Oral administration microrobots for drug delivery

Oral administration is the most simple, noninvasive, convenient treatment. With the increasing demands on thetargeted drug delivery, the traditional oral treatment now is facing some challenges: 1) biologics how toimplement the oral treatment and ensure the bioavailability is not lower than the subcutaneous injections;2)How to achieve targeted therapy of some drugs in the gastrointestinal tract? Based on these two issues, drugdelivery microrobots have shown great application prospect in oral drug delivery due to their characteristics offlexible locomotion or driven ability. Therefore, this paper summarizes various drug delivery microrobotsdeveloped in recent years and divides them into four categories according to different driving modes: magneticcontrolleddrug delivery microrobots, anchored drug delivery microrobots, self-propelled drug delivery microrobotsand biohybrid drug delivery microrobots. As oral drug delivery microrobots involve disciplines such asmaterials science, mechanical engineering, medicine, and control systems, this paper begins by introducing thegastrointestinal barriers that oral drug delivery must overcome. Subsequently, it provides an overview of typicalmaterials involved in the design process of oral drug delivery microrobots. To enhance readers’ understanding ofthe working principles and design process of oral drug delivery microrobots, we present a guideline for designingsuch microrobots. Furthermore, the current development status of various types of oral drug delivery microrobotsis reviewed, summarizing their respective advantages and limitations. Finally, considering the significantconcerns regarding safety and clinical translation, we discuss the challenges and prospections of clinical translationfor various oral drug delivery microrobots presented in this paper, providing corresponding suggestions foraddressing some existing challenges.

Milk-derived exosomes as a promising vehicle for oral delivery of hydrophilic biomacromolecule drugs

Exosomes,as promising vehicles,have been widely used in the research of oral drug delivery,but the generally low drug loading efficiency of exosomes seriously limits its application and transformation.In this study,we systematically investigated the effects of drug loading methods and physicochemical properties(lipophilicity and molecular weight)on drug loading efficiency of milk-derived exosomes to explore the most appropriate loading conditions.Our finding revealed that the drug loading efficiency of exosomes was closely related to the drug loading method,drug lipophilicity,drug molecular weight and exosome/drug proportions.Of note,we demonstrated the universality that hydrophilic biomacromolecule drugs were the most appropriate loading drugs for milk-derived exosomes,which was attributed to the efficient loading capacity and sustained release behavior.Furthermore,milk-derived exosomes could significantly improve the transepithelial transport and oral bioavailability of model hydrophilic biomacromolecule drugs(octreotide,exendin-4 and salmon calcitonin).Collectively,our results suggested that the encapsulation of hydrophilic biomacromolecule drugs might be the most promising direction for milk exosomes as oral drug delivery vehicles.

Mesoporous silica nanoparticles with chiral pattern topological structure function as“antiskid tires”on the intestinal mucosa to facilitate oral drugs delivery

The weak adhesion between nanocarriers and the intestinal mucosa was one of the main reasons caused the failure in oral delivery.Inspired by the“antiskid tires”with complex chiral patterns,mesoporous silica nanoparticles AT-R@CMSN exhibiting geometrical chiral structure were designed to improve the surface/interface roughness in nanoscale,and employed as the hosting system for insoluble drugs nimesulide(NMS)and ibuprofen(IBU).Once performing the delivery tasks,AT-R@CMSN with rigid skeleton protected the loaded drug and reduced the irritation of drug on gastrointestinal tract(GIT),while their porous structure deprived drug crystal and improved drug release.More importantly,AT-R@CMSN functioned as“antiskid tire”to produce higher friction on intestinal mucosa and substantively influencedmultiple biological processes,including“contact”,“adhesion”,“retention”,“permeation”and“uptake”,compared to the achiral S@MSN,thereby improving the oral adsorption effectiveness of such drug delivery systems.By engineering AT-R@CMSN to overcome the stability,solubility and permeability bottlenecks of drugs,orally administered NMS or IBU loaded AT-R@CMSN could achieve higher relative bioavailability(705.95%and 444.42%,respectively)and stronger anti-inflammation effect.In addition,AT-R@CMSN displayed favorable biocompatibility and biodegradability.Undoubtedly,the present finding helped to understand the oral adsorption process of nanocarriers,and provided novel insights into the rational design of nanocarriers.

Chitosan-g-PAA Hydrogels for Colon-Specific Drug Delivery: Preparation, Swelling Behavior and in vitro Degradability

A series of cross-linked hydrogels for colon-specific drug delivery were synthesized by graft copolymerization of Chitosan and acrylic acid using N, N＇-methylene-bis-（acrylamide） as a cross-linker. Their swelling behavior in different pH buffer solutions and colonic enzymatic degradability were studied. The obtained results show that these hydrogels have good pH sensitivity which can avoid drug release in stomach, and their swelling kinetics in stimulant intestinal environment follow second-order swelling kinetics equation. The factors influencing the swelling kinetics include the degree of cross-linking and the composition, which may control no release or a little amount release of drug inside the hydrogels in the small intestine by tailoring these factors. The gels are degradable by colonic enzymes and there is a correlativity between the degradation of networks and the swelling degree of the gels, which may trigger the release of drug in the colon. The hydrogels show a great potential for their application in oral colon-specific drug delivery system.

Homogeneous PLGA-lipid nanoparticle as a promising oral vaccine delivery system for ovalbumin

In this study,a polymeric lipid nanoparticle(NP)(simplified as Lipid NP)was reported as a promising oral vaccine delivery system.The Lipid NPs composed of a hydrophobic polymeric poly(D,L-lactide-co-glycolide)(PLGA)core and a surface coating of lipid monolayer.Membrane emulsification technique was used to obtain uniform-sized Lipid NPs.Ovalbumin(OVA)was used as a model vaccine.Compared with the pure PLGA NPs,the Lipid NPs achieved higher loading capacity(LC)and entrapment efficiency(EE)for the encapsulated OVA.An in vitro oral release profile showed that the OVA-Lipid NPs were with lower initial burst and could protect the loaded OVA from the harsh gastrointestinal(GI)environment for a long time.In addition,a human microfold cell(M-cell)transcytotic assay demonstrated that due to a lipid layer structure on the particle surface,the Lipid NPs showed higher affinity to the M-cells.Since the M-cell in the intestinal epithelium played an important role in particle transportation as well as intimately associated with the underlying immune cells,the OVA-Lipid NPs effectively induced mucosal and humoral immune responses.

Preparation of Ionic Liquid Functionalized Silica Nanoparticles for Oral Drug Delivery

The objective of this study is to utilize the pH sensitivity of modified silica nanoparticles (SNIL) by imidazole-based ionic liquid for oral delivery of insulin. In the first time, the imidazole was covalently attached to the 3-trimethoxysily-lpropyl chloride with replacement of all the chlorine atoms. Then, a silica nanoparticle was modified by N-(3-trimeth-oxysilylpropyl) imidazole. The nanocapsule (NCIL) was achieved after the etching of the modified silica nanoparticle template with hydrofluoric acid. The nanoparticles connected through an ionic liquid-like network were characterized by FTIR and SEM. Insulin was entrapped in these carriers and the in vitro release profiles were established separately in both enzyme-free simulated gastric and intestinal fluids (SGF, pH 1) and (SIF, pH 7.4), respectively. When these drug-loaded nanoparticles was placed in physiological buffer solution (pH 7.4), a partial negative surface charge on the modified silica nanoparticle was generated due to the deprotonation of silanol groups, and the strong electrostatic repulsion triggered a sustained release of the loaded molecules.

Integration of phospholipid-drug complex into self-nanoemulsifying drug delivery system to facilitate oral delivery of paclitaxel

Self-nanoemulsifying drug delivery system(SNEDDS) has emerged as a promising platform to improve oral absorption of drugs with poor solubility and low permeability. However,large polarity molecules with insufficient lipid solubility,such as paclitaxel(PTX),would suffer from inferior formulation of SNEDDS due to poor compatibility. Herein,phospholipid-drug complex(PLDC) and SNEDDS were integrated into one system to facilitate oral delivery of PTX. First,PTX was formulated into PLDC in response to its inferior physicochemical properties. Then,the prepared PLDC was further formulated into SNEDDS by integrating these two drug delivery technologies into one system(PLDC-SNEDDS). After PLDC-SNEDDS dispersed in aqueous medium,nanoemulsion was formed immediately with an average particle size of ~30 nm. Furthermore,the nanomulsion of PLDC-SNEDDS showed good colloidal stability in both HCl solution(0.1 mol/l,p H 1.0) and phosphate buffer solution(PBS,p H 6.8). In vivo,PTX-PLDC-SNEDDS showed distinct advantages in terms of oral absorption efficiency,with a3.42-fold and 2.13-fold higher bioavailability than PTX-PLDC and PTX solution,respectively.Our results suggest that the integration of PLDC into SNEDDS could be utilized to facilitate the oral delivery of hydrophobic drugs with large polarity.

UNIQUE ORAL DRUG DELIVERY SYSTEM

An oral drug delivery system using proteinoid microspheres is discussed with respect to itsunique dependence on pH. It has been found that certain drugs such as insulin and heparin canbe encapsulated in proteinoid spheres at stomach pH's (1--3). These spheres also dissemble atintestinal pH's (6--7) releasing the drug for absorption. Using this technique low molecularweight heparin and human growth hormone have been orally delivered successfully to severalanimal species. Future work has been proposed to study the interaction and binding of thespecific drugs with synthesized oligopeptides.

Mimicking natural cholesterol assimilation to elevate the oral delivery of liraglutide for type Ⅱ diabetes therapy

Glucagon-like peptide-1 receptor agonists(GLP-1 RA)are a series of polypeptides broadly applied in the long-term treatment of typeⅡdiabetes.However,administration of GLP-RA is mainly through repetitive subcutaneous injection,which may seriously decrease the compliance and safety.Herein,a bio-inspired oral delivery system was designed to enhance the oral absorption of liraglutide(Lira),a kind of GLP-1 RA,by mimicking the natural cholesterol assimilation.25-hydroxycholesterol(25HC),a cholesterol derivative,was modified on the surfaced of Lira-loaded PLGA nanoparticles(Lira 25HC NPs)and functioned as a“top-down”actuator to facilitate unidirectional transcytosis across the intestinal epithelium.After oral delivery,Lira 25HC NPs displayed improved therapeutic effect as compared with oral free Lira on typeⅡdiabetes db/db mice,as evidenced by multiple relieved diabetic symptoms including the enhanced glucose tolerance,repressed weight growth,improved liver glucose metabolism,decreased fasting blood glucose,HbA 1c,serum lipid,and increasedβcells activity.Surprisingly,the fasting blood glucose,liver glucose metabolism,and HbA1c of oral Lira-loaded 25HC NPs were comparable to subcutaneous injection of free Lira.Further mechanisms revealed that 25HC ligand could mediate the nanoparticles to mimic natural cholesterol absorption by exerting high affinity towards apical Niemann-Pick C1 Like 1(NPC1L1)and then basolateral ATP binding cassette transporter A1(ABCA1)overexpressed on the opposite side of intestinal epithelium.This cholesterol assimilation-mimicking strategy achieve the unidirectional transport across the intestinal epithelium,thus improving the oral absorption of liraglutide.In general,this study established a cholesterol simulated platform and provide promising insight for the oral delivery of GLP-1 RA.

From oral formulations to drug-eluting implants:using 3D and 4D printing to develop drug delivery systems and personalized medicine

Since the start of the Precision Medicine Initiative by the United States of America in 2015,interest in personalized medicine has grown extensively.In short,personalized medicine is a term that describes medical treatment that is tuned to the individual.One possible way to realize personalized medicine is 3D printing.When using materials that can be tuned upon stimulation,4D printing is established.In recent years,many studies have been exploring a new field that combines 3D and 4D printing with therapeutics.This has resulted in many concepts of pharmaceutical devices and formulations that can be printed and,possibly,tailored to an individual.Moreover,the first 3D printed drug,Spritam®,has already found its way to the clinic.This review gives an overview of various 3D and 4D printing techniques and their applications in the pharmaceutical field as drug delivery systems and personalized medicine.

Preparation and Evaluation of Insulin-loaded Nanoparticles based on Hydroxypropyl-β-cyclodextrin Modified Carboxymethyl Chitosan for Oral Delivery

Novel insulin-loaded nanoparticles based on hydroxypropyl-β-cyclodextrin modified carboxymethyl chitosan（CMC-HP-β-CD） were prepared to improve the oral bioavailability of insulin. The CMC-HP-β-CD was characterized by FT-IR spectroscopy and 1H-NMR spectra. The insulin-loaded nanoparticles were prepared through crosslinking with calcium ions, and the morphology and size of the prepared nanoparticles were characterized by transmission electron microscopy（TEM） and dynamic light scattering（DLS）. Cumulative release in vitro study was performed respectively in simulated gastric medium fluid（SGF, p H=1.2）, simulated intestinal fluid（SIF, p H=6.8） and simulated colonic fluid（SCF, p H=7.4）. The encapsulation efficiency of insulin was up to 87.14 ± 4.32% through high-performance liquid chromatography（HPLC）. Statistics indicated that only 15% of the encapsulated insulin was released from the CMC-HP-β-CD nanoparticles in 36 h in SGF, and about 50% of the insulin could be released from the nanoparticles in SIF, whereas more than 80% was released in SCF. In addition, the solution containing insulin nanoparticles could effectively reduce the blood glucose level of diabetic mice. The cytotoxicity test showed that the samples had no cytotoxicity. CMC-HP-β-CD nanoparticles are promising candidates as potential carriers in oral insulin delivery systems.

Advanced delivery strategies facilitating oral absorption of heparins

Heparins show great anticoagulant effect with few side effects,and are administered by subcutaneous or intravenous route in clinics.To improve patient compliance,oral administration is an alternative route.Nonetheless,oral administration of heparins still faces enormous challenges due to the multiple obstacles.This review briefly analyzes a series of barriers ranging from poorly physicochemical properties of heparins,to harsh biological barriers including gastrointestinal degradation and pre-systemic metabolism.Moreover,several approaches have been developed to overcome these obstacles,such as improving stability of heparins in the gastrointestinal tract,enhancing the intestinal epithelia permeability and facilitating lymphatic delivery of heparins.Overall,this review aims to provide insights concerning advanced delivery strategies facilitating oral absorption of heparins.

Oral delivery of insulin with Desmodium gangeticum root aqueous extract protects rat hearts against ischemia reperfusion injury in streptozotocin induced diabetic rats

Objective:To evaluate the effect of insulin administered via oral route with the help of aqueous extract of Desmodium gangeticum(DG) root in rendering cardio protection against ischemia reperfusion injury in diabetic rats.Methods:Diabetes mellitus was induced in rats by theβ-cell toxin,streptozotocin(STZ,60 mg/kg).Isolated rat(IR) heart was used to investigate the effect of insulin mixed DG pretreatment on ischemia reperfusion injury.Mitochondrial respiratory enzymes and microsomal enzymes were used to assess the metabolic recovery of myocardium. Cardiac marker enzymes were used to find the functional recovery,which were compared with that of the STZ treated IR rats.Results:Compared with IR control group,rat treated with insulin mixed DG showed a significant functional and metabolic recovery of myocardium from the insult of ischemia reperfusion.Even though orally administered insulin mixed DG displayed a slow but prolonged hypoglycemic effect,the cardio protection it provided was more significant than when it was given intra peritoneal.Furthermore the above result indicates that insulin mixed DG can overcome the barriers in the gastrointestinal tract and be absorbed.Conclusions:The above results indicate the efficacy of insulin mixed DG in protecting the heart from ischemia reperfusion induced injury in diabetic rats.Furthermore the study gives additional information that herbal extracts can be used to transport insulin across the membrane and found to be a feasible approach for developing the oral delivery of insulin,as well as other peptide drugs.

Cyclodextrin/chitosan nanoparticles for oral ovalbumin delivery: Preparation, characterization and intestinal mucosal immunity in mice

A novel oral protein delivery system with enhanced intestinal penetration and improved antigen stability based on chitosan(CS) nanoparticles and antigen-cyclodextrin(CD) inclusion complex was prepared by a precipitation/coacervation method. Ovalbumin(OVA) as a model antigen was firstly encapsulated by cyclodextrin, either β-cyclodextrin( β-CD) or carboxymethyl-hydroxypropyl-β-cyclodextrin(CM-HP-β-CD) and formed OVA-CD inclusion complexes, which were then loaded to chitosan nanoparticles to form OVA loaded β-CD/CS or CM-HP-β-CD/CS nanoparticles with uniform particle size(836.3 and 779.2 nm, respectively) and improved OVA loading efficiency(27.6% and 20.4%, respectively). In vitro drug release studies mimicking oral delivery condition of OVA loaded CD/CS nanoparticles showed low initial releases at p H 1.2 for 2 h less than 3.0% and a delayed release which was below to 30% at p H 6.8 for further 72 h. More importantly, after oral administration of OVA loaded β-CD/CS nanoparticles to Balb/c mice, OVA-specific sIgA levels in jejunum of OVA loaded β-CD/CS nanoparticles were 3.6-fold and 1.9-fold higher than that of OVA solution and OVA loaded chitosan nanoparticles, respectively. In vivo evaluation results showed that OVA loaded CD/CS nanoparticles could enhance its efficacy for inducing intestinal mucosal immune response. In conclusion, our data suggested that CD/CS nanoparticles could serve as a promising antigen-delivery system for oral vaccination.

Chitosan DNA nanoparticles for oral gene delivery

Gene therapy is a promising technology with potential applications in the treatment of medical conditions, both congenital and acquired. Despite its label as breakthrough technology for the 21st century, the simple concept of gene therapy - the introduction of a functional copy of desired genes in affected individuals - is proving to be more challenging than expected. Oral gene delivery has shown intriguing results and warrants further exploration. In particular, oral administration of chitosan DNA nano-particles, one the most commonly used formulations of therapeutic DNA, has repeatedly demonstrated successful in vitro and in vivo gene transfection. While oral gene therapy has shown immense promise as treatment options in a variety of diseases, there are still signifcant barriers to overcome before it can be considered for clinical applications. In this review we provide an over-view of the physiologic challenges facing the use of chitosan DNA nanoparticles for oral gene delivery at both the extracellular and intracellular level. From administration at the oral cavity, chitosan nanoparticles must traverse the gastrointestinal tract and protect its DNA contents from signifcant jumps in pH levels, various intestinal digestive enzymes, thick mucus layers with high turnover, and a proteinaceous glycocalyx meshwork. Once these extracellular barriers are overcome, chitosan DNA nanoparticles must enter intestinal cells, escape endolysosomes, and disassociate from genetic material at the appropriate time allowing transport of genetic material into the nucleus to deliver a therapeutic ef-fect. The properties of chitosan nanoparticles and modified nanoparticles are discussed in this review. An understanding of the barriers to oral gene delivery and how to overcome them would be invaluable for future gene therapy development.

Oral TNF-αsiRNA delivery via milk-derived exosomes for effective treatment of inflammatory bowel disease

Oral administration facilitates the direct delivery of drugs to lesions within the small intestine and colon,making it an ideal approach for treating patients with inflammatory bowel disease.However,multiple physical barriers impede the delivery of oral RNA drugs through the gastrointestinal tract.Herein,we developed a novel oral siRNA delivery system that protects nucleic acids in extreme environments by employing exosomes derived from milk to encapsulate tumor necrosis factor-alpha(TNF-α)siRNA completely.The remarkable structural stability of milk-derived exosomes(M-Exos),as opposed to those from HEK293T cells,makes them exceptional siRNA carriers.Results demonstrate that milk exosomes loaded with TNF-αsiRNA(M-Exo/siR)can effectively inhibit the expression of TNF-α-related inflammatory cytokines.Moreover,given that milk exosomes are composed of unique lipids with high bioavailability,orally administered M-Exo/siR effectively reach colonic tissues,leading to decreased TNF-αexpression and successful alleviation of colitis symptoms in a dextran sulfate sodium-induced inflammatory bowel disease murine model.Hence,milk-derived exosomes carrying TNF-αsiRNA can be effectively employed to treat inflammatory bowel disease.Indeed,using exosomes naturally derived from milk may shift the current paradigm of oral gene delivery,including siRNA.

壳聚糖虾青素纳米颗粒缓解小鼠结肠炎

炎症性肠病(inflammatory bowel disease,IBD)的发病率不断上升,但其传统药物疗法存在一定的局限性,包载天然活性物质的纳米颗粒缓解结肠炎成为研究热点。该文通过薄膜水合⁃高压均质化法制备了壳聚糖(chitosan,CS)包覆的负载虾青素(astaxanthin,AST)的纳米颗粒(chitosan⁃modified astaxanthin⁃loaded nanoparticles,CS⁃AST⁃NPs),对该纳米颗粒的粒径、Zeta电位、包封率、体外消化特性等进行检测,并评估纳米颗粒对葡聚糖硫酸钠(dextran sulfate sodium salt,DSS)诱导的小鼠结肠炎的缓解作用。结果表明该纳米颗粒的粒径集中在36 nm,Zeta电位为30.77 mV,包封率达到91.91%,且稳定性良好。体外模拟释放试验表明,CS⁃AST⁃NPs具有良好的缓释性。此外,CS⁃AST⁃NPs可以有效缓解DSS诱导的结肠炎的症状,表现为抑制结肠炎小鼠体质量的下降,降低疾病活动指数,抑制结肠缩短,改善小鼠结肠组织损伤和黏膜上皮细胞的完整性。同时,CS⁃AST⁃NPs能够降低促炎细胞因子的水平,减轻DSS诱导的炎症反应和氧化损伤。综上所述,CS⁃AST⁃NPs在IBD的改善中有良好的应用前景。

5-氨基水杨酸口服制剂及联合中药在炎症性肠病治疗中的应用

5-氨基水杨酸(5-ASA)是1种从中药柳树皮中分离提纯得到的天然抗炎活性成分水杨酸的衍生物,别名阿米诺水杨酸、美沙拉嗪,是临床治疗炎症性肠病(IBD)并预防其复发的一线药物。尽管目前莎尔福(Salofalk)、亚沙可(Asacol)和潘他沙(Pentasa)等5-ASA口服结肠靶向制剂已广泛用于IBD的临床治疗,但仍存在在小肠提前释药和受胃肠道生理状态影响显著等制剂缺陷、对克罗恩病和重度溃疡性结肠炎(UC)治疗效果不佳等临床未满足的需求,以及减少UC患者黏膜菌群多样性、长期使用增加用药风险和降低患者服药依从性等问题。开发硅胶纳米粒、水凝胶等新型递药载体,基于pH依赖、时滞控制和菌群/酶触发等多机制结合释药原理设计新型口服结肠靶向制剂从而解决制剂缺陷问题,提高5-ASA疗效和患者服药耐受性、依从性是目前制剂研究的重点。此外,5-ASA口服制剂联合中药保留灌肠、中药口服制剂和注射液等治疗IBD可发挥协同抗炎作用,实现增效减毒目的。对5-ASA口服制剂品种、近年来新型制剂和递药载体的研究进展,以及与中药联用的临床应用和研究现状等进行综述,为5-ASA口服制剂的剂型改造、载体材料研究和临床用药等提供参考。

吞咽困难患者新型口服抗肿瘤药物的替代给药方法

目的为吞咽困难的患者提供新型口服抗肿瘤药物的替代给药方法。方法根据“新型抗肿瘤药物临床应用指导原则(2022年版)”药品目录确定检索范围,通过查阅说明书,检索PubMed、Micromedex、UpToDate等数据库获得药品临时液体制剂的制备、稳定性、储存和相关临床信息。结果70种口服抗肿瘤药物被纳入文献检索,其中33种药物有相关的文献或数据支持替代给药方法,8种在说明书中有替代给药的相关信息,其他药物的证据水平各不相同。结论大部分药物临时液体制剂的证据水平较低,医疗团队在使用说明书以外的用法时应充分考虑利弊,谨慎使用。

一种双层多糖水凝胶用于增强益生菌肠道靶向口服递送

Transplantation of probiotics to the intestine can positively regulate the gut microbiota,thereby promoting the immune system and treating various diseases.However,the harsh gastrointestinal environment and short retention time in the gastrointestinal tract significantly limit the bioavailability and intestinal colonization of probiotics.Herein,we present a double-layer polysaccharide hydrogel(DPH)in the form of a double-layer structure composed of a carboxymethyl cellulose(CMCL)supramolecular inner layer and a dialdehyde alginate(DAA)cross-linked carboxymethyl chitosan(CMCS)outer layer.This doublelayer structure allows DPH to encapsulate and deliver probiotics in a targeted manner within the body.In the stomach,the cage structure of the DPH is closed,and the outer layer absorbs surrounding liquids to form a barrier to protect the probiotics from gastric fluids.In the intestine,the cage structure opens and disintegrates,releasing the probiotics.Thus,DPH endows probiotics with excellent intestine-targeted delivery,improved oral bioavailability,enhanced gastrointestinal tract tolerance,and robust mucoadhesion capacity.The encapsulated probiotics exhibit almost unchanged bioactivity in the gastrointestinal tract before release,as well as improved oral delivery.In particular,probiotics encapsulated by DPH exhibit 100.1 times higher bioavailability and 10.6 times higher mucoadhesion than free probiotics in an animal model 48 h post-treatment.In addition,with a remarkable ability to survive and be retained in the intestine,probiotics encapsulated by DPH show excellent in vitro and in vivo competition with pathogens.Notably,DAA-mediated dynamic crosslinking not only maintains the overall integrity of the hydrogels but also controls the release timing of the probiotics.Thus,it is expected that encapsulated substances(probiotics,proteins,etc.)can be delivered to specific sites of the intestinal tract by means of DPH,by controlling the dynamic covalent crosslinking.