In vitro release behavior and stability of insulin in complexation hydrogels as oral drug delivery carriers

Harnessing the Potential of Human Breast Milk to Boost Intestinal Permeability for Nanoparticles and Macromolecules

The intricate interplay between human breast milk, nanoparticles, and macromolecules holds promise for innovative nutritional delivery strategies. Compared to bovine milk and infant formula, this study explores human breast milk's role in modulating intestinal permeability and its impact on nanoparticle and macromolecule transport. Comparative analysis with bovine milk and infant formula reveals significant elevations in permeability with human breast milk, accompanied by a decrease in transepithelial electrical resistance, suggesting enhanced paracellular transport. Mechanistically, human breast milk reduces Zonula occludens-1 levels, suggesting a regulatory role in intestinal barrier function. Through in vitro and ex vivo evaluations, we aim to understand better the mechanisms behind enhanced permeability and how human breast milk affects nanoparticle physicochemical properties, potentially modulating their behavior. Specifically, human breast milk improves the intestinal permeability of liposomes in a porcine intestinal model, with associated changes in the composition of milk proteins corona related to liposome charge. These findings underscore the unexploited potential of human breast milk in facilitating transport across the intestinal barrier, offering novel avenues for human nutritional delivery and therapeutic interventions.

Therapeutic delivery systems for rheumatoid arthritis based on hydrogel carriers

Rheumatoid arthritis (RA) is an autoimmune disease suffered by millions of people worldwide. It can significantly affect the patient's quality of life by damaging not only the joints but also organs such as the lungs and the heart. RA is normally treated using nonsteroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, disease-modifying antirheumatic drugs (DMARDs), and biologics. These active agents often cause side effects and offer low efficacy due to their lack of specificity and limited retention time. In an attempt to improve RA treatments, hydrogel-based systems have been proposed as drug delivery carriers. Due to their exceptional adaptability and biocompatibility, hydrogels have the potential of enhancing the delivery of RA therapy through different administration routes in an efficient and effective manner. In this review, we explore the application of hydrogel systems as potential carriers in RA treatment. Additionally, we discuss recent work in the field and highlight the required hydrogel properties, depending on the administration route. The outstanding potential of hydrogel systems as carriers for RA was demonstrated; however, there is extensive research yet to be done to improve available treatments for RA.

Arabinoxylans-Based Oral Insulin Delivery System Targeting the Colon: Simulation in a Human Intestinal Microbial Ecosystem and Evaluation in Diabetic Rats

Arabinoxylans (AX) microcapsules loaded with insulin were prepared by enzymatic gelation of AX, using a triaxial electrospray method. The microcapsules presented a spherical shape, with an average size of 250 µm. The behavior of AX microcapsules was evaluated using a simulator of the human intestinal microbial ecosystem. AX microcapsules were mainly (70%) degraded in the ascending colon. The fermentation was completed in the descending colon, increasing the production of acetic, propionic, and butyric acids. In the three regions of the colon, the fermentation of AX microcapsules significantly increased populations of Bifidobacterium and Lactobacillus and decreased the population of Enterobacteriaceae. In addition, the results found in this in vitro model showed that the AX microcapsules could resist the simulated conditions of the upper gastrointestinal system and be a carrier for insulin delivery to the colon. The pharmacological activity of insulin-loaded AX microcapsules was evaluated after oral delivery in diabetic rats. AX microcapsules lowered the serum glucose levels in diabetic rats by 75%, with insulin doses of 25 and 50 IU/kg. The hypoglycemic effect and the insulin levels remained for more than 48 h. Oral relative bioavailability was 13 and 8.7% for the 25 and 50 IU/kg doses, respectively. These results indicate that AX microcapsules are a promising microbiota-activated system for oral insulin delivery in the colon.

Recent Advances in Glucose Responsive Insulin Delivery Systems: Novel Hydrogels and Future Applications

Over the past several decades, there have been major advancements in the field of glucose sensing and insulin delivery for the treatment of type I diabetes mellitus. The introduction of closed-loop insulin delivery systems that deliver insulin in response to specific levels of glucose in the blood has shifted significantly the research in this field. These systems consist of encapsulated glucose-sensitive components such as glucose oxidase or phenylboronic acid in hydrogels, microgels or nanoparticles. Since our previous evaluation of these systems in a contribution in 2004, new systems have been developed. Important improvements in key issues, such as consistent insulin delivery over an extended period of time have been addressed. In this contribution, we discuss recent advancements over the last 5 years and present persisting issues in these technologies that must be overcome in order for these systems to be applicable in patients.

Biopolymer Nano-Network for Antimicrobial Peptide Protection and Local Delivery

Antimicrobial resistance (AMR) develops when bacteria no longer respond to conventional antimicrobial treatment. The limited treatment options for resistant infections result in a significantly increased medical burden. Antimicrobial peptides offer advantages for treatment of resistant infections, including broad-spectrum activity and lower risk of resistance development. However, sensitivity to proteolytic cleavage often limits their clinical application. Here, a moldable and biodegradable colloidal nano-network is presented that protects bioactive peptides from enzymatic degradation and delivers them locally. An antimicrobial peptide, PA-13, is encapsulated electrostatically into positively and negatively charged nanoparticles made of chitosan and dextran sulfate without requiring chemical modification. Mixing and concentration of oppositely charged particles form a nano-network with the rheological properties of a cream or injectable hydrogel. After exposure to proteolytic enzymes, the formed nano-network loaded with PA-13 eliminates Pseudomonas aeruginosa during in vitro culture and in an ex vivo porcine skin model while the unencapsulated PA-13 shows no antibacterial effect. This demonstrates the ability of the nano-network to protect the antimicrobial peptide in an enzyme-challenged environment, such as a wound bed. Overall, the nano-network presents a useful platform for antimicrobial peptide protection and delivery without impacting peptide bioactivity.

Bioinspired tunable hydrogels: An update on methods of preparation, classification, and biomedical and therapeutic applications

Hydrogels exhibit water-insoluble three-dimensional polymeric networks capable of absorbing large amounts of biological fluids. Both natural and synthetic polymers are used for the preparation of hydrogel networks. Such polymeric networks are fabricated through chemical or physical mechanisms of crosslinking. Chemical crosslinking is accomplished mainly through covalent bonding, while physical crosslinking involves self-healing secondary forces like H-bonding, host-guest interactions, and antigen-antibody interactions. The building blocks of the hydrogels play an important role in determining the mechanical, biological, and physicochemical properties. Hydrogels are used in a variety of biomedical applications like diagnostics (biodetection and bioimaging), delivery of therapeutics (drugs, immunotherapeutics, and vaccines), wound dressing and skin materials, cardiac complications, contact lenses, tissue engineering, and cell culture because of the inherent characteristics like enhanced water uptake and structural similarity with the extracellular matrix (ECM). This review highlights the recent trends and advances in the roles of hydrogels in biomedical and therapeutic applications. We also discuss the classification and methods of hydrogels preparation. A brief outlook on the future directions of hydrogels is also presented.

Hydrogels as Potential Nano-, Micro- and Macro-Scale Systems for Controlled Drug Delivery

This review is an extensive evaluation and essential analysis of the design and formation of hydrogels (HGs) for drug delivery. We review the fundamental principles of HGs (their chemical structures, physicochemical properties, synthesis routes, different types, etc.) that influence their biological properties and medical and pharmaceutical applications. Strategies for fabricating HGs with different diameters (macro, micro, and nano) are also presented. The size of biocompatible HG materials determines their potential uses in medicine as drug carriers. Additionally, novel drug delivery methods for enhancing treatment are discussed. A critical review is performed based on the latest literature reports.

Synthesis of Submicrocontainers with “Green” Biocide and Study of Their Antimicrobial Activity

The synthesis and properties of submicrocontainers with a shell of nanoparticles of silicon dioxide and a core of polymerized 3-(Trimethoxysilyl) propyl methacrylate loaded with 5-Dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) are considered. The resulting containers were characterized by scanning electron microscopy SEM, laser correlation spectroscopy and thermogravimetric analysis. The obtained submicrocontainers show low polydispersity with a small increase in size in comparison with the initial droplet size of the Pickering emulsion. The Zeta potential of the final containers was sufficiently negative at pH7 to be stable. The maximum release of encapsulated biocide was observed over approximately 24–27 h with a lease of about 78% of the encapsulated biocide during 3.5 h. The effectiveness of the encapsulated biocide by the Pickering emulsion technique was studied by tests on the growth rate of a microfungi colony (Aspergillus niger, Aspergillus awamori) and the growth rate of the bacteria Bacillus cereus. The test shows that the submicrocontainers of DCOIT facilitate a growth inhibition of 70% against 52% for the free biocide after 5 days; this is due to the fact that free biocide loses its activity promptly, while the encapsulated biocide is released gradually, and thus retains its effectivity for a longer time.

Insulin delivery systems combined with microneedle technology

Diabetes, a metabolic disorder of glucose, is a serious chronic disease and an important public health problem. Insulin is one of the hormones for modulating blood glucose level and the products of which is indispensable for most diabetes patients. Introducing microneedles (MNs) to insulin delivery is promising to pave the way for modulating glucose level noninvasively of diabetes patients, as which born to be painless, easy to handle and no need of any power supply. In this work, we review the process of insulin delivery systems (IDSs) based on MN technology in terms of two categories: drug free MNs and drug loaded MNs. Drug free MNs include solid MNs ("poke and patch"), hollow MNs ("poke and flow") and reservoir-based swelling MNs ("poke and swell R-type"), and drug loaded MNs include coated MNs ("coat and poke"), dissolving MNs ("poke and release") and insulin incorporated swelling MNs ("poke and swell I-type"). Majority researches of MN-based IDSs have been conducted by using hollow MNs or dissolving MNs, and almost all clinical trials for MN-based IDSs have employed hollow MNs. "Poke and patch" approach dramatically increase skin permeability compared to traditional transdermal patch, but MNs fabricated from silicon or metal may leave sharp waste in the skin and cause a safety issue. "Poke and flow" approach, similar to transitional subcutaneous (SC) injection, is capable of producing faster insulin absorption and action than SC injection but may associate with blockage, leakage and low flow rate. Coated MNs are able of retaining the activity of drug, which loaded in a solid phase, for a long time, however have been relatively less studied for insulin application as the low drug dosing. "Poke and release" approach leaves no biohazardous sharp medical waste and is capable of rapid drug release. "Poke and swell R-type" can be seen as a combination of "poke and flow" and "poke and patch" approach, while "poke and swell I-type" is an approach between "coat and poke" and "poke and release" approach. Insulin MNs are promising for painless diabetes therapeutics, and additional efforts for addressing fundamental issues including the drug loading, the PK/PD profile, the storage and the safety of insulin MNs will accelerate the clinical transformation.

Salicylic acid-based pH-sensitive hydrogels as potential oral insulin delivery systems

Salicylic acid (SA)-based physically crosslinked pH-sensitive hydrogels were developed for oral insulin delivery using various ratios of salicylate-based poly(anhydride-ester) and poly(acrylic acid) (PAA). Pore size, swelling behavior, insulin loading, insulin and SA release rates of the gels were varied by changing PAA concentration. About 50% of insulin was incorporated within all of the hydrogels, with about 4-8% of insulin released in acidic conditions (pH 1.2) over 2 h. In pH simulating the intestine (pH 6.8), 90% of the insulin and 70% of SA were released within 24 h from the hydrogel system. These results suggest that hydrogels enable pH-dependent protein delivery and can be used for oral insulin and SA delivery to benefit diabetes patients.

Formulation, characterization and evaluation of the effect of polymer concentration on the release behavior of insulin-loaded Eudragit(®)-entrapped mucoadhesive microspheres

Introduction:

The aim of this study was to use Eudragit^® RL 100 (pH-independent polymer) and magnesium stearate (a hydrophobic droplet stabilizer) in combination to improve the controlled release effect of insulin-loaded Eudragit^® entrapped microspheres prepared by the emulsification-coacervation technique.

Materials and Methods:

Mucoadhesive insulin-loaded microspheres containing magnesium stearate and varying proportions of Eudragit^® RL 100 were prepared by the emulsification-coacervation technique and evaluated for thermal properties, physicochemical performance, and in vitro dissolution in acidic and subsequently basic media.

Results:

Stable, spherical, brownish, discrete, free-flowing and mucoadhesive insulin-loaded microspheres with size range of 14.20 ± 0.30-19.80 ± 0.60 μm and loading efficiency of 74.55 ± 1.05-75.90 ± 1.94% were formed. After 3 h, microspheres prepared with insulin: Eudragit^® RL 100 ratios of 1:4, 1:6, and 1:8 released 73.40 ± 1.38, 66.20 ± 1.59, and 71.30 ± 1.27 (%) of insulin, respectively.

Conclusion:

The physicochemical and physico-technical properties of the microspheres developed in this study demonstrated the effectiveness of the Eudragit^® RL entrapped mucoadhesive microspheres (prepared by the emulsification-coacervation technique using varying polymer concentration) as a carrier system for oral insulin delivery.

Poly-γ-glutamic acid microneedles with a supporting structure design as a potential tool for transdermal delivery of insulin

Incomplete insertion is a common problem associated with polymer microneedles (MNs) that results in a limited drug delivery efficiency and wastage of valuable medication. This paper presents a fully insertable MN system that is composed of poly-γ-glutamic acid (γ-PGA) MNs and polyvinyl alcohol (PVA)/polyvinyl pyrrolidone (PVP) supporting structures. The PVA/PVP supporting structures were designed to provide an extended length for counteracting skin deformation during insertion and mechanical strength for fully inserting the MNs into the skin. When inserted into the skin, both the supporting structures and MNs can be dissolved in the skin within 4min, thus quickly releasing the entire drug load from the MNs. To evaluate the feasibility and reproducibility of using the proposed system for treating diabetes, we administered insulin-loaded MNs to diabetic rats once daily for 2days. The results indicated that the hypoglycemic effect in the rats receiving insulin-loaded MNs was comparable to that observed in rats receiving subcutaneous insulin injections. The relative pharmacological availability and relative bioavailability of the insulin were in the range of 90-97%, indicating that the released insulin retained its pharmacological activity. We observed no significant differences in the plasma insulin concentration profiles between the first and second administrations, confirming the stability and accuracy of using the proposed MN system for insulin delivery. These results indicated that the γ-PGA MNs containing the supporting structure design enable complete and efficient delivery of encapsulated bioactive molecules and have great potential for the relatively rapid and convenient transdermal delivery of protein drugs.

STATEMENT OF SIGNIFICANCE

Incomplete insertion of microneedles largely limits drug delivery efficiency and wastage of valuable medication. To address this problem, we developed a fully insertable poly-glutamic acid microneedles with a supporting structure design to ensure complete and efficient delivery of encapsulated drugs. The supporting structures were designed to provide an extended length for counteracting skin compressive deformation during puncture and mechanical strength for fully inserting the microneedles into the skin. When inserted into the skin, both the supporting structures and microneedles can be dissolved in the skin within 4min, thus quickly releasing the entire drug load. This study demonstrated that the proposed microneedle system featuring this unique design allows more convenient and efficient self-administration of drugs into the skin.

Stimulus-responsive hydrogels: Theory, modern advances, and applications

Over the past century, hydrogels have emerged as effective materials for an immense variety of applications. The unique network structure of hydrogels enables very high levels of hydrophilicity and biocompatibility, while at the same time exhibiting the soft physical properties associated with living tissue, making them ideal biomaterials. Stimulus-responsive hydrogels have been especially impactful, allowing for unprecedented levels of control over material properties in response to external cues. This enhanced control has enabled groundbreaking advances in healthcare, allowing for more effective treatment of a vast array of diseases and improved approaches for tissue engineering and wound healing. In this extensive review, we identify and discuss the multitude of response modalities that have been developed, including temperature, pH, chemical, light, electro, and shear-sensitive hydrogels. We discuss the theoretical analysis of hydrogel properties and the mechanisms used to create these responses, highlighting both the pioneering and most recent work in all of these fields. Finally, we review the many current and proposed applications of these hydrogels in medicine and industry.

Planar bioadhesive microdevices: a new technology for oral drug delivery

The oral route is the most convenient and least expensive route of drug administration. Yet, it is accompanied by many physiological barriers to drug uptake including low stomach pH, intestinal enzymes and transporters, mucosal barriers, and high intestinal fluid shear. While many drug delivery systems have been developed for oral drug administration, the physiological components of the gastro intestinal tract remain formidable barriers to drug uptake. Recently, microfabrication techniques have been applied to create micron-scale devices for oral drug delivery with a high degree of control over microdevice size, shape, chemical composition, drug release profile, and targeting ability. With precise control over device properties, microdevices can be fabricated with characteristics that provide increased adhesion for prolonged drug exposure, unidirectional release which serves to avoid luminal drug loss and enhance drug permeation, and protection of a drug payload from the harsh environment of the intestinal tract. Here we review the recent developments in microdevice technology and discuss the potential of these devices to overcome unsolved challenges in oral drug delivery.

Assessment of the drug loading, in vitro and in vivo release behavior of novel pH-sensitive hydrogel

CONTEXT

As a glucocorticoid drug, dexamethasone has good therapeutic effects for ulcerative colitis. pH-sensitive hydrogels could make conventional changes of volume in response with different pH values. Meanwhile, they could load drugs depending on its internal three-dimensional network structure.

OBJECTIVE

Appropriate methods were used to improve the drug-loading capacity of hydrogel and exploring the colon-targeting character of dexamethasone hydrogel.

MATERIALS AND METHODS

Different solvents (ethanol and 1,2-propanediol) were employed to dissolve dexamethasone as well as hydrogel monomer materials (poly(ethylene glycol) methyl ether (MPEG)-poly(lactide acid)-acryloyl chloride macromonomer, itaconic acid (IA) and MPEG-methacrylate), then mixing them together to prepare hydrogel through the heat-initiated free radical polymerization method. Differential scanning calorimetry and X-ray diffraction methods were used to verify whether dexamethasone was loaded into hydrogels. In vitro drug release behavior and in vivo pharmacokinetic study were also investigated in detail.

RESULTS

Dexamethasone was successfully loaded into hydrogel, and its loading capacity was improved (5 mg/g). Both the in vitro release study and the in vivo pharmacokinetic study showed the good colon-targeting character of the pH-sensitive P(LE-IA-MEG) hydrogel (T max = 1.0 h, C max = 2.16 µg/ml of dexamethasone; T max = 3.9 h, C max = 0.43 µg/ml of dexamethasone hydrogel).

DISCUSSION

Dexamethasone could be targeted to the colon site by P(LE-IA-MEG) hydrogel, thereby improving its therapeutic effect and reduce its side effects.

CONCLUSION

P(LE-IA-MEG) hydrogel might have great potential application in colon-targeted drug delivery systems.

Influence of magnesium stearate on the physicochemical and pharmacodynamic characteristics of insulin-loaded Eudragit entrapped mucoadhesive microspheres

Effective oral insulin delivery has remained a challenge to the pharmaceutical industry. This study was designed to evaluate the effect of magnesium stearate on the properties of insulin-loaded Eudragit® RL 100 entrapped mucoadhesive microspheres. Microspheres containing Eudragit® RL 100, insulin, and varying concentrations of magnesium stearate (agglomeration-preventing agent) were prepared by emulsification-coacervation method and characterized with respect to differential scanning calorimetry (DSC), morphology, particle size, loading efficiency, mucoadhesive and micromeritics properties. The in vitro release of insulin from the microspheres was performed in simulated intestinal fluid (SIF, pH 7.2) while the in vivo hypoglycemic effect was investigated by monitoring the plasma glucose level of the alloxan-induced diabetic rats after oral administration. Stable, spherical, brownish, mucoadhesive, discrete and free flowing insulin-loaded microspheres were formed. While the average particle size and mucoadhesiveness of the microspheres increased with an increase in the proportion of magnesium stearate, loading efficiency generally decreased. After 12 h, microspheres prepared with Eudragit® RL 100: magnesium stearate ratios of 15:1, 15:2, 15:3 and 15:4 released 68.20 ± 1.57, 79.40 ± 1.52, 76.60 ± 1.93 and 70.00 ± 1.00 (%) of insulin, respectively. Reduction in the blood glucose level for the subcutaneously (sc) administered insulin was significantly (p ≤ 0.05) higher than for most of the formulations. However, the blood glucose reduction effect produced by the orally administered insulin-loaded microspheres prepared with four parts of magnesium stearate and fifteen parts of Eudragit® RL 100 after 12 h was equal to that produced by subcutaneously administered insulin solution. The results of this study can suggest that this carrier system could be an alternative for the delivery of insulin.

Smart hydrogels as functional biomimetic systems

This review discusses the principles underlying stimuli-responsive behavior of hydrogels and how these properties contribute to their biomimetic functions and applications.

Oral calcium pectinate-insulin nanoparticles: influences of alginate, sodium chloride and Tween 80 on their blood glucose lowering performance

Objective

Examine the formation of pectin-insulin nanoparticles and their blood glucose lowering properties.

Methods

The calcium pectinate nanoparticles were prepared by ionotropic gelation method, with alginate, sodium chloride or Tween 80 as additive. Their in vitro physicochemical, drug release and in vivo blood glucose lowering characteristics were evaluated.

Key findings

Spherical calcium pectinate-insulin nanoparticles were characterized by size, zeta potential, insulin content and insulin association efficiency of 348.4 ± 12.9 nm, −17.9 ± 0.8 mV, 8.4 ± 1.0% and 63.8 ± 7.4%, respectively. They released less than 25% insulin following 24 h in simulated intestinal medium and exhibited delayed blood glucose lowering effect in rats. Incorporation of solubilizer sodium chloride or Tween 80 into nanoparticles did not enhance blood glucose lowering capacity owing to sodium chloride reduced matrix insulin content and Tween 80 interacted with water and had its blood glucose dilution effect negated. Combination of nanoparticles with alginate gel to allow prolonged intestinal residence and more insulin release did not enhance their blood glucose lowering capacity because of calcium alginate-cross-linked gel formation that could retard insulin release and migration into systemic circulation.

Conclusion

Physicochemical responses of additives in vivo affected blood glucose regulation property of pectin-insulin nanoparticles.

Synthesis, characterization, and acute oral toxicity evaluation of pH-sensitive hydrogel based on MPEG, poly(ε-caprolactone), and itaconic acid

A kind of chemically cross-linked pH-sensitive hydrogels based on methoxyl poly(ethylene glycol)-poly(caprolactone)-acryloyl chloride (MPEG-PCL-AC, PECA), poly(ethylene glycol) methyl ether methacrylate (MPEGMA, MEG), N,N-methylenebisacrylamide (BIS), and itaconic acid (IA) were prepared without using any organic solvent by heat-initiated free radical method. The obtained macromonomers and hydrogels were characterized by ¹H NMR and FT-IR, respectively. Morphology study of hydrogels was also investigated in this paper, and it showed that the hydrogels had good pH-sensitivity. The acute toxicity test and histopathological study were conducted in BALB/c mice. The results indicated that the maximum tolerance dose of the hydrogel was higher than 10000 mg/kg body weight. No morality or signs of toxicity were observed during the whole 7-day observation period. Compared to the control groups, there were no important adverse effects in the variables of hematology routine test and serum chemistry analysis both in male or female treatment group. Histopathological study also did not show any significant lesions, including heart, liver, lung, spleen, kidney, stomach, intestine, and testis. All the results demonstrated that this hydrogel was nontoxic after gavage. Thus, the hydrogel might be the biocompatible potential candidate for oral drug delivery system.

Dissolving polymer microneedle patches for rapid and efficient transdermal delivery of insulin to diabetic rats

This study presents a dissolving microneedle patch, composed of starch and gelatin, for the rapid and efficient transdermal delivery of insulin. The microneedles completely dissolve after insertion into the skin for 5 min, quickly releasing their encapsulated payload into the skin. A histological examination shows that the microneedles have sufficient mechanical strength to be inserted in vitro into porcine skin to a depth of approximately 200 μm and in vivo into rat skin to 200-250 μm depth. This penetration depth does not induce notable skin irritation or pain sensation. To evaluate the feasibility of using these dissolving microneedles for diabetes treatment insulin-loaded microneedles were administered to diabetic rats using a homemade applicator. Pharmacodynamic and pharmacokinetic results show a similar hypoglycemic effect in rats receiving insulin-loaded microneedles and a subcutaneous injection of insulin. The relative pharmacological availability and relative bioavailability of insulin were both approximately 92%, demonstrating that insulin retains its pharmacological activity after encapsulation and release from the microneedles. Storage stability analysis confirms that more than 90% of the insulin remained in the microneedles even after storage at 25 or 37°C for 1 month. These results confirm that the proposed starch/gelatin microneedles enable stable encapsulation of bioactive molecules and have great potential for transdermal delivery of protein drugs in a relatively painless, rapid, and convenient manner.

Freeze-dried and spray-dried zinc-containing silica microparticles entrapping insulin

New approaches for oral administration of insulin are strongly related to novel insulin carriers. The aim of this study was the insulin microencapsulation in a new zinc-silica matrix for drug protection and controlled release. Zinc-silica microparticles loaded with insulin were obtained by sol-gel process via spray drying and freeze drying methods. Inorganic silica matrix isolates and constrains the movement of the biomolecules preventing their aggregation and denaturation, while the zinc oxide improves the system stability. Moreover, formation of insulin hexamers in the presence of zinc ions leads to an increased stability of the insulin three-dimensional structure during preparation, storage and release. The particles were characterized with respect to average size, specific surface area, porosity and morphology. In vitro behavior of insulin-loaded particles together with protein structural conformation was also evaluated. The release profile can be adapted by synthesis route of microparticles.

Polymeric hydrogels for oral insulin delivery

The search for an effective and reliable oral insulin delivery system has been a major challenge facing pharmaceutical scientists for over many decades. Even though innumerable carrier systems that protect insulin from degradation in the GIT with improved membrane permeability and biological activity have been developed, yet a clinically acceptable device is not available for human application. Efforts in this direction are continuing at an accelerated speed. One of the preferred systems widely explored is based on polymeric hydrogels that protect insulin from enzymatic degradation in acidic stomach and delivers effectively in the intestine. Swelling and deswelling mechanisms of the hydrogel under varying pH conditions of the body control the release of insulin. The micro and nanoparticle (NP) hydrogel devices based on biopolymers have been widely explored, but their applications in human insulin therapy are still far from satisfactory. The present review highlights the recent findings on hydrogel-based devices for oral delivery of insulin. Literature data are critically assessed and results from different laboratories are compared.

Folate-decorated PLGA nanoparticles as a rationally designed vehicle for the oral delivery of insulin

Aims: The present study reports a novel approach for enhancing the oral absorption and hypoglycemic activity of insulin via encapsulation in folate-(FA) coupled polyethylene glycol (PEG)ylated polylactide-co-glycolide (PLGA) nanoparticles (NPs; FA-PEG-PLGA NPs). Materials & methods: Insulin-loaded FA-PEG-PLGA NPs (size ∼260 nm; insulin loading ∼6.5% [w/w]; encapsulation efficiency: 87.0 ± 1.92%) were prepared by double-emulsion solvent evaporation method. The bioavailability and hypoglycemic activity of orally administered FA–insulin NPs were studied in diabetic rats. Results & conclusion: FA-PEG-PLGA NPs (50 U/kg) exhibited a twofold increase in the oral bioavailability (double hypoglycemia) without any hypoglycemic shock as compared to subcutaneously administered standard insulin solution. Insulin NPs maintained a continual blood glucose level for 24 h, which, however, was transient (<8 h) in the case of subcutaneous insulin and associated with severe hypoglycemic shock. Overall, we have developed a patient-compliant, oral nanoformulation of insulin, once-daily administration of which would be sufficient to control diabetes for at least 24 h.

Original submitted 16 November 2011; Revised submitted 2 February 2012; Published online 14 May 2012

Cellular evaluation of insulin transmucosal delivery

P(MAA-g-EG) microparticles have been extensively investigated as carriers for oral delivery of proteins such as insulin. In this study, we investigated the effect of the molecular weight of the PEG tethered chains in the copolymer network and of the microparticle size on the transepithelial electrical resistance (TEER) and insulin epithelial permeability, using monolayers of human intestinal epithelial Caco-2 cells. Two molecular weights of the PEG chains, 400 and 1000, were investigated, as well as three different dry microparticle sizes: 25-90, 90-150 and 150-212 microm. Their effect on the cell monolayer integrity was studied by monitoring TEER as a fraction of time and determining insulin permeability. The presence of insulin-loaded P(MAA-g-EG) microparticles decreases the TEERs value by 50% with respect to the control. This disruption of the cell monolayer was recovered in 3 h after the removal of the polymer microparticles. Within the range of PEG molecular weights studied, there was no significant change of the TEER values. However, decreased microparticle sizes and short PEG chains systems led to higher permeability values. Insulin-loaded P(MAA-g-EG) microparticles enhanced the transport of insulin through the Caco-2 cell monolayers.

Self-assembled nanomicelles using PLGA-PEG amphiphilic block copolymer for insulin delivery: a physicochemical investigation and determination of CMC values

Self-assembled nanomicelles can be used as synthetic biomaterials and colloidal carriers for poorly water-soluble drug delivery systems. Some of these micellar systems have been introduced in clinical trials and showed hopeful results relating to their therapeutic index in patients. Biodegradable nanomicelle was prepared from self-assembling amphiphilic block copolymer composed of poly(DL-lactic-co-glycolic acid) (PLGA) as a core and polyethylene glycol (PEG) as a corona. The PLGA-PEG block copolymer was first synthesized and characterized by FTIR, (1)H NMR, GPC and inherent viscosity measurements. The nanomicelle formed by PLGA-PEG block copolymer in the aqueous solution was characterized by dynamic light scattering, zeta potential, scanning electron microscopy (SEM) and fluorescence excitation and emission spectra of pyrene probe. The critical micelle concentration of obtained nanomicelle was about 0.006 mg/mL, with the size of about 160 nm and the zeta potential of -29 mV. Insulin-loaded PLGA-PEG nanomicelles were prepared by modified dialysis method and the physicochemical parameters of the micelles such as drug content, entrapment efficiency and in vitro drug release were characterized. The results showed that insulin was entrapped into PLGA-PEG nanomicelles with drug loading of 3.9 wt% and entrapment efficiency of 55 wt%. The nanomicelles containing insulin exhibited a controlled release profile. These observations suggested that the PLGA-PEG block copolymers nanomicelles have been prepared by a new synthetic route are potent nanocarrier for poorly water-soluble drugs as insulin.