Cyclodextrin-insulin complex encapsulated polymethacrylic acid based nanoparticles for oral insulin delivery

In vitro evaluation of quaternized polydimethylaminoethylmethacrylate sub-microparticles for oral insulin delivery

This investigation describes the synthesis and in vitro evaluation of cationic hydrogel sub-microparticles based on polydimethylaminoethylmethacrylate for oral insulin delivery. Polymerization of dimethylaminoethylmethacrylate was carried out in aqueous medium with potassium persulfate as the initiator. Quaternization of the resulting hydrogel was carried out to introduce cationic surface groups and the derivatization was confirmed by zeta potential measurements, nuclear magnetic resonance and infrared spectroscopies. Swelling behavior of these particles was evaluated for dependence of pH. Insulin-loaded particles were subjected to in vitro release experiments at gastric and intestinal pH. Moreover, cytotoxicity evaluation showed that both polydimethylaminoethylmethacrylate and its quaternized derivative were non-toxic to Caco-2 and L929 cell lines. The presence of quaternary ammonium groups improved the cationic charge and enhanced the mucoadhesive properties of the hydrogel. Confocal microscopic observations showed that these sub-microparticles were capable of opening tight junctions between the Caco-2 cells and thus increased the paracellular permeability. The above studies suggest that cationic hydrogel sub-microparticles can act as a good candidate for oral insulin delivery.

Novel preparation of PLGA/HP55 nanoparticles for oral insulin delivery

The aim of the present study was to develop the PLGA/HP55 nanoparticles with improved hypoglycemic effect for oral insulin delivery. The insulin-loaded PLGA/HP55 nanoparticles were produced by a modified multiple emulsion solvent evaporation method. The physicochemical characteristics, in vitro release of insulin, and in vivo efficacy in diabetic rats of the nanoparticles were evaluated. The insulin encapsulation efficiency was up to 94%, and insulin was released in a pH-dependent manner under simulated gastrointestinal conditions. When administered orally (50 IU/kg) to diabetic rats, the nanoparticles can decrease rapidly the blood glucose level with a maximal effect between 1 and 8 h. The relative bioavailability compared with subcutaneous injection (5 IU/kg) in diabetic rats was 11.3% ± 1.05%. This effect may be explained by the fast release of insulin in the upper intestine, where it is better absorbed by the high gradient concentration of insulin than other regions. These results show that the PLGA/HP55 nanoparticles developed in the study might be employed as a potential method for oral insulin delivery.

Recent advances in nanocarrier-based mucosal delivery of biomolecules

This review highlights the recent developments in the area of nanocarrier-based mucosal delivery of therapeutic biomolecules and antigens. Macromolecular drugs have the unique power to tackle challenging diseases but their structure, physicochemical properties, stability, pharmacodynamics, and pharmacokinetics place stringent demands on the way they are delivered into the body (e.g., inability to cross mucosal surfaces and biological membranes). Carrier-based drug delivery systems can diminish the toxicity of therapeutic biomolecules, improve their bioavailability and make possible their administration via less-invasive routes (e.g., oral, nasal, pulmonary, etc.). Thus, the development of functionalized nanocarriers and nanoparticle-based microcarriers for the delivery of macromolecular drugs is considered an important scientific challenge and at the same time a business breakthrough for the biopharmaceutical industry. In order to be translated to the clinic the nanocarriers need to be biocompatible, biodegradable, stable in biological media, non-toxic and non-immunogenic, to exhibit mucoadhesive properties, to cross mucosal barriers and to protect their sensitive payload and deliver it to its target site in a controlled manner, thus increasing significantly its bioavailability and efficacy.

Polymer-based oral peptide nanomedicines

Oral peptide delivery has been one of the major challenges of pharmaceutical sciences as it could lead to a great improvement of classical therapies, such as insulin, alongside making an important number of new therapies feasible. Successful oral delivery needs to fulfill two key tasks: to protect the macromolecules from degradation in the GI tract and to shuttle them across the intestinal epithelium in a safe and efficient fashion. Over the last decade, there have been numerous approaches based on the chemical modification of peptides and on the use of permeation enhancers, enzyme inhibitors and drug-delivery systems. Among the approaches developed to overcome these restrictions, the design of nanocarriers seems to be a particularly promising approach. This article is an overview on the state of the art of oral-peptide formulation strategies, with special attention to insulin delivery and the use of polymeric nanocarriers as delivery systems.

Insulin-loaded PLGA microparticles: flow focusing versus double emulsion/solvent evaporation

CONTEXT

Oral administration of insulin is severely limited by very low bioavailability. Biocompatible polymeric nanocarriers have been investigated to overcome this problem. Flow focusing (FF) has revolutionized current engineering of poly(D,L-lactide-co-glycolide) (PLGA) based micromedicines. This technique has never been used to formulate insulin-loaded PLGA microparticles.

OBJECTIVE

Investigation of the benefits rising from the synthesis of insulin-loaded PLGA microplatforms by FF, compared to double emulsion/solvent evaporation method.

MATERIALS AND METHODS

Both synthesis methodologies were compared in terms of geometry, surface physicochemical properties and insulin vehiculization capabilities. The stability of the peptide during the formulation procedure was further analysed.

RESULTS

FF permitted the preparation of insulin-loaded microcarriers with better geometry and physicochemical properties for the oral route, along with greater insulin loading capabilities and sustained insulin release kinetics.

DISCUSSION AND CONCLUSION

Results have lead to the identification of the best formulation conditions for the engineering of insulin-loaded PLGA microparticles against diabetes.

Efficacy of thiolated eudragit microspheres as an oral vaccine delivery system to induce mucosal immunity against enterotoxigenic Escherichia coli in mice

A vaccine delivery system based on thiolated eudragit microsphere (TEMS) was studied in vivo for its ability to elicit mucosal immunity against enterotoxigenic Escherichia coli (ETEC). Groups of mice were orally immunized with F4 or F18 fimbriae of ETEC and F4 or F18 loaded in TEMS. Mice that were orally administered with F4 or F18 loaded TEMS showed higher antigen-specific IgG antibody responses in serum and antigen-specific IgA in saliva and feces than mice that were immunized with antigens only. In addition, oral vaccination of F4 or F18 loaded TEMS resulted in higher numbers of IgG and IgA antigen-specific antibody secreting cells in the spleen, lamina propria, and Peyer's patches of immunized mice than other groups. Moreover, TEMS administration loaded with F4 or F18 induced mixed Th1 and Th2 type responses based on similarly increased levels of IgG1 and IgG2a. These results suggest that F4 or F18 loaded TEMS may be a promising candidate for an oral vaccine delivery system to elicit systemic and mucosal immunity against ETEC.

Nanotechnology as a promising strategy for alternative routes of insulin delivery

Since its discovery, insulin has been used as highly specific and effective therapeutic protein to treat type 1 diabetes and later was associated to oral antidiabetic agents in the treatment of type 2 diabetes. Generally, insulin is administered parenterally. Although this route is successful, it still has several limitations, such as discomfort, pain, lipodystrophy at the injection sites and peripheral hyperinsulinemia, which may be the cause of side effects and some complications. Thus, alternative routes of administration have been developed, namely, those based on nanotechnologies. Nanoparticles, made of synthetic or natural materials, have been shown to successfully overcome the inherent barriers for insulin stability, degradation, and uptake across the gastrointestinal tract and other mucosal membranes. This review describes some of the many attempts made to develop alternative and more convenient routes for insulin delivery.

Nanomedicine as an emerging approach against intracellular pathogens

Diseases such as tuberculosis, hepatitis, and HIV/AIDS are caused by intracellular pathogens and are a major burden to the global medical community. Conventional treatments for these diseases typically consist of long-term therapy with a combination of drugs, which may lead to side effects and contribute to low patient compliance. The pathogens reside within intracellular compartments of the cell, which provide additional barriers to effective treatment. Therefore, there is a need for improved and more effective therapies for such intracellular diseases. This review will summarize, for the first time, the intracellular compartments in which pathogens can reside and discuss how nanomedicine has the potential to improve intracellular disease therapy by offering properties such as targeting, sustained drug release, and drug delivery to the pathogen’s intracellular location. The characteristics of nanomedicine may prove advantageous in developing improved or alternative therapies for intracellular diseases.

Advanced technologies for oral controlled release: cyclodextrins for oral controlled release

Cyclodextrins (CDs) are used in oral pharmaceutical formulations, by means of inclusion complexes formation, with the following advantages for the drugs: (1) solubility, dissolution rate, stability, and bioavailability enhancement; (2) to modify the drug release site and/or time profile; and (3) to reduce or prevent gastrointestinal side effects and unpleasant smell or taste, to prevent drug-drug or drug-additive interactions, or even to convert oil and liquid drugs into microcrystalline or amorphous powders. A more recent trend focuses on the use of CDs as nanocarriers, a strategy that aims to design versatile delivery systems that can encapsulate drugs with better physicochemical properties for oral delivery. Thus, the aim of this work was to review the applications of the CDs and their hydrophilic derivatives on the solubility enhancement of poorly water-soluble drugs in order to increase their dissolution rate and get immediate release, as well as their ability to control (to prolong or to delay) the release of drugs from solid dosage forms, either as complexes with the hydrophilic (e.g., as osmotic pumps) and/or hydrophobic CDs. New controlled delivery systems based on nanotechnology carriers (nanoparticles and conjugates) have also been reviewed.

The oral delivery of proteins using interpolymer polyelectrolyte complexes

In spite of the numerous barriers inherent in the oral delivery of therapeutically active proteins, research into the development of functional protein-delivery systems is still intense. The effectiveness of such oral protein-delivery systems depend on their ability to protect the incorporated protein from proteolytic degradation in the GI tract and enhance its intestinal absorption without significantly compromising the bioactivity of the protein. Among these delivery systems are polyelectrolyte complexes (PECs) which are composed of polyelectrolyte polymers complexed with a protein via coulombic and other interactions. This review will focus on the current status of PECs with a particular emphasis on the potential and limitations of multi- or inter-polymer PECs used to facilitate oral protein delivery.

Chitosan-sodium lauryl sulfate nanoparticles as a carrier system for the in vivo delivery of oral insulin

The present work explores the possibility of formulating an oral insulin delivery system using nanoparticulate complexes made from the interaction between biodegradable, natural polymer called chitosan and anionic surfactant called sodium lauryl sulfate (SLS). The interaction between chitosan and SLS was confirmed by Fourier transform infrared spectroscopy. The nanoparticles were prepared by simple gelation method under aqueous-based conditions. The nanoparticles were stable in simulated gastric fluids and could protect the encapsulated insulin from the GIT enzymes. Additionally, the in vivo results clearly indicated that the insulin-loaded nanoparticles could effectively reduce the blood glucose level in a diabetic rat model. However, additional formulation modifications are required to improve insulin oral bioavailability.

Development and validation of an improved Bradford method for determination of insulin from chitosan nanoparticulate systems

CONTEXT

Blank chitosan nanoparticles are currently used as reference for the calibration curve, which fails to resolve the supernatant of the nanoparticles in the interference of Coomassie Brilliant Blue G-250 reagent; supernatants are generated at different chitosan nanoparticulate prescriptions, which have different interferences. There are notable errors in the experimental results, and the method is not feasible.

OBJECTIVE

In this study, an improved, rapid, and economic Bradford method was developed and validated.

MATERIALS AND METHODS

The pH of the supernatant of blank chitosan nanoparticles was adjusted to 7-9 through adding saturated NaOH. The precipitation (free chitosan) in the solution was separated by centrifuging for about 10 min (4000 r/min).

RESULTS

The method eliminated the interference of free chitosan of different prescriptions. The results showed that the method presented a linearity in the range of 50-300 microg/mL (R(2) = 0.9992), and possessed a good inter-day and intra-day precision based on relative standard deviation values (less than 3.10%). Recovery of the supernatant of blank chitosan nanoparticles was between 98.30 and 99.93%, and the recovery of blank chitosan nanoparticles was between 95.57 and 100.27%.

DISCUSSION AND CONCLUSION

The method was further tested for determination of the association efficiency of insulin to nanoparticulate carriers composed of chitosan. Encapsulant release under simulated gastrointestinal fluids was evaluated.

Multifunctional hybrid nanogel for integration of optical glucose sensing and self-regulated insulin release at physiological pH

Optical detection of glucose, high drug loading capacity, and self-regulated drug delivery are simultaneously possible using a multifunctional hybrid nanogel particle under a rational design in a colloid chemistry method. Such hybrid nanogels are made of Ag nanoparticle (NP) cores covered by a copolymer gel shell of poly(4-vinylphenylboronic acid-co-2-(dimethylamino)ethyl acrylate) [p(VPBA-DMAEA)]. The introduction of the glucose sensitive p(VPBA-DMAEA) gel shell onto Ag NPs makes the polymer-bound Ag NPs responsive to glucose. While the small sized Ag cores (10 +/- 3 nm) provide fluorescence as an optical code, the responsive polymer gel shell can adapt to a surrounding medium of different glucose concentrations over a clinically relevant range (0-30 mM), convert the disruptions in homeostasis of glucose level into optical signals, and regulate release of preloaded insulin. This shows a new proof-of-concept for diabetes treatment that exploits the properties from each building block of a multifunctional nano-object. The highly versatile multifunctional hybrid nanogels could potentially be used for simultaneous optical diagnosis, self-regulated therapy, and monitoring of the response to treatment.

Thiol functionalized polymethacrylic acid-based hydrogel microparticles for oral insulin delivery

In the present study thiol functionalized polymethacrylic acid-polyethylene glycol-chitosan (PCP)-based hydrogel microparticles were utilized to develop an oral insulin delivery system. Thiol modification was achieved by grafting cysteine to the activated surface carboxyl groups of PCP hydrogels (Cys-PCP). Swelling and insulin loading/release experiments were conducted on these particles. The ability of these particles to inhibit protease enzymes was evaluated under in vitro experimental conditions. Insulin transport experiments were performed on Caco-2 cell monolayers and excised intestinal tissue with an Ussing chamber set-up. Finally, the efficacy of insulin-loaded particles in reducing the blood glucose level in streptozotocin-induced diabetic rats was investigated. Thiolated hydrogel microparticles showed less swelling and had a lower insulin encapsulation efficiency as compared with unmodified PCP particles. PCP and Cys-PCP microparticles were able to inhibit protease enzymes under in vitro conditions. Thiolation was an effective strategy to improve insulin absorption across Caco-2 cell monolayers, however, the effect was reduced in the experiments using excised rat intestinal tissue. Nevertheless, functionalized microparticles were more effective in eliciting a pharmacological response in diabetic animal, as compared with unmodified PCP microparticles. From these studies thiolation of hydrogel microparticles seems to be a promising approach to improve oral delivery of proteins/peptides.

Acyl modified chitosan derivatives for oral delivery of insulin and curcumin

In the present investigation, bioadhesive property of chitosan (CS) was enhanced by the N-acylation with hexanoyl, lauroyl and oleoyl chlorides. The chemical structure of the modified polymer was characterized by FTIR and zeta potential measurements. The swelling ability was evaluated at alkaline pH. Mucin interactions and mucoadhesion experiments were performed under in vitro experimental conditions. Cytotoxicity experiments were employed to confirm the applicability of these particles as drug carriers. Finally in vitro evaluation of hydrophobic and hydrophilic drug release profile at acidic and alkaline pH was also conducted. A strong interaction between CS acyl derivatives and mucin was detected, which was further confirmed by an in situ mucoadhesion experiments with excised intestinal tissue. CS modified with oleoyl chloride showed better mucoadhesion property, as compared to the one modified with lower fatty acid groups. CS derivatives were found non-toxic on L-929 cell lines and provided sustained release of hydrophobic drugs under in vitro experimental conditions. From these studies it seems that hydrophobically modified CS is an interesting system for drug delivery applications.

Effective protection and controlled release of insulin by cationic beta-cyclodextrin polymers from alginate/chitosan nanoparticles

In an alginate/chitosan nanoparticle system, insulin was protected by forming complexes with cationic beta-cyclodextrin polymers (CPbetaCDs), which were synthesized from beta-cyclodextrin (beta-CD), epichlorohydrin (EP) and choline chloride (CC) through a one-step polycondensation. Due to the electrostatic attraction between insulin and CPbetaCDs, as well as the assistance of its polymeric chains, CPbetaCDs could effectively protect insulin under simulated gastrointestinal conditions. The nanoparticles have their mean size lower than 350 nm and can load insulin with the association efficiency (AE) up to 87%. It is notable that the cumulative insulin release in simulated intestinal fluid was significantly higher (40%) than that without CPbetaCDs (18%) because insulin was mainly retained in the core of the nanoparticles and well protected against degradation in simulated gastric fluid. Far-UV circular dichroism analysis also corroborated the preservation of insulin structure during the nanoparticle preparation and release process.

Nanodiamond-insulin complexes as pH-dependent protein delivery vehicles

Enhanced specificity in drug delivery aims to improve upon systemic elution methods by locally concentrating therapeutic agents and reducing negative side effects. Due to their robust physical properties, biocompatibility and drug loading capabilities, nanodiamonds serve as drug delivery platforms that can be applied towards the elution of a broad range of therapeutically-active compounds. In this work, bovine insulin was non-covalently bound to detonated nanodiamonds via physical adsorption in an aqueous solution and demonstrated pH-dependent desorption in alkaline environments of sodium hydroxide. Insulin adsorption to NDs was confirmed by FT-IR spectroscopy and zeta potential measurements, while both adsorption and desorption were visualized with TEM imaging, quantified using protein detection assays and protein function demonstrated by MTT and RT-PCR. NDs combined with insulin at a 4:1 ratio showed 79.8+/-4.3% adsorption and 31.3+/-1.6% desorption in pH-neutral and alkaline solutions, respectively. Additionally, a 5-day desorption assay in NaOH (pH 10.5) and neutral solution resulted in 45.8+/-3.8% and 2.2+/-1.2% desorption, respectively. MTT viability assays and quantitative RT-PCR (expression of Ins1 and Csf3/G-csf genes) reveal bound insulin remains inactive until alkaline-mediated desorption. For applications in sustained drug delivery and therapy we have developed a therapeutic protein-ND complex with demonstrated tunable release and preserved activity.

Effects of hydroxylpropyl-β-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.

Review on supermolecules as chemical drugs

Supramolecular medicinal chemistry field has been a quite rapidly developing, increasingly active and newly rising interdiscipline which is the new expansion of supramolecular chemistry in pharmaceutical sciences, and is gradually becoming a relatively independent scientific area. Supramolecular drugs could be defined as medicinal supermolecules formed by two or more molecules through non-covalent bonds. So far a lot of supermolecules as chemical drugs have been widely used in clinics. Supermolecules as chemical drugs, i.e. supramolecular chemical drugs or supramolecular drugs, which might have the excellences of lower cost, shorter period, higher potential as clinical drugs for their successful research and development, may possess higher bioavailability, better biocompatibility and drug-targeting, fewer multidrug-resistances, lower toxicity, less adverse effect, and better curative effects as well as safety, and therefore exhibit wide potential application. These overwhelming advantages have drawn enormous special attention. This paper gives the definition of supramolecular drugs, proposes the concept of supramolecular chemical drugs, and systematically reviews the recent advances in the research and development of supermolecules, including organic and inorganic complex ones as chemical drugs in the area of antitumor, anti-inflammatory, analgesic, antimalarial, antibacterial, antifungal, antivirus, anti-epileptic, cardiovascular agents and magnetic resonance imaging agents and so on. The perspectives of the foreseeable future and potential application of supramolecules as chemical drugs are also presented.

Nanoparticulate biopolymers deliver insulin orally eliciting pharmacological response

The aim of this study was to characterize and evaluate a novel oral insulin nanoparticulate system based on alginate-dextran sulfate core, complexed with a chitosan-polyethylene glycol-albumin shell. Insulin-loaded nanospheres (25, 50, 100 IU/kg) administered orally to diabetic rats reduced glycemia in a dose dependent manner. This effect lasted over 24 h with a maximal effect after 14 h. Nanospheres increased insulin plasma level and improved glycemic response to an oral glucose overload. After 4 days oral administration (50 IU/kg/day), the metabolic status of diabetic rats improved with a reduction in water intake, urine excretion and proteinuria. FITC-insulin-loaded nanospheres administered to an isolated intestinal loop were taken up by the intestinal mucosa. They strongly adhered to villus apical enterocytes and markedly labeled Peyer's patches. It is concluded that nanospheres preserve insulin and exert an antidiabetic effect after oral administration. This is explained by a protective effect against proteolytic enzymes by the albumin coating, by the mucoadhesive properties of chitosan-polyethylene glycol, and by the possibility of chitosan reversibly altering tight junctions leading to an improved absorption of insulin. This formulation demonstrates beneficial effects on diabetic symptoms and will be of interest in the treatment of diabetes with oral insulin.

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-β-CD-casein or HP-β-CD-protamine, most insulin was protected from degradation by intestinal enzymes. In addition, it was found that the complexation of insulin with HP-β-CD was characterized by UV absorption spectra. These results indicated that HP-β-CD, casein and protamine could offer some positive and useful results, and could protect insulin from degradation during their transit through the intestinal tract.

Improvement of water solubility of non-competitive AMPA receptor antagonists by complexation with beta-cyclodextrin

The (R,S)-2-acetyl-1-(4'-chlorophenyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline ((R,S)-1) was previously identified as a potent non-competitive AMPA receptor antagonist able to prevent epileptic seizures and reduce AMPA-induced current in electrophysiological experiments. Through the enantiomeric resolution of racemate by chiral HPLC we already demonstrated that the (R)-1 enantiomer was the eutomer. Considering the poor water solubility, these compounds have been complexed with beta-cyclodextrin (beta-CyD). The effect of beta-cyclodextrin on the spectral features of molecules was quantitatively investigated, in fully aqueous medium by phase-solubility study and the obtained diagrams suggested that it forms complexes with a molar ratio 1:1. The binding constant (K((R)-1)=15889M(-1), K((R,S)(-1))=1079 M(-1)) and the complexation efficiency (CE) were calculated. Then the solid complexes in 1:1 molar ratio were prepared by the co-precipitation method and the FTIR-ATR measurements were carried out in order to confirm the host-guest interactions that drive the complexation process, by monitoring the significant differences of the spectra of the complexes with respect to those of the corresponding physical mixtures in the same molar ratio. The experimental data have been compared with molecular modelling studies and we confirmed our hypothesis.