocompatible. After oral administration of insulin-loaded hydrogel to streptozotocin-induced diabetic rats at 75 IU/kg, a sustained reduction in blood glucose level was observed. Therefore, the semi-IPN PVA/P(HPMA-co-MAA) hydrogels are potential vehicles for oral delivery of protein drugs.

Development of an M cell targeted nanocomposite system for effective oral protein delivery: preparation, in vitro and in vivo characterization

BackgroundThere is a strong need for non-invasive and patient-friendly delivery systems of protein drugs for long-term therapy. However, oral delivery of protein drugs is a big challenge due to many barriers including instability in the gastrointestinal (GI) tract and low permeability. To overcome the absorption barriers in GI tract and improve the patient compliance, this study aimed to develop an M cell targeted-nanocomposite delivery system of protein drugs.ResultsAn aminoclay-protein core complex (AC-Ins) was prepared by using insulin as a model protein and then sequentially coated with Ulex europaeus agglutinin 1 (UEA-1) for M-cell targeting and the pH sensitive polymer, Eudragit® L100 (EUAC-Ins). All nanoparticles were obtained with a high entrapment efficiency (> 90%) and their structural characteristics were confirmed by Fourier transform-infrared spectroscopy, energy dispersive X-ray spectroscopy, and circular dichroism. Among the developed nanoparticles, EUAC-Ins effectively suppressed drug release at pH 1.2, while rapidly released drugs at pH 6.8 due to dissolution of the outer coating layer. The conformational stability of insulin entrapped in EUAC-Ins was well maintained in the presence of proteolytic enzymes. Compared to free insulin, EUAC-Ins increased the membrane transport of insulin by 4.4-fold in M cells. In parallel, oral administration of EUAC-Ins in mice enhanced insulin uptake by 4.1-fold in the intestinal Peyer’s patches and 2.6-fold in intestinal epithelium tissues with normal villi, compared to free insulin. Orally administered EUAC-Ins decreased significantly the blood glucose level in diabetic mice, while the effect of oral insulin solution was negligible.ConclusionAn M cell targeted-ternary nanocomposite system obtained by dual coating of the aminoclay-protein core complex with UEA-1 and a pH dependent polymer is promising as an effective oral protein delivery carrier.

Zwitterion-functionalized mesoporous silica nanoparticles for enhancing oral delivery of protein drugs by overcoming multiple gastrointestinal barriers

Oral delivery of protein or peptide drugs confronts several barriers, the intestinal epithelium and the mucus barrier on the gastrointestinal tract is deemed to be the toughest obstacles. However, overcoming these two obstacles requires contradictory surface properties of a nanocarrier. In the present work, mesoporous silica nanoparticles (MSNs) were modified with deoxycholic acid (DC) and coated with sulfobetaine 12 (SB12) for the first time to achieve both improved mucus permeation and transepithelial absorption. MSNs modified with stearic acid and coated with dilauroylphosphatidylcholine (DLPC) or Pluronic P123 were also prepared as controls. The SB12 coated DC modified MSN had high drug loading of 22.2%. The zwitterion coating endows the MSN improved mucus penetrating ability. In addition, the carrier also showed remarkable affinity with epithelial cells. The cellular uptake was significantly improved (10-fold for Caco-2 cells and 8-fold for E12 cells). The results also indicated that the DC modified carrier was able to avoid entry into lysosomes. It can increase the absorption of loaded insulin in all intestine segments and showed outstanding hypoglycemic effect in diabetic rats. The results suggest the zwitterion-functionalized MSNs might be a good candidate for oral protein delivery.

The Impact of Natural and Synthetic Polymers in Formulating Micro and Nanoparticles for Anti-Diabetic Drugs.

Diabetes mellitus is one of the long-known chronic diseases. Today, over 400 million people have been diagnosed with diabetes, yet curing it is still a challenge. Over the decades, the approaches of treating diabetes mellitus have evolved and polymeric materials have played an integral part in developing and manufacturing anti-diabetic medications. However, injection of insulin remains a conventional therapy for the treatment of diabetes. Oral administration is generally the most preferred route; yet, physiological barriers lead to a challenge in the formulation development for oral delivery of antidiabetic peptide and protein drugs. This present review focuses on the role of different types of biodegradable polymers (e.g., synthetic and natural) that have been used to develop micro and nanoparticles based formulations for anti-diabetic drugs (Type 1 and Type 2) and how the various encapsulation strategies impact its therapeutic effect, including pharmacokinetics studies, drug release profiles, and efficacy of the encapsulated drugs. This review also includes studies of different dosage forms such as oral, nasal, inhalation, and sublingual for the treatment of diabetes that have been investigated using synthetic and natural biodegradable polymers in order to develop an alternative route to subcutaneous route for better control of serum glucose levels.

Zwitterionic micelles efficiently deliver oral insulin without opening tight junctions.

Oral delivery of protein drugs is considered a life-changing solution for patients who require regular needle injections. However, clinical translation of oral protein formulations has been hampered by inefficient penetration of drugs through the intestinal mucus and epithelial cell layer, leading to low absorption and bioavailability, and safety concerns owing to tight junction openings. Here we report a zwitterionic micelle platform featuring a virus-mimetic zwitterionic surface, a betaine side chain and an ultralow critical micelle concentration, enabling drug penetration through the mucus and efficient transporter-mediated epithelial absorption without the need for tight junction opening. This micelle platform was used to fabricate a prototype oral insulin formulation by encapsulating a freeze-dried powder of zwitterionic micelle insulin into an enteric-coated capsule. The biocompatible oral insulin formulation shows a high oral bioavailability of >40%, offers the possibility to fine tune insulin acting profiles and provides long-term safety, enabling the oral delivery of protein drugs.

Ionic gelated β-cyclodextrin-biotin-carboxymethyl chitosan nanoparticles prepared as carrier for oral delivery of protein drugs

Abstract In this paper, the β-cyclodextrin (β-CD) and biotin (Bi) were successfully grafted onto carboxymethyl chitosan (CMCS). And then the β-CD-Bi-CMCS nanoparticles (NPs) were prepared as oral nano-delivery carrier of protein drugs by ionic gelation method. The morphological feature of fabricated drug carrier was determined by dynamic light scattering and transmission electron microscopy. The result showed that the prepared NPs presented spherical structure with an average diameter of 138 nm. Bovine serum albumin (BSA) was selected as model protein drug that was entrapped in prepared drug carrier with satisfactory entrapment efficiency (79.18%) and loading content (3.96%). The drug release profiles of BSA/β-CD-Bi-CMCS NPs were studied at different pH environment for simulated gastric fluid (SGF), simulated intestinal fluid (SIF) and simulated colonic fluid (SCF). It was found that the BSA/β-CD-Bi-CMCS NPs displayed a pH dependent drug release profiles. After 72 h, the cumulative release amount of BSA in SGF, SIF, and SCF was about 20.57, 74.46, and 91%, respectively. Furthermore, the enzymatic degradation and cytotoxicity studies showed the synthesized β-CD-Bi-CMCS NPs had high chemical stability and biocompatibility. This work indicated that the β-CD-Bi-CMCS NPs had the potentiality as promising nanocarriers for oral delivery of protein drugs.

Modulation of Entrapment Efficiency and In Vitro Release Properties of BSA-Loaded Chitosan Microparticles Cross-Linked with Citric Acid as a Potential Protein-Drug Delivery System.

Microparticles, aimed for oral protein and peptide drug delivery, were prepared via emulsion cross-linking using citric acid as cross-linker and polyglycerol polyricinoleate as surfactant. A comparative study of the interaction between chitosan and citric acid and its effect on the resulting microparticle properties was performed using different chitosan-to-cross-linker mass ratios and pH-values during fabrication of the microparticles. Non-cross-linked and cross-linked microparticles were studied in terms of size (4–12 μm), zeta potential (−15.7 to 12.8 mV), erosion (39.7–75.6%), a model protein encapsulation efficiency (bovine serum albumin) (6.8–27.6%), and loading capacity (10.4–40%). Fourier transform infrared spectroscopy and X-ray diffraction confirmed the ionic interaction between the protonated amine groups of chitosan and the carboxylate ions of the cross-linking agent. Scanning electron microscopy revealed that the non-cross-linked microparticles had an uneven shape with wrinkled surfaces, while the cross-linked formulations were spherical in shape with smooth surfaces. On the basis of these data, the role of the surfactant and microparticle structure on the release mechanism was proposed. Control of the microparticle shape and release mechanisms is expected to be crucial in developing carriers for the controlled delivery of proteins and peptides.

A Novel Oral Protein-Drug Delivery System with Bilayer Shell-Core Structure

For oral drug therapy, the inefficiency of protein/peptide drugs is a big concern due to inactivation and degradation induced by the gastric juice. In this study, a novel highly effective drug delivery system with the bilayer shell-core structure was developed for oral administration of protein/peptide drugs. In this design, chitosan microparticle was used as the carrier core to load protein drug via genipin crosslinking, and then covered by a casein protective shell via TG crosslinking to slow release the loaded drug and protect its bioactivity. In order to verify the effectiveness of this drug delivery system, the novel thrombolytic agent, nattokinase, was loaded and applied to prevent thrombosis via oral administration in mice. The results indicated that the bilayer shell-core structure could protect loaded nattokinase from destroy in the gastric juice, and then release both intact nattokinase and digested fragments with thrombolytic activity gradually in the intestine. Results from mouse black tail test indicated that oral administration of this microparticle could preclude thrombus formation in the tail. Overall, this study provides a feasible way to enhance the oral bioavailability and prolong the effective half-life of protein drugs, which has the potential to accelerate the development of oral drug therapy.

Materials for oral delivery of proteins and peptides

Throughout history, oral administration has been regarded as the most convenient mode of drug delivery, as it requires minimal expertise and invasiveness. Although oral delivery works well for small-molecule drugs, oral delivery of macromolecules (particularly proteins and peptides) has been limited by acidic conditions in the stomach and low permeability across the intestinal epithelium. Accordingly, the large numbers of biologic drugs that have become available in the past 10 years typically require administration by injection or infusion. As such, a renewed emphasis has been placed on the development of novel materials that overcome the physiological challenges of oral delivery for macromolecular agents. This Review provides an overview of physiological barriers to the oral delivery of biologics and highlights the advances made in materials across various length scales, from small molecules to macroscopic devices. This Review also describes the current status of materials for oral delivery of protein and peptide drugs. New materials, beyond those that have already obtained regulatory approval, are needed to improve the bioavailability of orally administered proteins. In this Review, barriers to the oral delivery of protein-based therapies are discussed, along with the current translational landscape and state of the art of materials for oral protein delivery.

SEDDS for intestinal absorption of insulin: Application of Caco-2 and Caco-2/HT29 co-culture monolayers and intra-jejunal instillation in rats

To face the challenges of oral delivery of peptide and protein (P/P) drugs, self-emulsifying drug delivery systems (SEDDSs) containing monoacyl phosphatidylcholine (MAPC), Labrasol (LAB) and medium-chain (MC) monoglycerides as permeation enhancers (PEs) were evaluated for their effect on intestinal absorption of insulin.In this study, insulin was complexed with phosphatidylcholine (SPC) to form an insulin-SPC complex (ins-SPC) with increased lipophilicity. The following three SEDDSs: MCT(MAPC) (MC triglycerides and MAPC included), MCT(RH40) (MC triglycerides and Kolliphor® RH40 included) and LCT(MAPC) (long-chain triglycerides and MAPC included) were loading with ins-SPC (4% or 8% w/w of SPC). Three SEDDSs generated emulsions with droplet sizes between 50 and 470 nm and with zeta potentials between −5 to −25 mV in a simulated intestinal medium. Mucus-secreting Caco-2/HT29-MTX-E12 co-culture and Caco-2 monolayers were used as in vitro cell transport models to investigate insulin permeability. In comparison to insulin HBSS solution, MCT(MAPC) significantly increased the insulin permeability across co-culture and Caco-2 monolayers (2.0–2.5 × 10–7 cm/s). In an intra-jejunal (i.j.) instillation model in rats, MCT(RH40) significantly decreased the rat blood glucose after 0.5 h by 17.0 ± 2.5% and for MCT(MAPC), it was 23.6 ± 10.6%. Furthermore, a lipase inhibitor orlistat was incorporated into MCT(MAPC) to evaluate the effect of lipid digestion on insulin absorption. Results indicated that the incorporation of orlistat did not significantly alter the in vivo insulin absorption. Overall, the SEDDS MCT(MAPC) composed of natural PEs (MAPC and MC glycerides) and synthetic PE (LAB) significantly increased the intestinal absorption of insulin upon i.j. instillation. Although it is not possible to conclude if a single PE is dominating the intestinal absorption of insulin, MCT(MAPC) seems to have the potential for oral insulin delivery.

Enhancement of oral bioavailability of salmon calcitonin through chitosan-modified, dual drug-loaded nanoparticles

Because numerous challenges limit the effective oral delivery of protein and peptide drugs, we developed promising chitosan (CS)-modified, dual drug-loaded nanoparticles (NPs) simultaneously containing salmon calcitonin (sCT) and puerarin (PR) (CS-sCT/PR-NPs), and to explore the potential of PR as a protease inhibitor. This oral delivery system showed efficient encapsulation of sCT (75.7%) and PR (50.9%), protection of encapsulated sCT and PR from premature release in simulated gastric fluid (SGJ, pH 1.2), and sustained-release behavior in phosphate buffer saline (PBS, pH 7.4). CS-sCT/PR-NPs were capable of sequential drug-release in which PR was partially released prior to sCT, allowing PR to play a role of enzyme inhibitor before sCT release. Compared with CS-sCT-NPs, CS-sCT/PR-NPs were more stable in simulated intestinal fluid containing pancreatinum. The internalization of fluorescein isothiocyanate-labeled sCT (FITC-sCT) by Caco-2 cells increased when incorporated into NPs compared with free sCT. In vivo, the oral absolute bioavailability of sCT in CS-sCT/PR-NPs was 12.52 ± 1.83%, approximately 1.74-fold higher than that of the NPs not co-loaded with PR. In conclusion, the CS-based NPs and introduction of PR as a protease inhibitor improved the oral bioavailability of sCT and had potential to be developed as an oral delivery system of peptide drug.