Recent advances in oral insulin delivery technologies.

With the rise in diabetes mellitus cases worldwide, oral delivery of insulin is preferred over subcutaneous insulin administration due to its good patient compliance and non-invasiveness, simplicity, and versatility. However, oral insulin delivery is hampered by various gastrointestinal barriers that result in low drug bioavailability and insufficient therapeutic efficiency. Numerous strategies have been developed to overcome these barriers and increase the bioavailability of oral insulin. Yet, no commercial oral insulin product is available to address all clinical hurdles because of various substantial obstacles related to the structural organization and physiological function of the gastrointestinal tract. Herein, we discussed the significant physiological barriers (including chemical, enzymatic, and physical barriers) that hinder the transportation and absorption of orally delivered insulin. Then, we showcased recent significant and innovative advances in oral insulin delivery technologies. Finally, we concluded the review with remarks on future perspectives on oral insulin delivery technologies and potential challenges for forthcoming clinical translation of oral insulin delivery technologies.

An injectable and biodegradable zwitterionic gel for extending the longevity and performance of insulin infusion catheters.

Continuous subcutaneous insulin infusion (CSII) is an essential insulin replacement therapy in the management of diabetes. However, the longevity of clinical CSII is limited by skin complications, by impaired insulin absorption and by occlusions associated with the subcutaneous insertion of CSII catheters, which require replacement and rotation of the insertion site every few days. Here we show that a biodegradable zwitterionic gel covering the tip end of commercial off-the-shelf CSII catheters fully resolves early skin irritations, extends the longevity of catheters and improves the rate of insulin absorption (also with respect to conventional syringe-based subcutaneous injection) for longer than 6 months in diabetic mice, and by 11 days in diabetic minipigs (from 2 to 13 days, under standard CSII-wearing conditions of insulin pump therapy and in a continuous basal-plus-bolus-infusion setting). The implanted gel displayed anti-inflammatory and anti-foreign-body-reaction properties and promoted the local formation of new blood vessels. The gel is subcutaneously injected before the tip of catheter is inserted into it, and should be generally applicable to CSII catheters and other implantable devices.

Biodegradable Zwitterionic Cream Gel for Effective Prevention of Postoperative Adhesion.

Postoperative peritoneal adhesions were frequent complications for almost any types of abdominal and pelvic surgery. This led to numerous medical problems and huge financial burden to the patients. Current anti-adhesion strategies focused mostly on physical barriers including films and hydrogels. However, they can only alleviate or reduce adhesions to certain level and their applying processes were far from ideal. This work reported the development of a biodegradable zwitterionic cream gel presenting a series of characters for an idea anti-adhesion material, including unique injectable yet malleable and self-supporting properties, which enabled an instant topical application, no curing, waiting or suturing, no hemostasis requirement, protein/cell resistance and biodegradability. The cream gel showed a major advancement in anti-adhesion efficacy by completely and reliably preventing a primary and a more severe recurrent adhesion in rat models.

Fouling-resistant zwitterionic polymers for complete prevention of postoperative adhesion.

Postoperative adhesions are most common issues for almost any types of abdominal and pelvic surgery, leading to adverse consequences. Pharmacological treatments and physical barrier devices are two main approaches to address postoperative adhesions but can only alleviate or reduce adhesions to some extent. There is an urgent need for a reliable approach to completely prevent postoperative adhesions and to significantly improve the clinical outcomes, which, however, is unmet with current technologies. Here we report that by applying a viscous, cream-like yet injectable zwitterionic polymer solution to the traumatized surface, postoperative adhesion was completely and reliably prevented in three clinically relevant but increasingly challenging models in rats. The success rate of full prevention is over 93% among 42 animals tested, which is a major leap in antiadhesion performance. Clinically used Interceed film can hardly prevent the adhesion in any of these models. Unlike current antiadhesion materials serving solely as physical barriers, the "nonfouling" zwitterionic polymer functioned as a protective layer for antiadhesion applications with the inherent benefit of resisting protein/cell adhesions. The nonfouling nature of the polymer prevented the absorption of fibronectins and fibroblasts, which contribute to the initial and late-stage development of the adhesion, respectively. This is the key working mechanism that differentiated our "complete prevention" approach from current underperforming antiadhesion materials. This work implies a safe, effective, and convenient way to fully prevent postoperative adhesions suffered by current surgical patients.

Zwitterionic micelles efficiently deliver oral insulin without opening tight junctions.

Oral delivery of protein drugs is considered a life-changing solution for patients who require regular needle injections. However, clinical translation of oral protein formulations has been hampered by inefficient penetration of drugs through the intestinal mucus and epithelial cell layer, leading to low absorption and bioavailability, and safety concerns owing to tight junction openings. Here we report a zwitterionic micelle platform featuring a virus-mimetic zwitterionic surface, a betaine side chain and an ultralow critical micelle concentration, enabling drug penetration through the mucus and efficient transporter-mediated epithelial absorption without the need for tight junction opening. This micelle platform was used to fabricate a prototype oral insulin formulation by encapsulating a freeze-dried powder of zwitterionic micelle insulin into an enteric-coated capsule. The biocompatible oral insulin formulation shows a high oral bioavailability of >40%, offers the possibility to fine tune insulin acting profiles and provides long-term safety, enabling the oral delivery of protein drugs.

Engineering and Application Perspectives on Designing an Antimicrobial Surface.

Infections, contaminations, and biofouling resulting from micro- and/or macro-organisms remained a prominent threat to the public health, food industry, and aqua-/marine-related applications. Considering environmental and drug resistance concerns as well as insufficient efficacy on biofilms associated with conventional disinfecting reagents, developing an antimicrobial surface potentially improved antimicrobial performance by directly working on the microbes surrounding the surface area. Here we provide an engineering perspective on the logic of choosing materials and strategies for designing antimicrobial surfaces, as well as an application perspective on their potential impacts. In particular, we analyze and discuss requirements and expectations for specific applications and provide insights on potential misconnection between the antimicrobial solution and its targeted applications. Given the high translational barrier for antimicrobial surfaces, future research would benefit from a comprehensive understanding of working mechanisms for potential materials/strategies, and challenges/requirements for a targeted application.

Biomaterial-tight junction interaction and potential impacts.

The active pharmaceutical ingredients (APIs) have to cross the natural barriers and get into the blood to impart the pharmacological effects. The tight junctions (TJs) between the epithelial cells serve as the major selectively permeable barriers and control the paracellular transport of the majority of hydrophilic drugs, in particular, peptides and proteins. TJs perfectly balance the targeted transport and the exclusion of other unexpected pathogens under the normal conditions. Many biomaterials have shown the capability to open the TJs and improve the oral bioavailability and targeting efficacy of the APIs. Nevertheless, there is limited understanding of the biomaterial-TJ interactions. The opening of the TJs further poses the risk of autoimmune diseases and infections. This review article summarizes the most updated literature and presents insights into the TJ structure, the biomaterial-TJ interaction mechanism, the benefits and drawbacks of TJ disruption, and methods for evaluating such interactions.

Traceable Nanoparticles with Dual Targeting and ROS Response for RNAi-Based Immunochemotherapy of Intracranial Glioblastoma Treatment.

The chemotherapy of glioblastoma is severely hindered by the immunosuppressive tumor microenvironment, especially the tumor growth factor ß (TGF-ß), an immunosuppressive cytokine. In this study, it is proposed to employ RNAi-based immunomodulation to modify the tumor immune microenvironment and improve the effect of chemotherapy. Herein, a nanotheranostic system (Angiopep LipoPCB(Temozolomide+BAP/siTGF-ß), ALBTA) with dual targeting and ROS response is established for intracranial glioblastoma treatment. The traceable nanoparticles exhibit strong siRNA condensation, high drug loading efficiency, good serum stability, and magnetic property. They can efficiently cross the blood-brain barrier and target to glioblastoma cells via receptor-mediated transcytosis. The zwitterionic lipid (distearoyl phosphoethanol-amine-polycarboxybetaine lipid) in ALBTA promotes endosomal/lysosomal escape, and thus enhances the cytotoxicity of temozolomide and improves gene silencing efficiency of siTGF-ß. ALBTA significantly improves the immunosuppressive microenvironment and prolongs the survival time of glioma-bearing mice. Moreover, ALBTA can be accurately traced by MRI in brain tumors. The study indicates that this immunochemotherapeutic platform can serve as a flexible and powerful synergistic system for treatment with brain tumors as well as other brain diseases in central nervous system.

Positively Charged Polyprodrug Amphiphiles with Enhanced Drug Loading and Reactive Oxygen Species-Responsive Release Ability for Traceable Synergistic Therapy.

Due to the vast differences in chemical properties among small molecule drugs, nucleotide drugs, and superparamagnetic iron oxide nanocubes (SPIONs), such as charge and hydrophobicity, entrapment of these within a single carrier for traceable synergistic therapy has been proven difficult. Herein, we synthesize positively charged polyprodrug amphiphiles. The hydrophobic polyprodrug unit of the amphiphiles is positively charged, which can simultaneously load hydrophobic SPIONs and absorb negative let-7b antisense oligonucleotide to construct traceable co-delivery nanoparticles (NPs). This characteristic avoids the use of inert materials and enhances drug loading of the traceable NPs. The traceable NPs can achieve controlled release of drugs to reduce the differentiation of exogenous neural stem cells (NSCs) and enhance their secretion of brain-derived neurotrophic factor (BDNF) synergistically. Exogenous NSCs treated with the NPs significantly rescue the memory deficits in 2xTg-AD mice. In addition, the transplantation site and migration of exogenous NSCs can be traced using the SPIONs with high r2 value for magnetic resonance imaging. Therefore, traceable NPs self-assembled from the positively charged polyprodrug amphiphiles may have the potential to open up a new avenue for treatment of Alzheimer's disease (AD), as well as other neurodegenerative disorders.

Dual-targeting Theranostic System with Mimicking Apoptosis to Promote Myocardial Infarction Repair via Modulation of Macrophages.

Currently unsatisfactory treatment of myocardial infarction (MI) is due to the unbridled inflammation and the delayed diagnosis at the early stage. To address these problems, firstly, phosphatidylserine (PS) was used to modulate the phenotypes of macrophages (MΦ) and resolve the early inflammation via binding to PS receptors (PSR) on macrophage surface. Secondly, highly-sensitive magnetic iron oxide nanocubes (MIONs) were adopted to realize the early visualization via magnetic resonance imaging (MRI). However, the major drawback for MIONs as contrast agents was their hydrophobic properties and insufficient delivery. Hence, zwitterionic biodegradable copolymer poly(lactide)-polycarboxybetaine (PLA-PCB, PP), companied with PS, was used to provide a good colloidal stability and long blood circulation for the nanocubes. Given the above, a theranostic nanosystem (PP/PS@MIONs) was constructed for early treatment of MI. With external magnetic field-induced targeting and PS targeting, the nanosystem enhanced the accumulation in infarcted area, and accelerated the resolution of early inflammatory responses. Moreover, the nanocubes in system were promoted to escape from endosomes/lysosomes via protonation of PCB, which contributes to accurate MRI. This nanosystem showed good inflammation-resolving effects and imaging ability in MI model rats. Therefore, this theranostic nanosystem can realize accurate visualization and significantly improve the treatment efficacy of MI at early stage.

Zwitterionic poly(carboxybetaine)-based cationic liposomes for effective delivery of small interfering RNA therapeutics without accelerated blood clearance phenomenon.

For efficient delivery of small interfering RNA (siRNA) to the target diseased site in vivo, it is important to design suitable vehicles to control the blood circulation of siRNA. It has been shown that surface modification of cationic liposome/siRNA complexes (lipoplexes) with polyethylene glycol (PEG) could enhance the circulation time of lipoplexes. However, the first injection of PEGylated lipoplexes in vivo induces accelerated blood clearance and enhances hepatic accumulation of the following injected PEGylated lipoplexes, which is known as the accelerated blood clearance (ABC) phenomenon. Herein, we developed zwitterionic poly(carboxybetaine) (PCB) modified lipoplexes for the delivery of siRNA therapeutics, which could avoid protein adsorption and enhance the stability of lipoplexes as that for PEG. Quite different from the PEGylation, the PCBylated lipoplexes could avoid ABC phenomenon, which extended the blood circulation time and enhanced the tumor accumulation of lipoplexes in vivo. After accumulation in tumor site, the PCBylation could promote the cellular uptake and endosomal/lysosomal escape of lipoplexes due to its unique chemical structure and pH-sensitive ability. With excellent tumor accumulation, cellular uptake and endosomal/lysosomal escape abilities, the PCBylated lipoplexes significantly inhibited tumor growth and induced tumor cell apoptosis.

Enhanced retention and anti-tumor efficacy of liposomes by changing their cellular uptake and pharmacokinetics behavior.

Although PEGylated liposome-based drug delivery systems hold great promising applications for cancer therapy due to their prolonged blood circulation time, PEGylation significantly reduces their cellular uptake, which markedly impairs the in vivo tumor retention and antitumor efficiency of drug-loaded liposomes. Most importantly, it has been proved that repeated injections of PEGylated liposomes with cell cycle specific drug such as topotecan (TPT) in the same animal at certain time intervals will induce "accelerated blood clearance" (ABC) phenomenon, which decreases the tumor accumulation of drug-loaded liposomes and presents a tremendous challenge to the clinical use of liposome-based drug delivery systems. Herein, we developed a zwitterionic poly(carboxybetaine) (PCB) modified liposome-based drug delivery system. The presence of PCB could avoid protein adsorption and enhance the stability of liposomes as that for PEG. Quite different from the PEGylated liposomes, the pH-sensitive PCBylated liposomes were internalized into cells via endocytosis with excellent cellular uptake and drug release ability. Furthermore, the PCBylated liposomes would avoid ABC phenomenon, which promoted the tumor accumulation of drug-loaded liposomes in vivo. With higher tumor accumulation and cellular uptake, the PCBylated drug-loaded liposomes significantly inhibited tumor growth and provided a promising approach for cancer therapy.

[Expression of IL-6 in cyclosporin A-induced gingival overgrowth].

PURPOSE: To estimate the role of IL-6 in cyclosporin A(CsA)-induced gingival overgrowth(GO) and collect the evidence of pathomechanism for CsA-induced GO. METHODS: Gingival fibroblasts and epithelial cells were treated with CsA of three different concentrations (600ng/mL, 800ng/mL, and 1000ng/mL) with different time (48h, 72h). After cell stretched preparation, the secretion of IL-6 was analyzed by ELISA while expression of IL-6 was analyzed by immunohistochemistry (ABC). SAS 6.0 software package was used for statistical analysis. RESULTS: The growth speed of gingival epithelial cells in the group treated with CsA was significantly faster than the control group (P<0.05). The IL-6 expression of gingival epithelial cells and fibroblasts had no significance difference, but changed depending on the concentration and treated time with CsA. During the first 24h, there was no significant difference between the experimental and control groups of gingival fibroblasts, while after stimulation of 1000ng/mL CsA for 24h or longer, the secretion of IL-6 in gingival fibroblasts was significantly higher than the control group (P<0.05). CONCLUSIONS: IL-6 is not the main cytokine of gingival epithelial cells, IL-6 in CsA-induced GO probably secreted by the gingival fibroblasts; the effect of CsA on the secretion of IL-6 in the gingival epithelial cells and gingival fibroblasts is associated with the time and concentrations of CsA.

[Expression of TGF-ß1 and PCNA in cyclosporin A-induced gingival overgrowth].

PURPOSE: To investigate the expression of transforming growth factor-ß1(TGF-ß1) and proliferating cell nuclear of antigen (PCNA) in cyclosporin A(CsA)-induced gingival overgrowth (GO) tissues. METHODS: After extraction of half of the maxillary molars, 20 male Sprague-Dawley rats were randomized into a CsA-injection group (10mg·kg⁻·d⁻¹) or a normal saline control group. Ten rats per group were sacrificed at the fourth week after injection. The gingival width was measured under a stereo-microscope. After full demineralization of the mandible, gingival specimens were taken. The linear measurements and the immunohistochemistry analysis of TGF-ß1 and PCNA were made using the software of Image Pro-plus 6.0. The data was analyzed with SAS6.12 software package. RESULTS: The percentage of cells positive staining for TGF-ß1 and PCNA was significantly higher in the CsA rats than in the control rats (P<0.05), but there was no significant difference between the edentulous and denti-gingiva in the same group(P>0.05). CONCLUSIONS: The upregulation of TGF-ß1 may have no direct relations with gingival inflammation in CsA-induced gingival overgrowth.In addition, TGF-ß1 may be one of the key cytokines for CsA-induced gingival overgrowth. Increased epithelial proliferative activity may be the main cause of epithelial hyperplasia.

[The effect of dental plaque in cyclosporin A-induced gingival overgrowth].

PURPOSE: To evaluate the role of dental plaque in cyclosporin A(CsA)-induced gingival overgrowth. METHODS: After extraction of half of the maxillary molars, twenty male Sprague-Dawley rats were assigned to a CsA-injection group (10mg/k x d) or a control group. Ten rats per group were sacrificed at week 4. The gingival width was measured under a stereomicroscope. Gingival specimens were taken, and the linear measurements were made with the help of software Image Pro-plus 6.0. The data was analyzed with SAS 6.12 software package. RESULTS: The gingival width of the CsA group was significantly greater than the control group in both macroscopic analysis and histomorphometrical analysis (P<0.05). CONCLUSIONS: Dental plaque seems not to be a essential but to be a co-factor for the CsA-induced gingival overgrowth.