Enhancement of oral insulin bioavailability: in vitro and in vivo assessment of nanoporous stimuli-responsive hydrogel microparticles

ABSTRACT

Objective: Oral insulin administration suffers gastrointestinal tract (GIT) degradation and inadequate absorption from the intestinal epithelium resulting in poor bioavailability. This study entails in vitro and in vivo assessment of stimuli-responsive hydrogel microparticles (MPs) in an attempt to circumvent GI barrier and enhance oral insulin bioavailability.

Methods: Bacterial cellulose-g-poly(acrylic acid) (BC-g-P(AA)) hydrogel MPs were evaluated for morphology, swelling, entrapment efficiency (EE), in vitro insulin release and enzyme inhibition. The ex vivo mucoadhesion, insulin degradation and transport were investigated in excised intestinal tissues. The effect of MPs on paracellular transport was studied in Caco-2/HT29-MTX monolayers. The in vivo hypoglycemic effect and pharmacokinetics of insulin-loaded MPs were investigated in diabetic rats.

Results: Hydrogel MPs efficiently entrapped insulin (EE up to 84%) and exhibited pH-responsive in vitro release. The MPs decreased the proteolytic activity of trypsin (up to 60%). Insulin transport across monolayers was increased up to 5.9-times by MPs. Histological assessment of GI tissues confirmed the non-toxicity of MPs. Orally administered insulin-loaded MPs showed higher hypoglycemic effect as compared to insulin solution and enhanced relative oral bioavailability of insulin up to 7.45-times.

Conclusion: These findings suggest that BC-g-P(AA) MPs are promising biomaterials to overcome the barriers of oral insulin delivery and enhancing its bioavailability.     

Effects of anti‐TNF‐α agents on circulating endothelial‐derived and platelet‐derived microparticles in psoriasis

Psoriasis involves TNF‐α secretion leading to release of microparticles into the bloodstream. We investigated the effect of TNF blockers on microparticles levels before and after treatment in patients (twenty treated by anti‐TNF‐α agents and 6 by methotrexate) with severe psoriasis. Plasmatic microparticles were labelled using fluorescent monoclonal antibodies and were analysed using cytometry. Three months later, 70% of patients treated with anti‐TNF‐α agents achieved a reduction in PASI score of at least 75%. The clinical improvement in patients treated with anti‐TNF‐α agents was associated with a significant reduction of the mean number of platelet microparticles (2837/μl vs 1849/μl, P = 0.02) and of endothelial microparticles (64/μl vs 22/μl, P = 0.001). Microparticles are significantly decreased in psoriatic patients successfully treated by anti‐TNF‐α. Microparticles levels as circulating endothelial cells represent signs of endothelial dysfunction and are elevated in psoriasis. Then, TNF blockade may be effective to reduce cardiovascular risk through the reduction of circulating microparticles.     

Microparticles in stored red blood cells: an approach using flow cytometry and proteomic tools

Background and Objectives Microparticles (MPs) are small phospholipid vesicles of less than 1 µm, shed in blood flow by various cell types. These MPs are involved in several biological processes and diseases. MPs have also been detected in blood products; however, their role in transfused patients is unknown. The purpose of this study was to characterize those MPs in blood bank conditions. Materials and Methods Qualitative and quantitative experiments using flow cytometry or proteomic techniques were performed on MPs derived from erythrocytes concentrates. In order to count MPs, they were either isolated by various centrifugation procedures or counted directly in erythrocyte concentrates. Results A 20-fold increase after 50 days of storage at 4°C was observed (from 3370 ± 1180 MPs/µl at day 5 to 64 850 ± 37 800 MPs/µl at day 50). Proteomic analysis revealed changes of protein expression comparing MPs to erythrocyte membranes. Finally, the expression of Rh blood group antigens was shown on MPs generated during erythrocyte storage. Conclusions Our work provides evidence that storage of red blood cell is associated with the generation of MPs characterized by particular proteomic profiles. These results contribute to fundamental knowledge of transfused blood products.     

Circulating endothelial microparticles in acute ischemic stroke: a link to severity, lesion volume and outcome

BACKGROUND: Endothelial membrane microparticles (EMP) in plasma are elevated in several vascular diseases. OBJECTIVES: To test the hypothesis that EMP would be increased in patients with acute ischemic stroke and would correlate with stroke severity, brain lesion volume and outcome. PATIENTS AND METHODS: Forty-one patients were studied and divided into two groups based on the National Institutes of Health Stroke Scale (NIHSS) score: 20 patients with mild stroke (NIHSS score < 5) and 21 patients with moderate-severe stroke (NIHSS score > or = 5). Lesion volume was measured using diffusion-weighted magnetic resonance imaging and discharge outcome was based on the discharge Barthel and Rankin scores. Twenty-three age-matched control subjects were also studied. Using flow cytometry, endoglin-positive EMP: CD105+ CD41a-CD45- (E(+)EMP), specific endothelial EMP expressing VE-cadherin and endoglin: CD105+CD144+ (C(+)EMP), EMP expressing phosphatidylserine: CD105+PS+ CD41a- (PS(+)EMP) and EMP expressing ICAM-1: CD105+CD54+ CD45- (I(+)EMP) were analyzed. RESULTS: Significantly higher PS(+)EMP counts were observed in the group of acute ischemic stroke patients [median 59 (25th-75th percentile: 28-86) MP microL(-1)] relative to the controls [28 (14-36) MP microL(-1)] (P = 0.002). All four EMP phenotypes studied were elevated in the subgroup of moderate-severe stroke patients relative to the controls (all P < 0.05). In the patients with acute ischemic stroke three EMP phenotypes (E(+)EMP, PS(+)EMP and I(+)EMP) correlated significantly with brain lesion volume, with I(+)EMP (P = 0.002) showing the strongest correlation. Admission counts of C(+)EMP (P = 0.0003) and E(+)EMP (P = 0.003) correlated significantly with discharge clinical outcome. CONCLUSIONS: Certain circulating EMP phenotypes may be associated with severity, lesion volume and outcome of acute ischemic stroke. EMP analysis shows promising contribution to understanding stroke pathophysiology.     

膜微粒子与造血调控

膜微粒子是细胞膜脱落下来形成的微粒样物质。多种细胞受到激活或者凋亡时产生膜微粒子并且释放到细胞外环境。膜微粒子成分取决于微粒子的起源细胞和微粒子形成过程。膜微粒子参与细胞之间的信息传递。某些细胞来源的膜微粒子具有调节造血干祖细胞的存活、增殖、分化、黏附及迁移的作用。本文就膜微粒子的成分，形成机制及其造血调控作用作一概述。     

Antigenic characterization of endothelial cell-derived microparticles and their detection ex vivo

Summary. Background: Endothelial activation and dysfunction are associated with several diseases. However, hardly any specific markers are available. Microparticles (MP) from endothelial cells (EC; EMP) were reported in patient groups and healthy individuals. The antibodies used to detect EMP, however, were mainly directed against antigens without EC specificity. Objectives: We evaluated the antigens on EC and EMP to establish proper markers for EMP detection. Methods: EMP were isolated from supernatants of resting and interleukin (IL)‐1α activated human umbilical vein EC (HUVEC; n = 3; 0–72 h), stained with annexin V and monoclonal antibodies, and analyzed by flow cytometry. Human platelet‐MP (PMP), the main MP population in plasma, were prepared in vitro. EMP and PMP were studied in plasma from systemic lupus erythematosus (SLE) patients (n = 11) and healthy individuals (n = 10). Results: Platelet–endothelial cell adhesion molecule‐1 (PECAM‐1), α_ν and β₃ were constitutively exposed on HUVEC, but (almost) absent on EMP (<15% positive for α_ν and β₃), or only exposed on a subpopulation (PECAM‐1; 30–60%). Activated HUVEC (>80%) and (subpopulations of) EMP exposed E‐selectin and tissue factor. PMP strongly exposed PECAM‐1, β₃, and glycoprotein (GP)Ib (CD42b), but not α_ν or E‐selectin. GPIb and P‐selectin (CD62P) were absent on EMP. Plasma samples contained 0.5% MP staining for E‐selectin and/or α_ν. Plasma from one SLE patient contained E‐selectin exposing MP (21%), but little α_ν‐positive MP. Conclusions: EC release EMP in vitro. The antigenic phenotype of EMP released from resting and IL‐1α‐stimulated EC differs among each other as well as from resting and stimulated EC, respectively. E‐selectin exposed on IL‐1α‐stimulated EC is a valid marker for EMP detection ex vivo to establish endothelial cell activation.     

Catechin-loaded Eudragit microparticles for the management of diabetes: formulation,characterization and in vivo evaluation of antidiabetic efficacy

Catechin (CT) is natural molecule proved for antidiabetic activity. Clinical application of CT is highly restricted because of its low bioavailability and ineffectiveness in in vivo conditions. Therefore, the main objective of the present investigation was to formulate CT-loaded Eudragit RS 100 microparticles and evaluated for its potential against diabetes. CT microparticles showing highest entrapment efficiency of 92.3?±?6.5% and higher percentage yield of 63.46?±?4.3% was selected as optimised formulation. CT microparticles treated rats showed significantly lower blood glucose, cholesterol, LDL, free fatty acid and triglyceride concentrations in comparison to pristine CT-treated rats. The glucose and lipid profiles of microparticle formulation were akin to normal rats. Moreover, CT microparticles did not produce obesity even after 60 days which is a comment side effect of antidiabetic drugs. These results indicate that the CT microparticles can be applied as potential and safe carrier for the treatment of diabetes.     

血小板衍生微颗粒在血管内皮损害中的作用机制

血小板衍生微颗粒(platelet-derived microparticle,PMP)是血小板在各种刺激作用下活化而释放的一种超微膜性囊泡,直径小于1.0 μm.这些血小板微粒由浆膜囊性碎片和α-颗粒组成.血液中PMP的形成、释放及水平可反映血小板活化.PMP可以促凝血,促进血小板和白细胞黏附于内皮下膜,促进血管生成和刺激血管平滑肌的增殖.在动脉粥样硬化、糖尿病、川崎病等多种血管性疾病患者血液中PMP水平升高,该文就血管内皮损伤过程中PMP的可能作用机制作一综述.     

A Comparison of Aerosolization and Homogenization Techniques for Production of Alginate Microparticles for Delivery of Corticosteroids to the Colon

Alginate microparticles incorporating hydrocortisone hemisuccinate were produced by aerosolization and homogenization methods to investigate their potential for colonic drug delivery. Microparticle stabilization was achieved by CaCl₂ crosslinking solution (0.5 M and 1 M), and drug loading was accomplished by diffusion into blank microparticles or by direct encapsulation. Homogenization method produced smaller microparticles (45-50 μm), compared to aerosolization (65-90 μm). High drug loadings (40% wt/wt) were obtained for diffusion-loaded aerosolized microparticles. Aerosolized microparticles suppressed drug release in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) prior to drug release in simulated colonic fluid (SCF) to a higher extent than homogenized microparticles. Microparticles prepared using aerosolization or homogenization (1 M CaCl₂, diffusion loaded) released 5% and 17% of drug content after 2 h in SGF and 4 h in SIF, respectively, and 75% after 12 h in SCF. Thus, aerosolization and homogenization techniques show potential for producing alginate microparticles for colonic drug delivery in the treatment of inflammatory bowel disease.     

The Preparation and Physicochemical Characterization of Aluminum Hydroxide/TLR7a,a Novel Vaccine Adjuvant Comprising a Small Molecule Adsorbed to Aluminum Hydroxide

Adjuvants are necessary to enable vaccine development against a significant number of challenging pathogens for which effective vaccines are not available. We engineered a novel small-molecule immune potentiator, a benzonaphthyridine agonist targeting toll-like receptor 7 (TLR7), as a vaccine adjuvant. TLR7 agonist (TLR7a) was engineered to be adsorbed onto aluminum hydroxide (AlOH), and the resulting AlOH/TLR7a was evaluated as a vaccine adjuvant. AlOH/TLR7a exploits the flexibility of AlOH formulations, has an application in many vaccine candidates, and induced good efficacy and safety profiles against all tested antigens (bacterial- and viral-derived protein antigens, toxoids, glycoconjugates, and so forth) in many animal models, including nonhuman primates. In this article, we describe the outcome of the physicochemical characterization of AlOH/TLR7a. Reverse-phase ultra performance liquid chromatography, confocal microscopy, flow cytometry, zeta potential, and phosphophilicity assays were used as tools to demonstrate the association of TLR7a to AlOH and to characterize this novel formulation. Raman spectroscopy, nuclear magnetic resonance, and mass spectroscopy were also used to investigate the interaction between TLR7a and AlOH (data not shown). This pivotal work paved the way for AlOH/TLR7a to progress into the clinic for evaluation as an adjuvant platform for vaccines against challenging preventable diseases.