A composite hydrogel system containing glucose-responsive nanocarriers for oral delivery of insulin

Advances in Hydrogel-Based Drug Delivery Systems

Hydrogels, with their distinctive three-dimensional networks of hydrophilic polymers, drive innovations across various biomedical applications. The ability of hydrogels to absorb and retain significant volumes of water, coupled with their structural integrity and responsiveness to environmental stimuli, renders them ideal for drug delivery, tissue engineering, and wound healing. This review delves into the classification of hydrogels based on cross-linking methods, providing insights into their synthesis, properties, and applications. We further discuss the recent advancements in hydrogel-based drug delivery systems, including oral, injectable, topical, and ocular approaches, highlighting their significance in enhancing therapeutic outcomes. Additionally, we address the challenges faced in the clinical translation of hydrogels and propose future directions for leveraging their potential in personalized medicine and regenerative healthcare solutions.

Evolution of Hybrid Hydrogels: Next-Generation Biomaterials for Drug Delivery and Tissue Engineering

Hydrogels, being hydrophilic polymer networks capable of absorbing and retaining aqueous fluids, hold significant promise in biomedical applications owing to their high water content, permeability, and structural similarity to the extracellular matrix. Recent chemical advancements have bolstered their versatility, facilitating the integration of the molecules guiding cellular activities and enabling their controlled activation under time constraints. However, conventional synthetic hydrogels suffer from inherent weaknesses such as heterogeneity and network imperfections, which adversely affect their mechanical properties, diffusion rates, and biological activity. In response to these challenges, hybrid hydrogels have emerged, aiming to enhance their strength, drug release efficiency, and therapeutic effectiveness. These hybrid hydrogels, featuring improved formulations, are tailored for controlled drug release and tissue regeneration across both soft and hard tissues. The scientific community has increasingly recognized the versatile characteristics of hybrid hydrogels, particularly in the biomedical sector. This comprehensive review delves into recent advancements in hybrid hydrogel systems, covering the diverse types, modification strategies, and the integration of nano/microstructures. The discussion includes innovative fabrication techniques such as click reactions, 3D printing, and photopatterning alongside the elucidation of the release mechanisms of bioactive molecules. By addressing challenges, the review underscores diverse biomedical applications and envisages a promising future for hybrid hydrogels across various domains in the biomedical field.

Preparation, Characterization and In vitro Evaluation of Insulin-PHBV Nanoparticles / Alginate Hydrogel Composite System for Prolonged Delivery of Insulin

PURPOSE

In the present study, biodegradable poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanoparticles (NPs) containing insulin were loaded in sodium alginate/jeffamine (ALG/jeff) hydrogel for prolonged delivery of insulin. The main aim of this work was to fabricate an efficient insulin delivery system to improve patient adherence by decreasing the repetition of injections.

METHODS

Swelling and morphological properties and crosslinking efficiency of ALG/jeff hydrogel were assessed. The composite hydrogel was prepared by adding PHBV NPs to ALG/jeff hydrogel concurrently with crosslinking process. The morphology and loading capacity of composite hydrogel were analyzed.

RESULTS

Circular dichroism measurement demonstrated that insulin remains stable following fabrication process. The release profile exhibited 54.6 % insulin release from composite hydrogel within 31 days with minor initial burst release equated to nanoparticles and hydrogels. MTT cell viability analysis was performed by applying L-929 cell line and no cytotoxic effect was observed.

CONCLUSIONS

Favorable results clearly introduced fabricated composite hydrogel as an excellent candidate for drug delivery systems and also paves the route for prolonged delivery systems of other proteins.

Ursodeoxycholic Acid-Decorated Zwitterionic Nanoparticles for Orally Liver-Targeted Close-Looped Insulin Delivery

Oral insulin therapies targeting the liver and further simulating close-looped secretion face significant challenges due to multiple trans-epithelial barriers. Herein, ursodeoxycholic acid (UDCA)-decorated zwitterionic nanoparticles (NPs) (UC-CMs@ins) are designed to overcome these barriers, target the liver, and respond to glycemia, thereby achieving oral one-time-per-day therapy. UC-CMs@ins show excellent mucus permeability through the introduction of zwitterion (carboxy betaine, CB). Furthermore, UC-CMs@ins possess superior cellular internalization via proton-assisted amino acid transporter 1 (PAT1, CB-receptor) and apical sodium-dependent bile acid transporter (ASBT, UDCA-receptor) pathways. Moreover, UC-CMs@ins exhibit excellent endolysosomal escape ability and improve the basolateral release of insulin into the bloodstream via the ileal bile acid-binding protein and the heteromeric organic solute transporter (OSTα- OSTβ) routes compared with non-UDCA-decorated C-CMs@ins. Therefore, CB and UDCA jointly overcome mucus and intestinal barriers. Additionally, UC-CMs@ins prevent insulin degradation in the gastrointestinal tract for crosslinked structure, improve insulin accumulation in the liver for UDCA introduction, and effectively regulate glycemia for "closed-loop" glucose control. Surprisingly, oral ingestion of UC-CMs@ins shows a superior effect on glycemia (≈22 h, normoglycemia) and improves postprandial glycemic levels in diabetic mice, illustrating the enormous potential of the prepared NPs as a platform for oral insulin administration in diabetes treatment.

pH-Responsive and Mucoadhesive Nanoparticles for Enhanced Oral Insulin Delivery: The Effect of Hyaluronic Acid with Different Molecular Weights

Drug degradation at low pH and rapid clearance from intestinal absorption sites are the main factors limiting the development of oral macromolecular delivery systems. Based on the pH responsiveness and mucosal adhesion of hyaluronic acid (HA) and poly[2-(dimethylamino)ethyl methacrylate] (PDM), we prepared three HA–PDM nano-delivery systems loaded with insulin (INS) using three different molecular weights (MW) of HA (L, M, H), respectively. The three types of nanoparticles (L/H/M-HA–PDM–INS) had uniform particle sizes and negatively charged surfaces. The optimal drug loadings of the L-HA–PDM–INS, M-HA–PDM–INS, H-HA–PDM–INS were 8.69 ± 0.94%, 9.11 ± 1.03%, and 10.61 ± 1.16% (w/w), respectively. The structural characteristics of HA–PDM–INS were determined using FT-IR, and the effect of the MW of HA on the properties of HA–PDM–INS was investigated. The release of INS from H-HA–PDM–INS was 22.01 ± 3.84% at pH 1.2 and 63.23 ± 4.10% at pH 7.4. The protective ability of HA–PDM–INS with different MW against INS was verified by circular dichroism spectroscopy and protease resistance experiments. H-HA–PDM–INS retained 45.67 ± 5.03% INS at pH 1.2 at 2 h. The biocompatibility of HA–PDM–INS, regardless of the MW of HA, was demonstrated using CCK-8 and live–dead cell staining. Compared with the INS solution, the transport efficiencies of L-HA–PDM–INS, M-HA–PDM–INS, and H-HA–PDM–INS increased 4.16, 3.81, and 3.10 times, respectively. In vivo pharmacodynamic and pharmacokinetic studies were performed in diabetic rats following oral administration. H-HA–PDM–INS exhibited an effective hypoglycemic effect over a long period, with relative bioavailability of 14.62%. In conclusion, these simple, environmentally friendly, pH-responsive, and mucoadhesive nanoparticles have the potential for industrial development. This study provides preliminary data support for oral INS delivery.

Cyclodextrin regulated natural polysaccharide hydrogels for biomedical applications-a review

Cyclodextrin and its derivative (CDs) are natural building blocks for linking with other components to afford functional biomaterials. Hydrogels are polymer network systems that can form hydrophilic three-dimensional network structures through different cross-linking methods and are developing as potential materials in biomedical applications. Natural polysaccharide hydrogels (NPHs) are widely adopted in biomedical field with good biocompatibility, biodegradability, low cytotoxicity, and versatility in emulating natural tissue properties. Compared with conventional NPHs, CD regulated natural polysaccharide hydrogels (CD-NPHs) maintain good biocompatibility, while improving poor mechanical qualities and unpredictable gelation times. Recently, there has been increasing and considerable usage of CD-NPHs while there is still no review comprehensively introducing their construction, classification, and application of these hydrogels from the material point of view regarding biomedical fields. To draw a complete picture of the current and future development of CD-NPHs, we systematically overview the classification of CD-NPHs, and provide a holistic view on the role of CD-NPHs in different biomedical fields, especially in drug delivery, wound dressing, cell encapsulation, and tissue engineering. Moreover, the current challenges and prospects of CD-NPHs are discussed rationally, providing an insight into developing vibrant fields of CD-NPHs-based biomedicine, and facilitating their translation from bench to clinical medicine.

A Dioscorea opposita Thunb Polysaccharide-Based Dual-Responsive Hydrogel for Insulin Controlled Release

A novel hydrogel (DOP/PEI-PBA) based on the “three-component” reaction of 2-formylphenylboric acid (2-FPBA), the primary amine group of polyethyleneimine (PEI) and the cis-o-dihydroxy groups of Dioscorea opposita Thunb polysaccharide (DOP) was designed in this work. The hydrogel can be easily prepared by simply mixing the three reactants at room temperature. The hydrogel had dual responsiveness to glucose and pH, and can realize the controllable release of insulin. Moreover, the hydrogel combining insulin and DOP can inhibit the reactive oxygen species (ROS) level and malondialdehyde (MDA) content, and promote glucose consumption as well as the level of superoxide dismutase (SOD), in high-glucose-induced injury in HL-7702 cells, which reflects the synergistic effect of insulin and DOP to protect hepatocytes from oxidative stress at the same time. Further in vitro cytotoxicity studies showed that the hydrogel had good biocompatibility and no obvious toxicity to cells. These indicate that the prepared hydrogel (DOP/PEI-PBA) can be expected to be applied in the clinical treatment of insulin deficiency in diabetes.

Cutting-Edge Progress in Stimuli-Responsive Bioadhesives: From Synthesis to Clinical Applications

With the advent of “intelligent” materials, the design of smart bioadhesives responding to chemical, physical, or biological stimuli has been widely developed in biomedical applications to minimize the risk of wounds reopening, chronic pain, and inflammation. Intelligent bioadhesives are free-flowing liquid solutions passing through a phase shift in the physiological environment due to stimuli such as light, temperature, pH, and electric field. They possess great merits, such as ease to access and the ability to sustained release as well as the spatial transfer of a biomolecule with reduced side effects. Tissue engineering, wound healing, drug delivery, regenerative biomedicine, cancer therapy, and other fields have benefited from smart bioadhesives. Recently, many disciplinary attempts have been performed to promote the functionality of smart bioadhesives and discover innovative compositions. However, according to our knowledge, the development of multifunctional bioadhesives for various biomedical applications has not been adequately explored. This review aims to summarize the most recent cutting-edge strategies (years 2015–2021) developed for stimuli-sensitive bioadhesives responding to external stimuli. We first focus on five primary categories of stimuli-responsive bioadhesive systems (pH, thermal, light, electric field, and biomolecules), their properties, and limitations. Following the introduction of principal criteria for smart bioadhesives, their performances are discussed, and certain smart polymeric materials employed in their creation in 2015 are studied. Finally, advantages, disadvantages, and future directions regarding smart bioadhesives for biomedical applications are surveyed.

Versatile Oral Insulin Delivery Nanosystems: From Materials to Nanostructures

Diabetes is a chronic metabolic disease characterized by lack of insulin in the body leading to failure of blood glucose regulation. Diabetes patients usually need frequent insulin injections to maintain normal blood glucose levels, which is a painful administration manner. Long-term drug injection brings great physical and psychological burden to diabetic patients. In order to improve the adaptability of patients to use insulin and reduce the pain caused by injection, the development of oral insulin formulations is currently a hot and difficult topic in the field of medicine and pharmacy. Thus, oral insulin delivery is a promising and convenient administration method to relieve the patients. However, insulin as a peptide drug is prone to be degraded by digestive enzymes. In addition, insulin has strong hydrophilicity and large molecular weight and extremely low oral bioavailability. To solve these problems in clinical practice, the oral insulin delivery nanosystems were designed and constructed by rational combination of various nanomaterials and nanotechnology. Such oral nanosystems have the advantages of strong adaptability, small size, convenient processing, long-lasting pharmaceutical activity, and drug controlled-release, so it can effectively improve the oral bioavailability and efficacy of insulin. This review summarizes the basic principles and recent progress in oral delivery nanosystems for insulin, including physiological absorption barrier of oral insulin and the development of materials to nanostructures for oral insulin delivery nanosystems.

Novel porous starch/alginate hydrogels for controlled insulin release with dual response to pH and amylase

An important principle in the development of oral insulin is to protect insulin from the harsh conditions of the stomach and release it in a controlled manner in the intestine. In the present study, novel insulin-loaded porous starch-alginate hydrogel systems (In-S-Alg) including In-MS-Alg (prepared with porous maize starch), In-WS-Alg (porous waxy maize starch), and In-RS-Alg (porous rice starch) were successfully developed. As a representative, In-MS-Alg was further coated with gelatinized-retrograded high amylose maize starch (HA) films with different thicknesses to prepare In-MS-HA/Alg hydrogel beads for improving the functionality of controlled release of insulin under the action of α-amylase. The In-S-Alg and In-MS-HA/Alg hydrogel beads were evaluated in terms of structural and morphological properties, encapsulation effect on insulin as well as its release behavior. The results show that insulin was distributed in the pores and cavities of porous starch granules. In In-MS-HA/Alg hydrogel beads, insulin was increasingly blocked inside porous starch with the increased thickness of the HA film. Encapsulation efficiency of insulin in all In-S-Alg and In-MS-HA/Alg hydrogel beads was >80%. Amazingly, both the hydrogel beads successfully achieved the goal of triggered release upon pH changes and α-amylase addition. Most of the insulin (about 90%) was retained in the simulated gastric fluid; while the release rate of insulin in the simulated intestinal fluid increased gradually, and was further accelerated in the presence of α-amylase. Furthermore, for the In-MS-HA/Alg hydrogel beads, the insulin release rate can be gradually reduced by increasing the thickness of the HA film, which provided the possibility to match the rate of increase of the blood glucose level after the intake of food with different glycemic indices. Therefore, the novel hydrogel prepared in this study may be a promising and safe delivery carrier for oral insulin.

Biodegradable phenylboronic acid-modified ε-polylysine for glucose-responsive insulin delivery via transdermal microneedles

Microneedles with insulin-loaded glucose-responsive particles are promising to control the blood glucose levels of diabetic patients. In particular, the long-term usage of these microneedles calls for biodegradable and cost-effective particles, which are still large challenges. In this paper, glucose-responsive 4-carboxy-3-fluorophenylboronic acid-grafted ε-polylysine (CFPBA-g-PL) was synthesized to meet these requirements. CFPBA-g-PL had low cytotoxicity, good hemocompatibility and no tissue reaction. The pharmacokinetics of CFPBA-g-PL were also studied. The self-assembled particles of CFPBA-g-PL were prepared via simple ultrasonic treatment. The insulin-loaded particles of CFPBA-g-PL (named INS/GRP-12.8) presented a glucose-responsive insulin delivery performance based on the disassembly-related mechanism in vitro. The INS/GRP-12.8-encapsulated microneedle patch with a uniform morphology and moderate skin penetration performance was prepared via a molding strategy. INS/GRP-12.8 lasted for more than 8 hours of normoglycemia on STZ-induced diabetic SD rats via subcutaneous injection and the INS/GRP-12.8-encapsulated microneedle patch also showed a blood-glucose-level-lowering performance in vivo via transdermal administration.

Recent Progress on Polysaccharide-Based Hydrogels for Controlled Delivery of Therapeutic Biomolecules

A plethora of applications using polysaccharides have been developed in recent years due to their availability as well as their frequent nontoxicity and biodegradability. These polymers are usually obtained from renewable sources or are byproducts of industrial processes, thus, their use is collaborative in waste management and shows promise for an enhanced sustainable circular economy. Regarding the development of novel delivery systems for biotherapeutics, the potential of polysaccharides is attractive for the previously mentioned properties and also for the possibility of chemical modification of their structures, their ability to form matrixes of diverse architectures and mechanical properties, as well as for their ability to maintain bioactivity following incorporation of the biomolecules into the matrix. Biotherapeutics, such as proteins, growth factors, gene vectors, enzymes, hormones, DNA/RNA, and antibodies are currently in use as major therapeutics in a wide range of pathologies. In the present review, we summarize recent progress in the development of polysaccharide-based hydrogels of diverse nature, alone or in combination with other polymers or drug delivery systems, which have been implemented in the delivery of biotherapeutics in the pharmaceutical and biomedical fields.

Oral administration co-delivery nanoparticles of docetaxel and bevacizumab for improving intestinal absorption and enhancing anticancer activity

In this study, to improve the intestinal absorption of small molecule chemotherapeutic drug docetaxel (DTX) and macromolecular monoclonal antibody drug bevacizumab (BVZ), we designed and prepared a type of co-delivery nanoparticles for the oral administration of DTX and BVZ. Carboxymethyl chitosan (CMC) and poly(lactic-co-glycolic acid) (PLGA) were used as the carrier of DTX nanoparticles (CPNP_DTX), and methoxy polyethylene glycol-poly (β-amino ester) (mPEG-PAE) was used as the carrier of BVZ nanoparticles (PPNP_BVZ). Then, the two nanoparticles were physically mixed in mass ratios to form mixed co-delivery nanoparticles, which was named as CPNP_DTX&PPNP_BVZ. The nanoparticles were characterized with pH-sensitive drug release property. CPNP_DTX&PPNP_BVZ could significantly increase the bioavailability of DTX and BVZ according to the more cellular uptake in Caco-2 cells and the higher absorption in the intestinal tissue. Compared with free DTX and BVZ, CPNP_DTX&PPNP_BVZ showed excellent cytotoxic effects on A549 cells. Our study revealed the potential of co-delivery nanoparticles of binary mixture of chemotherapeutic small molecule and macromolecular antibody drug as an oral administration therapeutic system.

Long-term treatment of polysaccharides-based hydrogel microparticles as oral insulin delivery in streptozotocin-induced type 2 diabetic mice

To develop a more effective and safer drug for the treatment of type 2 diabetes mellitus (T2DM), polysaccharides-based hydrogel microparticles as oral insulin delivery was prepared and explored. This study was aimed to evaluate the antidiabetic effects and hypoglycemic mechanism with long-term administration(four weeks) of oral insulin hydrogel microparticles in type 2 diabetic mice on a model of diabetes using a high fat diet combined with streptozotocin. The results revealed that the long-term treatment of oral insulin polysaccharides-based hydrogel microparticles could significantly alleviate the symptoms of polyphagia, polydipsia, polyuria and weight loss in diabetic mice. Also, oral administration of insulin hydrogel microparticles could significantly reduce fasting blood glucose levels, ameliorate insulin resistance and increase insulin sensitivity in the mice with T2DM. The concentration of plasma TG, TC, LDL-C, FFA, BUN, CRE significantly decreased and the levels of HDL-C increased showed that insulin polysaccharides-based hydrogel microparticles were effective in regulating lipid metabolism and prevent diabetic nephropathy complication in diabetic mice. In addition, the supplementation of insulin hydrogel microparticles could significant improve the antioxidant capacity by increasing the level of SOD, CAT and decreasing the level of MDA, GPT, NO, TNF-α, and reverse histological deterioration of kidney and pancreas in diabetic mice. The above outcome concluded that insulin polysaccharides-based hydrogel microparticles may exhibit promising anti-diabetic activity and the potential to be a drug candidate for T2DM.

Carboxymethyl β-cyclodextrin grafted carboxymethyl chitosan hydrogel-based microparticles for oral insulin delivery

This study was aimed at utilizing polysaccharides for the development of effective hydrogel microparticles for oral insulin delivery that has a controlled, and sustained release to enhance paracellular transcellular absorption. Carboxymethyl β-cyclodextrin grafted carboxymethyl chitosan hydrogels (CMCD-g-CMCs) were prepared from carboxymethyl β-cyclodextrin (CMCD) and carboxymethyl chitosan (CMC) using a water-soluble carbodiimide as a crosslinker in the presence of N-hydroxysuccinimide. After synthesis, the hydrogel structures were determined via FT-IR and XRD analyses. The porous structure of hydrogels was confirmed by SEM observations and swelling behaviours. The insulin release behaviours were found to betriggered by pH in vitro. Results showed that insulin was successfully retained inside the hydrogels in the gastric environment and slowly released following passage to intestinal conditions. The stability of the secondary structure of insulin was studied by dichroism circular (CD) and fluorescence (FL) spectrophotometer measurement. There was no significant difference in the secondary structure between the native and released insulin. In vitro studies revealed that the hydrogel microparticles exhibited non-cytotoxicity and were transported across the Caco-2 cell monolayers mainly via the paracellular pathway. In order to examine the effectiveness of hydrogel-based sustained release microparticles in delivering insulin in vivo, we administered different insulin-loaded hydrogel microparticles to diabetic mice. In these studies, we found that the insulin-loaded hydrogel microparticles provided a significant and sustained (ranging from 6 h to 12 h) reduction in the blood glucose levels of diabetic mice compared with subcutaneous injection. Overall, these findings demonstrate that CMCD-g-CMCs may be a promising protein carrier for use in oral drug delivery.

Preparation and characterization of polylactic-co-glycolic acid/insulin nanoparticles encapsulated in methacrylate coated gelatin with sustained release for specific medical applications

This study aimed to examine the possibility of using insulin orally with gelatin encapsulation to enhance the usefulness of the drug and increase the lifespan of insulin in the body using polylactic-co-glycolic acid (PLGA) nanoparticles alongside gelatin encapsulation. In this regard, PLGA was synthesized via ring opening polymerization, and PLGA/insulin nanoparticles were prepared by a modified emulsification-diffusion process. The resulting nanoparticles with various amounts of insulin were fully characterized using FTIR, DSC, DLS, zeta potential, SEM, and glucose uptake methods, with results indicating the interaction between the insulin and PLGA. The process efficiency of encapsulation was higher than 92%, while the encapsulation efficiency of nanoparticles, based on an insulin content of 20 to 40%, was optimized at 93%. According to the thermal studies, the PLGA encapsulation increases the thermal stability of the insulin. The morphological studies showed the fine dispersion of insulin in the PLGA matrix, which we further confirmed by the Kjeldahl method. According to the release studies and kinetics, in-vitro degradation, and particle size analysis, the sample loaded with 30% insulin showed optimum overall properties, and thus it was encapsulated with gelatin followed by coating with aqueous methacrylate coating. Release studies at pH values of 3 and 7.4, alongside the Kjeldahl method and standard dissolution test at pH 5.5, and glucose uptake assay tests clearly showed the capsules featured 3-4 h biodegradation resistance at a lower pH along with the sustained release, making these gelatin-encapsulated nanoparticles promising alternatives for oral applications.[Figure: see text].

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.

Oral Drug Delivery Technologies-A Decade of Developments

Advanced drug delivery technologies, in general, enable drug reformulation and administration routes, together contributing to life-cycle management and allowing the innovator to maintain the product monopoly. Over the years, there has been a steady shift from mere life-cycle management to drug repurposing-applying delivery technologies to tackle solubility and permeability issues in early stages or safety and efficacy issues in the late stages of drug discovery processes. While the drug and the disease in question primarily drive the choice of route of administration, the oral route, for its compliance and safety attributes, is the most preferred route, particularly when it comes to chronic conditions, including pain, which is not considered a disease but a symptom of a primary cause. Therefore, the attempt of this review is to take a stock of the advances in oral delivery technologies that are applicable for injectable to oral transformation, improve risk-benefit profiles of existing orals, and apply them in the early discovery program to minimize the drug attrition rates.

Strategies for improving diabetic therapy via alternative administration routes that involve stimuli-responsive insulin-delivering systems

The encapsulation of insulin in micro- or nanodelivery systems may eliminate the need for frequent subcutaneous injections, improving the quality of life of diabetic patients. Formulations for oral, intranasal, pulmonary, subcutaneous, and transdermal administration have been developed. The use of stimuli-responsive polymeric carriers that can release the encapsulated drug in response to changes of the environmental stimuli or external activation enables the design of less invasive or non-invasive systems for smart insulin delivery from depots in the body. This article will look at strategies for the development of responsive delivery systems and the future meeting of the demands of new modes of insulin delivery.

Synthesis and characterization of a novel peptide-grafted Cs and evaluation of its nanoparticles for the oral delivery of insulin, in vitro, and in vivo study

Background

Despite years of experience and rigorous research, injectable insulin is the sole trusted treatment method to control the blood glucose level in diabetes type 1 patients, but injection of insulin is painful and poses a lot of stress to the patients, especially children, therefore, development of a non-injectable formulation of insulin is a major breakthrough in the history of medicine and pharmaceutical sciences.

Methods

In this study, a novel peptide grafted derivative of chitosan (CPP-g- chitosan) is synthesized and its potential for oral delivery of proteins and peptides is evaluated. Drug-loaded nanoparticles were developed from this derivative using ionic gelation method with application of sodium tripolyphosphate (TPP) as a cross-linking agent. Human insulin was used as the model protein drug and release kinetic was studied at gastrointestinal pH. Finally the developed nanoparticles were filled into very tiny enteric protective capsules and its effects on blood glucose level are evaluated in laboratory animals.

Results

Presence of the positively charged cell-penetrating peptide moiety in the structure of chitosan polymer had slight inhibitory effects on the release of insulin from the nanoparticles in simulated gastric fluid (pH 1.2) comparing to native chitosan. The nanoparticles were positively charged in gastrointestinal pH with size ranging from 180 nm to 326 nm. The polypeptide grafted to chitosan is a novel analog of Penetratin, presenting both the hydrophilic and hydrophobic characteristics altering the release behavior of the nanoparticles and significantly increase the absorption of insulin into the rat epithelium comparing to nanoparticles from simple chitosan. In-vivo results in diabetic rat proved that this nanoparticulate system can significantly lower the blood glucose levels in diabetic rats and remain effective for a duration of 9–11 hours.

Conclusion

The results indicate that nanoparticles developed from this new peptide conjugated derivative of chitosan are very promising for oral delivery of proteins and peptides.

Preparation and Characterization of Insulin-Loaded Zein/Carboxymethylated Short-Chain Amylose Complex Nanoparticles

In this work, we use antisolvent precipitation to prepare zein/carboxymethylated short-chain amylose (CSA) complex nanoparticles for insulin encapsulation, showing that insulin-loaded zein/CSA complex nanoparticles are homogeneous, generally exhibiting sizes of <200 nm with a narrow distribution (polydispersity index < 0.100), spherical shape, and strong negative charge (-40 mV). Fourier transform infrared spectroscopy analysis reveals that the formation of the above nanoparticles is mainly driven by hydrophobic, hydrogen-bonding, and electrostatic interactions between CSA, insulin, and zein. In comparison to zein nanoparticles, zein/CSA complex nanoparticles feature much higher insulin encapsulation efficiency (45.8 versus 90.5%, respectively) and are essentially nontoxic to Caco-2 cells. Thus, this work provides new insights into the design of drug delivery systems and is expected to inspire their further development.

Encapsulation of Biological Agents in Hydrogels for Therapeutic Applications

Hydrogels are materials specially suited for encapsulation of biological elements. Their large water content provides an environment compatible with most biological molecules. Their crosslinked nature also provides an ideal material for the protection of encapsulated biological elements against degradation and/or immune recognition. This makes them attractive not only for controlled drug delivery of proteins, but they can also be used to encapsulate cells that can have therapeutic applications. Thus, hydrogels can be used to create systems that will deliver required therapies in a controlled manner by either encapsulation of proteins or even cells that produce molecules that will be released from these systems. Here, an overview of hydrogel encapsulation strategies of biological elements ranging from molecules to cells is discussed, with special emphasis on therapeutic applications.

A stimuli-responsive insulin delivery system based on reversible phenylboronate modified cyclodextrin with glucose triggered host-guest interaction

Injection of insulin is an effective therapy to treat most patients with the type I diabetes and some with type II diabetes. Additionally, the release of insulin under specific conditions has attracted widespread interest. In this study, a smart drug carrier that can release insulin depending on the changes in blood glucose levels was designed. Combining two popular molecules through facile synthetic processes, a drug carrier of reversible phenylboronate group modified cyclodextrin (β-CD-EPDME) was fabricated. The drug carrier is composed of cyclodextrin, which can encapsulate insulin, and phenylboronate, which is sensitive to the cis-diols in some saccharides. Moreover, β-CD-EPDME can successfully encapsulate insulin and almost completely release insulin in the presence of glucose. The detached phenylboronic acid moiety triggered by glucose can attack the β-CD cavity and form a host-guest complex, which can force out the encapsulated insulin within the cavity. In addition, the insulin released from the β-CD-EPDME@Insulin complex retains its secondary structure, and the drug carrier has been proven to have low cytotoxicity. Thus, this safe and glucose-responsive drug carrier shows the potential for use in the therapy of diabetes.

Glucose- and H2O2-Responsive Polymeric Vesicles Integrated with Microneedle Patches for Glucose-Sensitive Transcutaneous Delivery of Insulin in Diabetic Rats

Herein, a dual-responsive insulin delivery device by integrating glucose- and H₂O₂-responsive polymeric vesicles (PVs) with transcutaneous microneedles (MNs) has been designed. This novel microneedle delivery device achieves a goal of fast response, excellent biocompatibility, and painless administration. The PVs are self-assembled from a triblock copolymer including poly(ethylene glycol), poly(phenylboronic acid) (glucose-sensitive block), and poly(phenylboronic acid pinacol ester) (H₂O₂-sensitive block). After loading with insulin and glucose oxidase (GO _x), the drug-loaded PVs display a basal insulin release as well as a promoted insulin release in response to hyperglycemic states. The insulin release rate responds quickly to elevated glucose and can be further promoted by the incorporated GO _x, which will generate the H₂O₂ at high glucose levels and further break the chemical links of phenylboronic acid pinacol ester group. Finally, the transdermal delivery of insulin to the diabetic rats ((insulin + GO _x)-loaded MNs) presents an effective hypoglycemic effect compared to that of subcutaneous injection or only insulin-loaded MNs, which indicates the as-prepared MNs insulin delivery system could be of great importance for the applications in the therapy of diabetes.

Insulin Inclusion into a Tragacanth Hydrogel: An Oral Delivery System for Insulin

Nanoparticles or microparticles created by physical complexation between two polyelectrolytes may have a prospective use as an excipient for oral insulin administration. Natural polymers such as tragacanth, alginate, dextran, pullulan, hyaluronic acid, gelatin and chitosan can be potential candidates for this purpose. In this research, insulin particles were prepared by the inclusion of insulin into a tragacanth hydrogel. The effect of the pH and concentration relationship involving polyelectrolytes offering individual particle size and zeta potential was assessed by zetasizer and scanning electron microscopy (SEM). Insulin-tragacanth interactions at varying pH (3.7, 4.3, 4.6, or 6), and concentration (0.1%, 0.5%, or 1% w/w) were evaluated by differential scanning calorimetry (DSC) and ATR Fourier transform infrared (ATR-FTIR) analysis. Individual and smaller particles, approximately 800 nm, were acquired at pH 4.6 with 0.5% of tragacanth. The acid gelation test indicated that insulin could be entrapped in the physical hydrogel of tragacanth. DSC thermograms of insulin-tragacanth showed shifts on the same unloaded tragacanth peaks and suggested polyelectrolyte-protein interactions at a pH close to 4.3-4.6. FTIR spectra of tragacanth-insulin complexes exhibited amide absorption bands featuring in the protein spectra and revealed the creation of a new chemical substance.

Insulin-loaded PLGA microspheres for glucose-responsive release

Porous poly(lactic-co-glycolic acid) (PLGA) microspheres were prepared, loaded with insulin, and then coated in poly(vinyl alcohol) (PVA) and a novel boronic acid-containing copolymer [poly(acrylamide phenyl boronic acid-co-N-vinylcaprolactam); p(AAPBA-co-NVCL)]. Multilayer microspheres were generated using a layer-by-layer approach depositing alternating coats of PVA and p(AAPBA-co-NVCL) on the PLGA surface, with the optimal system found to be that with eight alternating layers of each coating. The resultant material comprised spherical particles with a porous PLGA core and the pores covered in the coating layers. Insulin could successfully be loaded into the particles, with loading capacity and encapsulation efficiencies reaching 2.83 ± 0.15 and 82.6 ± 5.1% respectively, and was found to be present in the amorphous form. The insulin-loaded microspheres could regulate drug release in response to a changing concentration of glucose. In vitro and in vivo toxicology tests demonstrated that they are safe and have high biocompatibility. Using the multilayer microspheres to treat diabetic mice, we found they can effectively control blood sugar levels over at least 18 days, retaining their glucose-sensitive properties during this time. Therefore, the novel multilayer microspheres developed in this work have significant potential as smart drug-delivery systems for the treatment of diabetes.

Binary and Tertiary Complex Based on Short-Chain Glucan and Proanthocyanidins for Oral Insulin Delivery

The present study was performed to investigate binary and tertiary nanocomposites between short-chain glucan (SCG) and proanthocyanidins (PAC) for the oral delivery of insulin. There was a large decrease in fluorescence intensity of insulin in the presence of SCG or the combination of SCG with PAC. Fourier transform infrared spectroscopy revealed that the binary and tertiary nanocomposites were synthesized due to the hydrogen bonding and hydrophobic interactions. The insulin entrapped in the nanocomposites was in an amorphous state confirmed by X-ray diffraction. The cell culture demonstrated that both the nanocomposites showed no detectable cytotoxicity with relative cell viability all above 85%. The pharmacological bioavailability after oral administration of insulin-SCG-PAC at a dose of 100 IU/kg was found to be 6.98 ± 1.20% in diabetic rats without any sharp fluctuations in 8 h.