Synergistic effects of photodynamic therapy and chemotherapy: Activating the intrinsic/extrinsic apoptotic pathway of anoikis for triple-negative breast cancer treatment.

Triple-negative breast cancer (TNBC) is a highly invasive and metastatic subtype of breast cancer that often recurs after surgery. Herein, we developed a cyclodextrin-based tumor-targeted nano delivery system that incorporated the photosensitizer chlorin e6 (Ce6) and the chemotherapeutic agent lonidamine (LND) to form the R6RGD-CMßCD-se-se-Ce6/LND nanoparticles (RCC/LND NPS). This nanosystem could target cancer cells, avoid lysosomal degradation and further localize within the mitochondria. The RCC/LND NPS had pH and redox-responsive to control the release of Ce6 and LND. Consequently, the nanosystem had a synergistic effect by effectively alleviating hypoxia, enhancing the production of cytotoxic reactive oxygen species (ROS) and amplifying the efficacy of photodynamic therapy (PDT). Furthermore, the RCC/LND NPS + light weakened anoikis resistance, disrupted extracellular matrix (ECM), activated both the intrinsic apoptotic pathway (mitochondrial pathway) and extrinsic apoptotic pathway (receptor death pathway) of anoikis. In addition, the nanosystem showed significant anti-TNBC efficacy in vivo. These findings collectively demonstrated that RCC/LND NPS + light enhanced the anticancer effects, induced anoikis and inhibited tumor cell migration and invasion through a synergistic effect of chemotherapy and PDT. Overall, this study highlighted the promising potential of the RCC/LND NPS + light for the treatment of TNBC.

Combined Photosensitive Gene Therapy Effective Against Triple-Negative Breast Cancer in Mice Model.

Introduction: Tumor hypoxia and invasion present significant challenges for the efficacy of photodynamic therapy (PDT) in triple-negative breast cancer (TNBC). This study developed a mitochondrial targeting strategy that combined PDT and gene therapy to promote each other and address the challenges. Methods: The positively charged amphiphilic material triphenylphosphine-tocopherol polyethylene glycol succinate (TPP-TPGS, TPS) and the photosensitizer chloride e6 (Ce6) formed TPS@Ce6 nanoparticles (NPs) by hydrophobic interaction. They electrostatically condensed microRNA-34a (miR-34a) to form stable TPS@Ce6/miRNA NPs. Results: Firstly, Ce6 disrupted the lysosomal membrane, followed by successful delivery of miR-34a by TPS@Ce6/miRNA NPs. Meanwhile, miR-34a reduced ROS depletion and further enhanced the effectiveness of PDT. Consequently, the mutual promotion between PDT and gene therapy led to enhanced anti-tumor effects. Furthermore, the TPS@Ce6/miRNA NPs promoted apoptosis by down-regulating Caspase-3 and inhibited tumor cell migration and invasion by down-regulating N-Cadherin. In addition, in vitro and in vivo experiments demonstrated that the TPS@Ce6/miRNA NPs achieved excellent anti-tumor effects. These findings highlighted the enhanced anticancer effects and reduced migration of tumor cells through the synergistic effects of PDT and gene therapy. Conclusion: Taken together, the targeted co-delivery of Ce6 and miR-34a will facilitate the application of photodynamic and genic nanomedicine in the treatment of aggressive tumors, particularly TNBC.

Glutathione Programmed Mitochondria Targeted Delivery of Lonidamine for Effective Against Triple Negative Breast Cancer.

Introduction: Mitochondria are a significant target of lonidamine (LND). However, its limited solubility and inability to specifically target mitochondria, LND can lead to hepatic toxicity and has shown only modest anticancer activity. The objective of this study is to establish a glutathione programmed mitochondria targeted delivery of LND for the effective treatment of triple negative breast cancer (TNBC). Methods: In this study, LND was encapsulated in poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) wrapped with mitochondria-targeting short-chain triphenylphosphonium-tocopherol polyethylene glycol succinate (TPP-TPGS, TPS) and tumor-targeting long-chain 1, 2-distearoyl-sn-glycero-3-phosphoethanolamine-S-S-polyethylene glycol-R6RGD (DSPE-S-S-PEG2000-R6RGD, DSSR), which were designated as LND-PLGA/TPS/DSSR NPs. The release behavior was evaluated, and cellular uptake, in vitro and in vivo antitumor activity of nanoparticles were investigated. The mechanism, including apoptosis of tumor cells and mitochondrial damage and respiratory rate detection, was also further investigated. Results: LND-PLGA/TPS/DSSR NPs were successfully prepared, and characterization revealed that they are globular particles with smooth surfaces and an average diameter of about 250 nm. Long-chain DSSR in LND-PLGA/TPS/DSSR NPs prevented positively charged LND-PLGA/TPS NPs from being cleared by the reticuloendothelial system. Furthermore, LND release rate from NPs at pH 8.0 was significantly higher than that at pH 7.4 and 5.5, which demonstrated specific LND release in mitochondria and prevented LND leakage in cytoplasm and lysosome. NPs could locate in mitochondria, and the released LND triggered apoptosis of tumor cells by damaging mitochondria and releasing apoptosis-related proteins. In addition, in TNBC mice model, programmed mitochondria targeted NPs improved efficacy and reduced LND toxicity. Conclusion: LND-PLGA/TPS/DSSR NPs may be a useful system and provide an effective approach for the treatment of TNBC.

Co-delivery of immunochemotherapeutic by classified targeting based on chitosan and cyclodextrin derivatives.

Herein, a cyclodextrin derivative (R6RGD-CMßCD) with tumor target and a carboxymethyl chitosan derivative (M2pep-CMCS) with tumor-associated macrophages 2 (TAM2) target were successfully synthesized, respectively. DOX-loaded nanoparticles (R6RGD-CMßCD@DOX NPs, RCNPDOX) and R848-loaded nanoparticles (M2pep-CMCS@R848 NPs, MCNPR848) were prepared. Furthermore, the RCNPDOX and MCNPR848 exhibited good DOX and R848 absorption. Meanwhile, the synergetic cell toxicity of RCNPDOX and MCNPR848 was found. Additionally, RCNPDOX + MCNPR848 nanoparticles greatly promoted the expression levels of cleaved Caspase3, which indicated that the nanoparticles could induce cell apoptosis. At the same time, the immunohistochemical images exhibited that RCNPDOX + MCNPR848 group could effectively transform the phenotype of tumor-associated macrophages. Importantly, in vivo experiments revealed that RCNPDOX + MCNPR848 NPs exerted excellent anticancer effects in tumor-bearing mice. To summarize, RCNPDOX + MCNPR848 NPs are effective anticancer treatment combining chemotherapy and immunotherapy, M2pep-CMCS and R6RGD-CMßCD are good delivery materials.

Biomimetic multifunctional nanozymes enhanced radiosensitization for breast cancer via an X-ray triggered cascade reaction.

Radiotherapy has been widely applied for breast cancer treatment in the clinic, while improving the radiation sensitivity of tumors and protecting normal tissues from radiation damage has drawn considerable attention. In this study, we reported a biomimetic multifunctional nanozyme (BSA@CeO/Fe2+), which can be used as a radiosensitizer for breast cancer treatment. It was demonstrated that BSA@CeO/Fe2+ presented a pH dependent multiple enzyme like activity that enhances the hydroxyl radical level by cascade catalytic reactions in a tumor microenvironment to obtain a desirable tumor-suppression rate (83.07%). Moreover, BSA@CeO/Fe2+ was also proved to reduce reactive oxygen species levels in normal cells. Additionally, BSA@CeO/Fe2+ nanozymes showed no obvious toxicity by routine blood examination and blood biochemistry assays. Therefore, this work provided a promising strategy for nanocatalytic tumor therapy by rationally designing biomimetic nanozymes with multienzymatic activities for achieving high radiotherapy efficacy and excellent biosafety simultaneously.

Development of oral curcumin based on pH-responsive transmembrane peptide-cyclodextrin derivative nanoparticles for hepatoma.

Herein, a pH-responsive cyclodextrin derivative (R6H4-CMßCD) with cell-penetrating ability was successfully synthesized, and curcumin-loaded nanoparticles (R6H4-CMßCD@CUR NPs, RCCNPs) were developed to improve its efficacy in hepatoma. RCCNPs could improve the cell uptake compared with CMßCD@CUR NPs (CCNPs) and were internalized into cells mainly through endocytosis mediated by reticulin and macropinocytosis. Furthermore, the accumulation of RCCNPs in hepatoma cells at pH 6.4 was higher than that at pH 7.4, indicating a pH-responsive uptake. Additionally, RCCNPs could escape from the lysosomes via the "proton sponge effect", and a high apoptosis rate was detected. Importantly, in vivo experiments revealed that orally administered RCCNPs could exert excellent anti-cancer effects in tumor-bearing mice. Hematoxylin-eosin staining did not show significant histological changes in the major organs. Thus, our findings indicate the potential of R6H4-CMßCD as a nanopharmaceutical material, and RCCNPs as an effective delivery system for oral curcumin in cancer management.

Effective Antitumor of Orally Intestinal Targeting Penetrating Peptide-Loaded Tyroserleutide/PLGA Nanoparticles in Hepatocellular Carcinoma.

PURPOSE: Hepatocellular carcinoma (HCC) is a common malignant tumor that seriously threatens human life and health. Currently, the majority of antitumor drugs are administered in an injectable manner, which can cause pain and side effects to patients. Objective of this study is to establish an effective oral drug delivery system for anti hepatoma drugs. METHODS: In this study, intestinal targeting cell penetrating peptide (R6LRVG) was obtained by binding cell penetrating peptide (R6) with the polypeptide of LRVG (targeting intestinal epithelial cells). Next, R6LRVG-modified tyroserleutide-poly(lactic-co-glycolic acid) (PLGA) nanoparticles (YSL-PLGA/R6LRVG NPs) were prepared. After that, the nanoparticles were characterized and their stability was evaluated. The cellular uptake, in vitro bioactivity and in vivo antitumor activity of the nanoparticles were investigated. In addition, the mechanism, including the endocytic pathway and respiratory rate detection of mitochondria, was further investigated. RESULTS: YSL-PLGA/R6LRVG NPs were successfully prepared. Characterization revealed YSL-PLGA/R6LRVG NPs to be globular particles with smooth surfaces and an average diameter of 222.6 nm. The entrapment efficiency and drug loading of tyroserleutide were 70.27% and 19.69%, respectively. Furthermore, the YSL-PLGA/R6LRVG NPs group exhibited the largest amount of YSL uptake. We also found that cell uptake of YSL-PLGA/R6LRVG NPs could be related to the endocytosis pathways mediated by reticulin and caveolae/lipid rafts. Additionally, the YSL-PLGA/R6LRVG NPs could interfere with mitochondrial function. In vivo experiments revealed that orally administered YSL-PLGA/R6LRVG NPs exerted excellent anticancer effects in tumor-bearing mice. Hematoxylin-eosin staining did not show any histological changes in the major organs. CONCLUSION: To summarize, YSL-PLGA/R6LRVG NPs could be a useful oral delivery system of YSL and may provide a new platform for the oral delivery of anticancer drugs.

Effect and mechanism of actionin vitroof cyclodextrin derivative nanoparticles loaded with tyroserleutide on hepatoma.

In this study, a cyclodextrin derivative (R6RGD-CMßCD) nanoparticle with tumor targeting and cell penetration ability was successfully synthesized and loaded with tyroserleutide (YSL) to obtain YSL-loaded nanoparticles (YSL/R6RGD-CMßCD NPs). The characterization of these NPs revealed a smooth surfaces and an average diameter of approximately 170 nm. YSL/R6RGD-CMßCD NPs increased the NP uptake in Caco-2 cells. As regard the mechanism of action, the cell uptake was related to endocytosis mediated by reticulin and megacytosis. In addition, YSL/R6RGD-CMßCD NPs induced significantly higher cytotoxicity on tumor cells and better tumor targeting compared with the effect of CMßCD NPs. Most importantly, the good anti-cancer effect of YSL/R6RGD-CMßCD NPs might be due to the interference with the function of mitochondria. On the other hand, YSL/R6RGD-CMßCD NPs were not toxic for normal cells. Taken together, our results indicated that R6RGD-CMßCD could be considered as a nanopharmaceutical material with good tumor targeting abilities, and their combination with YSL could represent an effective anti-cancer system.

Design and Investigation of Penetrating Mechanism of Octaarginine-Modified Alginate Nanoparticles for Improving Intestinal Insulin Delivery.

The aim of the study is to design octaarginine (R8)-modified insulin-alginate nanoparticles (INS-SA/R8 NPs) as the oral insulin delivery system, and further investigate its penetrating mechanism. The characterization results indicated that the surface of INS-SA/R8 NPs was smooth and the average diameter was about 300 nm. INS-SA/R8 NPs exhibited a stronger stability in the simulated gastrointestinal fluids and had a better controlled release than unmodified alginate nanoparticles (INS-SA NPs). Moreover, INS-SA/R8 NPs group had the strongest insulin transport capacity and the largest amount of insulin uptake in all experimental groups. Most importantly, the improvement of insulin intestinal uptake was further confirmed in rat intestine in vivo, and its penetrating mechanism might be involved in the production of endogenous nitric oxide (NO) signal molecule. In addition, in vivo hypoglycemic studies showed that orally administrated INS-SA/R8 NPs produced a better hypoglycemic effect as compared with INS-SA NPs in diabetic rats. Meanwhile, from the cytotoxicity analysis, INS-SA/R8 NPs were safe for oral administration. Taken together, INS-SA/R8 NPs was a good oral insulin delivery system, which might also be suitable for other protein drugs.

Collagen/Chitosan Complexes: Preparation, Antioxidant Activity, Tyrosinase Inhibition Activity, and Melanin Synthesis.

Bioactive collagen/chitosan complexes were prepared by an ion crosslinking method using fish skin collagen and chitosan solution as raw materials. Scanning electron microscopy observation confirmed that the collagen/chitosan complexes were of a uniform spherical shape and uniform particle size. The complexes were stable at different pH values for a certain period of time through swelling experiments. Differential scanning calorimetry (DSC) showed the collagen/ chitosan complexes were more stable than collagen. X-ray diffraction (XRD) showed that the complexes had a strong crystal structure, and Fourier transform infrared spectroscopy (FTIR) data revealed the changes in the secondary structure of the protein due to chitosan and TPP crosslinking. The content of malondialdehyde (MDA) in the complex treatment group was considerably lower, but the content of SOD was significantly higher than that of the collagen group or chitosan group. In addition, the collagen/chitosan complexes could considerably reduce melanin content, inhibit tyrosinase activity, and down-regulate tyrosinase mRNA expression. In conclusion, the collagen/chitosan complexes were potential oral protein preparation for antioxidant enhancement and inhibiting melanin synthesis.

Oligoarginine mediated collagen/chitosan gel composite for cutaneous wound healing.

In this study, the collagen/chitosan gel composite supplemented with a cell-penetrating peptide (CPP) (Oligoarginine, R8) was prepared. Then, the physicochemical properties of the new collagen/chitosan/CPPs gel obtained were analyzed and the related characteristics were evaluated by scanning electron microscopy (SEM), fourier transform infrared (FTIR), differential scanning calorimetry (DSC), differential thermal analyzer (DTA). Furthermore, we found that collagen/chitosan/CPPs gel composite was capable of inhibiting Staphylococcus aureus growth and had good ability to heal wounds. The mice test results showed that collagen/chitosan/CPPs gel had the highest healing rate, fastest healing speed in all the treatments. After 14 days, the group treated by collagen/chitosan/CPPs gel showed nearly complete wound surface healing rate of 98 ±â€¯4.71%. In addition, histopathological examination suggested that collagen/chitosan/CPPs could promote cutaneous wound healing through enhancing granulation tissue formation, increasing collagen deposition and promoting angiogenesis in the wound tissue. Meanwhile, no significant cytotoxicity of the gel was observed. In conclusion, the collagen/chitosan/CPPs gel composite which has antibacterial activity renders a high therapeutic efficiency to heal wounds.

Enhancing the oral bioavailability of baicalein via Solutol® HS15 and Poloxamer 188 mixed micelles system.

OBJECTIVES: To increase the solubility of baicalein (BAI) by preparing BAI-micelles (BAI-M) with Solutol HS15 (HS15) and Poloxamer 188 (F68), thereby improving its oral bioavailability. METHODS: Baicalein micelles were prepared with HS15 and F68 by thin-film dispersion method and optimized by central composite design (CCD) approach. Physicochemical, in vitro release, Caco-2 cell transport and pharmacokinetic studies of BAI-M were performed. KEY FINDINGS: The optimal formulation showed spherical shape by characterization of the transmission electron microscope with average small size (23.14 ± 1.46 nm) and high entrapment efficiency (92.78±0.98%) and drug loading (6.45±1.54%). The in vitro release study of BAI-M showed a significantly sustained release pattern compared with free BAI. Caco-2 cell transport study demonstrated that high permeability of BAI was achieved after loading it into micelles. Meanwhile, pharmacokinetics study of BAI-M showed a 3.02-fold increase in relative oral bioavailability compared with free BAI. CONCLUSIONS: Based on our findings, we concluded that HS15 can be used as a carrier in this drug delivery system that includes F68, and BAI-M has great potential in improving solubility and oral bioavailability.

A cell-penetrating peptide conjugated carboxymethyl-ß-cyclodextrin to improve intestinal absorption of insulin.

In this study, a cell-penetrating peptide conjugate, R8-carboxymethyl-ß-cyclodextrin (R8-CM-ß-CD), was synthesized, and then we prepared the supramolecular complex (insulin/R8-CM-ß-CD). The physicochemical properties of the complex were characterized. The supramolecular complex could facilitate the uptake of insulin, meanwhile, induce a significantly higher internalization of insulin. Interestingly, the transportation efficiency of insulin/R8-CM-ß-CD across the Caco-2 cell monolayer was about 3 times greater than that of insulin/CM-ß-CD. Further studies on the mechanism in increasing uptake efficiency showed that R8-CM-ß-CD was internalized via different styles of endocytosis and could inhibit P-glycoprotein (P-gp) efflux pumps. Importantly, the formulation of insulin/R8-CM-ß-CD showed the highest increase in the permeability of insulin and the best biological response in diabetic rats of all the treatments. In addition, no sign of toxicity was observed after administrations of R8-CM-ß-CD. These results demonstrated that R8-CM-ß-CD was a promising carrier for use in protein drug delivery.

A cell-penetrating peptide mediated chitosan nanocarriers for improving intestinal insulin delivery.

To overcome barriers for oral delivery of insulin, the chitosan(CS)-based nanocarriers with a novel cell penetrating peptide (SAR6EW) have been prepared and evaluated in this study. Characterization measurements showed that SAR6EW/CS/insulin-NPs displayed global particles with smooth surfaces and an average diameter about 150nm. The entrapment efficiency and loading rates of insulin were 75.36% and 7.58%, respectively. Insulin could be released constantly from SAR6EW/CS/insulin-NPs in vitro. Furthermore, SAR6EW/CS/insulin-NPs could facilitate the uptake of insulin and induce a significantly higher internalization of insulin via adding clathrin and caveolae mediated endocytosis. In addition, in vivo hypoglycemic studies showed that orally administrated SAR6EW/CS/insulin-NPs produced a better hypoglycemic effect as compared with CS/insulin-NPs in diabetic rats. Meanwhile, no significant cytotoxicity of the nanoparticles was observed. In conclusion, SAR6EW-mediated chitosan nanocarriers showed sufficient effectiveness for oral delivery of insulin. This delivery system is also promising for the delivery of other protein drugs by oral administration.

Role of Muscarinic Acetylcholine Receptor-2 in the Cerebellar Cortex in Cardiovascular Modulation in Anaesthetized Rats.

Our previous investigations have demonstrated that microinjection of acetylcholine (ACh) or muscarinic ACh receptor activation in the cerebellar cortex induces a systemic blood pressure depressor response. This study aimed to determine the role of muscarinic ACh receptor-2 (M2 receptor) in the cerebellar cortex in cardiovascular function regulation in rats. A nonselective muscarinic receptor agonist (oxotremorine M, OXO; 30 mM), a selective M2 receptor agonist (arecaidine but-2-ynyl ester tosylate, ABET; 3, 10, and 30 mM), 30 mM OXO mixed with a selective M2 receptor antagonist (methoctramine hydrate, MCT; 0.3, 1, and 3 mM), and normal saline (0.9 % NaCl) were separately microinjected (0.5 µl/5 s) into the cerebellar cortex (lobule VI) of anaesthetized rats. We measured the mean arterial pressure (MAP), maximum change in MAP, and reactive time (RT; the duration required for the blood pressure to return to basal levels), heart rate (HR) and the maximum change in HR during the RT in response to drug activation. The results demonstrated that ABET dose-dependently decreased MAP and HR, increased the maximum change in MAP and the maximum change in HR, and prolonged the RT. Furthermore, MCT dose-dependently blocked the OXO-mediated cardiovascular depressor response. This study provides the first evidence that M2 receptors in the cerebellar cortex are involved in cardiovascular regulation, the activation of which evokes significant depressor and bradycardic responses.

Amphiphilic Lipopeptide-Mediated Transport of Insulin and Cell Membrane Penetration Mechanism.

Arginine octamer (R8) and its derivatives were developed in this study for the enhanced mucosal permeation of insulin. R8 was substituted with different aminos, then modified with stearic acid (SA). We found that the SAR6EW-insulin complex had stronger intermolecular interactions and higher complex stability. The amphiphilic lipopeptide (SAR6EW) was significantly more efficient for the permeation of insulin than R8 and R6EW both in vitro and in vivo. Interestingly, different cellular internalization mechanisms were observed for the complexes. When the effectiveness of the complexes in delivering insulin in vivo was examined, it was found that the SAR6EW-insulin complex provided a significant and sustained (six hours) reduction in the blood glucose levels of diabetic rats. The improved absorption could be the comprehensive result of stronger intermolecular interactions, better enzymatic stability, altered internalization pathways, and increased transportation efficacy. In addition, no sign of toxicity was observed after consecutive administrations of SAR6EW. These results demonstrate that SAR6EW is a promising epithelium permeation enhancer for insulin and suggest that the chemical modification of cell-penetrating peptides is a feasible strategy to enhance their potential.

Synthesis and evaluation of a novel ß-cyclodextrin derivative for oral insulin delivery and absorption.

In this paper, we describe the synthesis and testing of a novel ß-cyclodextrin derivative, carboxymethy-hydroxypropyl-ß-cyclodextrin (CM-HP-ß-CD). After synthesis, we verified that carboxymethyl and hydroxypropyl groups were successfully substituted onto ß-cyclodextrin to form CM-HP-ß-CD. Then, we performed in vitro experiments to investigate (1) the ability of CM-HP-ß-CD to bind insulin, (2) the transportation of insulin-CM-HP-ß-CD complexes across a Caco-2 cell monolayer, and (3) the cytotoxicity of CM-HP-ß-CD. CM-HP-ß-CD showed the strongest insulin-binding ability and the best transport properties compared with the other ß-cyclodextrin derivatives we evaluated. In addition, CM-HP-ß-CD showed no cytotoxicity up to 200 mM (IC50>200 mM). To examine the effectiveness of the cyclodextrin complexes in delivering insulin in vivo, we administered different insulin-cyclodextrin complexes to diabetic rats. In these studies, we found that the insulin-CM-HP-ß-CD complex provided a significant and sustained (5 h) reduction in the blood glucose levels of diabetic rats. Overall, our study showed that CM-HP-ß-CD may be a promising protein carrier for use in oral protein drug delivery.

Fe-chlorophyllin promotes the growth of wheat roots associated with nitric oxide generation.

Effects of Fe-chlorophyllin on the growth of wheat root were investigated in this study. We found that Fe-chlorophyllin can promote root growth. The production of nitric oxide in wheat root was detected using DAF-2DA fluorescent emission. The intensity of fluorescent in the presence of 0.1 mg/L Fe-chlorophyllin was near to that observed with the positive control of sodium nitroprusside (SNP), the nitric oxide donor. IAA oxidase activity decreased with all treatments of Fe-chlorophyllin from 0.01 to 10 mg/L. At the relatively lower Fe-chlorophyllin concentration of 0.1 mg/L, the activity of IAA oxidase displayed a remarkable decrease, being 40.1% lower than the control. Meanwhile, Fe-chlorophyllin treatment could increase the activities of reactive oxygen scavenging enzymes, such as superoxide dismutase (SOD) and peroxidase (POD), as determined using non-denaturing polyacrylamide gel electrophoresis. These results indicate that Fe-chlorophyllin contributes to the growth of wheat root associated with nitric oxide generation.

Effects of hydroxylpropyl-ß-cyclodextrin on in vitro insulin stability.

The objective of this study was to elucidate the effects of hydroxylpropyl-beta-cyclodextrin (HP-beta-CD) on the in vitro stability of insulin. It was found that HP-beta-CD had positive effects on the stability of insulin in acid and base and under high temperature conditions. Furthermore, use of HP-beta-CD could also increase the stability of disulfide bonds which are important to the conformation of insulin. Through (1)H-NMR experiments it was found that the protective effect of HP-beta-CD was due to complexation with insulin. The results suggest that the presence of HP-beta-CD could improve the stability of insulin in different environments.

Improving the stability of insulin in solutions containing intestinal proteases in vitro.

Degradation of insulin was studied in this work. Casein and protamine could obviously suppress degradation of insulin by intestinal enzymes, and could protect insulin from degradation by the mechanism of competition and combination with proteolysis enzyme. What is more, co-incubated with HP-beta-CD-casein or HP-beta-CD-protamine, most insulin was protected from degradation by intestinal enzymes. In addition, it was found that the complexation of insulin with HP-beta-CD was characterized by UV absorption spectra. These results indicated that HP-beta-CD, casein and protamine could offer some positive and useful results, and could protect insulin from degradation during their transit through the intestinal tract.