Crucial Impact of Residue Chirality on the Gelation Process and Biodegradability of Thermoresponsive Polypeptide Hydrogels.

Thermosensitive polypeptide hydrogels have gained considerable attention in potential biomedical applications, of which the polymer structure may be tuned by residue chirality. In this study, polypeptide-based block copolymers with different chiralities were synthesized by ring-opening polymerization of γ-ethyl-l-glutamate N-carboxyanhydride and/or γ-ethyl-d-glutamate N-carboxyanhydride using amino-terminated monomethoxy poly(ethylene glycol) as a macroinitiator. All mPEG-polypeptide copolymers underwent sol-gel transition with an increase in temperature. The block copolymers with mixed enantiomeric residues of γ-ethyl-l-glutamate (ELG) and γ-ethyl-d-glutamate (EDG) in the polypeptide blocks exhibited lower critical gelation concentrations and lower critical gelation temperatures compared with those composed of pure ELG or EDG residues. We established that the difference in gelation properties between the copolymers was derived from the distinction of the secondary structures. We further demonstrated the influence of polypeptide chirality on the degradability and biocompatibility of hydrogels in vivo. Our findings provide insights into the design of hydrogels having tailored secondary conformation, gelation property, and biodegradability.

Rapidly Thermoreversible and Biodegradable Polypeptide Hydrogels with Sol-Gel-Sol Transition Dependent on Subtle Manipulation of Side Groups.

Thermoreversible hydrogels are attractive materials for biomedical applications, but their applications are still limited by nonbiodegradability and/or slow temperature-dependent gel-to-sol transition rates. In this research, we prepared a range of amphiphilic diblock, triblock, and four-armed star block copolymers composed of poly(ethylene glycol) (PEG) and poly(γ-(2-(2-ethoxyethoxy)ethyl)-l-glutamate) (P(EEO2LG)) segments, which can form rapidly thermoreversible hydrogels at physiological temperature. Intriguingly, the obtained hydrogels can transform from gel to sol within 10-70 s in response to the temperature decrease from 37 to 0 °C. The thermosensitive sol-gel-sol transitions are markedly faster than previously reported thermoreversible PEG-poly(l-glutamate) derivative hydrogels with subtle differences in the side groups and a widely studied poly(d,l-lactide-co-glycolide)-b-PEG-b-poly(d,l-lactide-co-glycolide) (PLGA-PEG-PLGA) hydrogel that required a much longer time of 40∼150 min. Further investigation of the relationship between the hydrogel property and polymer structure is performed, and the self-assembly mechanisms of different copolymers are proposed. Cytotoxicity assays and subcutaneous degradation experiments reveal that the PEG/P(EEO2LG) block copolymers are biocompatible and biodegradable. The polypeptide hydrogel can therefore be used as a three-dimensional platform for facile cell culture and collection by regulating the temperature.

pH- and Amylase-Responsive Carboxymethyl Starch/Poly(2-isobutyl-acrylic acid) Hybrid Microgels as Effective Enteric Carriers for Oral Insulin Delivery.

Oral delivery of insulin has the potential to revolutionize diabetes care since it is regarded as a noninvasive therapeutic approach without the side effects caused by frequent subcutaneous injection. However, the insulin delivery efficiency through oral route was still limited, likely due to the chemical, enzymatic and absorption barriers. In this study, a novel type of pH- and amylase-responsive microgels as an insulin drug carrier for oral administration was developed to improve the drug delivery efficiency. The microgels were prepared via aqueous dispersion copolymerization of acrylate- grafted-carboxymethyl starch (CMS- g-AA) and 2-isobutyl-acrylic acid ( iBAA). The resulting hybrid microgels with the P iBAA contents of 13.6-45.3 wt% exhibited sharp pH-sensitivity, which was revealed by the changes in particle size of the microgels and the transmittance of the microgel aqueous solution. The accelerated decomposition of the CMS-containing microgels in response to amylase was demonstrated by chromogenic reaction and morphology change. Insulin was loaded into the microgels by swelling-diffusion method, and the insulin release from the insulin-loaded microgels in vitro was found to be triggered by pH change and addition of amylase, which was highly dependent on the microgel component. Cytotoxicity assay was performed to show the good biocompatibility of the microgels. In addition, the tests of cellular uptake by Caco-2 cells and transmembrane transport through the Caco-2 cell monolayers were carried out to confirm the intestinal absorption ability of the insulin-loaded microgels. Finally, the oral administration of insulin-loaded microgels to STZ-induced diabetic rats led to a continuous decline in the fasting blood glucose level within 2 to 4 h, and the hypoglycemic effect maintained over 6 h in vivo. The relative pharmacological availability of the insulin-loaded microgels was enhanced 23-38 times compared to free-form insulin solution through oral route. Therefore, the novel starch-based microgels may have potential as an efficient platform for oral insulin delivery.

Injectable Thermosensitive Polypeptide-Based CDDP-Complexed Hydrogel for Improving Localized Antitumor Efficacy.

In this study, a type of novel thermosensitive polypeptide-based hydrogel with tunable gelation behavior through changing the content of carboxyl groups was developed for the purpose of improving the cisplatin (CDDP) release behavior and enhancing the localized antitumor efficiency. The introduction of carboxyl groups in methoxy-poly(ethylene glycol)-b-(poly(γ-ethyl-l-glutamate-co-l-glutamic acid) (mPEG-b-P(ELG-co-LG)) not only led to adjustable mechanical properties of the hydrogel but also significantly reduced the burst release of the drug through the complexation between the carboxyl groups of polypeptide and CDDP. Furthermore, both the good biocompatibility and the biodegradable properties of mPEG-b-P(ELG-co-LG) hydrogel were observed in vivo. Interestingly, the CDDP-complexed mPEG-b-P(ELG-co-LG) hydrogel exhibited significantly enhanced antitumor efficacy in vivo compared to the mPEG-b-PELG hydrogel loaded with CDDP without complexation, although a lower cytotoxicity and IC50 of the CDDP-complexed hydrogel was observed in vitro. Overall, the new type of injectable CDDP-complexed hydrogel may serve as an efficient platform for sustained CDDP delivery in localized tumor therapy.

Injectable Polypeptide Hydrogels with Tunable Microenvironment for 3D Spreading and Chondrogenic Differentiation of Bone-Marrow-Derived Mesenchymal Stem Cells.

Bone-marrow-derived mesenchymal stem cells (BMSCs) possess vast potential for tissue engineering and regenerative medicine. In this study, an injectable hydrogel comprising poly(l-glutamic acid)-graft-tyramine (PLG-g-TA) with tunable microenvironment was developed via enzyme-catalyzed cross-linking and used as an artificial extracellular matrix (ECM) to explore the behaviors of BMSCs during three-dimensional (3D) culture. It was found that the mechanical property, porous structure as well as degradation process of the hydrogels could be tuned by changing the copolymer concentration. The PLG-g-TA hydrogels showed good cytocompatibility in vitro. After being subcutaneously injected into the back of rats, the hydrogels degraded gradually within 8 weeks and exhibited good biocompatibility in vivo. BMSCs were then encapsulated in the polypeptide-based hydrogels with different copolymer concentration to investigate the influence of 3D matrix microenvironment on stem cell behaviors. It is intriguing to note that the BMSCs within the 2% hydrogel showed a well-spread morphology after 24 h and a higher proliferation rate during 7 days of culture, in contrast to a rounded morphology and lower proliferation rate of BMSCs in the 4% hydrogel. Furthermore, the hydrogels with different microenvironment also regulated the matrix biosynthesis and the gene expression of BMSCs. After incubation in the 2% hydrogel for 4 weeks, the BMSCs produced more type II collagen and expressed higher amounts of chondrogenic markers, compared to the cells in the 4% hydrogel. Therefore, the PLG-g-TA hydrogels with tunable microenvironment may serve as an efficient 3D platform for guiding the lineage specification of BMSCs.

N-Isopropylacrylamide Modified Polyethylenimines as Effective siRNA Carriers for Cancer Therapy.

N-isopropylacrylamide modified PEI (PEN) was synthesized via Michael addition and was developed as an efficient siRNA delivery system both in vitro and in vivo. PEN showed significant enhanced cytocompatibility compared with commercial PEI-25k. The complexation of PEN with siRNA was studied by gel retardation, particle size and zeta potential measurement. The in vitro transfection ability of PEN was measured by qRT-PCR assay, and achieved obviously enhanced gene silencing efficiency compared with PEI-25k. The confocal imaging and flow cytometric analysis further validated its excellent intracellular trafficking ability. For antitumor treatment experiment, PEN mediated siVEGF showed obviously therapeutic effects for the treatment of CT26 tumor. Therefore, the present study demonstrated a useful strategy for constructing efficient siRNA delivery vehicles for antitumor therapy.

Stimuli-Responsive Hydrogel Adhesives for Wound Closure and Tissue Regeneration.

Sutures and staplers, as gold standards for clinical wound closure, usually cause secondary tissue injury and require professional technicians and equipment. The noninvasive hydrogel adhesives are used in various biomedical applications, such as wound closure, tissue sealing, and tissue regeneration, due to their remarkable properties. Recently-developed hydrogel adhesives, especially stimuli-responsive hydrogels, have shown great potential owing to their advantages in regulating their performance and functions according to the wound situations or external conditions, thus allowing the wounds to heal gradually. However, comprehensive summary on stimuli-responsive hydrogels as tissue adhesives is rarely reported to date. This review focuses on the advances in the design of various stimuli-responsive hydrogel adhesives over the past decade, including the systems responsive to pH, temperature, photo, and enzymes. Their potential biomedical applications, such as skin closure, cardiovascular and liver hemostasis, and gastrointestinal sealing, are emphasized. Meanwhile, the challenges and future development of stimuli-responsive hydrogel adhesives are discussed. This review aims to provide meaningful insights for the further design of next-generation of hydrogel adhesives for wound closure and tissue regeneration.

ROS-responsive thermosensitive polypeptide hydrogels for localized drug delivery and improved tumor chemoimmunotherapy.

In this study, we developed a ROS-responsive thermosensitive poly(ethylene glycol)-polypeptide hydrogel loaded with a chemotherapeutic drug, doxorubicin (Dox), an antiviral imidazoquinoline, resiquimod (R848), and antibody targeting programmed cell death protein 1 (aPD-1) for local chemoimmunotherapy. The hydrogel demonstrated controllable degradation and sustained drug release behavior according to the concentration of ROS in vitro. Following intratumoral injection into mice bearing B16F10 melanoma, the Dox/R848/aPD-1 co-loaded hydrogel effectively inhibited tumor growth, prolonged animal survival time and promoted anti-tumor immune responses with low systemic toxicity. In the postoperative model, the Dox/R848/aPD-1 co-loaded hydrogel exhibited enhanced tumor recurrence prevention and long-term immune memory effects. Thus, the hydrogel-based local chemoimmunotherapy system demonstrates potential for effective anti-tumor treatment and suppression of tumor recurrence.

Injectable, Adhesive Albumin Nanoparticle-Incorporated Hydrogel for Sustained Localized Drug Delivery and Efficient Tumor Treatment.

Injectable hydrogels are receiving increasing attention as local depots for sustained anticancer drug delivery. However, most current hydrogel-based carriers lack tissue-adhesive ability, a property that is important for the immobilization of drug-loaded systems at tumor sites to increase local drug concentration. In this study, we developed a paclitaxel (PTX)-loaded injectable hydrogel with firm tissue adhesion for localized tumor therapy. PTX-loaded bovine serum albumin (BSA) nanoparticles (PTX@BN) were prepared, and the drug-loaded hydrogel was then fabricated by cross-linking PTX@BN with o-phthalaldehyde (OPA)-terminated 4-armed poly(ethylene glycol) (4aPEG-OPA) via a condensation reaction between OPA and the amines in BSA. The hydrogel showed firm adhesion to various organs and tumor tissues ex vivo due to the condensation reaction of unreacted OPA groups and amines in the tissues. The PTX-loaded nanocomposite hydrogels sustained PTX release over 30 days following the Korsmeyer-Peppas model and exhibited notable inhibition activities against mouse C26 colon and 4T1 breast cancer cells in vitro. Following peritumoral injection into mice with C26 or 4T1 tumors, the PTX@BN-loaded hydrogel significantly enhanced the antitumor efficacy and prolonged animal survival time compared to free PTX solutions with low systemic toxicity. Therefore, the adhesive, PTX-loaded nanocomposite hydrogels have the potential for efficient localized tumor therapy.

Biodegradable stereocomplex micelles based on dextran-block-polylactide as efficient drug deliveries.

Biodegradable stereocomplex micelles (SCMs) based on amphiphilic dextran-block-polylactide (Dex-b-PLA) were designed and used for efficient intracellular drug deliveries. The Dex-b-PLA copolymers were successfully synthesized by click reaction. The structures of the resultant copolymers were verified by (1)H NMR and FT-IR spectra. The formation of stable micelles through self-assembly driven by the stereocomplexation between enantiomeric l- and d-PLA blocks was characterized by transmission electron microscopy (TEM), dynamic laser scattering (DLS), and fluorescence techniques. It was interesting to observe that the SCMs showed lower critical micelle concentration values (CMCs) because of the stereocomplex interaction between PLLA and PDLA. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis provided information on the thermal and crystal properties of the copolymers and SCMs. The improved stability of SCMs should be attractive for intracellular drug delivery. Thus, a model anticancer drug doxorubicin (DOX) was loaded into micelles, and the in vitro drug release in was also studied. The release kinetics of DOX showed DOX-loaded SCMs exhibited slower DOX release. Confocal laser scanning microscopy (CLSM) and flow cytometry studies also showed that the DOX-loaded SCMs exhibited a slower drug release behavior. Meanwhile, the MTT assay demonstrated that DOX-loaded SCMs show lower cellular proliferation inhibition against HepG2. In sum, the micelles through self-assembly driven by stereocomplex interaction would have great potential to be used as stable delivery vehicles for pharmaceutical and biomedical applications.

Versatile biofunctionalization of polypeptide-based thermosensitive hydrogels via click chemistry.

In this study, we report thermosensitive hydrogels based on poly(ethylene glycol)-block-poly(γ-propargyl-l-glutamate) (PEG-PPLG). (13)C NMR spectra, DLS, and circular dichroism spectra were employed to study the mechanism of the sol-gel phase transition. Mouse fibroblast L929 cells were encapsulated and cultured within the hydrogel matrices, and the encapsulated cells were shown to be highly viable in the gel matrices, suggesting that the hydrogels have excellent cytocompatibilities. The mass loss of the hydrogels in vitro was accelerated by the presence of proteinase K compared to the control group. In vivo biocompatibility studies revealed that the in situ formed gels in the subcutaneous layer last for ∼21 days, and H&E staining study suggested acceptable biocompatibility of our materials in vivo. The presence of alkynyl side groups in the PEG-PPLG copolymers allowed convenient further functionalization with azide-modified bioactive molecules, such as biotin and galactose. The biofunctionalized PEG-polypeptide block copolymers showed sol-gel phase transitions similar to the parent copolymers. Interestingly, the incorporation of galactose groups into the hydrogels was found to improve cell adhesion, likely due to the adsorption of fibronectin (FN) in cell-extracellular matrix (ECM). Because bioactive materials have shown unique advantages in biomedical applications, especially tissue engineering and regenerative medicine applications, we believe our novel functionalizable thermosensitive hydrogels have potential to serve as a versatile platform for the development of new biofunctional materials, for example, bioadhesive and bioresponsive hydrogels.

pH- and Temperature-responsive Hydrogels Based on Tertiary Amine-modified Polypeptides for Stimuli-responsive Drug Delivery.

pH- and temperature-responsive hydrogels have attracted considerable attention due to their responsiveness to dual physiologically-relevant stimuli. In this study, we developed stimuli-responsive hydrogels based on monomethoxy poly(ethylene glycol) (mPEG)-polypeptide block copolymers containing various tertiary amine pendants (EEP-TAs). The EEP-TAs were synthesized via ring-opening copolymerization of α-amino acid N-carboxyanhydrides, and further modified post-polymerization with click chemistry. The EEP-TAs exhibited an α-helix-to-ß-sheet transition when the pH was increased from 4.0 to 7.4. At elevated polymer concentrations, aqueous solutions of the EEP-TAs underwent thermo-induced sol-gel phase transitions, which were dependent on the pH. The hydrogels almost fully degraded within 3 weeks in the subcutaneous layer of mice and exhibited good histocompatibility in vivo. Additionally, doxorubicin (DOX)-loaded hydrogels exhibited pH-responsive drug release profiles in vitro, which were composed of rapid release at acidic pH and more sustained release at neutral pH. Thus, these polypeptide hydrogels hold potential as depots for environment-responsive delivery of therapeutic agents.

Injectable, self-healing hydrogel adhesives with firm tissue adhesion and on-demand biodegradation for sutureless wound closure.

Tissue adhesives have garnered extensive interest as alternatives and supplements to sutures, whereas major challenges still remain, including weak tissue adhesion, inadequate biocompatibility, and uncontrolled biodegradation. Here, injectable and biocompatible hydrogel adhesives are developed via catalyst-free o-phthalaldehyde/amine (hydrazide) cross-linking reaction. The hydrogels demonstrate rapid and firm adhesion to various tissues, and an o-phthalaldehyde-mediated tissue adhesion mechanism is established. The hydrogel adhesives show controlled degradation profiles of 6 to 22 weeks in vivo through the incorporation of disulfide bonds into hydrogel network. In liver and blood vessel injury, the hydrogels effectively seal the incisions and rapidly stop bleeding. In rat and rabbit models of full-thickness skin incision, the hydrogel adhesives quickly close the incisions and accelerate wound healing, which exhibit efficacies superior to those of commercially available fibrin glue and cyanoacrylate glue. Thus, the hydrogel adhesives show great potential for sutureless wound closure, hemostasis sealing, and prevention of leakage in surgical applications.

Injectable antibacterial tissue-adhesive hydrogel based on biocompatible o-phthalaldehyde/amine crosslinking for efficient treatment of infected wounds.

Injectable antibacterial hydrogels have attracted considerable attention in wound management. However, the development of injectable hydrogels with excellent antibacterial activity, good biocompatibility, and strong tissue adhesion remains a challenge. In this study, an antibacterial tissue-adhesive hydrogel was developed based on a catalyst-free o-phthalaldehyde (OPA)/amine reaction by simply mixing OPA-terminated four-arm poly(ethylene glycol) (4aPEG-OPA) and ε-poly-l-lysine (ε-PLL) solutions. The hydrogel showed tunable gelation time, storage moduli, and degradation rate depending on the polymer concentration and 4aPEG-OPA/ε-PLL mass ratio. The hydrogel exhibited nearly 100% bacterial inhibition rates in-vitro against Gram-negative E. coli and Gram-positive S. aureus, while maintaining good biocompatibility. The hydrogel matched well in shape and tightly adhered to the tissue after in-situ formation at the wound sites. Following the treatment of rat models of full-thickness skin incisions and round wounds, the hydrogel effectively closed the wounds and promoted wound healing. Moreover, after administering to S. aureus infected full-thickness skin wounds, the hydrogel exhibited remarkable efficacy in inhibiting wound infection with a bacterial inhibition rate over 99.94%, achieving a significantly accelerated wound healing compared with the commercially available Prontosan® gel. Therefore, the hydrogel exhibits great potential as a wound dressing for infection prevention and promotion of healing.

Decisive role of hydrophobic side groups of polypeptides in thermosensitive gelation.

Thermosensitive hydrogels based on PEG and poly(l-glutamate)s bearing different hydrophobic side groups were separately synthesized by the ring-opening polymerization (ROP) of l-glutamate N-carboxyanhydrides containing different alkyl protected groups, that is, methyl, ethyl, n-propyl, and n-butyl, using mPEG(45)-NH(2) as macroinitiator. The resulting copolymers underwent sol-gel transitions in response to temperature change. Interestingly, the polypeptides containing methyl and ethyl showed significantly lower critical gelation temperatures (CGTs) than those bearing n-propyl and butyl side groups. Based on the analysis of (13)C NMR spectra, DLS, circular dichroism spectra, and ATR-FTIR spectra, the sol-gel transition mechanism was attributed to the dehydration of poly(ethylene glycol) and the increase of ß-sheet conformation content in the polypeptides. The in vivo gelation test indicated that the copolymer solution (6.0 wt %) immediately changed to a gel after subcutaneous injection into rats. The mass loss of the hydrogel in vitro was accelerated in the presence of proteinase K, and the MTT assay revealed that the block copolymers exhibited no detectable cytotoxicity. The present work revealed that subtle variation in the length of a hydrophobic side group displayed the decisive effect on the gelation behavior of the polypeptides. In addition, the thermosensitive hydrogels could be promising materials for biomedical applications due to their good biocompatibility, biodegradability, and the fast in situ gelation behavior.

Mucoadhesive, Antibacterial, and Reductive Nanogels as a Mucolytic Agent for Efficient Nebulized Therapy to Combat Allergic Asthma.

Asthma is an intractable disease involving the infiltration of inflammatory cells and mucus plugging. Despite small molecular mucolytics having the ability to break the disulfide bonds of mucins, offering a potential way to overcome the airflow obstruction and airway infection, these mucolytics have limited therapeutic effects in vivo. Therefore, in this work, arginine-grafted chitosan (CS-Arg) is ionically cross-linked with tris(2-carboxyethyl)phosphine (TCEP) to obtain nanogels as a mucolytic agent. The positively charged nanogels effectively inhibit the formation of large aggregates of mucin in vitro, probably thanks to the formation of an ionic interaction between CS-Arg and mucin, as well as the breakage of disulfide bonds in mucin by the reductive TCEP. Moreover, the nanogels show good cytocompatibility at concentrations up to 5 mg mL-1, exhibiting effective inhibitory effects against the proliferation of both Staphylococcus aureus and Escherichia coli at 5 mg mL-1. After the administration of the nanogels by nebulization into a Balb/c mouse model with allergic asthma, they can efficiently reduce the mucus obstruction in bronchioles and alveoli and relieve airway inflammation. Therefore, these CS-Arg/TCEP nanogels potentially represent a promising mucolytic agent for the efficient treatment of allergic asthma and other muco-obstructive diseases.

Effect of Polymer Topology and Residue Chirality on Biodegradability of Polypeptide Hydrogels.

Polypeptide-based injectable hydrogels have attracted the attention of biomedical researchers due to their unique biocompatibility and biodegradability, tunable residue chirality, and secondary conformation of polypeptide chains. In the present study, four types of poly(ethylene glycol)-block-poly(glutamic acid)s with different topological structures and residue chirality of polypeptide segments were developed, which were grafted with tyramine side groups for further cross-linking. The results demonstrated that the covalent conjugation between the tyramine groups in the presence of horseradish peroxidase and hydrogen peroxide could form porous hydrogels rapidly. Additionally, the gelation time and mechanical strength of the hydrogels were measured. All the polymer precursors and hydrogels exhibited good cytocompatibility in vitro. Further assessment of the enzymatic degradability of the hydrogels and copolymers in vitro revealed that the degradation rate was influenced by the adjustment of polymer topology or residue chirality of polypeptide copolymers. Subsequently, the effect of copolymer topology and polypeptide chirality on in vivo biodegradability and biocompatibility was assessed. This study will provide insights into the relationship between copolymer structures and hydrogel properties and benefit future polypeptide-based hydrogel studies in biomedical applications.

Design of an Injectable Polypeptide Hydrogel Depot Containing the Immune Checkpoint Blocker Anti-PD-L1 and Doxorubicin to Enhance Antitumor Combination Therapy.

Combination therapy can be used to enhance the therapeutic response and decrease side effects during cancer treatment. In this study, a system is developed to locally deliver the immune checkpoint blockade antibody targeting programmed death-ligand 1 (anti-PD-L1 or aPD-L1) and doxorubicin (Dox), by an injectable, biocompatible polypeptide hydrogel as a drug depot. The localized and sustained release of Dox after the intratumoral injection of the co-loaded hydrogel induces immunogenic tumor cell death, thus promoting an antitumor immunological response. The tumor inhibitory effect is significantly enhanced by the simultaneous release of aPD-L1 at the tumor site thanks to its action on the inhibition of the PD-1/PD-L1 pathway and restoration of the tumor-killing effect of cytotoxic T cells. Treatment of the B16F10 melanoma model with the aPD-L1 and Dox co-loaded hydrogel leads to a remarkable inhibition of tumor progression and prolongation of animal survival.

Biopolymer Immune Implants' Sequential Activation of Innate and Adaptive Immunity for Colorectal Cancer Postoperative Immunotherapy.

Surgical resection is the first-line therapy for colorectal cancer (CRC). However, for advanced CRC, the curative effect of surgical resection is limited due to either local recurrence or distal metastasis. Postoperative in situ immunotherapy, presents a promising option for preventing tumor recurrence and metastasis, owing to the fact that surgeons have unique opportunities and direct access to the surgical site. Herein, a designed biopolymer immune implant for CRC post-surgical therapy, characterized with tissue adhesion, sustained drug release, and sequential elicitation of innate immunity, adaptive immunity, and immune memory effects, is reported. With gradual release of the loaded resiquimod (R848) and anti-OX40 antibody (aOX40), the immune implant can eradicate residual tumors post-surgery (with no tumor recurrence in 150 days), inhibit the growth of distal tumors and elicit immune memory effects to resist tumor re-challenge. Immunological analysis reveal that the biopolymer immune plant treatment leads to a two-stage action, with enhanced natural killer cells (NK cells) infiltration and activation of dendritic cells (DCs) in the first several days, then a greatly increased population of infiltrating T cells, and finally immune memory effects are established. The reported biopolymer immune implants provide a valuable and clinically-relevant option for post-surgical CRC management.

A Nanocomposite Vehicle Based on Metal-Organic Framework Nanoparticle Incorporated Biodegradable Microspheres for Enhanced Oral Insulin Delivery.

Oral insulin delivery has revolutionized diabetes treatment, but challenges including degradation in the gastrointestinal environment and low permeation across the intestinal epithelium remain. Herein, to overcome these barriers, we developed a novel biodegradable nanocomposite microsphere embedded with metal-organic framework (MOF) nanoparticles. An iron-based MOF nanoparticle (NP) (MIL-100) was first synthesized as a carrier with an insulin loading capacity of 35%. The insulin-loaded MIL-100 nanoparticles modified with sodium dodecyl sulfate (Ins@MIL100/SDS) promoted insulin permeation across Caco-2 monolayer models in vitro. To improve resistance to the gastric acid environment, Ins@MIL100/SDS nanoparticles were embedded into a biodegradable microsphere to construct the nanocomposite delivery system (Ins@MIL100/SDS@MS). The microspheres effectively protected the MOF NPs from rapid degradation under acidic conditions and could release insulin-loaded MOF NPs in the simulated intestinal fluid. After the oral administration of Ins@MIL100/SDS@MS into BALB/c nude mice, increased intestinal absorption of the insulin was detected compared to the oral administration of free insulin or Ins@MIL100/SDS. Furthermore, significantly enhanced plasma insulin levels were obtained for over 6 h after oral administration of Ins@MIL100/SDS@MS into diabetic rats, leading to a remarkably enhanced effect in lowering blood glucose level with a relative pharmacological availability of 7.8%. Thus, the MOF-nanoparticle-incorporated microsphere may provide a new strategy for effective oral protein delivery.