Bioinspired butyrate-functionalized nanovehicles for targeted oral delivery of biomacromolecular drugs

Transepithelial transport of nanoparticles in oral drug delivery: From the perspective of surface and holistic property modulation

Despite the promising prospects of nanoparticles in oral drug delivery, the process of oral administration involves a complex transportation pathway that includes cellular uptake, intracellular trafficking, and exocytosis by intestinal epithelial cells, which are necessary steps for nanoparticles to enter the bloodstream and exert therapeutic effects. Current researchers have identified several crucial factors that regulate the interaction between nanoparticles and intestinal epithelial cells, including surface properties such as ligand modification, surface charge, hydrophilicity/hydrophobicity, intestinal protein corona formation, as well as holistic properties like particle size, shape, and rigidity. Understanding these properties is essential for enhancing transepithelial transport efficiency and designing effective oral drug delivery systems. Therefore, this review provides a comprehensive overview of the surface and holistic properties that influence the transepithelial transport of nanoparticles, elucidating the underlying principles governing their impact on transepithelial transport. The review also outlines the chosen of parameters to be considered for the subsequent design of oral drug delivery systems.

Geniposide dosage and administration time: Balancing therapeutic benefits and adverse reactions in liver disease treatment

Gardenia jasminoides Ellis, a staple in herbal medicine, has long been esteemed for its purported hepatoprotective properties. Its primary bioactive constituent, geniposide, has attracted considerable scientific interest owing to its multifaceted therapeutic benefits across various health conditions. However, recent investigations have unveiled potential adverse effects associated with its metabolite, genipin, particularly at higher doses and prolonged durations of administration, leading to hepatic injury. Determining the optimal dosage and duration of geniposide administration while elucidating its pharmacological and toxicological mechanisms is imperative for safe and effective clinical application. This study aimed to evaluate the safe dosage and administration duration of geniposide in mice and investigate its toxicological mechanisms within a comprehensive dosage-duration-efficacy/toxicity model. Four distinct mouse models were employed, including wild-type mice, cholestasis-induced mice, globally farnesoid X-activated receptor (FXR) knock out mice, and high-fat diet-induced (HFD) NAFLD mice. Various administration protocols, spanning one or four weeks and comprising two or three oral doses, were tailored to each model's requirements. Geniposide has positive effects on bile acid and lipid metabolism at doses below 220 mg/kg/day without causing liver injury in normal mice. However, in mice with NAFLD, this dosage is less effective in improving liver function, lipid profiles, and bile acid metabolism compared to lower doses. In cholestasis-induced mice, prolonged use of geniposide at 220 mg/kg/day worsened liver damage. Additionally, in NAFLD mice, this dosage of geniposide for four weeks led to intestinal pyroptosis and liver inflammation. These results highlight the lipid-lowering and bile acid regulatory effects of geniposide, but also warn of potential negative impacts on intestinal epithelial cells, particularly with higher doses and longer treatment durations. Therefore, achieving optimal therapeutic results requires a decrease in treatment duration as the dosage increases, in order to maintain a balanced approach to the use of geniposide in clinical settings.

Biological activity, limitations and steady-state delivery of functional substances for precision nutrition

Food-related functional substances with biological activity serve as a crucial material foundation for achieving precision nutrition, which has gained increasing attraction in regulating physiological functions, preventing chronic diseases, and maintaining human health. Nutritional substances typically include bioactive proteins, peptides, polysaccharides, polyphenols, functional lipids, carotenoids, probiotics, vitamins, saponins, and terpenes. These functional substances play an essential role in precise nutrition. This chapter introduces and summarizes typical functional substances to demonstrate the challenges in precision nutrition for their stability, solubility, and bioavailability. The current status of delivery systems of functional substances is described to give an insight into the development of desirable characteristics, such as food grade status, high loading capacity, site targeting, and controlled release capacity. Finally, the applications of food-borne delivery systems of functional substances for precision nutrition are emphasized to meet the requirement for precision nutrition during nutritional intervention for chronic diseases.

Beyond nanoparticle-based oral drug delivery: transporter-mediated absorption and disease targeting

Various strategies at the microscale/nanoscale have been developed to improve oral absorption of therapeutics. Among them, gastrointestinal (GI)-transporter/receptor-mediated nanosized drug delivery systems (NDDSs) have drawn attention due to their many benefits, such as improved water solubility, improved chemical/physical stability, improved oral absorption, and improved targetability of their payloads. Their therapeutic potential in disease animal models (e.g., solid tumors, virus-infected lungs, metastasis, diabetes, and so on) has been investigated, and could be expanded to disease targeting after systemic/lymphatic circulation, although the detailed paths and mechanisms of endocytosis, endosomal escape, intracellular trafficking, and exocytosis through the epithelial cell lining in the GI tract are still unclear. Thus, this review summarizes and discusses potential GI transporters/receptors, their absorption and distribution, in vivo studies, and potential sequential targeting (e.g., oral absorption and disease targeting in organs/tissues).

Enhanced oral and pulmonary delivery of biomacromolecules via amplified transporter targeting

Ligand-modified nanocarriers can promote oral or inhalative administration of macromolecular drugs across the intestinal or pulmonary mucosa. However, enhancing the unidirectional transport of the nanocarriers through "apical uptake→intracellular transport→basolateral exocytosis" route remains a hot topic and challenge in current research. Forskolin is a naturally occurring diterpenoid compound extracted from the roots of C. forskohlii. In our studies, we found that forskolin could increase the transcellular transport of butyrate-modified nanoparticles by 1.67-fold and 1.20-fold in Caco-2 intestinal epithelial cell models and Calu-3 lung epithelial cell models, respectively. Further mechanistic studies revealed that forskolin, on the one hand, promoted the cellular uptake of butyrate-modified nanoparticles by upregulating the expression of monocarboxylic acid transporter-1 (MCT-1) on the apical membrane. On the other hand, forskolin facilitated the binding of MCT-1 to caveolae, thereby mediating butyrate-modified nanoparticles hijacking caveolae to promote the basolateral exocytosis of butyrate-modified nanoparticles. Studies in normal mice model showed that forskolin could promote the transmucosal absorption of butyrate-modified nanoparticles by >2-fold, regardless of oral or inhalative administration. Using semaglutide as the model drug, both oral and inhalation delivery approaches demonstrated significant hypoglycemic effects in type 2 diabetes mice model, in which inhalative administration was more effective than oral administration. This study optimized the strategies aimed at enhancing the transmucosal absorption of ligand-modified nanocarriers in the intestinal or pulmonary mucosa.

Lipoic acid-mediated oral drug delivery system utilizing changes on cell surface thiol expression for the treatment of diabetes and inflammatory diseases

Lipoic acid (LA), which has good safety and oral absorption, is obtained from various plant-based food sources and needs to be supplemented through human diet. Moreover, substances with a disulfide structure can enter cells through dynamic covalent disulfide exchange with thiol groups on the cell membrane surface. Based on these factors, we constructed LA-modified nanoparticles (LA NPs). Our results showed that LA NPs can be internalized into intestinal epithelial cells through surface thiols, followed by intracellular transcytosis via the endoplasmic reticulum-Golgi pathway. Further mechanistic studies indicated that disulfide bonds within the structure of LA play a critical role in this transport process. In a type I diabetes rat model, the oral administration of insulin-loaded LA NPs exhibited a more potent hypoglycemic effect, with a pharmacokinetic bioavailability of 5.42 ± 0.53%, representing a 1.6 fold enhancement compared to unmodified PEG NPs. Furthermore, a significant upregulation of surface thiols in inflammatory macrophages was reported. Thus, we turned our direction to investigate the uptake behavior of inflammatory macrophages with increased surface thiols towards LA NPs. Inflammatory macrophages showed a 2.6 fold increased uptake of LA NPs compared to non-inflammatory macrophages. Surprisingly, we also discovered that the antioxidant resveratrol facilitates the uptake of LA NPs in a concentration-dependent manner. This is mainly attributed to an increase in glutathione, which is involved in thiol uptake. Consequently, we employed LA NPs loaded with resveratrol for the treatment of colitis and observed a significant alleviation of colitis symptoms. These results suggest that leveraging the variations of thiol expression levels on cell surfaces under both healthy and diseased states through an oral drug delivery system mediated by the small-molecule nutrient LA can be employed for the treatment of diabetes and certain inflammatory diseases.

The Current and Promising Oral Delivery Methods for Protein- and Peptide-Based Drugs

Drugs based on peptides and proteins (PPs) have been widely used in medicine, beginning with insulin therapy in patients with diabetes mellitus over a century ago. Although the oral route of drug administration is the preferred one by the vast majority of patients and improves compliance, medications of this kind due to their specific chemical structure are typically delivered parenterally, which ensures optimal bioavailability. In order to overcome issues connected with oral absorption of PPs such as their instability depending on digestive enzymes and pH changes in the gastrointestinal (GI) system on the one hand, but also their limited permeability across physiological barriers (mucus and epithelium) on the other hand, scientists have been strenuously searching for novel delivery methods enabling peptide and protein drugs (PPDs) to be administered enterally. These include utilization of different nanoparticles, transport channels, substances enhancing permeation, chemical modifications, hydrogels, microneedles, microemulsion, proteolytic enzyme inhibitors, and cell-penetrating peptides, all of which are extensively discussed in this review. Furthermore, this article highlights oral PP therapeutics both previously used in therapy and currently available on the medical market.

Butyrate Modification Promotes Intestinal Absorption and Hepatic Cancer Cells Targeting of Ferroptosis Inducer Loaded Nanoparticle for Enhanced Hepatocellular Carcinoma Therapy

Sorafenib is an oral-administered first-line drug for hepatocellular carcinoma (HCC) treatment. However, the therapeutic efficacy of sorafenib is relatively low. Here, an oral delivery platform that increases sorafenib uptake by HCC and induces potent ferroptosis is designed. This platform is butyrate-modified nanoparticles separately encapsulated with sorafenib and salinomycin. The multifunctional ligand butyrate interacts with monocarboxylate transporter 1 (MCT-1) to facilitate transcytosis. Specifically, MCT-1 is differentially expressed on the apical and basolateral sides of the intestine, highly expressed on the surface of HCC cells but lowly expressed on normal hepatocytes. After oral administration, this platform is revealed to boost transepithelial transport effectively and continuously in the intestine, drug accumulation in the liver, and HCC cell uptake. Following drug release in cancer cells, sorafenib depletes glutathione peroxidase 4 and glutathione, consequently initiating ferroptosis. Meanwhile, salinomycin enhances intracellular iron and lipid peroxidation, thereby accelerating ferroptosis. In vivo experiments performed on the orthotopic HCC model demonstrate that this combination strategy induces pronounced ferroptosis damage and ignites a robust systemic immune response, leading to the effective elimination of tumors and establishment of systemic immune memory. This work provides a proof-of-concept demonstration that an oral delivery strategy for ferroptosis inducers may be beneficial for HCC treatment.

A multifunctional integrated biomimetic spore nanoplatform for successively overcoming oral biological barriers

The biological barriers have seriously restricted the efficacious responses of oral delivery system in diseases treatment. Utilizing a carrier based on the single construction means is hard to overcome these obstacles simultaneously because the complex gastrointestinal tract environment requires carrier to have different or even contradictory properties. Interestingly, spore capsid (SC) integrates many unique biological characteristics, such as high resistance, good stability etc. This fact offers a boundless source of inspiration for the construction of multi-functional oral nanoplatform based on SC without further modification. Herein, we develop a type of biomimetic spore nanoplatform (SC@DS NPs) to successively overcome oral biological barriers. Firstly, doxorubicin (DOX) and sorafenib (SOR) are self-assembled to form carrier-free nanoparticles (DS NPs). Subsequently, SC is effectively separated from probiotic spores and served as a functional vehicle for delivering DS NPs. As expect, SC@DS NPs can efficaciously pass through the rugged stomach environment after oral administration and further be transported to the intestine. Surprisingly, we find that SC@DS NPs exhibit a significant improvement in the aspects of mucus penetration and transepithelial transport, which is related to the protein species of SC. This study demonstrates that SC@DS NPs can efficiently overcome multiple biological barriers and improve the therapeutic effect.

Modulation of Autophagy Direction to Enhance Antitumor Effect of Endoplasmic-Reticulum-Targeted Therapy: Left or Right?

Strategies that induce dysfunction in the endoplasmic reticulum (ER) hold great promise for anticancer therapy, but remain unsatisfactory due to the compensatory autophagy induction after ER disruption. Moreover, as autophagy can either promote or suppress cell survival, which direction of autophagy better suits ER-targeting therapy remains controversial. Here, a targeted nanosystem is constructed, which efficiently escorts anticancer therapeutics into the ER, triggering substantial ER stress and autophagy. Concurrently, an autophagy enhancer or inhibitor is combined into the same nanoparticle, and their impacts on ER-related activities are compared. In the orthotopic breast cancer mouse model, the autophagy enhancer increases the antimetastasis effect of ER-targeting therapy and suppresses over 90% of cancer metastasis, while the autophagy inhibitor has a bare effect. Mechanism studies reveal that further enhancing autophagy accelerates central protein snail family transcriptional repressor 1 (SNAI1) degradation, suppressing downstream epithelial-mesenchymal transition, while inhibiting autophagy does the opposite. With the same trend, ER-targeting therapy combined with an autophagy enhancer provokes stronger immune response and tumor inhibition than the autophagy inhibitor. Mechanism studies reveal that the autophagy enhancer elevates Ca2+ release from the ER and functions as a cascade amplifier of ER dysfunction, which accelerates Ca2+ release, resulting in immunogenic cell death (ICD) induction and eventually triggering immune responses. Together, ER-targeting therapy benefits from the autophagy-enhancing strategy more than the autophagy-inhibiting strategy for antitumor and antimetastasis treatment.

Progress and prospects of polysaccharide-based nanocarriers for oral delivery of proteins/peptides

The oral route has long been recognized as the most preferred route for drug delivery as it offers high patient compliance and requires minimal expertise. Unlike small molecule drugs, the harsh environment of the gastrointestinal tract and low permeability across the intestinal epithelium make oral delivery extremely ineffective for macromolecules. Accordingly, delivery systems that are rationally constructed with suitable materials to overcome barriers to oral delivery are exceptionally promising. Among the most ideal materials are polysaccharides. Depending on the interaction between polysaccharides and proteins, the thermodynamic loading and release of proteins in the aqueous phase can be realized. Specific polysaccharides (dextran, chitosan, alginate, cellulose, etc.) endow systems with functional properties, including muco-adhesiveness, pH-responsiveness, and prevention of enzymatic degradation. Furthermore, multiple groups in polysaccharides can be modified, which gives them a variety of properties and enables them to suit specific needs. This review provides an overview of different types of polysaccharide-based nanocarriers based on different kinds of interaction forces and the influencing factors in the construction of polysaccharide-based nanocarriers. Strategies of polysaccharide-based nanocarriers to improve the bioavailability of orally administered proteins/peptides were described. Additionally, current restrictions and future trends of polysaccharide-based nanocarriers for oral delivery of proteins/peptides were also covered.

A nano-delivery system based on preventing degradation and promoting absorption to improve the oral bioavailability of insulin

Oral insulin delivery can improve patient compliance and simulate the portal-peripheral insulin concentration gradient produced by endogenous insulin, so oral insulin delivery has a broad prospect. However, some characteristics of the gastrointestinal tract, lead to low oral bioavailability. Therefore, a "ternary mutual-assist" nano-delivery system based on poly(lactide-co-glycolide) (PLGA) as the backbone combined with ionic liquids (IL) and vitamin B12-chitosan (VB12-CS) was constructed in this study, the protein protection performance of IL improves the room temperature stability of the loaded insulin during nanocarrier preparation, transportation and storage to a certain extent, and the protein protection function of IL combined with the slow degradation property of PLGA and the pH-responsive function of VB12-CS to prevent the degradation of insulin in the gastrointestinal tract. In addition, the mucosal adhesion function of VB12-CS, VB12 receptor- and clathrin-mediated transcellular transport involving VB12-CS and IL, and paracellular transport mediated by IL and CS can be combined to improve the intestinal epithelial transport efficiency of insulin, thus, the nanocarrier has stronger preventing degradation and promoting absorption effects. Pharmacodynamic studies showed that after oral administration of VB12-CS-PLGA@IL@INS NPs to diabetic mice, the blood glucose level decreased to about 13 mmol/L, below the critical point of 16.7 mmol/L, and the blood glucose reached a normal level, which was 0.4 times of the blood glucose value before administration, its relative pharmacological bioavailability was 31.8 %, higher than the general nanocarriers (10-20 %) and more beneficial to the clinical transformation of oral insulin.

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.

Transporter-Mediated Drug Delivery

Transmembrane transport of small organic and inorganic molecules is one of the cornerstones of cellular metabolism. Among transmembrane transporters, solute carrier (SLC) proteins form the largest, albeit very diverse, superfamily with over 400 members. It was recognized early on that xenobiotics can directly interact with SLCs and that this interaction can fundamentally determine their efficacy, including bioavailability and intertissue distribution. Apart from the well-established prodrug strategy, the chemical ligation of transporter substrates to nanoparticles of various chemical compositions has recently been used as a means to enhance their targeting and absorption. In this review, we summarize efforts in drug design exploiting interactions with specific SLC transporters to optimize their therapeutic effects. Furthermore, we describe current and future challenges as well as new directions for the advanced development of therapeutics that target SLC transporters.

Association of body mass index and intestinal (faecal) Streptococcus in adults in Xining city, China P.R

Body mass index (BMI) and gut microbiota show significant interaction, but most studies on the relationship between BMI and gut microbiota have been done in Western countries. Relationships that are also identified in other cultural backgrounds are likely to have functional importance. Hence here we explore gut microbiota in adults living in Xining city (China P.R.) and relate results to subject BMI. Analysis of bacterial 16s rRNA gene was performed on faecal samples from participants with normal-weight (n=24), overweight (n=24), obesity (n=11) and type 2 diabetes (T2D) (n=8). The results show that unweighted but not weighted Unifrac distance was significantly different when gut microbiota composition was compared between the groups. Importantly, the genus Streptococcus was remarkably decreased in both obese subjects and subjects suffering from T2D, as compared to normal-weight subjects. Accordingly, strong association was identified between the genus Streptococcus and BMI and especially Streptococcus salivarius subsp. thermophiles was a major contributor in this respect. As previous studies have shown that Streptococcus salivarius subsp. thermophiles is also negatively associated with obesity in Western cohorts, our results suggest that this species is a potential probiotic for the prevention of obesity and related disorders.

Glucose-Modified Zein Nanoparticles Enhance Oral Delivery of Docetaxel

Based on glucose (G) transporters (GLUTs), structuring nanoparticles with G as a target are an effective strategy to enhance oral bioavailability and anti-tumor effects of drugs. A novel drug delivery system using G-modified zein (GZ) nanoparticles loaded with docetaxel (DTX) (DTX-GNPs) was prepared and characterized in vitro and in vivo via assessment of cellular uptake, absorption site, pharmacokinetics, ex vivo distribution, and anti-tumor effects. The DTX-GNPs were approximately 120 nm in size. Compared with DTX-NPs, G modification significantly enhanced cellular uptake of DTX-GNPs by 1.22 times in CaCo-2 cells, which was related to GLUT mediation and the enhancement of endocytosis pathways via clathrin, micropinocytosis, and caveolin. Compared to DTX-NPs, G modification significantly enhanced DTX-NP absorption in the jejunum and ileum, delayed plasma concentration peak time, prolonged the average residence time in vivo, and increased oral bioavailability (from 43.82% to 96.04%). Cellular uptake and oral bioavailability of DTX were significantly affected by the G modification ratio. Compared with DTX-NPs, G modification significantly reduced drug distribution in the liver, lungs, and kidneys and increased tumor distribution and tumor growth inhibition rate without obvious systemic toxicity. This study demonstrated the potential of GZ-NPs as nanocarriers for DTX to enhance oral bioavailability and anti-tumor effects.

Split bullets loaded nanoparticles for amplified immunotherapy

Dendritic cells (DCs) play central role in adaptive antitumor immunity, while their function is often hampered by low immunogenicity of tumor tissues and surrounding hostile microenvironment. Herein, a "split bullets" loaded nanoplatform that can bidirectionally injure mitochondria (MT) and endoplasmic reticulum (ER) of tumor cells is developed. After cellular uptake, the released "split bullets" separately target to different subcellular destinations and exert distinct effects on DCs: (1) MT-targeted "bullet" recruits peripheral DCs into tumor sites, due to its capability to trigger adenosine triphosphate release from tumor cells; (2) ER-targeted "bullet" activates tumor-infiltrating DCs, which is attributed to its ability to evoke calreticulin exposure on tumor cells. These effects collectively improve the tropism and reactivity of DCs to tumor-specific antigen in a two-pronged way. As a result of enhanced function of DCs in antigen capture, treatment of the "split bullets" loaded nanoplatform ignites robust immune response to suppress primary melanoma, and establishes systemic immune memory against post-surgical tumor recurrence. Overall, this nanoplatform offers a generalizable approach to boost DCs and augment immunotherapy.

Advances in oral peptide drug nanoparticles for diabetes mellitus treatment

Peptide drugs play an important role in diabetes mellitus treatment. Oral administration of peptide drugs is a promising strategy for diabetes mellitus because of its convenience and high patient compliance compared to parenteral administration routes. However, there are a series of formidable unfavorable conditions present in the gastrointestinal (GI) tract after oral administration, which result in the low oral bioavailability of these peptide drugs. To overcome these challenges, various nanoparticles (NPs) have been developed to improve the oral absorption of peptide drugs due to their unique in vivo properties and high design flexibility. This review discusses the unfavorable conditions present in the GI tract and provides the corresponding strategies to overcome these challenges. The review provides a comprehensive overview on the NPs that have been constructed for oral peptide drug delivery in diabetes mellitus treatment. Finally, we will discuss the rational application and give some suggestions that can be utilized for the development of oral peptide drug NPs. Our aim is to provide a systemic and comprehensive review of oral peptide drug NPs that can overcome the challenges in GI tract for efficient treatment of diabetes mellitus.

•Oral administration of peptide drugs is a promising strategy for diabetes mellitus treatment

•A series of formidable unfavorable conditions in gastrointestinal tract result in the low oral bioavailability of peptide drugs

•Nanoparticles can improve the oral bioavailability of peptide drugs

Orally administered intelligent self-ablating nanoparticles: a new approach to improve drug cellular uptake and intestinal absorption

Oral drug delivery to treat diabetes is being increasingly researched. The mucus and the epithelial cell layers hinder drug delivery. We designed a self-ablating nanoparticle to achieve smart oral delivery to overcome the gastrointestinal barrier. We used the zwitterionic dilauroyl phosphatidylcholine, which exhibits a high affinity toward Oligopeptide transporter 1, to modify poly(lactic-co-glycolic acid) nanoparticles and load hemagglutinin-2 peptide to facilitate its escape from lysosomes. Nanoparticles exhibit a core–shell structure, the lipid layer is degraded by the lysosomes when the nanoparticles are captured by lysosomes, then the inner core of the nanoparticles gets exposed. The results revealed that the self-ablating nanoparticles exhibited higher encapsulation ability than the self-assembled nanoparticles (77% vs 64%) and with better stability. Quantitative cellular uptake, cellular uptake mechanisms, and trans-monolayer cellular were studied, and the results revealed that the cellular uptake achieved using the self-ablating nanoparticles was higher than self-assembling nanoparticles, and the number of uptake pathways via which the self-ablating nanoparticles functioned were higher than the self-assembling nanoparticles. Intestinal mucus permeation, in vivo intestinal circulation, was studied, and the results revealed that the small self-assembling nanoparticles exhibit a good extent of intestinal uptake in the presence of mucus. In vitro flip-flop, intestinal circulation revealed that the uptake of the self-ablating nanoparticles was 1.20 times higher than the self-assembled nanoparticles. Pharmacokinetic study and the pharmacodynamic study showed that the bioavailability and hypoglycemic effect of self-ablating nanoparticles were better than self-assembled nanoparticles.

Advances in Chitosan-Based Nanoparticles for Drug Delivery

Nanoparticles (NPs) have an outstanding position in pharmaceutical, biological, and medical disciplines. Polymeric NPs based on chitosan (CS) can act as excellent drug carriers because of some intrinsic beneficial properties including biocompatibility, biodegradability, non-toxicity, bioactivity, easy preparation, and targeting specificity. Drug transport and release from CS-based particulate systems depend on the extent of cross-linking, morphology, size, and density of the particulate system, as well as physicochemical properties of the drug. All these aspects have to be considered when developing new CS-based NPs as potential drug delivery systems. This comprehensive review is summarizing and discussing recent advances in CS-based NPs being developed and examined for drug delivery. From this point of view, an enhancement of CS properties by its modification is presented. An enhancement in drug delivery by CS NPs is discussed in detail focusing on (i) a brief summarization of basic characteristics of CS NPs, (ii) a categorization of preparation procedures used for CS NPs involving also recent improvements in production schemes of conventional as well as novel CS NPs, (iii) a categorization and evaluation of CS-based-nanocomposites involving their production schemes with organic polymers and inorganic material, and (iv) very recent implementations of CS NPs and nanocomposites in drug delivery.

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.

Angiopep-2-functionalized nanoparticles enhance transport of protein drugs across intestinal epithelia by self-regulation of targeted receptors

Ligand-modified nanoparticles (NPs) have been widely used in oral drug delivery systems to promote endocytosis on intestinal epithelia. However, their transcytosis across the intestinal epithelia is still limited. Except for complex intracellular trafficking, recycling again from the apical sides into the intestinal lumen of the endocytosed NPs cannot be ignored. In this study, we modified NP surfaces with angiopep-2 (ANG) that targeted the low-density lipoprotein receptor-related protein 1 (LRP-1) expressed on the intestine to increase both the apical endocytosis and basolateral transcytosis of NPs. Notably, our finding revealed that ANG NPs could increase the apical expression and further basolateral redistribution of LRP-1 on Caco-2 cells, thus generating an apical-to-basolateral absorption pattern. Because of the enhanced transcytosis, insulin loaded ANG NPs possessed much stronger absorption efficiency and induced maximal blood glucose reduction to 61.46% in diabetic rats. Self-regulating the distribution of receptors on polarized intestine cells to promote basolateral transcytosis will provide promising insights for the rational design of oral delivery systems of protein/peptide drugs.

Charge-switchable zwitterionic polycarboxybetaine particle as an intestinal permeation enhancer for efficient oral insulin delivery

Insulin, a peptide hormone, is one of the most common and effective antidiabetic drugs. Although oral administration is considered to be the most convenient and safe choice for patients, the oral bioavailability of insulin is very low due to the poor oral absorption into blood circulation. Intestinal epithelium is a major barrier for the oral absorption of insulin. Therefore, it is vital to develop intestinal permeation enhancer to increase the antidiabetic efficacy of insulin after oral administration.

Methods: Charge-switchable zwitterionic polycarboxybetaine (PCB) was used to load insulin to form PCB/insulin (PCB/INS) particles through the electrostatic interaction between positively charged PCB in pH 5.0 and negatively charged insulin in 0.01 M NaOH. The opening effect of PCB/INS particles on intestinal epithelium was evaluated by detecting the changes of claudin-4 (CLDN4) protein and transepithelial electrical resistance (TEER) after incubation or removal. The mechanism was further elucidated based on the results of Western blot and fluorescence images. The PCB/INS particles were then used for type 1 diabetes mellitus therapy after oral administration.

Results: PCB could load insulin with the loading efficiency above 86% at weight ratio of 8:1. PCB/INS particles achieved sustained release of insulin at pH 7.4 due to their charge-switchable ability. Surprisingly, PCB/INS particles induced the open of the tight junctions of intestinal epithelium in endocytosis-mediated lysosomal degradation pathway, which resulted in increased intestinal permeability of insulin. Additionally, the opening effect of PCB/INS particles was reversible, and the decreased expression of CLDN4 protein and TEER values were gradually recovered after particles removal. In streptozotocin-induced type 1 diabetic rats, oral administration of PCB/INS particles with diameter sub-200 nm, especially in capsules, significantly enhanced the bioavailability of insulin and achieved longer duration of hypoglycemic effect than the subcutaneously injected insulin. Importantly, there was no endotoxin and pathological change during treatment, indicating that PCB/INS particles were safe enough for in vivo application.

Conclusion: These findings indicate that this system can provide a platform for oral insulin and other protein drugs delivery.

Protein corona formed in the gastrointestinal tract and its impacts on oral delivery of nanoparticles

The interaction of nanoparticles (NPs) with proteins and the formation of protein corona in the biological fluids are of great interest and significance for drug delivery. In the past decade, the corona formation in the blood and its impacts on the in vitro and in vivo fate of NPs has been well investigated and reviewed. Recently, more and more attention is paid to the nano-protein interactions taking place in the gastrointestinal tract (GIT) between the orally administered NPs and the digestive enzymes. The enzyme corona formed in the GIT can significantly affect the properties, gastrointestinal transit, and oral absorption of NPs. Since oral delivery is the most preferred delivery route, comprehensively understanding the corona formation in the GIT and its impacts on oral delivery NPs are of great importance. Herein, we aim to summarize the recent updates on the nano-protein interactions between NPs and digestive enzymes, and launch an interesting discussion on the potentials of using the digestive enzyme corona for the colon targeted delivery.

Acetic acid transporter-mediated, oral, multifunctional polymer liposomes for oral delivery of docetaxel

Nanoparticle-structuring aimed at the acetic acid (A) transporter on intestinal epithelial cells and tumor cells is a new potential strategy to enhance oral bioavailability and anti-tumor efficacy. In this study, chitosan (CS) was modified with hydrophilic A and hydrophobic lipoic acid (L), to produce ACSL. A novel ACSL-modified multifunctional liposomes (Lip) loaded with docetaxel (DTX; DTX-ACSL-Lip) was then prepared and characterized. DTX-ACSL-Lip recorded higher pH sensitivity and slower release than DTX-Lip and showed dithiothreitol (DTT) response release. DTX-ACSL-Lip uptake by Caco-2 cells was also significantly enhanced mainly viaA transporters compared with DTX-Lip. ACSL modification of DTX-Lip also improved oral bioavailability by 10.70-folds, with a 3.45-fold increase in C_max and a 1.19-fold prolongation in retention time of DTX in the blood. Moreover, the grafting degree of A significantly affected cell uptake and oral bioavailability. They also showed a significant (1.33-fold) increase in drug intratumoral distribution, as well as an increase in tumor growth inhibition rate from 54.34% to 87.51% without weight loss, compared with DTX-Lip. Therefore, modification of DTX-Lip with ACSL can significantly enhance the oral bioavailability and anti-tumor efficacy of DTX without obvious toxicity, confirming the potential of the dual strategy of targeting A transporter and controlled drug release in tumor cells in oral therapy of tumor.

Absorption, distribution, metabolism, and excretion of nanocarriers in vivo and their influences

As one of the most promising and effective delivery systems for targeted controlled-release drugs, nanocarriers (NCs) have been widely studied. Although the development of nanoparticle preparations is very prosperous, the safety and effectiveness of NCs are not guaranteed and cannot be precisely controlled due to the unclear processes of absorption, distribution, metabolism, and excretion (ADME), as well as the drug release mechanism of NCs in the body. Thus, the approval of NCs for clinical use is extremely rare. This paper reviews the research progress and challenges of using NCs in vivo based on a review of several hundred closely related publications. First, the ADME of NCs under different administration routes is summarized; second, the influences of the physical, chemical, and biosensitive properties, as well as targeted modifications of NCs on their disposal process, are systematically analyzed; third, the tracer technology related to the in vivo study of NCs is elaborated; and finally, the challenges and perspectives of nanoparticle research in vivo are introduced. This review may help readers to understand the current research progress and challenges of nanoparticles in vivo, as well as of tracing technology in nanoparticle research, to help researchers to design safer and more efficient NCs. Furthermore, this review may aid researchers in choosing or exploring more suitable tracing technologies to further advance the development of nanotechnology.

Transporter-Targeted Nano-Sized Vehicles for Enhanced and Site-Specific Drug Delivery

Nano-devices are recognized as increasingly attractive to deliver therapeutics to target cells. The specificity of this approach can be improved by modifying the surface of the delivery vehicles such that they are recognized by the target cells. In the past, cell-surface receptors were exploited for this purpose, but plasma membrane transporters also hold similar potential. Selective transporters are often highly expressed in biological barriers (e.g., intestinal barrier, blood-brain barrier, and blood-retinal barrier) in a site-specific manner, and play a key role in the vectorial transfer of nutrients. Similarly, selective transporters are also overexpressed in the plasma membrane of specific cell types under pathological states to meet the biological needs demanded by such conditions. Nano-drug delivery systems could be strategically modified to make them recognizable by these transporters to enhance the transfer of drugs across the biological barriers or to selectively expose specific cell types to therapeutic drugs. Here, we provide a comprehensive review and detailed evaluation of the recent advances in the field of transporter-targeted nano-drug delivery systems. We specifically focus on areas related to intestinal absorption, transfer across blood-brain barrier, tumor-cell selective targeting, ocular drug delivery, identification of the transporters appropriate for this purpose, and details of the rationale for the approach.

Small Morph Nanoparticles for Deep Tumor Penetration via Caveolae-Mediated Transcytosis

The tumor penetration of nanomedicines constitutes a great challenge in the treatment of solid tumors, leading to the highly compromised therapeutic efficacy of nanomedicines. Here, we developed small morph nanoparticles (PDMA) by modifying polyamidoamine (PAMAM) dendrimers with dimethylmaleic anhydride (DMA). PDMA achieved deep tumor penetration via an active, energy-dependent, caveolae-mediated transcytosis, which circumvented the obstacles in the process of deep penetration. PDMA remained negatively charged under normal physiological conditions and underwent rapid charge reversal from negative to positive under acidic conditions in the tumor microenvironment (pH < 6.5), which enhanced their uptake by tumor cells and their deep penetration into tumor tissues in vitro and in vivo. The deep tumor penetration of PDMA was achieved mainly by caveolae-mediated transcytosis, which could be attributed to the small sizes (5-10 nm) and positive charge of the morphed PDMA. In vivo studies demonstrated that PDMA exhibited increased tumor accumulation and doxorubicin-loaded PDMA (PDMA/DOX) showed better antitumor efficacy. Overall, the small morph PDMA for enhanced deep tumor penetration via caveolae-mediated transcytosis could provide new inspiration for the design of anticancer drug delivery systems.

Drug Delivery System in the Treatment of Diabetes Mellitus

Diabetes mellitus has been described as a chronic endocrine and metabolic disease, which is characterized by hyperglycemia and the coexistence of multiple complications. At present, the drugs widely applied in clinical treatment of diabetes mellitus mainly include insulin, insulin analogs, non-insulin oral hypoglycemic drugs and genetic drugs. Nevertheless, there is still no complete therapy strategy for diabetes mellitus management by far due to the intrinsic deficiencies of drugs and limits in administration routes such as the adverse reactions caused by long-term subcutaneous injection and various challenges in oral administration, such as enzymatic degradation, chemical instability and poor gastrointestinal absorption. Therefore, it is remarkably necessary to develop appropriate delivery systems and explore complete therapy strategies according to the characters of drugs and diabetes mellitus. Delivery systems have been found to be potentially beneficial in many aspects for effective diabetes treatment, such as improving the stability of drugs, overcoming different biological barriers in vivo to increase bioavailability, and acting as an intelligent automatized system to mimic endogenous insulin delivery and reduce the risk of hypoglycemia. This review aims to provide an overview related with the research advances, development trend of drug therapy and the application of delivery systems in the treatment diabetes mellitus, which could offer reference for the application of various drugs in the field of diabetes mellitus treatment.

Intelligent Escape System for the Oral Delivery of Liraglutide: A Perfect Match for Gastrointestinal Barriers

Epithelial cells are known to impede the oral delivery of polypeptides, and the accumulation of mucus and regular dynamic renewal also significantly impede drug absorption. In this work, we prepared a core-shell (COS) nanosystem using poly-N-(2-hydroxypropyl)methacrylamide (pHPMA)/chitosan (CTS). Liraglutide (NN2211) was isolated from the gastrointestinal environment and smoothly passes through the mucous layer. CSKSSDYQC (CSK) peptide and hemagglutinin-2 (HA₂) were introduced into the COS nanosystem to establish a complete path from the oral cavity to the epithelial basal side. The fate of nanocapsules in vivo was studied by fluorescence detection. The results showed that the nanocapsules escaped smoothly from the mucus. Taking into account the characteristics of CSK targeting goblet cells, we conducted cell-level studies, and the results showed that after the modification of CSK and pHPMA, more nanocapsules entered the cells. In vitro and in vivo evaluation results showed that the system successfully established a complete path from mucus to epithelial cells by responding to the gastrointestinal environment multiple times.

Intestinal OCTN2- and MCT1-targeted drug delivery to improve oral bioavailability

Various drug transporters are widely expressed throughout the intestine and play important roles in absorbing nutrients and drugs, thus providing high quality targets for the design of prodrugs or nanoparticles to facilitate oral drug delivery. In particular, intestinal carnitine/organic cation transporter 2 (OCTN2) and mono-carboxylate transporter protein 1 (MCT1) possess high transport capacities and complementary distributions. Therefore, we outline recent developments in transporter-targeted oral drug delivery with regard to the OCTN2 and MCT1 proteins in this review. First, basic information of the two transporters is reviewed, including their topological structures, characteristics and functions, expression and key features of their substrates. Furthermore, progress in transporter-targeting prodrugs and nanoparticles to increase oral drug delivery is discussed, including improvements in the oral absorption of anti-inflammatory drugs, antiepileptic drugs and anticancer drugs. Finally, the potential of a dual transporter-targeting strategy is discussed.

Cholesterol moieties as building blocks for assembling nanoparticles to achieve effective oral delivery of insulin

The amphiphilic cholesterol-phosphate conjugate can fabricate into cholesterol-coated nanoparticles by reverse emulsion method. The nanoparticles generated a rapid-onset and long-lasting hypoglycemic effect following gavage in T1DM rats.

Cell-penetrating peptide together with PEG-modified mesostructured silica nanoparticles promotes mucous permeation and oral delivery of therapeutic proteins and peptides

Poor permeation across intestinal mucous barriers often limits the oral delivery of prospective therapeutic proteins and peptides (TPPs). In order to address this issue, cell penetrating peptide (CPP) together with PEG modified and pore-enlarged mesostructured silica nanoparticle (NP) were constructed to form the mucus-penetrating electrostatic particle-complexes, CPP/TPP/NP. Alone, CPP and TPP often present with poor stability, and their traditional electrostatic complex shows reduced pharmacodynamics. To provide satisfactory protection, silica NPs were loaded with CPP and TPP (CPP@NP and TPP@NP), respectively, and then CPP@NP and TPP@NP could together form CPP/TPP/NP via electrostatic interaction. As a result, CPP involvement with PEG modification showed an 8.45-, 1.62- and 5.09-fold increase in cellular uptake, exocytosis and final transcellular permeation in mucous conditions, respectively. It was found that CPP involvement mainly affected transport and exocytosis, and the PEG polymer significantly influenced mucous penetration and cellular uptake, which could further promote CPP ability for uptake and exocytosis. Additionally, NP-mediated CPP/TPP/NP showed a similar uptake mechanism with supporting carriers (clathrin-mediated endocytosis), and could strengthen transcellular routes (the endoplasmic reticulum-Golgi apparatus pathway and the lysosome route). Utilizing recombinant growth hormone (RGH) as a model TPP, oral administration of the RGH-loaded CPP/TPP/LMSN-PEG10k with hydrophilic and electroneutral properties induced 5.41- and 4.91-fold increases in pharmacodynamics in vitro and in vivo, respectively. Thus, CPP/TPP/NP significantly promoted mucous permeation and shows promising potential for oral delivery of TPPs.

Surface engineering of nanomaterials with phospholipid-polyethylene glycol-derived functional conjugates for molecular imaging and targeted therapy

In recent years, phospholipid-polyethylene glycol-derived functional conjugates have been widely employed to decorate different nanomaterials, due to their excellent biocompatibility, long blood circulation characteristics, and specific targeting capability. Numerous in vivo studies have demonstrated that nanomedicines peripherally engineered with phospholipid-polyethylene glycol-derived functional conjugates show significantly increased selective and efficient internalization by target cells/tissues. Targeting moieties including small-molecule ligands, peptides, proteins, and antibodies are generally conjugated onto PEGylated phospholipids to decorate liposomes, micelles, hybrid nanoparticles, nanocomplexes, and nanoemulsions for targeted delivery of diagnostic and therapeutic agents to diseased sites. In this review, the synthesis methods of phospholipid-polyethylene glycol-derived functional conjugates, biophysicochemical properties of nanomedicines decorated with these conjugates, factors dominating their targeting efficiency, as well as their applications for in vivo molecular imaging and targeted therapy were summarized and discussed.

Oral delivery system for low molecular weight protamine-dextran-poly(lactic-co-glycolic acid) carrying exenatide to overcome the mucus barrier and improve intestinal targeting efficiency

Aim: This study aimed to explore the effect of nanoparticles loaded with exenatide in overcoming the mucus barrier and improving intestinal targeting efficiency, to improve the oral bioavailability. Materials & methods: Low molecular weight protamine (LMWP)-dextran-poly(lactic-co-glycolic acid) was used to create LMWP-dextran-poly(lactic-co-glycolic acid)-nanoparticles (LDPs) encapsulating exenatide-Zn²⁺ complex.Results & conclusion: LDPs showed improved penetration of the mucus barrier, and LMWP was helpful for mediating cell translocation through protein transduction domains. The absorption sites and distribution rates of LDPs were verified by intestinal localization experiments and in vivo distribution experiments. Cell uptake and transmembrane experiments confirmed the absorption efficiency in the intestinal epithelium. Furthermore, the relative bioavailability after oral administration of exenatide-Zn²⁺-LDPs was 8.4%, with a significant hypoglycemic effect on Type 2 diabetic mice.

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.

Slowing down lipolysis significantly enhances the oral absorption of intact solid lipid nanoparticles

Only a limited amount of orally administered lipid nanoparticles are absorbed as intact particles due to lipolysis by lipases in the gastrointestinal tract. It is hypothesized that by counteracting lipolysis, more particles will survive gastrointestinal digestion and be absorbed as intact particles. In this study, incorporation of a lipase inhibitor orlistat (OLST), as well as polyethylene glycol (PEG) coating, is employed to slow down the lipolysis using solid lipid nanoparticles (SLNs) as model particles. To explore the in vivo behaviors of the particles, near-infrared fluorescent probes with absolute aggregation-caused quenching (ACQ) properties are used to label and track the unmodified, PEG-coated and OLST-loaded SLNs. The in vitro lipolysis study indicates very fast first-order degradation of unmodified SLNs and significantly decreased degradation of OLST-SLNs. Live imaging reveals the same trend of slowed-down lipolysis in vivo which correlates well with the in vitro lipolysis. The scanning of ex vivo gastrointestinal segments confirms the considerably prolonged residence time of OLST-SLNs, mirroring the significantly decreased lipolysis rate. The observation of fluorescence in the blood, though very weak, and in the liver speaks of the oral absorption of intact SLNs. The substantially higher hepatic levels of OLST-SLNs than unmodified SLNs should be attributed to the significantly enhanced survival rate because both particles exhibit similar cellular recognition as well as similar physicochemical properties except for the survival rate. Similarly, slowing down lipolysis also contributes to the significantly enhanced cumulative lymphatic transport of OLST-SLNs (7.56% vs. 1.27% for the unmodified SLNs). The PEG coating slows down the lipolysis rate as well but not to the degree as done by OLST. As a result, the gastrointestinal residence time of PEG-SLNs has been moderately prolonged and the hepatic levels moderately increased. The weakened cellular recognition of PEG-SLNs implies that the enhanced oral absorption is solely ascribed to the slowed-down lipolysis and enhanced mucus penetration. In conclusion, the oral absorption of intact SLNs can be significantly enhanced by slowing down lipolysis, especially by OLST, showing potential as carriers for the oral delivery of labile biomacromolecules.

Phospholipid complex based nanoemulsion system for oral insulin delivery: preparation, in vitro, and in vivo evaluations

Purpose: The aim of this research was to develop a phospholipid complex based nanoemulsion system for oral insulin delivery.

Methods: Insulin-phospholipid complex (IPC) was firstly prepared by an anhydrous co-solvent lyophilization method, and then encapsulated into the oil phase of nanoemulsion to obtain the IPC-based nanoemulsion (IPC-NE). Both water-in-oil (W/O) IPC-NE and oil-in-water (O/W) IPC-NE were formulated and evaluated for comparison.

Results: The obtained W/O IPC-NE and O/W IPC-NE were both spherical in shape with a mean particle size of 18.6±0.79 nm and 27.3±1.25 nm, respectively. While both IPC-NEs exhibited enhanced Caco-2 cell monolayers permeability than IPC and insulin solution, W/O IPC-NE showed relatively greater protective effects against enzymatic degradation than O/W IPC-NE. Moreover, oral administration of W/O IPC-NE exhibited significant hypoglycemic effects, with 12.4-fold and 1.5-fold higher oral bioavailability compared with insulin solution and O/W IPC-NE, respectively.

Conclusion: IPC-NEs, especially the W/O IPC-NE showed promising efficiency in vitro and in vivo, thus could be a potential strategy for oral insulin delivery.

Viral nanoparticles can elude protein barriers: exploiting rather than imitating nature

Protein-corona formation in body fluids and/or entrapment of nanoparticles in protein matrices (e.g. food and mucus) can hinder the delivery of nanoparticles, irrespective of the route of administration. Here we demonstrate that certain viral nanoparticles (VNPs) can evade the adhesion of a broad panel of macromolecules from several biological milieus. We also show that the permeability of VNPs through mucin gels is far superior to that of synthetic nanoparticles. The non-sticky nature of VNPs implies that they will be able to readily cross most non-specific protein and glycoprotein barriers encountered, ubiquitously, upon administration through mucosal, and non-mucosal routes.

Synthesis of CSK-DEX-PLGA Nanoparticles for the Oral Delivery of Exenatide to Improve Its Mucus Penetration and Intestinal Absorption

The oral absorption of exenatide, a drug for type 2 diabetes treatment, can be improved by using nanoparticles (NPs) for its delivery. To improve the mucus penetration and intestinal absorption of exenatide, we designed a block copolymer, CSKSSDYQC-dextran-poly(lactic-co-glycolic acid) (CSK-DEX-PLGA), and used it for the preparation of exenatide-loaded NPs. The functionalized exenatide-loaded NPs composed of CSK-DEX-PLGA were able to target intestinal epithelial cells and reduce the mucus-blocking effect of the intestine. Moreover, the CSK modification of DEX-PLGA was found to significantly promote the absorption efficiency of NPs in the small intestine based on in vitro ligation of the intestinal rings and an examination of different intestinal absorption sites. Compared to DEX-PLGA-NPs (DPs), the absorption of CSK-DEX-PLGA-NPs (CDPs) was increased in the villi, allowing the drug to act on gobletlike Caco-2 cells through clathrin-, caveolin-, and gap-mediated endocytosis. Furthermore, the enhanced transport ability of CDPs was observed in a study on Caco-2/HT-29-MTX cocultured cells. CDPs exhibited a prolonged hypoglycemic response with a relative bioavailability of 9.2% in diabetic rats after oral administration. In conclusion, CDPs can target small intestinal goblet cells and have a beneficial effect on the oral administration of macromolecular peptides as a nanometer-sized carrier.