Design and intestinal mucus penetration mechanism of core-shell nanocomplex

Muco-Adhesive and Muco-Penetrative Formulations for the Oral Delivery of Insulin

Insulin, a pivotal anabolic hormone, regulates glucose homeostasis by facilitating the conversion of blood glucose to energy or storage. Dysfunction in insulin activity, often associated with pancreatic β cells impairment, leads to hyperglycemia, a hallmark of diabetes. Type 1 diabetes (T1D) results from autoimmune destruction of β cells, while type 2 diabetes (T2D) stems from genetic, environmental, and lifestyle factors causing β cell dysfunction and insulin resistance. Currently, insulin therapy is used for most of the cases of T1D, while it is used only in a few persistent cases of T2D, often supplemented with dietary and lifestyle changes. The key challenge in oral insulin delivery lies in overcoming gastrointestinal (GI) barriers, including enzymatic degradation, low permeability, food interactions, low bioavailability, and long-term safety concerns. The muco-adhesive (MA) and muco-penetrative (MP) formulations aim to enhance oral insulin delivery by addressing these challenges. The mucus layer, a hydrogel matrix covering epithelial cells in the GI tract, poses significant barriers to oral insulin absorption. Its structure, composition, and turnover rate influence interactions with insulin and other drug carriers. Some of the few factors that influence mucoadhesion and mucopenetration are particle size, surface charge distribution, and surface modifications. This review discusses the challenges associated with oral insulin delivery, explores the properties of mucus, and evaluates the strategies for achieving excellent MA and MP formulations, focusing on nanotechnology-based approaches. The development of effective oral insulin formulations holds the potential to revolutionize diabetes management, providing patients with a more convenient and patient-friendly alternative to traditional insulin administration methods.

Inhaled immunoantimicrobials for the treatment of chronic obstructive pulmonary disease

Effective therapeutic modalities and drug administration strategies for the treatment of chronic obstructive pulmonary disease (COPD) exacerbations are lacking. Here, mucus and biofilm dual-penetrating immunoantimicrobials (IMAMs) are developed for bridging antibacterial therapy and pro-resolving immunotherapy of COPD. IMAMs are constructed from ceftazidime (CAZ)-encapsulated hollow mesoporous silica nanoparticles (HMSNs) gated with a charge/conformation-transformable polypeptide. The polypeptide adopts a negatively charged, random-coiled conformation, masking the pores of HMSNs to prevent antibiotic leakage and allowing the nebulized IMAMs to efficiently penetrate the bronchial mucus and biofilm. Inside the acidic biofilm, the polypeptide transforms into a cationic and rigid α helix, enhancing biofilm retention and unmasking the pores to release CAZ. Meanwhile, the polypeptide is conditionally activated to disrupt bacterial membranes and scavenge bacterial DNA, functioning as an adjuvant of CAZ to eradicate lung-colonizing bacteria and inhibiting Toll-like receptor 9 activation to foster inflammation resolution. This immunoantibacterial strategy may shift the current paradigm of COPD management.

The effect of in vitro digestion on the interaction between polysaccharides derived from Pleurotus eryngii and intestinal mucus

Pleurotus eryngii polysaccharides (PEPs) have been proven to display multiple activities through digestive system action, from which the digestion products should first interact with intestinal mucus (MUC), followed by the function of intestinal cells. Hence, possible interacting characterizations between MUC and in vitro simulated digestion products of P. eryngii polysaccharides (DPEPs) and PEP were carried out in the present study. Results showed that both PEP and DPEP could significantly interact with MUC. Moreover, digestion can modify the interaction between polysaccharides and MUC; the degree of interaction also changes with time incrementing. Viscosity could be decreased after digesting. According to the zeta potential and stability analysis result, the digestive behavior could be regular and stable between polysaccharides and MUC interactions. Following fluorescence and infrared spectra, the structure of polysaccharides and mucin might be changed by digestion between polysaccharides and MUC. The study indicates that the interaction formed between DPEP and MUC might indirectly impact the exercise and immune activities of polysaccharides and influence the transportation of other nutrients. Overall, our results, the absorption and transport pathways of PEP, can be initially revealed and may provide a novel research viewpoint on the active mechanism of PEP in the intestinal tract.

Rubropunctatin-silver composite nanoliposomes for eradicating Helicobacter pylori in vitro and in vivo

Helicobacter pylori (H. pylori) is a major factor in peptic ulcer disease and gastric cancer, and its infection rate is rising globally. The efficacy of traditional antibiotic treatment is less effective, mainly due to bacterial biofilms and the formation of antibiotic resistance. In addition, H. pylori colonizes the gastrointestinal epithelium covered by mucus layers, the drug must penetrate the double barrier of mucus layer and biofilm to reach the infection site and kill H. pylori. The ethanol injection method was used to synthesize nanoliposomes (EPI/R-AgNPs@RHL/PC) with a mixed lipid layer containing rhamnolipids (RHL) and phosphatidylcholine (PC) as a carrier, loaded with the urease inhibitor epiberberine (EPI) and the antimicrobial agent rubropunctatin silver nanoparticles (R-AgNPs). EPI/R-AgNPs@RHL/PC had the appropriate size, negative charge, and acid sensitivity to penetrate mucin-rich mucus layers and achieve acid-responsive drug release. In vitro experiments demonstrated that EPI/R-AgNPs@RHL/PC exhibited good antibacterial activity, effectively inhibited urease activity, removed the mature H. pylori biofilm, and inhibited biofilm regeneration. In vivo antibacterial tests showed that EPI/R-AgNPs@RHL/PC exhibited excellent activity in eradicating H. pylori and protecting the mucosa compared to the traditional clinical triple therapy, providing a new idea for the treatment of H. pylori infection.

Orally-administered nanomedicine systems targeting colon inflammation for the treatment of inflammatory bowel disease: latest advances

Inflammatory bowel disease (IBD) is a chronic and idiopathic condition that results in inflammation of the gastrointestinal tract, leading to conditions such as ulcerative colitis and Crohn's disease. Commonly used treatments for IBD include anti-inflammatory drugs, immunosuppressants, and antibiotics. Fecal microbiota transplantation is also being explored as a potential treatment method; however, these drugs may lead to systemic side effects. Oral administration is preferred for IBD treatment, but accurately locating the inflamed area in the colon is challenging due to multiple physiological barriers. Nanoparticle drug delivery systems possess unique physicochemical properties that enable precise delivery to the target site for IBD treatment, exploiting the increased permeability and retention effect of inflamed intestines. The first part of this review comprehensively introduces the pathophysiological environment of IBD, covering the gastrointestinal pH, various enzymes in the pathway, transport time, intestinal mucus, intestinal epithelium, intestinal immune cells, and intestinal microbiota. The second part focuses on the latest advances in the mechanism and strategies of targeted delivery using oral nanoparticle drug delivery systems for colitis-related fields. Finally, we present challenges and potential directions for future IBD treatment with the assistance of nanotechnology.

Mesoporous silica nanoparticles: An emerging approach in overcoming the challenges with oral delivery of proteins and peptides

Proteins and peptides (PPs), as therapeutics are widely explored in the past few decades, by virtue of their inherent advantages like high specificity and biocompatibility with minimal side effects. However, owing to their macromolecular size, poor membrane permeability, and high enzymatic susceptibility, the effective delivery of PPs is often challenging. Moreover, their subjection to varying environmental conditions, when administered orally, results in PPs denaturation and structural conformation, thereby lowering their bioavailability. Hence, for effective delivery with enhanced bioavailability, protection of PPs using nanoparticle-based delivery system has gained a growing interest. Mesoporous silica nanoparticles (MSNs), with their tailored morphology and pore size, high surface area, easy surface modification, versatile loading capacity, excellent thermal stability, and good biocompatibility, are eligible candidates for the effective delivery of macromolecules to the target site. This review highlights the different barriers hindering the oral absorption of PPs and the various strategies available to overcome them. In addition, the potential benefits of MSNs, along with their diversifying role in controlling the loading of PPs and their release under the influence of specific stimuli, are also discussed in length. Further, the tuning of MSNs for enhanced gene transfection efficacy is also highlighted. Since extensive research is ongoing in this area, this review is concluded with an emphasis on the potential risks of MSNs that need to be addressed prior to their clinical translation.

Comparison of virus-capsid mimicking biologic-shell based versus polymeric-shell nanoparticles for enhanced oral insulin delivery

Virus-capsid mimicking mucus-permeable nanoparticles are promising oral insulin carriers which surmount intestinal mucus barrier. However, the impact of different virus-capsid mimicking structure remains unexplored. In this study, utilizing biotin grafted chitosan as the main skeleton, virus-mimicking nanoparticles endowed with biologic-shell (streptavidin coverage) and polymeric-shell (hyaluronic acid/alginate coating) were designed with insulin as a model drug by self-assembly processes. It was demonstrated that biologic-shell mimicking nanoparticles exhibited a higher intestinal trans-mucus (>80%, 10 min) and transmucosal penetration efficiency (1.6-2.2-fold improvement) than polymeric-shell counterparts. Uptake mechanism studies revealed caveolae-mediated endocytosis was responsible for the absorption of biologic-shell mimicking nanoparticles whereas polymeric-shell mimicking nanoparticles were characterized by clathrin-mediated pathway with anticipated lysosomal insulin digestion. Further, in vivo hypoglycemic study indicated that the improved effect of regulating blood sugar levels was virus-capsid structure dependent out of which biologic-shell mimicking nanoparticles presented the best performance (5.1%). Although the findings of this study are encouraging, much more work is required to meet the standards of clinical translation. Taken together, we highlight the external structural dependence of virus-capsid mimicking nanoparticles on the muco-penetrating and uptake mechanism of enterocytes that in turn affecting their in vivo absorption, which should be pondered when engineering virus-mimicking nanoparticles 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.

In situ rearranged multifunctional lipid nanoparticles via synergistic potentiation for oral insulin delivery

Oral administration of therapeutic peptides/proteins (TPPs) is confronted with multiple gastrointestinal (GI) barriers such as mucus and intestinal epithelium, and the first-pass metabolism in the liver is also responsible for low bioavailability. In situ rearranged multifunctional lipid nanoparticles (LNs) were developed to overcome these obstacles via synergistic potentiation for oral insulin delivery. After the reverse micelles of insulin (RMI) containing functional components were gavaged, LNs formed in situ under the hydration effect of GI fluid. The nearly electroneutral surface generated by the rearrangement of sodium deoxycholate (SDC) and chitosan (CS) on the reverse micelle core facilitated LNs (RMI@SDC@SB12-CS) to overcome mucus barrier and the sulfobetaine 12 (SB12) modification further promoted epithelial uptake of LNs. Subsequently, chylomicron-like particles formed by the lipid core in the intestinal epithelium were easily transported to the lymphatic circulation and then into the systemic circulation, thus avoiding hepatic first-pass metabolism. Eventually, RMI@SDC@SB12-CS achieved a high pharmacological bioavailability of 13.7% in diabetic rats. In conclusion, this study provides a versatile platform for enhanced oral insulin delivery.

Surface design of nanocarriers: Key to more efficient oral drug delivery systems

As nanocarriers (NCs) can improve the solubility of drugs, prevent their degradation by gastrointestinal (GI) enzymes and promote their transport across the mucus gel layer and absorption membrane, the oral bioavailability of these drugs can be substantially enhanced. All these properties of NCs including self-emulsifying drug delivery systems (SEDDS), solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), liposomes, polymeric nanoparticles, inorganic nanoparticles and polymeric micelles depend mainly on their surface chemistry. In particular, interaction with food, digestive enzymes, bile salts and electrolytes, diffusion behaviour across the mucus gel layer and fate on the absorption membrane are determined by their surface. Bioinert surfaces limiting interactions with gastrointestinal fluid and content as well as with mucus, adhesive surfaces providing an intimate contact with the GI mucosa and absorption enhancing surfaces can be designed. Furthermore, charge converting surfaces shifting their zeta potential from negative to positive directly at the absorption membrane and surfaces providing a targeted drug release are advantageous. In addition to these passive surfaces, even active surfaces cleaving mucus glycoproteins on their way through the mucus gel layer can be created. Within this review, we provide an overview on these different surfaces and discuss their impact on the performance of NCs in the GI tract.

Oral Cell-Targeted Delivery Systems Constructed of Edible Materials: Advantages and Challenges

Cell-targeted delivery is an advanced strategy which can effectively solve health problems. However, the presence of synthetic materials in delivery systems may trigger side effects. Therefore, it is necessary to develop cell-targeted delivery systems with excellent biosafety. Edible materials not only exhibit biosafety, but also can be used to construct cell-targeted delivery systems such as ligands, carriers, and nutraceuticals. Moreover, oral administration is the appropriate route for cell-targeted delivery systems constructed of edible materials (CDSEMs), which is the same as the pattern of food intake, resulting in good patient compliance. In this review, relevant studies of oral CDSEMs are collected to summarize the construction method, action mechanism, and health impact. The gastrointestinal stability of delivery systems can be improved by anti-digestible materials. The design of the surface structure, shape, and size of carrier is beneficial to overcoming the mucosal barrier. Additionally, some edible materials show dual functions of a ligand and carrier, which is conductive to simplifying the design of CDSEMs. This review can provide a better understanding and prospect for oral CDSEMs and promote their application in the health field.

Zinc insulin hexamer loaded alginate zinc hydrogel: preparation, characterization and in vivo hypoglycemic ability

Alginate zinc hydrogel loaded with zinc insulin hexamer was prepared and characterized for oral insulin administration. The hydrogel was fabricated by dripping zinc insulin hexamer into sodium alginate solution and followed by crosslinking by zinc chloride. SEM image reveals the zinc insulin hexamer was integrated into the matrix of hydrogel. Zinc insulin hexamer loaded hydrogel shows no obvious cytotoxicity to both HT29 and Caco-2 cells. The developed hydrogel retards the burst release of insulin in simulated gastric fluid but promotes the release when in simulated intestinal fluid. In the diabetic mice, zinc insulin hexamer loaded alginate hydrogel demonstrates significant and prolonged hypoglycemic effect.

Updated design strategies for oral delivery systems: maximized bioefficacy of dietary bioactive compounds achieved by inducing proper digestive fate and sensory attributes

Interest in the application of dietary bioactive compounds (DBC) in healthcare and pharmaceutical industries has motivated researchers to develop functional delivery systems (FDS) aiming to maximize their bioefficacy. As the direct and indirect health benefiting effects of DBC are acknowledged, traditional design principle of FDS aiming at improving the bioavailability of intact DBC is challenged by the updated one, where the maximized bioefficacy of DBC delivered by FDS will be achieved via rationally absorbed at target sites with proper metabolism pathways. This article briefly summarized the absorption and metabolic fates of orally digested DBC along with their direct and indirect mechanisms to perform health benefiting effects. Current strategies in designing the next generation FDS with an emphasis on their modulation effects on the distribution portion between the upper and lower digestive tract, portal vein and lymphatic absorption, human digestive and gut microbiota enzymatic mediated metabolism were highlighted. Updated research progresses of FDS in adjusting sensory attributes of food end products and inducing synergistic effects rooting from matrix materials and co-delivered cargos were also discussed. Challenges as well as future perspectives concerning the precise nutrition and the critical role of delivery systems in dietary intervention were proposed.

Alginate-based nanocarriers for the delivery and controlled-release of bioactive compounds

Alginate-based nanocarriers are propitious vehicles used for the delivery of bioactive compounds (bioactives). In this area, calcium alginate and sodium alginate are the most promising wall materials because they are nontoxic, comparatively cheap, simple in production, biocompatible and biodegradable. In this review, we have highlighted different alginate-based nanocarriers such as nanoparticles, nanofibers, nanoemulsions, nanocomplexes, and nanohydrogels; also entrapment of different bioactives within alginate nanocarriers and their bioavailability in the gastric environment has been comprehensively discussed. Being biopolymers, alginates can be exploited as emulsifiers/ encapsulants for entrapment and delivery of different bioactives such as vitamins, minerals, essential fatty acids, peptides, essential oils, bioactive oils, polyphenols and carotenoids. Furthermore, the use of alginate-based nanocarriers in combination with other polysaccharides/ emulsifiers was recognized as the most effective and favorable approach for the protection, delivery and sustained release of bioactives.

Mucus-Penetrating Alginate-Chitosan Nanoparticles Loaded with Berberine Hydrochloride for Oral Delivery to the Inflammation Site of Ulcerative Colitis

The rectal enemas of berberine hydrochloride (BH) have emerged as one of the most effective strategies in the clinical treatment of ulcerative colitis (UC). However, oral dosages of BH exhibit a poor anti-inflammatory effect of UC, which may attribute to premature absorption of BH by the upper gastrointestinal tract. Moreover, the thick colonic mucus layer obstructs the penetration of the drug, resulting in low bioavailability to the inflammatory site of the colon. The aim of this study was to develop the mucus-penetrating sodium alginate-chitosan nanoparticles (SA-CS NPs) for oral delivery of BH to the site of colonic ulcer lesions. BH-loaded SA-CS NPs were developed through the ionic gelation method and analyzed for physicochemical characteristics, release performance, penetrability, site retention, and therapeutic efficacy. The results showed that the NPs have a particle size of 257 nm with a negative charge, presenting desired pH-dependent release behavior. The permeation studies elucidated that negatively charged SA-CS NPs had 2.9 times higher mucus penetration ability than positively charged CS NPs. An ex vivo retention study indicated the high retention of BH-SA-CS NPs at the colon site for more than 16 h. In vivo therapeutic effectiveness demonstrated that the prepared NPs could not only alleviate colonic injury by decreasing the disease activity index and colon mucosa damage index, but also improve the immunologic function by decreasing the spleen index. In conclusion, the BH-SA-CS NPs could enhance the mucus permeability and deliver drugs to the colonic inflammation site, providing new insights into improving the therapeutic effect of UC.

From Static to Dynamic: A Review on the Role of Mucus Heterogeneity in Particle and Microbial Transport

Mucus layers (McLs) are on the front line of the human defense system that protect us from foreign abiotic/biotic particles (e.g., airborne virus SARS-CoV-2) and lubricates our organs. Recently, the impact of McLs on human health (e.g., nutrient absorption and drug delivery) and diseases (e.g., infections and cancers) has been studied extensively, yet their mechanisms are still not fully understood due to their high variety among organs and individuals. We characterize these variances as the heterogeneity of McLs, which lies in the thickness, composition, and physiology, making the systematic research on the roles of McLs in human health and diseases very challenging. To advance mucosal organoids and develop effective drug delivery systems, a comprehensive understanding of McLs' heterogeneity and how it impacts mucus physiology is urgently needed. When the role of airway mucus in the penetration and transmission of coronavirus (CoV) is considered, this understanding may also enable a better explanation and prediction of the CoV's behavior. Hence, in this Review, we summarize the variances of McLs among organs, health conditions, and experimental settings as well as recent advances in experimental measurements, data analysis, and model development for simulations.

Complexation behavior of carboxymethyl short-chain amylose and quaternized chitosan

The complexation of carboxymethyl short-chain amylose (CSA) and hydroxypropyl trimethyl ammonium chloride chitosan (HACC) and the stability of CSA/HACC nanocomplex were investigated. Resonance light scattering (RLS), turbidity, nanoparticle size and zeta potential analyses revealed that the complex coacervation occurred between CSA and HACC. The mass ratio and pH markedly influenced the complexation behavior; CSA with a higher degree of substitution (DS0.2) altered the complexation at a lower mass ratio and pH, increasing the turbidity and RLS intensity. The results of particle size and zeta potential analyses indicated that CSA/HACC complexes possessed the good pH and ionic strength stability. In addition to electrostatic interactions, hydrogen bonding and hydrophobic effects were also determined to be involved in the complexation process using thermal titration calorimetry (ITC). Additionally, the process was spontaneous, and CSA with a higher DS showed stronger complexation ability. These results may enable the understanding of polysaccharide complex behaviors.

Pulmonary delivery nanomedicines towards circumventing physiological barriers: Strategies and characterization approaches

Pulmonary delivery of nanomedicines is very promising in lung local disease treatments whereas several physiological barriers limit its application via the interaction with inhaled nanomedicines, namely bio-nano interactions. These bio-nano interactions may affect the pulmonary fate of nanomedicines and impede the distribution of nanomedicines in its targeted region, and subsequently undermine the therapeutic efficacy. Pulmonary diseases are under worse scenarios as the altered physiological barriers generally induce stronger bio-nano interactions. To mitigate the bio-nano interactions and regulate the pulmonary fate of nanomedicines, a number of manipulating strategies were established based on size control, surface modification, charge tuning and co-delivery of mucolytic agents. Visualized and non-visualized characterizations can be employed to validate the robustness of the proposed strategies. This review provides a guiding overview of the physiological barriers affecting the in vivo fate of inhaled nanomedicines, the manipulating strategies, and the validation methods, which will assist with the rational design and application of pulmonary nanomedicine.

Ionic Liquids: Promising Approach for Oral Drug Delivery

Oral administration is the most preferred route for drug administration in clinic. However, due to unsatisfactory physicochemical properties of drugs and various physiological barriers, the oral bioavailability of most poorly water-soluble and macromolecules drugs is low and the therapeutic effect is unsatisfactory. Ionic liquids (ILs), molten salts with unique properties, show amazing potential for oral delivery. In addition to being able to form active pharmaceutical ingredients based ILs (API-ILs) to overcome drug solubility and polymorphism issues, ILs have also been used to enhance the solubility of poorly soluble drugs, enhance drug stability in the gastrointestinal environment, improve drug permeability in intestinal mucus, and facilitate drug penetration across the intestinal epithelial barrier. Furthermore, ILs were attempted as formulation components to develop novel oral drug delivery systems. This review focus on the application progress of ILs in oral drug delivery and the mechanisms. The challenges and perspectives of the development of ILs-based oral delivery systems are also discussed. This article reviews the latest advances of ionic liquids for oral drug delivery, focusing on the application and related mechanisms of ionic liquids in improving the drug physicochemical properties and enhancing drug delivery across physiological barriers.

Untangling Mucosal Drug Delivery: Engineering, Designing, and Testing Nanoparticles to Overcome the Mucus Barrier

Mucus is a complex viscoelastic gel and acts as a barrier covering much of the soft tissue in the human body. High vascularization and accessibility have motivated drug delivery to various mucosal surfaces; however, these benefits are hindered by the mucus layer. To overcome the mucus barrier, many nanomedicines have been developed, with the goal of improving the efficacy and bioavailability of drug payloads. Two major nanoparticle-based strategies have emerged to facilitate mucosal drug delivery, namely, mucoadhesion and mucopenetration. Generally, mucoadhesive nanoparticles promote interactions with mucus for immobilization and sustained drug release, whereas mucopenetrating nanoparticles diffuse through the mucus and enhance drug uptake. The choice of strategy depends on many factors pertaining to the structural and compositional characteristics of the target mucus and mucosa. While there have been promising results in preclinical studies, mucus-nanoparticle interactions remain poorly understood, thus limiting effective clinical translation. This article reviews nanomedicines designed with mucoadhesive or mucopenetrating properties for mucosal delivery, explores the influence of site-dependent physiological variation among mucosal surfaces on efficacy, transport, and bioavailability, and discusses the techniques and models used to investigate mucus-nanoparticle interactions. The effects of non-homeostatic perturbations on protein corona formation, mucus composition, and nanoparticle performance are discussed in the context of mucosal delivery. The complexity of the mucosal barrier necessitates consideration of the interplay between nanoparticle design, tissue-specific differences in mucus structure and composition, and homeostatic or disease-related changes to the mucus barrier to develop effective nanomedicines for mucosal delivery.

Application of chitosan/alginate nanoparticle in oral drug delivery systems: prospects and challenges

Oral drug delivery systems (ODDSs) have various advantages of simple operation and few side effects. ODDSs are highly desirable for colon-targeted therapy (e.g. ulcerative colitis and colorectal cancer), as they improve therapeutic efficiency and reduce systemic toxicity. Chitosan/alginate nanoparticles (CANPs) show strong electrostatic interaction between the carboxyl group of alginates and the amino group of chitosan which leads to shrinkage and gel formation at low pH, thereby protecting the drugs from the gastrointestinal tract (GIT) and aggressive gastric environment. Meanwhile, CANPs as biocompatible polymer, show intestinal mucosal adhesion, which could extend the retention time of drugs on inflammatory sites. Recently, CANPs have attracted increasing interest as colon-targeted oral drug delivery system for intestinal diseases. The purpose of this review is to summarize the application and treatment of CANPs in intestinal diseases and insulin delivery. And then provide a future perspective of the potential and development direction of CANPs as colon-targeted ODDSs.

Hyaluronic Acid Coated Chitosan Nanoparticles for Insulin Oral Delivery: Fabrication, Characterization and Hypoglycemic Ability

Oral administration of insulin faces multiple biological challenges, such as varied digestive environments, mucin exclusion and low epithelial cells absorption. In the present study, a hyaluronic acid coated chitosan nanoparticle delivery system was fabricated for insulin oral delivery. It is hypothesized that the developed nanoparticles will protect insulin from digestive degradation, promote intestinal epithelial cell absorption and exert strong in vivo hyperglycemic ability. Nanoparticles formulated by chitosan (CS) and sodium tripolyphosphate (TPP) was optimized to form the core nanoparticles (CNP). Hyaluronic acid (HA) was further applied to coat CNP (HCP) to improve stability, reduce enzymatic degradation and promote absorption of insulin. HCP promoted insulin uptake by Caco-2 cells, absorbed less mucin and improved intestinal absorption. Moreover, in vivo test demonstrated that oral administration of insulin-loaded HCP exerts strong and continuous hyperthermia effect (with PA of 13.8%). In summary, HCP is a promising delivery platform for insulin oral administration in terms of protecting insulin during digestion, facilitating its absorption and ultimately promoting its oral bioavailability. This article is protected by copyright. All rights reserved.

Exploring the potential of redispersible nanocomplex-in-microparticles for enhanced oral insulin delivery

Polyelectrolyte nanocomplex (PEC) is a promising carrier for insulin encapsulation. However, tenacious enzymatic degradation and insufficient penetration in mucus and enterocyte are the dominating obstacles for their oral insulin delivery. Besides, the rate of insulin release should be tuned to achieve desired therapeutic effect and meanwhile with scale-up potential. Thus, PEC embedded microparticles were fabricated in this study to solve the above dilemma. First of all, insulin loaded PEC with sodium dodecyl sulfate (SDS) coating was prepared by self-assembly method and then spray-dried using different ratio chitosan (CS)/ polyvinyl alcohol (PVA) as the matrix to obtain the microparticles. Influence of the CS/PVA ratio on the in vitro and in vivo properties of the redispersed PEC was investigated systemically. It was demonstrated that when CS 50 kDa was used in the matrix, all the PEC could be well redispersed with particle size less than 250 nm, and good stability in the gastrointestinal tract, further improved enzymatic stability was achieved by nanoparticles-in-microparticles design, with CS/PVA 1:1 and 4:1 groups showing better and comparable protection. Insulin release from the microparticles decreased with the increase of CS ratio in the CS/PVA matrix. Spray-dried microparticles had less influence on the mucus penetration of the in situ redispersed PEC, with enhanced insulin permeation observed in different intestinal segments in a CS/PVA ratio dependent manner. And the CS/PVA 1:1 group, which presented good enzymatic stability, enhanced mucus penetration and moderate insulin release rate, exhibited the highest relative pharmacological availability of 6.80%. In conclusion, PEC in microparticles design using CS/PVA as the composite matrix is a potential platform for enhanced oral insulin delivery.

Biosensing, Characterization of Biosensors, and Improved Drug Delivery Approaches Using Atomic Force Microscopy: A Review

Since its invention, atomic force microscopy (AFM) has come forth as a powerful member of the “scanning probe microscopy” (SPM) family and an unparallel platform for high-resolution imaging and characterization for inorganic and organic samples, especially biomolecules, biosensors, proteins, DNA, and live cells. AFM characterizes any sample by measuring interaction force between the AFM cantilever tip (the probe) and the sample surface, and it is advantageous over other SPM and electron micron microscopy techniques as it can visualize and characterize samples in liquid, ambient air, and vacuum. Therefore, it permits visualization of three-dimensional surface profiles of biological specimens in the near-physiological environment without sacrificing their native structures and functions and without using laborious sample preparation protocols such as freeze-drying, staining, metal coating, staining, or labeling. Biosensors are devices comprising a biological or biologically extracted material (assimilated in a physicochemical transducer) that are utilized to yield electronic signal proportional to the specific analyte concentration. These devices utilize particular biochemical reactions moderated by isolated tissues, enzymes, organelles, and immune system for detecting chemical compounds via thermal, optical, or electrical signals. Other than performing high-resolution imaging and nanomechanical characterization (e.g., determining Young’s modulus, adhesion, and deformation) of biosensors, AFM cantilever (with a ligand functionalized tip) can be transformed into a biosensor (microcantilever-based biosensors) to probe interactions with a particular receptors of choice on live cells at a single-molecule level (using AFM-based single-molecule force spectroscopy techniques) and determine interaction forces and binding kinetics of ligand receptor interactions. Targeted drug delivery systems or vehicles composed of nanoparticles are crucial in novel therapeutics. These systems leverage the idea of targeted delivery of the drug to the desired locations to reduce side effects. AFM is becoming an extremely useful tool in figuring out the topographical and nanomechanical properties of these nanoparticles and other drug delivery carriers. AFM also helps determine binding probabilities and interaction forces of these drug delivery carriers with the targeted receptors and choose the better agent for drug delivery vehicle by introducing competitive binding. In this review, we summarize contributions made by us and other researchers so far that showcase AFM as biosensors, to characterize other sensors, to improve drug delivery approaches, and to discuss future possibilities.

Synthesis and Validation of a Bioinspired Catechol-Functionalized Pt(IV) Prodrug for Preclinical Intranasal Glioblastoma Treatment

Simple Summary

Glioblastoma (GB) is a type of brain cancer with a poor prognosis and few improvements in its treatment. One of the greatest difficulties in GB therapy lies in the fact that most of the drugs with high anticancer potential do not reach the brain and exert high therapeutic activity while minimizing side effects. To overcome these limitations, we focused on a catechol-based Pt(IV) prodrug (able to reverse cisplatin in a cellular environment) with the intention of repurposing Pt-based drugs as GB chemotherapeutic agents. Our in vitro results have corroborated the therapeutic effect of the synthesized complexes as comparable to cisplatin, and in vivo studies have demonstrated the potential of nose-to-brain delivery of this Pt(IV) prodrug for GB treatment.

Abstract

Glioblastoma is the most malignant and frequently occurring type of brain tumors in adults. Its treatment has been greatly hampered by the difficulty to achieve effective therapeutic concentration in the tumor sites due to its location and the blood–brain barrier. Intranasal administration has emerged as an alternative for drug delivery into the brain though mucopenetration, and rapid mucociliary clearance still remains an issue to be solved before its implementation. To address these issues, based on the intriguing properties of proteins secreted by mussels, polyphenol and catechol functionalization has already been used to promote mucopenetration, intranasal delivery and transport across the blood–brain barrier. Thus, herein we report the synthesis and study of complex 1, a Pt(IV) prodrug functionalized with catecholic moieties. This complex considerably augmented solubility in contrast to cisplatin and showed a comparable cytotoxic effect on cisplatin in HeLa, 1Br3G and GL261 cells. Furthermore, preclinical in vivo therapy using the intranasal administration route suggested that it can reach the brain and inhibit the growth of orthotopic GL261 glioblastoma. These results open new opportunities for catechol-bearing anticancer prodrugs in the treatment for brain tumors via intranasal administration.

Impact of nanomaterials on the intestinal mucosal barrier and its application in treating intestinal diseases

The intestinal mucosal barrier (IMB) is one of the important barriers to prevent harmful substances and pathogens from entering the body environment and to maintain intestinal homeostasis. The dysfunction of the IMB is associated with intestinal diseases and disorders. Nanomaterials have been widely used in medicine and as drug carriers due to their large specific surface area, strong adsorbability, and good biocompatibility. In this review, we comprehensively discuss the impact of typical nanomaterials on the IMB and summarize the treatment of intestinal diseases by using nanomaterials. The effects of nanomaterials on the IMB are mainly influenced by factors such as the dosage, size, morphology, and surface functional groups of nanomaterials. There is huge potential and a broad prospect for the application of nanomaterials in regulating the IMB for achieving an optimal therapeutic effect for antibiotics, oral vaccines, drug carriers, and so on.

Mucoadhesive versus mucopenetrating nanoparticles for oral delivery of insulin

Mucoadhesive and mucopenetrating nanoparticles are commonly designed to improve mucosal drug delivery efficiency. Herein, in order to better understand the contribution of mucoadhesion and mucopenetration in oral delivery of biomacromolecules, insulin-loaded poly (n-butylcyanoacrylate) nanoparticles (Ins/PBCA NPs) with different coating layers, chitosan (CS) or alginate (Alg), were designed and their different absorption enhancing mechanisms were explored. It was demonstrated that both the mucoadhesive (Ins/PBCA/CS) and the mucopenetrating (Ins/PBCA/CS/Alg) nanoparticles showed good stability and similar release profiles in the gastrointestinal fluid, the mucoadhesive nanoparticles presented an enrichment in mucus (70%, 10 min) while most of the mucopenetrating nanoparticles penetrated through the mucus (80%, 10 min). Uptake mechanism studies revealed clathrin- and caveolae-mediated endocytosis were mainly involved in the intestinal transport of mucoadhesive nanoparticles while caveolae-mediated endocytosis and macropinocytosis contributed to the absorption of mucopenetrating nanoparticles, and especially, M cells favored the absorption of mucoadhesive nanoparticles. In vivo studies revealed that the mucopenetrating nanoparticles had a fast onset of action while the mucoadhesive nanoparticles presented a sustained hypoglycemic effect in diabetic rats, and overall no significant difference in pharmacological availability was found between the mucopenetrating (8.80%) and mucoadhesive nanoparticles (8.44%). To sum up, due to the varied absorption mechanism in intestine, the mucoadhesive nanoparticles designed herein had a comparable effect in enhancing oral insulin absorption compared with the mucopenetrating nanoparticles. STATEMENT OF SIGNIFICANCE: In order to improve oral delivery efficiency of insulin, insulin-loaded nanoparticles with opposite properties namely mucoadhesion and mucopenetration have been widely developed to either prolong their residence at the absorption site or improve their penetration across mucus. However, their individual contribution in oral insulin absorption is still unclear. In this paper, insulin-loaded poly (n-butylcyanoacrylate) nanoparticles with both properties were designed via different surface coating and their absorption enhancing mechanisms were explored. It was demonstrated that the mucoadhesive and mucopenetrating nanoparticles showed varied retention and mucus-penetration ability in mucus, with different absorption mechanism in intestine, but no statistical difference in pharmacological availability was found between them. Overall, the present work provides us a guidance for the design of oral nano-delivery system.

Purified mucins in drug delivery research

One of the main challenges in the field of drug delivery remains the development of strategies to efficiently transport pharmaceuticals across mucus barriers, which regulate the passage and retention of molecules and particles in all luminal spaces of the body. A thorough understanding of the molecular mechanisms, which govern such selective permeability, is key for achieving efficient translocation of drugs and drug carriers. For this purpose, model systems based on purified mucins can contribute valuable information. In this review, we summarize advances that were made in the field of drug delivery research with such mucin-based model systems: First, we give an overview of mucin purification procedures and discuss the suitability of model systems reconstituted from purified mucins to mimic native mucus. Then, we summarize techniques to study mucin binding. Finally, we highlight approaches that made use of mucins as building blocks for drug delivery platforms or employ mucins as active compounds.

Advancedoral vaccine delivery strategies for improving the immunity

Infectious diseases continue to inflict a high global disease burden. The consensus is that vaccination is the most effective option against infectious diseases. Oral vaccines have unique advantages in the prevention of global pandemics due to their ease of use, high compliance, low cost, and the ability to induce both systemic and mucosal immune responses. However, challenges of adapting vaccines for oral administration remain significant. Foremost among these are enzymatic and pH-dependent degradation of antigens in the stomach and intestines, the low permeability of mucus barrier, the nonspecific uptake of antigens at the intestinal mucosal site, and the immune suppression result from the elusive immune tolerance mechanisms. Innovative delivery techniques promise great potential for improving the flexibility and efficiency of oral vaccines. A better understanding of the delivery approaches and the immunological mechanisms of oral vaccine delivery systems may provide new scientific insight and tools for developing the next-generation oral vaccine. Here, an overview of the advanced technologies in the field of oral vaccination is proposed, including mucus-penetrating nanoparticle (NP), mucoadhesive delivery vehicles, targeting antigen-presenting cell (APC) nanocarriers and enhanced paracellular delivery strategies and so on. Meanwhile, the mechanisms of delivery vectors interact with mucosal barriers are discussed.

Membrane-disruptive peptides/peptidomimetics-based therapeutics: Promising systems to combat bacteria and cancer in the drug-resistant era

Membrane-disruptive peptides/peptidomimetics (MDPs) are antimicrobials or anticarcinogens that present a general killing mechanism through the physical disruption of cell membranes, in contrast to conventional chemotherapeutic drugs, which act on precise targets such as DNA or specific enzymes. Owing to their rapid action, broad-spectrum activity, and mechanisms of action that potentially hinder the development of resistance, MDPs have been increasingly considered as future therapeutics in the drug-resistant era. Recently, growing experimental evidence has demonstrated that MDPs can also be utilized as adjuvants to enhance the therapeutic effects of other agents. In this review, we evaluate the literature around the broad-spectrum antimicrobial properties and anticancer activity of MDPs, and summarize the current development and mechanisms of MDPs alone or in combination with other agents. Notably, this review highlights recent advances in the design of various MDP-based drug delivery systems that can improve the therapeutic effect of MDPs, minimize side effects, and promote the co-delivery of multiple chemotherapeutics, for more efficient antimicrobial and anticancer therapy.

Oral delivery of proteins and peptides: Challenges, status quo and future perspectives

Proteins and peptides (PPs) have gradually become more attractive therapeutic molecules than small molecular drugs due to their high selectivity and efficacy, but fewer side effects. Owing to the poor stability and limited permeability through gastrointestinal (GI) tract and epithelia, the therapeutic PPs are usually administered by parenteral route. Given the big demand for oral administration in clinical use, a variety of researches focused on developing new technologies to overcome GI barriers of PPs, such as enteric coating, enzyme inhibitors, permeation enhancers, nanoparticles, as well as intestinal microdevices. Some new technologies have been developed under clinical trials and even on the market. This review summarizes the history, the physiological barriers and the overcoming approaches, current clinical and preclinical technologies, and future prospects of oral delivery of PPs.

Undigestible Gliadin Peptide Nanoparticles Penetrate Mucus and Reduce Mucus Production Driven by Intestinal Epithelial Cell Damage

Wheat protein is the most consumed plant protein in our diet, and there is an increased prevalence of wheat/gluten intolerance and adherence to a gluten-free diet in many countries. Despite the known immunodominant effect of undigested gliadin peptides responsible for gluten-related intolerance, it remains unclear if and how gliadin peptides self-assemble into ordered nanostructures during gastrointestinal digestion, as well as their biological impact on the mucus barrier function. In this study, we purified undigestible gliadin peptide nanoparticles (UGPNs) by ultracentrifugation and characterized their structural and physiochemical properties. The results demonstrate that the UGPNs are self-assembled nanostructures generated by cationic amino acids (Lys and Arg)-capped surfactant-like peptides (SLPs), mainly derived from γ-gliadin and α-gliadin. SLPs trigger the concentration-dependent self-assembly driven by β-sheet conformational transitions above their critical aggregation concentration (cac, ∼0.1 mg/mL). UGPNs can easily penetrate the mucus layer in Caco-2/HT29-MTX cocultures with a high P_app value (∼5.7 × 10^-6 cm/s) and reduce the production and thickness of the mucus layer driven by intestinal epithelial cell damage. Isothermal titration calorimetry and Langmuir monolayer studies indicate that the self-assembled state of UGPNs significantly affects their binding to DPPC/DOPE lipid membrane models. These results highlight the relevance of the self-assembly of gliadin peptides as a trigger of mucosal inflammation-related wheat/gluten intolerance.

Current strategies for oral delivery of BCS IV drug nanocrystals: challenges, solutions and future trends

INTRODUCTION

Oral absorption of BCS IV drug benefits little from improved dissolution. Therefore, the absorption of BCS IV drug nanocrystals 'as a whole' strategy is preferred, and structural modification of nanocrystals is required. Surface modification helps the nanocrystals maintain particle structure before drug dissolution is needed, thus enhancing the oral absorption of BCS IV drugs and promoting therapeutic effect. Here, the main challenges and solutions of oral BCS IV drug nanocrystals delivery are discussed. Moreover, strategies for nanocrystal surface modification that facilitates oral bioavailability of BCS IV drugs are highlighted, and provide insights for the innovation in oral drug delivery.

AREAS COVERED

Promising size, shape, and surface modification of nanocrystals have gained interests for application in oral BCS IV drugs.

EXPERT OPINION

Nanocrystal surface modification is a feasible method to maintain the structural integrity of nanocrystals, and the introduced materials can also be modified to integrate additional functions to further facilitate the absorption of nanocrystals. It is expected that the absorption 'as a whole' strategy of nanocrystals will provide different choices for the oral BCS IV drugs.

Advances in regulating physicochemical properties of mesoporous silica nanocarriers to overcome biological barriers

Mesoporous silica nanoparticles (MSNs) with remarkable structural features have been proven to be an excellent platform for the delivery of therapeutic molecules. Biological barriers in various forms (e.g., mucosal barrier, cellular barrier, gastrointestinal barrier, blood-brain barrier, and blood-tumor barrier) present substantial obstacles for MSNs. The physicochemical parameters of MSNs are known to be effective and tunable not only for load and release of therapeutic molecules but also for their biological responsiveness that is beneficial for cells and tissues. This review innovatively provides a description of how and why physicochemical properties (e.g., particle size, morphology, surface charge, hydrophilic-hydrophobic property, and surface modification) of MSNs influence their ability to cross the biological barriers prior to reaching targeted sites. First, the structural and physiological features of biological barriers are outlined. Next, the recent progresses in the critical physicochemical parameters of MSNs are highlighted from physicochemical and biological aspects. Surface modification, as an important strategy for achieving rapid transport, is also reviewed with special attention to the latest findings of bioactive groups and molecular mechanisms. Furthermore, advanced designs of multifunction intelligent MSNs to surmount the blood-tumor barrier and to actively target tumor sites are demonstrated in detail. Lastly, the biodegradability and toxicity of MSNs are evaluated. With perspectives for their potential application and biosafety, the clues in summary might lead to drug delivery with high efficiency and provide useful knowledge for rational design of nanomaterials.

Design of folic acid decorated virus-mimicking nanoparticles for enhanced oral insulin delivery

Mucus penetration and intestinal cells targeting are two main strategies to improve insulin oral delivery efficiency. However, few studies are available regarding the effectiveness of combining these two strategies into one nano-delivery system. For this objective, the folic acid (FA) decorated virus-mimicking nanoparticles were designed and influence of FA graft ratio on the in vitro and in vivo properties of insulin loaded nanoparticles was studied systemically. Firstly, using folic acid as active ligand, different folic acid grafted chitosan copolymers (FA-CS) were synthesized and characterized. Thereafter, using insulin-loaded poly(n-butylcyanoacrylate) nanoparticles as the core, virus-mimicking nanoparticles were fabricated by coating of positively charged FA-CS copolymer and negatively charged hyaluronic acid. Irrespective of the FA graft ratio, all the nanoparticles showed good stability, similar insulin release in the gastrointestinal fluid, excellent and similar penetration in mucus. The nanoparticles permeability in intestine was FA graft ratio and segment dependent, with FA graft ratio at/over 12.51% presenting better effect in the order of duodenum > jejunum ≈ ileum. Both mechanism studies and confocal microscopy observation demonstrated FA-mediated process was involved in the transport of FA decorated nanoparticles. In vivo studies revealed hypoglycemic effect of the nanoparticles was FA graft ratio dependent, a saturation phenomenon was observed when FA graft ratio was at/over 12.51%. In conclusion, folic acid decorated virus-mimicking nanoparticles presented improved insulin absorption, implying combining mucus penetration and active transcellular transport is an effective way to promote oral insulin absorption, while the modification ratio of active ligand needs optimization.

Antibacterial self-assembled nanodrugs composed of berberine derivatives and rhamnolipids against Helicobacter pylori

The prevalence of infections with Helicobacter pylori (H. pylori) has progressively increased worldwide, which demonstrated to be closely correlated to its biofilm formation. H. pylori biofilms protect the bacteria by significantly decreasing their sensitivity to antibiotics. Moreover, H. pylori colonizes on the gastrointestinal tract epithelium which is covered by mucus layer, acting as another barrier to prevent antibacterial agents from reaching the colonization sites. Herein, we prepared four types of versatile self-assembled nanodrugs (BD/RHL NDs) containing lipophilic alkyl berberine derivatives (BDs) and rhamnolipids (RHL) to overcome the dual obstructions of both mucus layer and biofilms. Molecular dynamics simulations estimated that the driving forces for self-assembly of BD/RHL NDs were electrostatic and hydrophobic interactions. BD/RHL NDs, characterized by appropriate size, negative charge and enhanced hydrophilicity, successfully penetrated through mucus layer without interacting with mucins. In in vitro experiments, BD/RHL NDs exhibited substantial ability to eradicate H. pylori biofilms by destroying their extracellular polymeric substances (EPS) and killing planktonic H. pylori. Furthermore, BD/RHL NDs inhibited the adherence of H. pylori on both biotic and abiotic surfaces, therefore cut off the critical step of the biofilm re-formation which was associated with the recrudescence of infections. In an H. pylori-infected mice model, C10-BD/RHL NDs group showed 40 folds less remnant H. pylori and greater mucosal protection compared with the conventional clinical triple therapy. In conclusion, BD/RHL NDs could penetrate through mucus layer and effectively eradicate H. pylori biofilms in vitro and in vivo, providing a novel strategy for clinical treatment of biofilm-related infections.

Overcoming negatively charged tissue barriers: Drug delivery using cationic peptides and proteins

Negatively charged tissues are ubiquitous in the human body and are associated with a number of common diseases yet remain an outstanding challenge for targeted drug delivery. While the anionic proteoglycans are critical for tissue structure and function, they make tissue matrix dense, conferring a high negative fixed charge density (FCD) that makes drug penetration through the tissue deep zones and drug delivery to resident cells extremely challenging. The high negative FCD of these tissues is now being utilized by taking advantage of electrostatic interactions to create positively charged multi-stage delivery methods that can sequentially penetrate through the full thickness of tissues, create a drug depot and target cells. After decades of work on attempting delivery using strong binding interactions, significant advances have recently been made using weak and reversible electrostatic interactions, a characteristic now considered essential to drug penetration and retention in negatively charged tissues. Here we discuss these advances using examples of negatively charged tissues (cartilage, meniscus, tendons and ligaments, nucleus pulposus, vitreous of eye, mucin, skin), and delve into how each of their structures, tissue matrix compositions and high negative FCDs create barriers to drug entry and explore how charge interactions are being used to overcome these barriers. We review work on tissue targeting cationic peptide and protein-based drug delivery, compare and contrast drug delivery designs, and also present examples of technologies that are entering clinical trials. We also present strategies on further enhancing drug retention within diseased tissues of lower FCD by using synergistic effects of short-range binding interactions like hydrophobic and H-bonds that stabilize long-range charge interactions. As electrostatic interactions are incorporated into design of drug delivery materials and used as a strategy to create properties that are reversible, tunable and dynamic, bio-electroceuticals are becoming an exciting new direction of research and clinical work.

Design and Investigation of Penetrating Mechanism of Octaarginine-Modified Alginate Nanoparticles for Improving Intestinal Insulin Delivery

The aim of the study is to design octaarginine (R8)-modified insulin-alginate nanoparticles (INS-SA/R8 NPs) as the oral insulin delivery system, and further investigate its penetrating mechanism. The characterization results indicated that the surface of INS-SA/R8 NPs was smooth and the average diameter was about 300 nm. INS-SA/R8 NPs exhibited a stronger stability in the simulated gastrointestinal fluids and had a better controlled release than unmodified alginate nanoparticles (INS-SA NPs). Moreover, INS-SA/R8 NPs group had the strongest insulin transport capacity and the largest amount of insulin uptake in all experimental groups. Most importantly, the improvement of insulin intestinal uptake was further confirmed in rat intestine in vivo, and its penetrating mechanism might be involved in the production of endogenous nitric oxide (NO) signal molecule. In addition, in vivo hypoglycemic studies showed that orally administrated INS-SA/R8 NPs produced a better hypoglycemic effect as compared with INS-SA NPs in diabetic rats. Meanwhile, from the cytotoxicity analysis, INS-SA/R8 NPs were safe for oral administration. Taken together, INS-SA/R8 NPs was a good oral insulin delivery system, which might also be suitable for other protein drugs.

Chitosan and its Derivatives for Ocular Delivery Formulations: Recent Advances and Developments

Chitosan (CS) is a hemi-synthetic cationic linear polysaccharide produced by the deacetylation of chitin. CS is non-toxic, highly biocompatible, and biodegradable, and it has a low immunogenicity. Additionally, CS has inherent antibacterial properties and a mucoadhesive character and can disrupt epithelial tight junctions, thus acting as a permeability enhancer. As such, CS and its derivatives are well-suited for the challenging field of ocular drug delivery. In the present review article, we will discuss the properties of CS that contribute to its successful application in ocular delivery before reviewing the latest advances in the use of CS for the development of novel ophthalmic delivery systems. Colloidal nanocarriers (nanoparticles, micelles, liposomes) will be presented, followed by CS gels and lenses and ocular inserts. Finally, instances of CS coatings, aiming at conferring mucoadhesiveness to other matrixes, will be presented.

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.

Flash Fabrication of Orally Targeted Nanocomplexes for Improved Transport of Salmon Calcitonin across the Intestine

Salmon calcitonin (sCT) is a potent calcium-regulating peptide hormone and widely applied for the treatment of some bone diseases clinically. However, the therapeutic usefulness of sCT is hindered by the frequent injection required, owing to its short plasma half-life and therapeutic need for a high dose. Oral delivery is a popular modality of administration for patients because of its convenience to self-administration and high patient compliance, while orally administered sCT remains a great challenge currently due to the existence of multiple barriers in the gastrointestinal (GI) tract. Here, we introduced an orally targeted delivery system to increase the transport of sCT across the intestine through both the paracellular permeation route and the bile acid pathway. In this system, sCT-based glycol chitosan-taurocholic acid conjugate (GC-T)/dextran sulfate (DS) ternary nanocomplexes (NC-T) were produced by a flash nanocomplexation (FNC) process in a kinetically controlled mode. The optimized NC-T exhibited well-controlled properties with a uniform and sub-60 nm hydrodynamic diameter, high batch-to-batch reproducibility, good physical or chemical stability, as well as sustained drug release behaviors. The studies revealed that NC-T could effectively improve the intestinal uptake and permeability, owing to its surface functionalization with the taurocholic acid ligand. In the rat model, orally administered NC-T showed an obvious hypocalcemia effect and a relative oral bioavailability of 10.9%. An in vivo assay also demonstrated that NC-T induced no observable side effect after long-term oral administration. As a result, the orally targeted nanocomplex might be a promising candidate for improving the oral transport of therapeutic peptides.

Thermal protection and pH-gated release of folic acid in microparticles and nanoparticles for food fortification

Dispersed folic acid was successfully encapsulated in alginate–pectin hydrogels, proliposomes, and combinations thereof, providing an efficient pH-responsive delivery system.

Multifunctional oral delivery systems for enhanced bioavailability of therapeutic peptides/proteins

In last few years, therapeutic peptides/proteins are rapidly growing in drug market considering their higher efficiency and lower toxicity than chemical drugs. However, the administration of therapeutic peptides/proteins is mainly limited in parenteral approach. Oral therapy which was hampered by harsh gastrointestinal environment and poorly penetrating epithelial barriers often results in low bioavailability (less than 1%-2%). Therefore, delivery systems that are rationally designed to overcome these challenges in gastrointestinal tract and ameliorate the oral bioavailability of therapeutic peptides/proteins are seriously promising. In this review, we summarized various multifunctional delivery systems, including lipid-based particles, polysaccharide-based particles, inorganic particles, and synthetic multifunctional particles that achieved effective oral delivery of therapeutic peptides/proteins.

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.