Effects of interpenetration of thermo-sensitive gels by crosslinking of chitosan on nasal delivery of insulin: In vitro characterization and in vivo study

Injectable systems for long-lasting insulin therapy

Insulin therapy is the mainstay to treat diabetes characterizedd by hyperglycemia. However, its short half-life of only 4-6 min limits its effectiveness in treating chronic diabetes. Advances in recombinant DNA technology and protein engineering have led to several insulin analogue products that have up to 42 h of glycemic control. However, these insulin analogues still require once- or twice-daily injections for optimal glycemic control and have poor patient compliance and adherence issues. To achieve insulin release for more than one day, different injectable delivery systems including microspheres, in situ forming depots, nanoparticles and composite systems have been developed. Several of these delivery systems have advanced to clinical trials for once-weekly insulin injection. This review comprehensively summarizes the developments of injectable insulin analogs and delivery systems covering the whole field of injectable long-lasting insulin technologies from prototype design, preclinical studies, clinical trials to marketed products for the treatment of diabetes.

Antioxidative NAC-Loaded Silk Nanoparticles with Opening Mucosal Tight Junctions for Nasal Drug Delivery: An In Vitro and In Vivo Study

Using nasal routes to deliver drugs to the brain using multifunctional nanoparticles (NPs) to bypass the blood–brain barrier (BBB) might enhance the delivery efficacy. Anti-oxidative N-Acetyl-L-cysteine (NAC)-loaded silk fibroin (SF/NAC) NPs are produced, characterized and studied as a potential delivery vehicle for NAC delivered to the brain via nasal for both in vitro and in vivo studies. The NPs are not cytotoxic to RPMI 2650 cells, mucosal model cells, at a concentration of 6000 μg/mL. The anti-oxidative activities of SF/NAC NPs are demonstrated by high H₂O₂ scavenge capacities of the NPs and shown by mitochondrial superoxide (MitoSOX) immunostaining of human mesenchymal stem cells. Tight junctions in RPMI 2650 cells are opened after 30 min of incubation with SF/NAC NPs, which are demonstrated by measuring the decrease in trans-epithelial electrical resistance (TEER) values and discreteness in ZO-1 stains. The cellular uptake of SF/NAC NPs by RPMI 2650 cells is significantly greater than that for SF NPs and increased with increasing incubation time. In an in vivo imaging study (IVIS) using rats shows that the amount of NAC that is delivered to the brain by SF/NAC NPs increased by 1.40–2.60 times and NAC is retained longer in the nasal cavity than NAC solutions in a 2-h study.

Emerging Fabrication Strategies of Hydrogels and Its Applications

Recently, hydrogels have been investigated for the controlled release of bioactive molecules, such as for living cell encapsulation and matrices. Due to their remote controllability and quick response, hydrogels are widely used for various applications, including drug delivery. The rate and extent to which the drugs reach their targets are highly dependent on the carriers used in drug delivery systems; therefore the demand for biodegradable and intelligent carriers is progressively increasing. The biodegradable nature of hydrogel has created much interest for its use in drug delivery systems. The first part of this review focuses on emerging fabrication strategies of hydrogel, including physical and chemical cross-linking, as well as radiation cross-linking. The second part describes the applications of hydrogels in various fields, including drug delivery systems. In the end, an overview of the application of hydrogels prepared from several natural polymers in drug delivery is presented.

Recent progress in polymeric non-invasive insulin delivery

The design of carriers for insulin delivery has recently attracted major research attentions in the biomedical field. In general, the release of drug from polymers is driven via a variety of polymers. Several mechanisms such as matrix release, leaching of drug, swelling, and diffusion are usually adopted for the release of drug through polymers. Insulin is one of the most predominant therapeutic drugs for the treatment of both diabetes mellitus; type-I (insulin-dependent) and type II (insulin-independent). Currently, insulin is administered subcutaneously, which makes the patient feel discomfort, pain, hyperinsulinemia, allergic responses, lipodystrophy surrounding the injection area, and occurrence of miscarried glycemic control. Therefore, significant research interest has been focused on designing and developing new insulin delivery technologies to control blood glucose levels and time, which can enhance the patient compliance simultaneously through alternative routes as non-invasive insulin delivery. The aim of this review is to emphasize various non-invasive insulin delivery mechanisms including oral, transdermal, rectal, vaginal, ocular, and nasal. In addition, this review highlights different smart stimuli-responsive insulin delivery systems including glucose, pH, enzymes, near-infrared, ultrasound, magnetic and electric fields, and the application of various polymers as insulin carriers. Finally, the advantages, limitations, and the effect of each non-invasive route on insulin delivery are discussed in detail.

Chitosan for biomedical applications, promising antidiabetic drug delivery system, and new diabetes mellitus treatment based on stem cell

Since chitosan's excellent pharmacokinetic and chemical properties, it is an attractive and promising carbohydrate biopolymer in biomedical applications. Chitosan's beneficial function in the defense and propagation of pancreatic β cells, reducing hyperglycemia, and avoiding diabetes mellitus associated with impaired lipid metabolism has been demonstrated in several studies. Additionally, chitosan has also been used in various nanocarriers to deliver various antidiabetic drugs to reduce glucose levels. Herein, the first to provide the currently available potential benefits of chitosan in diabetes mellitus treatment focuses on chitosan-based nanocarriers for oral administration of various antidiabetic drugs nasal and subcutaneous passages. Moreover, chitosan is used to activate and deliver stem cells and differentiate them into cells similar to pancreatic beta cells as a new type of treatment for type one diabetes mellitus. The results of this review will be helpful in the development of promising treatments and better control of diabetes mellitus.

Delivery and Anti-Psoriatic Effect of Silibinin-Loaded Polymeric Micelles: An Experimental Study in the Psoriatic Skin Model

OBJECTIVE

Psoriasis is an inflamed skin disorder associated with the activation of phosphorylation signals in keratinocytes, which leads to proliferation. Phosphorylation signal inhibitors, such as silibinin can inhibit cell proliferation. Unlike current psoriasis treatment approaches that are associated with dangerous side effects; natural components can introduce new trends in psoriasis treatment. The major problem in the topical treatment of psoriasis is drug localization through the psoriasis lesions.

METHODS

In this study, silibinin-loaded polymeric micelles prepared and characterized for drug loading and release and ex vivo permeation through psoriatic and normal mice skin. The optimized batch was used for the treatment of psoriasis lesions in the mice model.

RESULTS

The optimized batch demonstrated mean particle size 18.3 ± 2.1 nm, entrapment efficiency 75.8 ± 5.8%, and prolonged silibinin release. % Silibinin permeated through psoriatic skin after 48 treated by polymeric micelle and aqueous control was 80.35, and 92.6, respectively. Polymeric micelles increased silibinin localization in the psoriatic skin in comparison with control. In psoriatic skin after 7- 10 days treatment by silibinin- loaded polymeric micelle, there was no evidence of psoriasis and the histological evaluation showed no sign of psoriasis. Silibinin-loaded polymeric micelles reduced Psoriasis area index by more than 78% after 14 days.

CONCLUSION

It seems that polymeric micelles increased the effectiveness of silibinin by drug localization into the psoriatic plaque. Topical STAT- 3inhibitors can be introduced as a new strategy in psoriasis treatment.

Addition of free poloxamer 407 to a new gene vector P407-PEI-K12 solution forms a sustained-release in situ hypergel that enhances cell transfection and extends gene expression

To address the concern around the efficiency/cytotoxicity ratio and the tumor-targeting effects of polyethylenimine (PEI), is a non-viral gene vector used for the delivery of the cancer therapy gene, poloxamer 407 (P407)-PEI-K12, was synthesized by cross-linking low-molecular weight PEI with P407 and further coupling a bifunctional peptide, K12, which is comprised of the tumor-targeting peptide tLyP-1 and the nuclear localization sequence. Furthermore, the addition of free P407 into the polymer/DNA complex solution produced a temperature-sensitive in situ gel-P407/P407-PEI-K12/DNA complex, which improved the effects of sustained-release gene delivery and transfection efficiency. The specificity, cytotoxicity and gene transfection efficiency of P407-PEI-K12 was investigated in Hela cells in vitro. The polymer efficiently prevented the degradation of plasmid DNA by DNase I and had a marked ability for serum tolerance. Agarose gel electrophoresis revealed that plasmid DNA was efficiently condensed and protected. The higher transfection efficiency of P407-PEI-K12h (the molar ratio of P407-PEI and K12 is 1:10) was achieved with a polymer and plasmid DNA ratio (w/w) of 20:1. The ability of free P407 to promote the transfection of the polymer/DNA complex was high (0.09%). The half-life of the P407/P407-PEI-K12-h/DNA gel complex was 228 min, and the transfection efficiency of the P407/P407-PEI-K12-h/DNA complex was markedly higher compared to that of the P407-PEI-K12-h/DNA complex at various release times.

Updates on thermosensitive hydrogel for nasal, ocular and cutaneous delivery

Thermosensitive hydrogels are in situ gelling systems composed of hydrophilic homopolymers or block copolymers which remain as solutions at room temperature and form gels after administration into the body. Its application in advanced drug delivery has gained significant attention in recent years. The tunable characteristics of thermosensitive hydrogels make them versatile and capable of incorporating both hydrophilic and lipophilic compounds and macromolecules. The drug molecules can be included as free molecules or preformulated into nano- or micro-particles or liposomes. Although there were several reviews on the materials of thermosensitive hydrogels, the compatibility between the drug and thermosensitive material as well as its in vitro release mechanisms and in vivo performance have barely been investigated. The current review is proposed aiming to not only provide an update on the recent development in thermosensitive hydrogel formulations for nasal, ocular and cutaneous deliveries, but also identify the relationship between the drug characteristics and the loading strategies, and their impacts on the release mechanisms and the in vivo performance. Our current update for the first time highlights the essential features for successful development of in situ thermosensitive hydrogels to facilitate nasal, ocular or cutaneous drug deliveries.

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.

A hybrid genipin-crosslinked dual-sensitive hydrogel/nanostructured lipid carrier ocular drug delivery platform

The objective of this study was to develop a novel hybrid genipin-crosslinked dual-sensitive hydrogel/nanostructured lipid carrier (NLC) drug delivery platform. An ophthalmic anti-inflammatory drug, baicalin (BN) was chosen as the model drug. BN-NLC was prepared using melt-emulsification combined with ultra-sonication technique. Additionally, a dual pH- and thermo-sensitive hydrogel composed of carboxymethyl chitosan (CMCS) and poloxamer 407 (F127) was fabricated by a cross-linking reaction with a nontoxic crosslinker genipin (GP). GP-CMCS/F127 hydrogel was characterized by FTIR, NMR, XRD and SEM. The swelling studies showed GP-CMCS/F127 hydrogel was both pH- and thermo-sensitive. The results of in vitro release suggested BN-NLC gel can prolong the release of baicalin comparing with BN eye drops and BN-NLC. Ex vivo cornea permeation study was evaluated using Franz diffusion cells. The apparent permeability coefficient (P_app ) of BN-NLC gel was much higher (4.46-fold) than that of BN eye drops. Through the determination of corneal hydration levels, BN-NLC gel was confirmed that had no significant irritation to cornea. Ex vivo precorneal retention experiments were carried out by a flow-through approach. The results indicated that the NLC-based hydrogel can prolong precorneal residence time. In conclusion, the hybrid NLC-based hydrogel has a promising potential for application in ocular drug delivery.

Study of sodium hyaluronate-based intranasal formulations containing micro- or nanosized meloxicam particles

This article reports on the micro- and nanonization of meloxicam (MEL) with the aim of developing pre-dispersions as intermediates for the design of intranasal formulations. As a new approach, combined wet milling technology was developed in order to reduce the particle size of the MEL. Different milling times resulted in micro- or nanosized MEL in the pre-dispersions with polyvinyl alcohol as stabilizer agent, which were directly used for preparing intranasal liquid formulations with the addition of sodium hyaluronate as mucoadhesive agent. Reduction of the MEL particle size into the nano range led to increased saturation solubility and dissolution velocities, and increased adhesiveness to surfaces as compared with microsized MEL particles. A linear correlation was demonstrated between the specific surface area of MEL and the AUC. The in vitro and in vivo studies indicated that the longer residence time and the uniform distribution of nano MEL spray throughout an artificial membrane and the nasal mucosa resulted in better diffusion and a higher AUC. Nanosized MEL may be suggested for the development of an innovative dosage form with a different dose of the drug, as a possible administration route for pain management.

Poloxamer-based in situ hydrogels for controlled delivery of hydrophilic macromolecules after intramuscular injection in rats

This study is aimed to investigate the applicability of poloxamer 407 (P407) and 188 (P188)-based temperature-sensitive in situ hydrogel (TSHG) in sustained delivery of hydrophilic macromolecules following intramuscular administration. Polyethylene glycols (PEGs) with molecular weight of 5-, 20-, and 40-kDa were used as model drugs, which can represent the common size range of hydrophilic macromolecular drugs using TSHG. The correlation between the level of poloxamers and thermogelling transition temperatures (Tsol-gel) was established and two formulations "20% P407/10% P188" and "24% P407/10% P188" were chosen for further study. The results showed that the release kinetics of PEGs was close to zero order. Sustained in vivo behaviors were achieved by both of the two formulations for all the PEGs though variations were seen. Lower molecular weight PEG showed more remarkable pharmacokinetic improvements. No significant differences in pharmacokinetics were observed between the two formulations for the same PEG. This suggested that 20-24% P407/10% P188 formulations, with accordingly Tsol-gel in the range of 24.6 °C-31.7 °C, might be freely chosen to achieve comparable pharmacokinetics for hydrophilic macromolecular drugs after intramuscular injection.

Mucoadhesive in situ nasal gelling drug delivery systems for modulated drug delivery

INTRODUCTION

The nasal route is an attractive target for administration of the drug of choice, particularly in overcoming disadvantages such as high first-pass metabolism and drug degradation in the gastrointestinal environment that are associated with the oral and other modes of administration. The major limitation associated is of rapid mucociliary clearance in the nasal delivery that results in low absorption and hence poor bioavailability. In order to overcome this, mucoadhesive in situ nasal gelling drug delivery systems have been explored to develop sustained/controlled delivery via nasal route.

AREAS COVERED

The present review critically evaluates the importance of in situ gel for the nasal delivery of drugs, and the polymers used in the formulation of in situ gel along with their mechanism of gelation. It also encompasses the research reports made in this arena of delivery system.

EXPERT OPINION

The challenges of drug delivery through nose has led to development of in situ nasal gelling systems using a myriad of polymers to deliver the drugs, proteins, amino acids, hormones, vaccines and plasmid DNA for the local, systemic and central nervous system effects. Though a range of preclinical reports are available, clinical intricacies need to be critically worked out.

Advancement in stimuli triggered in situ gelling delivery for local and systemic route

INTRODUCTION

Current research efforts focused on the design and evaluation of drug delivery systems that are easy to administer require decreased administration frequency, and provide sustained drug release in order to increase clinical efficacy and compliance of the patients. The gel forming smart polymeric formulations offer numerous applications resemble sustained and prolonged action in contrast to conventional drug delivery systems.

AREAS COVERED

Article summarizes type of bioactive, sol-gel triggering factors, dose, rationales, and polymers involved in gelation with respect to their route of administration. A lot of work has been done with smart polymeric gelling system taking the advantage of stimuli (temperature and pH) triggered sol-gel phase-transition in the administered area that have great prospective in biomedical and pharmaceutical applications, particularly in target-specific controlled drug delivery systems.

EXPERT OPINION

Although the principle of gelation is so attractive, key issues remain to be solved which include (i) variability of the drug release, (ii) avoidance of burst release in case of depot formulation, and (iii) issues related to toxicity. Unfortunately, till now area concerning the detailed processes of the gelling formation is still not much explored. Despite this proclamation, many efforts are made in industry and institutions to improve concerned approaches. New materials and approaches enter the preclinical and clinical phases and one can be sure that this strategy will gain further clinical importance within the next years. Thus, this review article will assuredly serve as an informative tool for the innovators working in the concern area.

Dual stimuli-responsive N-phthaloylchitosan-graft-(poly(N-isopropylacrylamide)-block-poly(acrylic acid)) copolymer prepared via RAFT polymerization

In order to develop stimuli-responsive hydrogel, chitosan graft copolymer with chitosan back-bone and poly(N-isopropylacrylamide)-block-poly(acrylic acid) (PNIPAAm-b-PAA) branch chains was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization in DMF. The chain transfer agent was obtained by modification of chitosan with 3-benzylsulfanyl thiocarbonylsulfanyl propionic acid (BPATT) with 68% the degree of substitute. The graft polymerizations possessed controlled/living characteristics. The behavior of the graft copolymer in aqueous solution was investigated by dynamic light scattering, transmission electron microscopy, and UV-visible spectrophotometer. N-Phthaloylchitosan-graft-(poly(N-isopropylacrylamide)-block-poly(acrylic acid)) copolymer (N-phthaloylchitosan-g-(PNIPAAm-b-PAA)) could assemble to micelles in aqueous solution in range of 200-300 nm with narrow size distribution, and the hydrodynamic diameter could be controlled dependent on length of branch chains and temperature. The LCST values of micelle could be modulated from 34 to 40 °C by controlling the constitution of branch chains, pH, and concentration.