Safety and efficacy of self-assembling bubble carriers stabilized with sodium dodecyl sulfate for oral delivery of therapeutic proteins

"Enhancing Oral Drug Absorption: Overcoming Physiological and Pharmaceutical Barriers for Improved Bioavailability"

The oral route stands out as the most commonly used method for drug administration, prized for its non-invasive nature, patient compliance, and easy administration. Several elements influence the absorption of oral medications, including their solubility, permeability across mucosal membranes, and stability within the gastrointestinal (GI) environment. Research has delved into comprehending physicochemical, biochemical, metabolic, and biological obstacles that impact the bioavailability of a drug. To improve oral drug absorption, several pharmaceutical technologies and delivery methods have been studied, including cyclodextrins, micelles, nanocarriers, and lipid-based carriers. This review examines both traditional and innovative drug delivery methods, as well as the physiological and pharmacological barriers influencing medication bioavailability when taken orally. Additionally, it describes the challenges and advancements in developing formulations suitable for oral use.

The involvement of signaling pathways in the pathogenesis of osteoarthritis: An update

Osteoarthritis (OA) is one of the most common disabling pathologies, characterized by joint pain and reduced function, significantly worsening the quality of life. Even if important progresses have been made in OA research, little is yet known about the precise cellular and molecular mechanisms underlying OA. Understanding dysregulated signaling networks and their crosstalk in OA may offer a strong opportunity for the development of combined targeted therapies. Hence, this review highlights the recent findings on the main pathways involved in OA development, including Wnt, Notch, Hedgehog, MAPK, AMPK, and JAK/STAT, providing insights on current targeted therapies in OA patients' management.

The translational potential of this article

The identification of key signaling pathways involved in OA development and the investigation of their signaling crosstalk could pave the way for more effective treatments and improved management of OA patients in the future.

Mucus-penetrating and permeation enhancer albumin-based nanoparticles for oral delivery of macromolecules: Application to bevacizumab

The oral administration of therapeutic proteins copes with important challenges (mainly degradation and poor absorption) making their potential therapeutic application extremely difficult. The aim of this study was to design and evaluate the potential of the combination between mucus-permeating nanoparticles and permeation enhancers as a carrier for the oral delivery of the monoclonal antibody bevacizumab, used as a model of therapeutic protein. For this purpose, bevacizumab was encapsulated in PEG-coated albumin nanoparticles as a hydrophobic ion-pairing complex with either sodium deoxycholate (DS) or sodium docusate (DOCU). In both cases, complex formation efficiencies close to 90% were found. The incorporation of either DS or DOCU in PEG-coated nanoparticles significantly increased their mean size, particularly when DOCU was used. Moreover, the diffusion in mucus of DOCU-loaded nanoparticles was significantly reduced, compared with DS ones. In a C. elegans model, DS or DOCU (free or nanoencapsulated) disrupted the intestinal epithelial integrity, but the overall survival of the worms was not affected. In rats, the relative oral bioavailability of bevacizumab incorporated in PEG-coated nanoparticles as a complex with DS (B-DS-NP-P) was 3.7%, a 1000-fold increase compared to free bevacizumab encapsulated in nanoparticles (B-NP-P). This important effect of DS may be explained not only by its capability to transiently disrupt tight junctions but also to their ability to increase the fluidity of membranes and to inhibit cytosolic and brush border enzymes. In summary, the current strategy may be useful to allow the therapeutic use of orally administered proteins, including monoclonal antibodies.

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

Purpose

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.

Methods

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).

Results

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.

Conclusion

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.

Multiresponsive Nanoscale Self-Assembly of Azurin-Elastin-like Polypeptide Fusion Protein for Enhanced Prostate Cancer Therapy

A fusion protein composed of a bacterial protein, azurin, having antineoplastic properties and a thermally responsive structural cationic elastin-like protein (ELP), is designed, cloned, expressed, and purified. A simple method of inverse transition cycle (ITC) is employed to purify the fusion protein azurin-ELP diblock copolymer (d-bc). The molecular weight of the azurin-ELP fusion protein is ∼32 kDa. Further, its self-assembly properties are investigated. Interestingly, the engineered azurin-ELP d-bc in response to increasing temperature shows a dual-step phase separation into biofunctional nanostructures. Around the physiological temperature, azurin-ELP d-bc forms stable coacervates, which is dependent on the concentration and time of incubation. These coacervates are formed below the lower critical solubility temperature (LCST) of the ELP block at physiological temperature. Above LCST, i.e., 50-55°C, micelles of size ranging from 25 to 30 nm are formed. The cytotoxicity of azurin-ELP d-bc depends on the size of the coacervates formed and their cellular uptake at physiological temperature. Further, MTT assay of azurin-ELP d-bc in the cross-linked micelles prepared ex situ shows > six times higher killing of LNCaP cells than the unimeric form of azurin-ELP at 5 μM concentration. The flow cytometric results of these micelles at 20 μM concentration show ∼97% LNCaP cells in the apoptotic phase. Thus, azurin-ELP cross-linked micelles have enhanced potential for anticancer therapy due to their higher avidity.

Aflibercept Loaded Eye-Drop Hydrogel Mediated with Cell-Penetrating Peptide for Corneal Neovascularization Treatment

Corneal neovascularization (CoNV) is a major cause of visual impairment worldwide. Currently, available treatment options have limited efficacy and are associated with adverse effects due to biological barriers and clearance mechanisms. To address this challenge, a novel topical delivery system is developed-Gel 2_1&Eylea-an aflibercept-loaded eye-drop hydrogel mediated with cell-penetrating peptide 1. Gel 2_1&Eylea demonstrates superior membrane permeability, increased stability, and prolonged drug retention time on the ocular surface, and thus may improve drug efficacy. In a rabbit CoNV model, Gel 2_1&Eylea significantly reduces the density of neovascularization with no adverse effects on normal corneoscleral limbal vessels, demonstrating high efficacy and biocompatibility. This work identifies a promising treatment for CoNV which has the potential to benefit other ocular neovascular diseases.

Bioinspired pH-Responsive Microalgal Hydrogels for Oral Insulin Delivery with Both Hypoglycemic and Insulin Sensitizing Effects

The oral form of insulin is more convenient and has better patient compliance than subcutaneous or intravenous insulin. Current oral insulin preparations, however, cannot overcome the enzyme barrier, chemical barrier, and epithelial barrier of the gastrointestinal tract completely. In this study, a microalgae-based oral insulin delivery strategy (CV@INS@ALG) was developed using Chlorella vulgaris (CV)-based insulin delivery system cross-linking with sodium alginate (ALG). CV@INS@ALG could overcome the gastrointestinal barrier, protect insulin from harsh gastric conditions, and achieve a pH-responsive drug release in the intestine. CV@INS@ALG might contribute to two mechanisms of insulin absorption, including direct insulin release from the delivery system and endocytosis by M cells and macrophages. In the streptozotocin (STZ)-induced type 1 diabetic mouse model, CV@INS@ALG showed a more effective and long-lasting hypoglycemic effect than direct insulin injection and did not cause any damage to the intestinal tract. Additionally, the long-term oral administration of the carrier CV@ALG effectively ameliorated gut microbiota disorder, and significantly increased the abundance of probiotic Akkermansia in db/db type 2 diabetic mice, thereby enhancing the insulin sensitivity of mice. Microalgal insulin delivery systems could be degraded and metabolized in the intestinal tract after oral administration, showing good biodegradability and biosafety. This insulin delivery strategy based on microalgal biomaterials provides a natural, efficient, and multifunctional solution for oral insulin delivery.

Oral delivery of biomacromolecules by overcoming biological barriers in the gastrointestinal tract: an update

INTRODUCTION

Biomacromolecules have proven to be an attractive choice for treating diseases due to their properties of strong specificity, high efficiency, and low toxicity. Besides greatly improving the patient's complaint, oral delivery of macromolecules also complies with hormone physiological secretion, which has become one of the most innovative fields of research in recent years.

AREAS COVERED

Oral delivery biological barriers for biomacromolecule, transport mechanisms, and various administration strategies were discussed in this review, including absorption enhancers, targeting nanoparticles, mucoadhesion nanoparticles, mucus penetration nanoparticles, and intelligent bionic drug delivery systems.

EXPERT OPINION

The oral delivery of biomacromolecules has important clinical implications; however, these are still facing the challenges of low bioavailability due to certain barriers. Various promising technologies have been developed to overcome the barriers and improve the therapeutic effect of oral biomacromolecules. By considering safety and efficacy comprehensively, the development of intelligent nanoparticles based on the GIT environment has demonstrated some promise in overcoming these barriers; however, a more comprehensive understanding of the oral fate of oral biomacromolecules is still required.

Advances in Oral Drug Delivery Systems: Challenges and Opportunities

The oral route is the most preferred route for systemic and local drug delivery. However, the oral drug delivery system faces the harsh physiological and physicochemical environment of the gastrointestinal tract, which limits the bioavailability and targeted design of oral drug delivery system. Innovative pharmaceutical approaches including nanoparticulate formulations, biomimetic drug formulations, and microfabricated devices have been explored to optimize drug targeting and bioavailability. In this review, the anatomical factors, biochemical factors, and physiology factors that influence delivering drug via oral route are discussed and recent advance in conventional and novel oral drug delivery approaches for improving drug bioavailability and targeting ability are highlighted. We also address the challenges and opportunities of oral drug delivery systems in future.

Mitochondrion-targeting and in situ photocontrolled protein delivery via photocages

Defects in mitochondrial proteostasis contribute to many disorders, including cancer, neurodegeneration, and metabolic and genetic diseases. A strategy aimed at restoring the damaged mitochondrial proteostasis is the mitochondrion-targeting and carrier-free delivery of exogenous functional proteins that can replace the endogenous dysfunctional proteins. The modification of a protein with a photolabile protecting group (PPG, i.e., photocage group) can be activated in situ by response to illumination, leading to release of the protein from its photocage. Here, the Cys and peptide photocages with coumarin were first prepared and characterized for proof of concept. Then, we designed a pair of photocage groups PPG-RhB and PPG-TPP using coumarin and mitochondrion-targeting Rhodamine B (RhB) and triphenylphosphine (TPP), and another pair of organelle-nontarget photocage groups Br-PPG and NO₂-PPG for comparison. The proteins modified with these two pairs of photocage groups undergo photolysis in solutions, and can penetrate cell membrane toward their destinations in the carrier-free fashions. The intracellular protein photocages are in situ activated by illumination at 405 nm, and the proteins are released from their photocages in mitochondria and cytoplasm, respectively. This strategy of light-responsive and carrier-free cellular delivery enables mitochondrial and cytoplasmic accumulation of exogenous proteins.

Polyelectrolyte/surfactant films: from 2D to 3D structural control

Reversible control of the 3D structure of polyelectrolyte/surfactant films at the air/water interface is showcased. A recently discovered mechanism is exploited to form highly efficient, stable and biocompatible films by...

Development and Evaluation of Tannic Acid-Coated Nanosuspension for Enhancing Oral Bioavailability of Curcumin

Curcumin (CUR) has been used in the treatment of various diseases such as cough, fever, skin disease, and infection because of various biological benefits such as anti-inflammatory, antiviral, antibacterial, and antitumor activity. However, CUR is a BCS class 4 group and has a limitation of low bioavailability due to low solubility and permeability. Therefore, the purpose of this study is to prepare a nanosuspension (NSP) loaded with CUR (CUR-NSP) using a statistical design approach to improve the oral bioavailability of CUR, and then to develop CUR-NSP coated with tannic acid to increase the mucoadhesion in the GI tract. Firstly, the optimized CUR-NSP, composed of sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone/vinyl acetate (PVP/VA), was modified with tannic acid (TA). The particle size and polydispersity index of the formulation measured by laser scattering analyzer were 127.7 ± 1.3 nm and 0.227 ± 0.010, respectively. In addition, the precipitation in distilled water (DW) was 1.52 ± 0.58%. Using a differential scanning calorimeter and X-ray diffraction analysis, the stable amorphous form of CUR was confirmed in the formulation, and it was confirmed that CUR-NSP formulation was coated with TA through a Fourier transform-infrared spectroscopy. In the mucoadhesion assay using the turbidity, it was confirmed that TA-CUR-NSP had higher affinity for mucus than CUR-NSP under all pH conditions. This means that the absorption of CUR can be improved by increasing the retention time in the GI tract of the formulation. In addition, the drug release profile showed more than 80% release, and in the cellular uptake study, the absorption of the formulation (TA-CUR-NSP) containing TA acting as an inhibitor of P-gp was increased by 1.6-fold. In the evaluation of antioxidant activity, the SOD activity of TA-CUR-NSP was remarkably high due to TA, which improves cellular uptake and has antioxidant activity. In the pharmacokinetic evaluation, the maximum drug plasma concentration of the TA-coated NSP formulation was 7.2-fold higher than that of the pure drug. In all experiments, it was confirmed that the TA-CUR-NSP is a promising approach to overcome the low oral bioavailability of CUR.

Endogenous Conjugation of Biomimetic Dinitrosyl Iron Complex with Protein Vehicles for Oral Delivery of Nitric Oxide to Brain and Activation of Hippocampal Neurogenesis

Nitric oxide (NO), a pro-neurogenic and antineuroinflammatory gasotransmitter, features the potential to develop a translational medicine against neuropathological conditions. Despite the extensive efforts made on the controlled delivery of therapeutic NO, however, an orally active NO prodrug for a treatment of chronic neuropathy was not reported yet. Inspired by the natural dinitrosyl iron unit (DNIU) [Fe(NO)₂], in this study, a reversible and dynamic interaction between the biomimetic [(NO)₂Fe(μ-SCH₂CH₂OH)₂Fe(NO)₂] (DNIC-1) and serum albumin (or gastrointestinal mucin) was explored to discover endogenous proteins as a vehicle for an oral delivery of NO to the brain after an oral administration of DNIC-1. On the basis of the in vitro and in vivo study, a rapid binding of DNIC-1 toward gastrointestinal mucin yielding the mucin-bound dinitrosyl iron complex (DNIC) discovers the mucoadhesive nature of DNIC-1. A reversible interconversion between mucin-bound DNIC and DNIC-1 facilitates the mucus-penetrating migration of DNIC-1 shielded in the gastrointestinal tract of the stomach and small intestine. Moreover, the NO-release reactivity of DNIC-1 induces the transient opening of the cellular tight junction and enhances its paracellular permeability across the intestinal epithelial barrier. During circulation in the bloodstream, a stoichiometric binding of DNIC-1 to the serum albumin, as another endogenous protein vehicle, stabilizes the DNIU [Fe(NO)₂] for a subsequent transfer into the brain. With aging mice under a Western diet as a disease model for metabolic syndrome and cognitive impairment, an oral administration of DNIC-1 in a daily manner for 16 weeks activates the hippocampal neurogenesis and ameliorates the impaired cognitive ability. Taken together, these findings disclose the synergy between biomimetic DNIC-1 and endogenous protein vehicles for an oral delivery of therapeutic NO to the brain against chronic neuropathy.

Improving Oral Bioavailability of Luteolin Nanocrystals by Surface Modification of Sodium Dodecyl Sulfate

Luteolin suffers from drawbacks like low solubility and bioavailability, thus hindering its application in the clinic. In this study, we employed sodium dodecyl sulfate (SDS), an efficient tight junction opening agent, to modify the surface of luteolin nanocrystals, aiming to enhance the bioavailability of luteolin (LUT) and luteolin nanocrystals (LNC). The particle sizes of SDS-modified luteolin nanocrystals (SLNC) were slightly larger than that of LNC, and the zeta potential of LNC and SLNC was -25.0 ± 0.7 mV and -43.5 ± 0.4 mV, respectively. Both LNC and SLNC exhibited enhanced saturation solubility and high stability in the liquid state. In the cellular study, we found that SDS has cytotoxicity on caco-2 cells and could open the tight junction of the caco-2 monolayer, which could lead to an enhanced transport of luteolin across the intestinal membrane. The bioavailability of luteolin was enhanced for 1.90-fold by luteolin nanocrystals, and after modification with SDS, the bioavailability was enhanced to 3.48-fold. Our experiments demonstrated that SDS could efficiently open the tight junction and enhance the bioavailability of luteolin thereafter, revealing the construction of SDS-modified nanocrystals is a good strategy for enhancing the oral bioavailability of poorly soluble drugs like luteolin.

A fast and facile platform for fabricating phase-change materials-based drug carriers powered by chemical Marangoni effect

Emulsions of oil droplets as drug carriers are typically formulated by emulsification, which is complex and time-consuming and requires high energy input. To address these concerns, a fast and facile method for fabricating lipid-based oil droplets, using propulsive forces that arise from the chemical Marangoni effect, is developed for the oral delivery of lipophilic drugs, such as vitamin D. The oil droplets are prepared by solubilizing vitamin D in a phase-changeable fatty acid with the addition of ethanol as an oil phase, which is then deposited on a water bath. As a result of the differing surface tensions of water and ethanol (chemical energy), propulsive Marangoni forces are generated (kinetic energy), rapidly spreading the oil phase into many tiny oil droplets. To prevent their coalescence, the generated oil droplets are solidified by reducing their environmental temperature. Following oral administration, the fluidity of the solidified droplets increases at body temperature; they can be further emulsified into the vitamin D-containing micelles by intestinal bile salts. The micelles are then taken up by the intestinal epithelial cells, enabling their contained vitamin D to be absorbed into systemic circulation, improving its oral bioavailability.

Nanocomposite systems for precise oral delivery of drugs and biologics

Oral delivery is considered the favoured route of administration for both local and systemic delivery of active molecules. Formulation of drugs in conventional systems and nanoparticles has provided opportunities for targeting the gastrointestinal (GI) tract, increasing drug solubility and bioavailability. Despite the achievements of these delivery approaches, the development of a product with the ability of delivering drug molecules at a specific site and according to patients' needs remains a challenging endeavour. The complexity of the physicochemical properties of colloidal systems, their stability in different regions of the gastrointestinal tract, and interaction with the restrictive biological barriers hampered their success for oral precise medicine. To overcome these issues, nanoparticles have been combined with polymers to create hybrid nanosystems, namely nanocomposites. They offer enormous possibilities of structural and mechanical modifications to both nanoparticles and polymeric matrixes to generate systems with new properties, functions, and applications for oral delivery. In this review, nanocomposites' physicochemical and functional properties intended to target specific regions of the GI tract-oral cavity, stomach, small bowel, and colon-are analysed. In parallel, it is provided an insight in the nanocomposite solutions for oral delivery intended for systemic and local absorption, together with a focus on inflammatory bowel diseases (IBDs). Additional difficulties in managing IBD related to the alteration in the physiology of the intestine are described. Finally, future perspectives and opportunities for advancement in this field are discussed.

Review of recently used techniques and materials to improve the efficiency of orally administered proteins/peptides

OBJECTIVES

The main objective of present review is to explore and evaluate the effectiveness of recently developed methods to improve the bioavailability of orally administered biopharmaceutical drugs.

METHODS

A systematic search of sciencedirect, tandfonline and Google Scholar databases based on various sets of keywords was performed. All results were evaluated based on their abstracts, and irrelevant studies were neglected during further evaluation.

RESULTS

At present, biopharmaceuticals are used as injectable therapies as they are not absorbed adequately from the different routes of drug administration, particularly the oral one. Their insufficient absorption is attributed to their high molecular weight, degradation by proteolytic enzymes, high hydrophilicity and rigidity of the absorptive tissues. From industrial aspect incorporation of enzyme inhibitors (EIs) and permeation enhancers (PEs) and mucoadhesive polymers into conventional dosage forms may be the easiest way of formulation of orally administered macromolecular drugs, but the effectiveness of protection and absorption enhancement here is the most questionable. Conjugation may be problematic from regulatory aspect. Encapsulation into lipid-based vesicles sufficiently protects the incorporated macromolecule and improves intestinal uptake but have considerable stability issues. In contrast, polymeric nanocarriers may provide good stability but provides lower internalization efficacy in comparison with the lipid-based carriers.

CONCLUSION

It can be concluded that the combination of the advantages of mucoadhesive polymeric and lid-based carriers in hybrid lipid/polymer nanoparticles may result in improved absorption and might represent a potential means for the oral administration of therapeutic proteins in the near future. Graphical abstract Delivery systems for oral protein daministration.

Oral Delivery of Biologics for Precision Medicine

The emerging field of precision medicine is rapidly growing, fostered by the advances in genome mapping and molecular diagnosis. In general, the translation of these advances into precision treatments relies on the use of biological macromolecules, whose structure offers a high specificity and potency. Unfortunately, due to their complex structure and limited ability to overcome biological barriers, these macromolecules need to be administered via injection. The scientific community has devoted significant effort to making the oral administration of macromolecules plausible thanks to the implementation of drug delivery technologies. Here, an overview of the current situation and future prospects in the field of oral delivery of biologics is provided. Technologies in clinical trials, as well as recent and disruptive delivery systems proposed in the literature for local and systemic delivery of biologics including peptides, antibodies, and nucleic acids, are described. Strategies for the specific targeting of gastrointestinal regions-stomach, small bowel, and colon-cell populations, and internalization pathways, are analyzed. Finally, challenges associated with the clinical translation, future prospects, and identified opportunities for advancement in this field are also discussed.

Design of self-polymerized insulin loaded poly(n-butylcyanoacrylate) nanoparticles for tunable oral delivery

Macromolecular drugs, characterized by low stability and large molecular weight, still faced various difficulties by oral administration. And controlling drugs' release rate to reach the physiological concentration in the blood was recognized as one of the main challenges in this field but no studies are available so far. Thus, the objective of this study was to investigate the effect of insulin release rate on its in vitro and in vivo behavior when other obstacles (drug stability, mucus penetration and retention in gastrointestinal tract) was firstly overcome. Using n-butylcyanoacrylate (BCA) as the carrier, insulin-loaded Poly (n-butylcyanoacrylate) nanoparticles (Ins/PBCA NPs) were prepared by self-polymerization and the release rate of insulin was controlled by adjusting the mass ratio of Insulin/BCA. The NPs exhibited good stability in gastric fluid with controlled release in intestine and the release rate increased with the increase of Insulin/BCA mass ratio. All the Ins/PBCA NPs with different release rate showed excellent mucus penetration (>60%, 10 min) and strong gastrointestinal retention (~70%, 12 h). Especially, all the NPs showed promising hypoglycemic effect with the extent depending on drug release rate. Ins/BCA = 2/10 NPs exhibited fast hypoglycemic effect, while Ins/BCA = 2/15 NPs showed slow and outstanding performance. In conclusion, Ins/PBCA NPs could not only overcome the oral barriers of insulin delivery but also provide desired hypoglycemic effect by controlling insulin release rate.

Advances in oral peptide therapeutics

Protein and peptide therapeutics require parenteral administration, which can be a deterrent to medication adherence. For this reason, there have been extensive efforts to develop alternative delivery strategies, particularly for peptides such as insulin that are used to treat endocrine disorders. Oral delivery is especially desirable, but it faces substantial barriers related to the structural organization and physiological function of the gastrointestinal tract. This article highlights strategies designed to overcome these barriers, including permeation enhancers, inhibitors of gut enzymes, and mucus-penetrating and cell-penetrating peptides. It then focuses on the experience with oral peptides that have reached clinical trials, including insulin, calcitonin, parathyroid hormone and vasopressin, with an emphasis on the advances that have recently led to the landmark approval of an oral formulation of the glucagon-like peptide 1 receptor agonist semaglutide for the treatment of type 2 diabetes.

Protein Corona Liposomes Achieve Efficient Oral Insulin Delivery by Overcoming Mucus and Epithelial Barriers

Oral delivery of peptide/protein drugs has attracted worldwide attention due to its good patient compliance and convenience of administration. Orally administered nanocarriers always encounter the rigorous defenses of the gastrointestinal tract, which mainly consist of mucus and epithelium barriers. However, diametrically opposite surface properties of nanocarriers are required for good mucus penetration and high epithelial uptake. Here, bovine serum albumin (BSA) is adsorbed to cationic liposomes (CLs) to form protein corona liposomes (PcCLs). The aim of using PcCLs is to conquer the mucus and epithelium barriers, eventually improving the oral bioavailability of insulin. Investigations using in vitro and in vivo experiments show that the uptake amounts and transepithelial permeability of PcCLs are 3.24- and 7.91-fold higher than that of free insulin, respectively. Further study of the behavior of PcCLs implies that BSA corona can be shed from PcCLs as they cross the mucus layer, which results in the exposure of CLs to improve the transepithelial transport. Intrajejunal administration of PcCLs in type I diabetic rats produces a remarkable hypoglycemic effect and increases the oral bioavailability up to 11.9%. All of these results imply that PcCLs may provide a new insight into the method for oral insulin delivery by overcoming the multiple barriers.

Novel polymeric biomaterial poly(butyl-2-cyanoacrylate) nanowires: synthesis, characterization and formation mechanism

Poly(butyl-2-cyanoacrylate) (PBCA) nanoparticles have been widely elaborated for nearly half a century. However, PBCA nanowires (PNWs) were seldom investigated. Here, new polymeric biomaterial PNWs were prepared via emulsion polymerization based on the sodium dodecyl sulfate (SDS)-assisted emulsion process. Results indicated that SDS micelles and PBCA polymer can develop surfactant-polymer complexes by self-assembly at room temperature. SDS concentration was confirmed to be the critical parameter for the association of the surfactant and the polymer. With the addition of SDS (0-40 mM), the interaction between SDS and PBCA led to a series of transitions from nanoparticles to nanowires. These morphology transitions were triggered by changing the electrostatic repulsion in the SDS-PBCA system, confirmed by the variety of zeta potential with increasing molar contents of SDS. To overcome the electrostatic repulsion, the complexes underwent transitions from spherical, worm-like (short-cylindrical), to elongated-cylindrical form. Finally, associated with the results from scanning / transmission electron microscopy (SEM / TEM), the elongated-cylindrical PNWs acquired at 20 mM of SDS were chosen to execute cell viability assay, which showed that they had no toxicity but with good-biocompatibility at the doses ≤ 50 μg/ml. These results indicate that the PNWs prepared by this facile-green and low-toxic strategy can potentially work as promising biomaterials in the biomedicine field.

An Intestinal "Transformers"-like Nanocarrier System for Enhancing the Oral Bioavailability of Poorly Water-Soluble Drugs

Increasing the intestinal dissolution of orally administered poorly water-soluble drugs that have poor oral bioavailability to a therapeutically effective level has long been an elusive goal. In this work, an approach that can greatly enhance the oral bioavailability of a poorly water-soluble drug such as curcumin (CUR) is developed, using a "Transformers"-like nanocarrier system (TLNS) that can self-emulsify the drug molecules in the intestinal lumen to form nanoemulsions. Owing to its known anti-inflammation activity, the use of CUR in treating pancreatitis is evaluated herein. Structural changes of the TLNS in the intestinal environment to form the CUR-laden nanoemulsions are confirmed in vitro. The therapeutic efficacy of this TLNS is evaluated in rats with experimentally induced acute pancreatitis (AP). Notably, the CUR-laden nanoemulsions that are obtained using the proposed TLNS can passively target intestinal M cells, in which they are transcytosed and then transported into the pancreatic tissues via the intestinal lymphatic system. The pancreases in rats that are treated with the TLNS yield approximately 12 times stronger CUR signals than their counterparts receiving free CUR, potentially improving the recovery of AP. These findings demonstrate that the proposed TLNS can markedly increase the intestinal drug dissolution, making oral delivery a favorable noninvasive means of administering poorly water-soluble drugs.

Advance in oral delivery systems for therapeutic protein

Oral delivery is the most common method of drug administration with high safety and good compliance for patients. However, delivering therapeutic proteins to the target site via oral route involves tremendous challenge due to unfavourable conditions like biochemical barrier, mucus barrier and epithelial barriers. According to the functional differences of various protein drug delivery systems, the recent advances in pH responsive polymer-based drug delivery system, mucoadhesive polymer-based drug delivery system, absorption enhancers-based drug delivery system and composite polymer-based delivery system all were briefly summarised in this review, which not only clarified the clinic potential of these novel drug delivery systems, but also described the way for increasing oral bioavailability of therapeutic protein.