Progress in the Development of Chitosan Based Insulin Delivery Systems: A Systematic Literature Review

Diabetes mellitus is a chronic disease that is considered a worldwide epidemic, and its control is a constant challenge for health systems. Since insulin had its first successful use, scientists have researched to improve the desired effects and reduce side-effects. Over the years, the challenge has been to increase adherence to treatment and improve the quality of life for diabetics by developing an insulin delivery system. This systematic review (SR) analyses experimental articles from 1998 to 2018 related to the development of the chitosan/insulin delivery system (CIDS). Automated support: Start tool was used to perform part of these activities. The search terms “insulin”, “delivery or release system”, and “chitosan” were used to retrieve articles in PubMed, Science Direct, Engineering Village, and HubMed. A total of 55 articles were selected. The overview, phase, model, way of administration, and the efficiency of CIDS were analyzed. According to SR results, most of the articles were published from 2010 onwards, representing 72.7% of the selected papers, and research groups from China publicized 23.6% of the selected articles. According to the SR, 51% of the studies were carried out in vivo and 45% in vitro. Most of the systems were nanoparticle based (54.8%), and oral administration was proposed by 60.0% of the selected articles. Only 36.4% performed loaded capacity and encapsulation efficiency assays, and 24 h (16.4%), 12 h (12.7%), and 6 h (11.0%) were the most frequent insulin release times. Chitosan’s intrinsic characteristics, which include biodegradability, biocompatibility, adhesiveness, the ability to open epithelial tight junctions to allow an increase in the paracellular transport of macromolecular drugs, such as insulin, and the fact that it does not result in allergic reactions in the human body after implantation, injection, topical application or ingestion, have contributed to the increase in research of CIDS over the years. However, the number of studies is still limited and the use of an alternative form of insulin administration is not yet possible. Thus, more studies in this area, aiming for the development of an insulin delivery system that can promote more adherence to the treatment and patient comfort, are required.


h
Diabetes is a serious public health problem affecting 422 million people worldwide. Traditional diabetes management often requires multiple daily insulin injections, associated with pain and inadequate glycemia control. Herein, we have developed an ultrasound-triggered insulin delivery system capable of pulsatile insulin release that can provide both longterm sustained and fast on-demand responses. In this system, insulin-loaded poly(lactic-co-glycolic acid) (PLGA) nanocapsules are encapsulated within chitosan microgels. The encapsulated insulin in nanocapsules can passively diffuse from the nanoparticle but remain restricted within the microgel. Upon ultrasound treatment, the stored insulin in microgels can be rapidly released to regulate blood glucose levels. In a chemicallyinduced type 1 diabetic mouse model, we demonstrated that this system, when activated by 30 s ultrasound administration, could effectively achieve glycemic control for up to one week in a noninvasive, localized, and pulsatile manner.  2 h A polyelectrolyte complex system of chitosan-pectin nanoand microparticles was developed to encapsulate the hormone insulin. The aim of this work was to obtain small particles for Oral insulin delivery without chemical crosslinkers based on natural and biodegradable polysaccharides. The nano-and microparticles were developed using chitosans (with different degrees of acetylation: 15.0% and 28.8%) and pectin solutions at various charge ratios (n+/ngiven by the chitosan/pectin mass ratio) and total charge. Nano-and microparticles were characterized regarding particle size, zeta potential, production yield, encapsulation efficiency, stability in different media, transmission electron microscopy and cytotoxicity assays using Caco-2 cells. The insulin release was evaluated in vitro in simulated gastric and intestinal media. Small-sized particles (~240-~1900 nm) with a maximum production yield of ~34.0% were obtained. The highest encapsulation efficiency (~62.0%) of the system was observed at a charge ratio (n+/n-) 5.00. The system was stable in various media, particularly in simulated gastric fluid (pH 1.2). Transmission electron microscopy (TEM) analysis showed spherical shape particles when insulin was added to the system. In simulated intestinal fluid (pH 6.8), controlled insulin release occurred over 2 h. In vitro tests indicated that the proposed system presents potential as a drug delivery for Oral administration of bioactive peptides. The objective of this work was to explore the potential of polyethylene glycolgrafted chitosan (PEGg-chitosan) nanoparticles as a system for improving the systemic absorption of insulin following Nasal administration. Insulinloaded PEG-g-chitosan nanoparticles were prepared by the ionotropic gelation of PEG-g-chitosan solution using tripolyphosphate ions as the crosslinking agent. The nanoparticles were in the size range 150-300 nm, had a positive electrical charge (+16 to +30 mV) and were associated with insulin (loading efficiency 20-39%). The physicochemical properties of nanoparticles were affected by the composition of the copolymer. In vitro insulin release studies showed an initial burst followed by a slow release of insulin. IntraNasal administration of PEGg-chitosan nanoparticles in rabbits enhanced the absorption of insulin by the Nasal mucosa to a greater extent than a suspension of insulin-PEG-g-chitosan and control insulin solution. PEG-gchitosan nanoparticles are promising vehicles for insulin transport through the Nasal mucosa. The drugloading and the encapsulation efficiency for the two drugs loaded alone were respectively attained a different value (0.204 ± 0.023% (inner) and 0.241 ± 0.017% (outer), 1.641 ± 0.180% (inner) and 1.804 ± 0.121% (outer) were for MET; 2.296 ± 0.120% (inner) and 9.357 ± 0.751% (outer), 11.662 ± 0.708% (inner) and 85.534 ± 1.511% (outer) were for INS).

h
To improve the efficacy and reduce the systemic toxicity of the diabetes mellitus, herewith, we developed a novel microparticlesembedded microcapsules (MEMs) system, synthesized from calcium alginate/ chitosan (Ca-Alg/CS), by emulsion gelation using a high voltage electrostatic droplet generator. In our study, we selected two antidiabetic drugs insulin (INS) and metformin (MET) as model drugs to investigate different spatial distribution appropriate of MEMs system. Characterization based on particle size and morphology, encapsulation efficiency and drug loading, as well as drug delivery properties were carried out on the MEMs system. Typical multi-chamber structure was shown by SEM and the optical spectra. The average diameters of microparticles and Ca-Alg/CS MEMs were 2100 nm and 410 μm, respectively. Insulin and MET were embedded into MEMs via electrostatic reaction according to FT-IR spectra. Moreover, drug loading and encapsulation efficiency of INS were higher than that of MET in this system when drugs were loaded alone or together. More importantly, this system has potential for orderly drug release and well sustained release when MET in the inner and INS in the outer space could be applied as a combination therapy for diabetes. The obtained in vivo experimental data on diabetes rats has shown that the designed MEMs system resulted in a higher hypoglycemic effect within add-on therapy. The most promising formulation (F8) was based on HTCC-33% and the EE was 52 ± 3%.

3,33h
Chitosan and chitosan derivative-based nanoparticles loaded with insulin were prepared by selfassembly, via electrostatic interactions between the negatively charged drug and the positively charged polymers. In the investigated chitosan derivatives, the amine groups were substituted to different extents (33, 52 or 99%) by 2hydroxypropyl-3trimethyl ammonium groups, rendering the polymers permanently positively charged, irrespective of the pH. This is an important property for this type of advanced drug delivery system, since the pH value changes throughout the gastrointestinal tract and electrostatic interactions are of crucial importance for the stability of the nanoparticles. Permanent positive charges are also in favor of mucoadhesion. In contrast, the electric charges of chitosan molecules depend on the pH of the surrounding medium. Since the solubility of the chitosan derivatives increased due to the introduction of quaternary ammonium groups, sodium tripolyphosphate (TPP) was added to the systems to create supplementary crosslinks and stabilize the nanoparticles. The presence of TPP influenced both the dissolution of the polymer matrix as well as the resulting release kinetics. The underlying drug release mechanisms were found to be more complex than simple diffusion under constant conditions, likely involving also ionic interactions and matrix dissolution. The most promising formulation was based on a chitosan derivative with 33% substitution degree and characterized by a Z-average of 142 ± 10 nm, a zeta potential of 29 ± 1 mV, an encapsulation efficacy of 52 ± 3% and, most importantly, the release of insulin was sustained for more than 210 min. about 800 minutes Chitosan (CS) and polyurethane-chitosan (PU-CS) nano-particles (NPs) were prepared for the core formation by complex coacervation method whereas alginate (ALG) and PU-ALG were crosslinked by ionic gelation method to form the protective shelllayer over the core. Effects of PU incorporation either within the core or shell or both were investigated by different in vitro and in vivo parameters. Fourier transform infrared (FTIR) spectroscopy of different compositions of nano-particles showed distinct characteristic peaks for CS, PU, and ALG, indicating their presence in variable ratios. Significance of polyurethaneincorporated systems towards insulin encapsulation efficiency, swelling parameters, insulin release, and in vivo pharmacological effect were also studied. Particle sizes, zeta potential, morphological analysis, mucoadhesion study, and in vivo acute toxicity studies of these core-shell nanoparticles were also performed. Bioavailability of insulin ranged from 9.04 to 11.6% for polyurethaneincorporated chitosanalginate core-shell nano-particle formulations which was significantly higher than the insulin bioavailability of basic CS/ALG core-shell nanoparticle system. The insulin encapsulation efficiency was 33.3 ± 5.2% and 34.0 ± 5.0% for alginate and alginate/chitosa n beads, for insulin concentration of 10 wt%, respectively.

hours
The challenge of this work was to investigate the potential of alginate/chitosan beads containing magnetite nanoparticles as a drug delivery system. The insulin beads were prepared by dripping a solution of sodium alginate containing insulin into a CaCl2 solution. Magnetite nanoparticles of 5nm mean size were synthesized inside the alginate egg-box structure by coprecipitation of Fe(III) and Fe(II) in the presence of NH4OH. Quantitative analysis revealed that insulin encapsulation depends on the initial protein content and 35% of insulin was entrapped by alginate beads for a protein concentration of 10wt%. It was verified that approximately 50% of the insulin was released to Milli-Q water in 800h release experiments. The application of oscillating magnetic field increased three fold the insulin release. The results suggest that the alginate/chitosan system containing magnetite nanoparticles is a promising system for clinical applications of controlled release of insulin in the presence of an oscillating magnetic field in a subcutaneous implant approach.

hours
In an alginate/chitosan nanoparticle system, insulin was protected by forming complexes with cationiccyclodextrin polymers (CPCDs), which were synthesized fromcyclodextrin (-CD), epichlorohydrin (EP) and choline chloride (CC) through a onestep polycondensation. Due to the electrostatic attraction between insulin and CPCDs, as well as the assistance of its polymeric chains, CPCDs 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 CPCDs (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. Insulin was encapsulated in calcium alginate beads coated with chitosan. Its release from alginate-chitosan and alginatechitosanglutaraldehyd e beads was studied in artificial gastric (pH 1.2) and intestinal (pH 7.5) fluids. By comparing the release amounts, the ionic interaction between alginate-chitosan matrix with the medium pH's, intestinal fluid was found to be the better. The degradation of released insulin was also searched, even after 6 h incubation, the beads remained stable and the undegraded insulin seemed to be sufficient for the physiological conditions. Consequently, it can be said that the system can be offered for Oral delivery of the therapeutic peptide drug insulin.

Strings of search*:
PubMed: ((((chitosan) AND insulin) AND ((delivery system) OR controlled delivery system)) Science Direct: ((((chitosan) AND insulin) AND ((delivery system) OR controlled delivery system)) Engineering Village: (1) chitosan and insulin and controlled delivery system (2) (chitosan and insulin and delivery system) HubMed: ((((chitosan) AND insulin) AND ((delivery system) OR controlled delivery system)) * All the searches were performed in the search advanced model of the websites.