Current challenges in non-invasive insulin delivery systems: a comparative review

Recent advances in the development of poly(ester amide)s-based carriers for drug delivery

Biodegradable and biocompatible biomaterials have several important applications in drug delivery. The biomaterial family known as poly(ester amide)s (PEAs) has garnered considerable interest because it exhibits the benefits of both polyester and polyamide, as well as production from readily available raw ingredients and sophisticated synthesis techniques. Specifically, α-amino acid-based PEAs (AA-PEAs) are promising carriers because of their structural flexibility, biocompatibility, and biodegradability. Herein, we summarize the latest applications of PEAs in drug delivery systems, including antitumor, gene therapy, and protein drugs, and discuss the prospects of drug delivery based on PEAs, which provides a reference for designing safe and efficient drug delivery carriers.

Advancing immunotherapy using biomaterials to control tissue, cellular, and molecular level immune signaling in skin

Immunotherapies have been transformative in many areas, including cancer treatments, allergies, and autoimmune diseases. However, significant challenges persist in extending the reach of these technologies to new indications and patients. Some of the major hurdles include narrow applicability to patient groups, transient efficacy, high cost burdens, poor immunogenicity, and side effects or off-target toxicity that results from lack of disease-specificity and inefficient delivery. Thus, there is a significant need for strategies that control immune responses generated by immunotherapies while targeting infection, cancer, allergy, and autoimmunity. Being the outermost barrier of the body and the first line of host defense, the skin presents a unique immunological interface to achieve these goals. The skin contains a high concentration of specialized immune cells, such as antigen-presenting cells and tissue-resident memory T cells. These cells feature diverse and potent combinations of immune receptors, providing access to cellular and molecular level control to modulate immune responses. Thus, skin provides accessible tissue, cellular, and molecular level controls that can be harnessed to improve immunotherapies. Biomaterial platforms - microneedles, nano- and micro-particles, scaffolds, and other technologies - are uniquely capable of modulating the specialized immunological niche in skin by targeting these distinct biological levels of control. This review highlights recent pre-clinical and clinical advances in biomaterial-based approaches to target and modulate immune signaling in the skin at the tissue, cellular, and molecular levels for immunotherapeutic applications. We begin by discussing skin cytoarchitecture and resident immune cells to establish the biological rationale for skin-targeting immunotherapies. This is followed by a critical presentation of biomaterial-based pre-clinical and clinical studies aimed at controlling the immune response in the skin for immunotherapy and therapeutic vaccine applications in cancer, allergy, and autoimmunity.

Biomaterials for Protein Delivery: Opportunities and Challenges to Clinical Translation

The development of biomaterials for protein delivery is an emerging field that spans materials science, bioengineering, and medicine. In this review, we highlight the immense potential of protein-delivering biomaterials as therapeutic options and discuss the multifaceted challenges inherent to the field. We address current advancements and approaches in protein delivery that leverage stimuli-responsive materials, harness advanced fabrication techniques like 3D printing, and integrate nanotechnologies for greater targeting and improved stability, efficacy, and tolerability profiles. We also discuss the demand for highly complex delivery systems to maintain structural integrity and functionality of the protein payload. Finally, we discuss barriers to clinical translation, such as biocompatibility, immunogenicity, achieving reliable controlled release, efficient and targeted delivery, stability issues, scalability of production, and navigating the regulatory landscape for such materials. Overall, this review summarizes insights from a survey of the current literature and sheds light on the interplay between innovation and the practical implementation of biomaterials for protein delivery.

Fenugreek derived diosgenin as an emerging source for diabetic therapy

Diabetes is a chronic metabolic disease that endangers the entire body's tissues and organs. Diabetes impairs glucose and insulin regulation in the human body by causing pancreatic cell damage. Diabetes modifies pathways such as serine/threonine protein kinase (Akt) and Protein kinase C (PKC)/- glucose transporter 4 (GLUT4), peroxisome proliferator-activated receptor (PPAR) glucose absorption, and inhibits α-amylase and α-glucosidase, Sodium/glucose cotransporter 1 (SGLT-1), and Na+-K+-ATPase activity. Diabetes may also be caused by a decrease in the expression of sterol regulatory element binding protein 1 (SREBP-1) and its target genes, fatty acid synthase (FAS), stearoyl-CoA desaturase-1 (SCD-1), and acetyl-CoA carboxylase α (ACC), as well as a decrease in the levels of C/EBP homologous protein (CHOP), Caspase12, and Caspase3 proteins. Diabetes has long been linked to diseases of the cardiovascular, nervous, skeletal, reproductive, hepatic, ocular, and renal systems. Diosgenin, a steroidal compound derived from fenugreek, aids in the prevention of diabetes by altering cellular pathways in favor of healthy bodily functions. Diosgenin is a new nutraceutical on the market that claims to cure diabetes in particular. This article focuses on diosgenin extraction and purification, fenugreek bioactive compounds, pharmacological properties of diosgenin, mode of action of diosgenin to cure diabetes, and dosages.

Efficacy of oral insulin nanoparticles for the management of hyperglycemia in a rat model of diabetes induced with streptozotocin

Insulin is the cornerstone of treatment in type 1 diabetes mellitus. However, because of its protein structure, insulin has to be administered via injection, and many attempts have been made to create oral formulations, especially using nanoparticles (NPs). The aim of this study was to compare the hypoglycemic effect of insulin-loaded NPs to that of subcutaneous insulin in an in vivo rat model of diabetes. We used biodegradable D-α-tocopherol polyethylene glycol succinate-emulsified, chitosan-capped poly(lactic-co-glycolic acid) NPs loaded with soluble human insulin in a dose of 20 IU/kg body weight, and examined the physical characteristics of NPs in vivo and in vitro. Serum glucose levels were reduced after 6 h, but the difference was not significant compared to subcutaneous insulin; at 12 h and 24 h, insulin levels were significantly higher in rats treated with NPs than in rats treated with subcutaneous insulin. There was no significant difference in serum insulin levels at 12 h and 24 h compared to non-diabetic rats. Our findings suggest that chitosan-based NPs are able to maintain good glycemic control for up to 24 h and can be considered a potential carrier for oral insulin delivery.

Non-Invasive Delivery of Insulin for Breaching Hindrances against Diabetes

Insulin is recognized as a crucial weapon in managing diabetes. Subcutaneous (s.c.) injections are the traditional approach for insulin administration, which usually have many limitations. Numerous alternative (non-invasive) slants through different routes have been explored by the researchers for making needle-free delivery of insulin for attaining its augmented absorption as well as bioavailability. The current review delineating numerous pros and cons of several novel approaches of non-invasive insulin delivery by overcoming many of their hurdles. Primary information on the topic was gathered by searching scholarly articles from PubMed added with extraction of data from auxiliary manuscripts. Many approaches (discussed in the article) are meant for the delivery of a safe, effective, stable, and patient friendly administration of insulin via buccal, oral, inhalational, transdermal, intranasal, ocular, vaginal and rectal routes. Few of them have proven their clinical efficacy for maintaining the glycemic levels, whereas others are under the investigational pipe line. The developed products are comprising of many advanced micro/nano composite technologies and few of them might be entering into the market in near future, thereby garnishing the hopes of millions of diabetics who are under the network of s.c. insulin injections.

Formulation and Evaluation of Insulin-Loaded Sodium-Alginate Microparticles for Oral Administration

The development of oral insulin drug delivery systems is still an ongoing challenge for pharmaceutical technology researchers, as the formulation process has to overcome a number of obstacles due to the adverse characteristics of peptides. The aim of this study was to formulate different sodium-alginate microparticles as a possible method for oral insulin administration. In our previous studies, the method has been successfully optimized using a small model peptide. The incorporation of insulin into alginate carriers containing nonionic surfactants has not been described yet. In order to enhance the absorption of insulin through biological barriers, Labrasol ALF and Labrafil M 2125 CS were selected as permeation-enhancing excipients. They were applied at a concentration of 0.10% (v/v%), along with various combinations of the two, to increase oral bioavailability. Encapsulation efficiency showed sufficient drug incorporation, as it resulted in over 80% in each composition. In vitro dissolution and enzymatic stability test results proved that, as a pH-responsive polymer, alginate bead swelling and drug release occur at higher pH, thus protecting insulin against the harsh environment of the gastrointestinal tract. The remaining insulin content was 66% due to SIF degradation after 120 min. Permeability experiments revealed the impact of permeation enhancers and natural polymers on drug absorption, as they enhanced drug transport significantly through Caco-2 cells in the case of alginate microparticle formulations, as opposed to the control insulin solution. These results suggest that these formulations are able to improve the oral bioavailability of insulin.

PEGylated insulin loaded complexation hydrogels for protected oral delivery

While a number of enteric coatings and pH-sensitive oral delivery vehicles have been developed, they lack the ability to sufficiently protect proteins from proteolytic degradation once released from the carrier. In this work, we show that H-bonded, pH-sensitive poly(methacrylic acid-grafted ethylene glycol) glycol (henceforth designated as P(MAA-g-EG) gels) exhibit great promise as protein carriers, as they utilize poly(ethylene glycol) (PEG) chains to promote mucoadhesion in the small intestine, increasing the chances that the drug is released within the villus of the absorptive intestinal wall. Importantly, PEG was also conjugated to the B29-lysine (LysB29) position of insulin in order to protect the drug from proteolytic degradation once released in the small intestine and adhere the drug to the intestinal epithelium through improved mucoadhesion. PEG-conjugated (PEGylated) molecules were found to actively participate in the carrier loading and release mechanism, with the drug conjugate hydrogen bonding to the MAA while in the collapsed state and subsequently repulse the drug above the polymer's isoelectric point. This effect was enhanced through the evaluation of PEG graft density within the carrier. Cellular transport and changes in transepithelial resistance caused by the PEGylated insulin (PI) in the presence of P(MAA-g-EG) microparticles were analyzed using a 1:1 co-culture of human colon adenocarcinoma (Caco-2) and: the mucus-secreting human colon carcinoma cell(HT-29-MTX). Finally, the in vivo absorption of insulin was measured in Sprague-Dawley rats to ensure that the PEGylated insulin conjugates are biologically active, as well as to compare the bioavailability to control insulin. Collectively, these results lead toward the development of a novel system for improved insulin delivery, with improved stability of insulin through PEGylation.

Transdermal Delivery of Insulin Using Combination of Iontophoresis and Deep Eutectic Solvents as Chemical Penetration Enhancers: In Vitro and in Vivo Evaluations

A serious challenge in transdermal iontophoresis (IP) delivery of insulin (INS) is the low permeability of the drug across the skin. In this paper, we introduced deep eutectic solvent (DESs) as novel chemical penetration enhancers (CPEs) for transdermal IP of INS across rat skin, both in vitro and in vivo. Three different DESs based on choline chloride (ChCl), namely, ChCl/UR (ChCl and urea), ChCl/GLY (ChCl and glycerol), and ChCl/EG (ChCl and ethylene glycol) in the 1:2 molar ratios have been prepared. To evaluate the capability of studied DESs as CPEs for IP delivery of INS, the rat skin sample was treated with each DES. The effects of different experimental parameters (current density, formulation pH, INS concentration, NaCl concentration, and treatment time) on the in vitro transdermal iontophoretic delivery of INS were investigated. The in vitro permeation studies exhibited that INS was easily delivered employing ChCl/EG, and ChCl/GLY treatments, compared with ChCl/UR: the cumulative amount of permeated INS at the end of the experiment (Q24h) was found to be 131.0, 89.4, and 29.6 µg cm-2 in the presence of ChCl/EG, ChCl/GLY, and ChCl/UR, respectively. The differences in Q24h values of INS are due to the different capabilities of the studied DESs to treat the epidermis layer of skin. In vivo experiments revealed that the blood glucose level in diabetic rats could be decreased using ChCl/EG, and ChCl/GLY as novel CPEs in the IP delivery of INS. The presented work will open new doors towards searching for novel CPEs in the development of transdermal IP of INS.

Recent advances in respiratory immunization: A focus on COVID-19 vaccines

The development of vaccines has always been an essential task worldwide since vaccines are regarded as powerful weapons in protecting the global population. Although the vast majority of currently authorized human vaccinations are administered intramuscularly or subcutaneously, exploring novel routes of immunization has been a prominent area of study in recent years. This is particularly relevant in the face of pandemic diseases, such as COVID-19, where respiratory immunization offers distinct advantages, such as inducing systemic and mucosal responses to prevent viral infections in both the upper and lower respiratory tracts and also leading to higher patient compliance. However, the development of respiratory vaccines confronts challenges due to the physiological barriers of the respiratory tract, with most of these vaccines still in the research and development stage. In this review, we detail the structure of the respiratory tract and the mechanisms of mucosal immunity, as well as the obstacles to respiratory vaccination. We also examine the considerations necessary in constructing a COVID-19 respiratory vaccine, including the dosage form of the vaccines, potential excipients and mucosal adjuvants, and delivery systems and devices for respiratory vaccines. Finally, we present a comprehensive overview of the COVID-19 respiratory vaccines currently under clinical investigation. We hope this review can provide valuable insights and inspiration for the future development of respiratory vaccinations.

A Comprehensive Review on Nanomedicine: Promising Approach for Treatment of Brain Tumor through Intranasal Administration

Brain tumors have become one of the deadliest cancers; however, their treatment is still limited by conventional approaches. Brain tumors, among other CNS diseases, are the most lethal form of cancer due to ineffective diagnosis and profiling. The major limiting factor in treating brain tumors is the blood-brain barrier (BBB), and the required therapeutic concentration is not achieved. Hence, most drugs are prescribed at higher doses, which have several unwanted side effects. Nanotechnology has emerged as an interesting and promising new approach for treating neurological disorders, including brain tumors, with the potential to overcome concerns related to traditional therapeutic approaches. Moreover, biomimetic nanomaterials have been introduced to successfully cross the blood-brain barrier and be consumed by deep skin cancer for imaging brain tumors using multimodal functional nanostructures for more specific and reliable medical assessment. These nanomedicines can address several challenges by enhancing the bioavailability of therapeutics through controlled pharmacokinetics and pharmacodynamics. Further nasal drug delivery has been considered as an alternative approach for the brain's targeting for the treatment of several CNS diseases. A drug can be directly delivered to the brain by bypassing the BBB through intranasal administration. This review discusses intranasal nanomedicine-based therapies for brain tumor targeting, which can be explored from different perspectives.

Transdermal drug delivery systems for the effective management of type 2 diabetes mellitus: A review

Type 2 Diabetes mellitus (T2DM) is characterized by either insufficient insulin production or the inability to take it up for the glycemic regulation in the human body. According to WHO reports, T2DM will be the seventh-largest syndrome resulting in mortality by 2030. To tackle this chronic metabolic disorder, the person with diabetes population depends on subcutaneous administration (Sub-Q) of insulin and certain oral hypoglycemic drugs. However, these current invasive practices suffered from painful injections, needle phobia, multiple doses, risk of infection and poor-patient compliance. Hence, the search for a non-invasive and patient-friendly insulin administration system was high in the past decades leading to the development of Transdermal Drug Delivery Systems (TDDS). These can offer rapid and sustained release of therapeutic compounds at controlled rates with no pain during the administration. In recent years, the usage of such TDDS has been increasing at an exponential rate in Type 2 diabetes management. In the present review, the scholarly works on the different modes of TDDS were comprehensively reported chronlogically to appreciate their developments. Conclusively, this review critically identified prevailing research gaps in the current TDDS research and presented potential research hotspots for the prospect development in T2DM management.

Hydroxyethylcellulose-Based Hydrogels Containing Liposomes Functionalized with Cell-Penetrating Peptides for Nasal Delivery of Insulin in the Treatment of Diabetes

Liposomes functionalized with cell-penetrating peptides are a promising strategy to deliver insulin through the nasal route. A hydrogel based on hydroxyethylcellulose (HEC) aqueous solution was prepared, followed by a subsequent addition of liposomes containing insulin solution functionalized with trans-activator of transcription protein of HIV-1 (TAT) or Penetratin (PNT). The formulations were characterized for rheological behavior, mucoadhesion, syringeability, in vitro release and in vivo efficacy. Rheological tests revealed non-Newtonian fluids with pseudoplastic behavior, and the incorporation of liposomes (HLI, HLI_TAT and HLI_PNT) in hydrogels did not alter the behavior original pseudoplastic characteristic of the HEC hydrogel. Pseudoplastic flow behavior is a desirable property for formulations intended for the administration of drugs via the nasal route. The results of syringeability and mucoadhesive strength from HEC hydrogels suggest a viable vehicle for nasal delivery. Comparing the insulin release profile, it is observed that HI was the system that released the greatest amount while the liposomal gel promoted greater drug retention, since the liposomal system provides an extra barrier for the release through the hydrogel. Additionally, it is observed that both peptides tested had an impact on the insulin release profile, promoting a slower release, due to complexation with insulin. The in vitro release kinetics of insulin from all formulations followed Weibull's mathematical model, reaching approximately 90% of release in the formulation prepared with HEC-based hydrogels. Serum insulin levels and the antihyperglycemic effects suggested that formulations HI and HLI have potential as carriers for insulin delivery by the nasal pathway, a profile not observed when insulin was administered by subcutaneous injection or by the nasal route in saline. Furthermore, formulations functionalized with TAT and PNT can be considered promoters of late and early absorption, respectively.

Deformable Nanovesicle-Loaded Gel for Buccal Insulin Delivery

Deformable nanovesicles (DNVs) have been widely used in oral mucosal delivery studies of biomolecular drugs. However, their development for oral mucosal preparations has been limited by their physical and chemical instability, the need for small oral volumes, and the complexity of the oral microenvironment. This study aimed to develop a more suitable buccal delivery system for DNVs with improved storage stability. Preliminary stability studies investigated different gel types, the effects of different hydrophilic gel matrices, and matrix temperature sensitivity using DNVs loaded with insulin-phospholipid complex (IPC-DNVs). A temperature-sensitive gel encapsulating IPC-DNVs (IPC-DNV-TSG) prepared with 2% w/v gelatin was stable at 4 °C for three months and maintained an excellent hypoglycemic effect. The delivery efficiency of IPC-DNVs and IPC-DNV-TSG was compared using a TR146 cell model, revealing that cell viability remained high. Cellular uptake was slightly lower for IPC-DNV-TSG than for IPC-DNVs, but total transport did not differ significantly between the two groups, which may have been related to the viscosity of IPC-DNV-TSG and the hydrophilicity, cell adhesion properties, and biocompatibility of gelatin. Moreover, neither IPC-DNVs nor IPC-DNV-TSG induced significant mucosal irritation in rabbit tongue tissue sections. The study findings demonstrate a promising method for possible use as oral mucosal delivery of peptide drugs.

A Review of Non-Invasive Drug Delivery through Respiratory Routes

With rapid and non-invasive characteristics, the respiratory route of administration has drawn significant attention compared with the limitations of conventional routes. Respiratory delivery can bypass the physiological barrier to achieve local and systemic disease treatment. A scientometric analysis and review were used to analyze how respiratory delivery can contribute to local and systemic therapy. The literature data obtained from the Web of Science Core Collection database showed an increasing worldwide tendency toward respiratory delivery from 1998 to 2020. Keywords analysis suggested that nasal and pulmonary drug delivery are the leading research topics in respiratory delivery. Based on the results of scientometric analysis, the research hotspots mainly included therapy for central nervous systems (CNS) disorders (Parkinson’s disease, Alzheimer’s disease, depression, glioblastoma, and epilepsy), tracheal and bronchial or lung diseases (chronic obstructive pulmonary disease, asthma, acute lung injury or respiratory distress syndrome, lung cancer, and idiopathic pulmonary fibrosis), and systemic diseases (diabetes and COVID-19). The study of advanced preparations contained nano drug delivery systems of the respiratory route, drug delivery barriers investigation (blood-brain barrier, BBB), and chitosan-based biomaterials for respiratory delivery. These results provided researchers with future research directions related to respiratory delivery.

The modern pharmacological approach to diabetes: innovative methods of monitoring and insulin treatment

INTRODUCTION

Diabetes mellitus, commonly known as just diabetes, is a group of metabolic disorders characterised by a high blood sugar level over a prolonged period of time. In order to maintain this blood glucose value in normal parameters, a careful monitoring of it and insulin administration are necessary.

AREAS COVERED

Thus, to facilitate this procedure, new blood glucose monitoring systems have been studied. The smart lens, the nano tattoo, non-invasive sensors based on reverse ionthophoresis and glucose oxidase - based continuous blood glucose monitoring systems, are the methods described in this study. Of course, not only is blood glucose monitoring important, but also the lifestyle of a drug or the way a drug is administered, especially in the cae of insulin. How insulin is administered is also a topic that we address in this article. In an attempt to promote compliance with the administration, we have discussed about new forms of administering insulin such as: oral, intranasal, administration on the oral mucosa and last but not least, transdermal administration.

EXPERT OPINION

Further, the attention of specialists should be directed to devices based on sensors, with a role in the interruption of insulin administration, in case of detection of hypoglycemia or the additional dose of insulin, if hyperglycemia is detected.

Biocompatible nanocarriers for passive transdermal delivery of insulin based on self-adjusting N-alkylamidated carboxymethyl cellulose polysaccharides

In this work, we present biocompatible nanocarriers based on modified polysaccharides capable of transporting insulin macromolecules through human skin without any auxiliary techniques. N-Alkylamidated carboxymethyl cellulose (CMC) derivatives CMC-6 and CMC-12 were synthesized and characterized using attenuated total reflectance Fourier transform infrared (ATR-FTIR) and nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography and thermogravimetric, calorimetric and microscopic techniques. The prepared modified polysaccharides spontaneously assemble into soft nanoaggregates capable of adjusting to both aqueous and lipid environments. Due to this remarkable self-adjustment ability, CMC-6 and CMC-12 were examined for transdermal delivery of insulin. First, a significant increase in the amount of insulin present in lipid media upon encapsulation in CMC-12 was observed in vitro. Then, ex vivo studies on human skin were conducted. Those studies revealed that the CMC-12 carrier led to an enhancement of transdermal insulin delivery, showing a remarkable 85% insulin permeation. Finally, toxicity studies revealed no alteration in epidermal viability upon treatment and the absence of any skin irritation or amplified cytokine release, verifying the safety of the prepared carriers. Three-dimensional (3D) molecular modeling and conformational dynamics of CMC-6 and CMC-12 polymer chains explained their binding capacities and the ability to transport insulin macromolecules. The presented carriers have the potential to become a biocompatible, safe and feasible platform for the design of effective systems for transdermal delivery of bioactive macromolecules in medicine and cosmetics. In addition, transdermal insulin delivery reduces the pain and infection risk in comparison to injections, which may increase the compliance and glycemic control of diabetic patients.

Surface Adsorption-Mediated Ultrahigh Efficient Peptide Encapsulation with a Precise Ratiometric Control for Type 1 and 2 Diabetic Therapy

A surface adsorption strategy is developed to enable the engineering of microcomposites featured with ultrahigh loading capacity and precise ratiometric control of co-encapsulated peptides. In this strategy, peptide molecules (insulin, exenatide, and bivalirudin) are formulated into nanoparticles and their surface is decorated with carrier polymers. This polymer layer blocks the phase transfer of peptide nanoparticles from oil to water and, consequently, realizes ultrahigh peptide loading degree (up to 78.9%). After surface decoration, all three nanoparticles are expected to exhibit the properties of adsorbed polymer materials, which enables the co-encapsulation of insulin, exenatide, and bivalirudin with a precise ratiometric control. After solidification of this adsorbed polymer layer, the release of peptides is synchronously prolonged. With the help of encapsulation, insulin achieves 8 days of glycemic control in type 1 diabetic rats with one single injection. The co-delivery of insulin and exenatide (1:1) efficiently controls the glycemic level in type 2 diabetic rats for 8 days. Weekly administration of insulin and exenatide co-encapsulated microcomposite effectively reduces the weight gain and glycosylated hemoglobin level in type 2 diabetic rats. The surface adsorption strategy sets a new paradigm to improve the pharmacokinetic and pharmacological performance of peptides, especially for the combination of peptides.

Revisiting the Physicochemical Properties and Applications of Deep Eutectic Solvents

Recently, deep eutectic solvent (DES) or ionic liquid (IL) analogues have been considered as the newest green solvent, demonstrating the potential to replace harsh volatile organic solvents. DESs are mainly a combination of two compounds: hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD), which have the ability to interact through extensive hydrogen bonds. A thorough understanding of their physicochemical properties is essential, given their successful applications on an industrial scale. The appropriate blend of HBA to HBD can easily fine-tune DES properties for desired applications. In this context, we have reviewed the basic information related to DESs, the two most studied physicochemical properties (density and viscosity), and their performance as a solvent in (i) drug delivery and (ii) extraction of biomolecules. A broader approach of various factors affecting their performance has been considered, giving a detailed picture of the current status of DESs in research and development.

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.

Controlled Transdermal Iontophoresis of Insulin from Water-Soluble Polypyrrole Nanoparticles: An In Vitro Study

The iontophoresis delivery of insulin (INS) remains a serious challenge due to the low permeability of the drug through the skin. This work aims to investigate the potential of water-soluble polypyrrole nanoparticles (WS-PPyNPs) as a drug donor matrix for controlled transdermal iontophoresis of INS. WS-PPyNPs have been prepared via a simple chemical polymerization in the presence of sodium dodecyl sulfate (SDS) as both dopant and the stabilizing agent. The synthesis of the soluble polymer was characterized using field emission scanning electron microscopy (FESEM), dynamic light scattering (DLS), fluorescence spectroscopy, and Fourier transform infrared (FT–IR) spectroscopy. The loading mechanism of INS onto the WS-PPyNPs is based on the fact that the drug molecules can be replaced with doped dodecyl sulfate. A two-compartment Franz-type diffusion cell was employed to study the effect of current density, formulation pH, INS concentration, and sodium chloride concentration on anodal iontophoresis (AIP) and cathodal iontophoresis (CIP) of INS across the rat skin. Both AIP and CIP delivery of INS using WS-PPyNPs were significantly increased compared to passive delivery. Furthermore, while the AIP experiment (60 min at 0.13 mA cm^–2) show low cumulative drug permeation for INS (about 20.48 µg cm⁻²); the CIP stimulation exhibited a cumulative drug permeation of 68.29 µg cm⁻². This improvement is due to the separation of positively charged WS-PPyNPs and negatively charged INS that has occurred in the presence of cathodal stimulation. The obtained results confirm the potential applicability of WS-PPyNPs as an effective approach in the development of controlled transdermal iontophoresis of INS.

Inhalable polymeric micro and nano-immunoadjuvants for developing therapeutic vaccines in the treatment of non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a leading cause of death in millions of cancer patients. Lack of diagnosis at an early stage in addition to no specific guidelines for its treatment, and a higher rate of treatment-related toxicity further deteriorate the conditions. Current therapies encompass surgery, chemotherapy, radiation therapy, and immunotherapy according to the pattern and the stage of lung cancer. Among all, with a longlasting therapeutic action, reduced side-effects, and a higher rate of survival, therapeutic cancer vaccine is a new, improved strategy for treating NSCLC. Immunoadjuvants are usually incorporated into the therapeutic vaccines to shield the antigen against environmental and physiological harsh conditions in addition to boosting the immune potential. Conventional immunoadjuvants are often associated with an inadequate cellular response, poor target specificity, and low antigen load. Recently, inhalable polymeric nano/micro immunoadjuvants have exhibited immense potential in the development of therapeutic vaccines for the treatment of NSCLC with improved mucosal immunization. The development of polymeric micro/nano immunoadjuvants brought a new era for vaccines with increased strength and efficiency. Therefore, in the present review, we explained the potential application of micro/nano immunoadjuvants for augmenting the stability and efficacy of inhalable vaccines in the treatment of NSCLC. In addition, the role of biodegradable, biocompatible, and non-toxic polymers has also been discussed with case studies.

Strategies for the delivery of antidiabetic drugs via intranasal route

Diabetes is a metabolic disorder defined by higher blood glucose levels in the body generally controlled by antidiabetic agents (oral) and insulin (subcutaneous). To avoid the limitations of the conventional routes such as lower bioavailability and pain at the site of injection in case of parenteral route modified delivery systems are proposed like transdermal, pulmonary and inhalation delivery and among the other delivery systems nasal drug delivery system that shows the advantages such as reduced frequency of dose, higher patient compliance, safety, ease of administration, prolonged residence time, improved absorption of drug in the body, higher bioavailability and stability. This review article discusses the strategies adopted for the delivery of antidiabetic drugs by the intranasal delivery system. The insulin and glucagon-like peptides on experimentation show results of improved therapeutic levels and patient compliance. The drugs are transported by the paracellular route and absorbed through the epithelial tight junctions successfully by utilising different strategies. The limitations of the nasal delivery such as irritation or burning on administration, degradation by the enzymes, mucociliary clearance, lesser volume of the nasal cavity and permeation through the nasal mucosa. To overcome the challenges different strategies for the nasal administration are studied such as polymers, particulate delivery systems, complexation with peptides and smart delivery using glucose-responsive systems. A vast scope of intranasal preparations exists for antidiabetic drugs in the future for the management of diabetes and more clinical studies are the requirement for the societal impact to battle against diabetes.

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.

Can the Nasal Cavity Help Tackle COVID-19?

Despite the progress made in the fight against the COVID-19 pandemic, it still poses dramatic challenges for scientists around the world. Various approaches are applied, including repurposed medications and alternative routes for administration. Several vaccines have been approved, and many more are under clinical and preclinical investigation. This review aims to systemize the available information and to outline the key therapeutic strategies for COVID-19, based on the nasal route of administration.

Structurally Based Design of Glucagon Mutants That Inhibit Fibril Formation

The peptide hormone glucagon is prescribed as a pharmaceutical compound to treat diabetic hypoglycemia. However, at the acidic pH where it is highly soluble, glucagon rapidly aggregates into inactive and cytotoxic amyloid fibrils. The recently determined high-resolution structure of these fibrils revealed various stabilizing molecular interactions. On the basis of this structure, we have now designed four arginine mutants of glucagon that resist fibrillization at pharmaceutical concentrations for weeks. An S2R, T29R double mutant and a T29R single mutant remove a hydrogen-bonding interaction in the wild-type fibril, whereas a Y13R, A19R double mutant and a Y13R mutant remove a cation-π interaction. 1H solution nuclear magnetic resonance spectra and ultraviolet absorbance data indicate that these mutants remain soluble in pH 2 buffer under quiescent conditions at concentrations of ≤4 mg/mL for weeks. Under stressed conditions with high salt concentrations and agitation, these mutants fibrillize significantly more slowly than the wild type. The S2R, T29R mutant and the T29R mutant exhibit a mixture of random coil and α-helical conformations, while the Y13R mutant is completely random coil. The mutation sites are chosen to be uninvolved in strong interactions with the glucagon receptor in the active structure of the peptide. Therefore, these arginine mutants of glucagon are promising alternative compounds for treating hypoglycemia.

A Brief Overview of the Oral Delivery of Insulin as an Alternative to the Parenteral Delivery

Diabetes mellitus greatly affects the quality of life of patients and has a worldwide prevalence. Insulin is the most commonly used drug to treat diabetic patients and is usually administered through the subcutaneous route. However, this route of administration is ineffective due to the low concentration of insulin at the site of action. This route of administration causes discomfort to the patient and increases the risk of infection due to skin barrier disturbance caused by the needle. The oral administration of insulin has been proposed to surpass the disadvantages of subcutaneous administration. In this review, we give an overview of the strategies to deliver insulin by the oral route, from insulin conjugation to encapsulation into nanoparticles. These strategies are still under development to attain efficacy and effectiveness that are expected to be achieved in the near future.

Alginate oligosaccharides can maintain activities of lysosomes under low pH condition

The objective of this study was to report that lysosome extracted from egg white could be used as a drug through oral administration for treating diseases by using pH sensitive alginate oligosaccharides. Lysosome-alginate oligosaccharides composite were formulated for oral administration of lysosomes. The dissolution test confirmed the availability of the oral dosage form. When lysosome were used as an independent drug, the activity of protein was lost due to influence of low pH. Its antibacterial activity was also remarkably reduced. However, when lysosome-alginate oligosaccharides composite form was used, antimicrobial activity of lysozyme was maintained. At low pH, a gel-like matrix was formed by alginate oligosaccharides to protect the lysosome. When the pH was increased, alginate oligosaccharides were dissolved and the lysosome was released. SDS–polyacrylamide gel electrophoresis analysis of released lysosomes revealed that alginate oligosaccharide could effectively protect the lysosome from degradation or hydrolysis under acidic conditions for at least 2 h. The results of this study are important for application of lysosomes as therapeutic agents, and also it was confirmed that alginate oligosaccharides have potential as direct delivery system for the oral application of protein derived therapies.

Wearable patch delivery system for artificial pancreas health diagnostic-therapeutic application: A review

The advanced stimuli-responsive approaches for on-demand drug delivery systems have received tremendous attention as they have great potential to be integrated with sensing and multi-functional electronics on a flexible and stretchable single platform (all-in-one concept) in order to develop skin-integration with close-loop sensation for personalized diagnostic and therapeutic application. The wearable patch pumps have evolved from reservoir-based to matrix patch and drug-in-adhesive (single-layer or multi-layer) type. In this review, we presented the basic requirements of an artificial pancreas, surveyed the design and technologies used in commercial patch pumps available on the market and provided general information about the latest wearable patch pump. We summarized the various advanced delivery strategies with their mechanisms that have been developed to date and representative examples. Mechanical, electrical, light, thermal, acoustic and glucose-responsive approaches on patch form have been successfully utilized in the controllable transdermal drug delivery manner. We highlighted key challenges associated with wearable transdermal delivery systems, their research direction and future development trends.

Performance of Choline Geranate Deep Eutectic Solvent as Transdermal Permeation Enhancer: An In Vitro Skin Histological Study

In the present research work, we addressed the changes in skin by which deep eutectic solvents (DES) enhanced transdermal permeation of bioactive compounds and propose a rationale for this mechanism. Several studies showed that these unusual liquids were ideal solvents for transdermal delivery of biomolecules, but to date, no histological studies relating the action of DES to changes in the structure of the outer skin barrier have been reported. In the research effort described herein, we presented an in-depth analysis of the changes induced in the skin by choline geranate DES, a compound with proven capabilities of enhancing transdermal permeation without deleterious impacts on the cells. The results obtained showed that a low percentage of DES acted as a transient disruptor of the skin structure, facilitating the passage of bioactive compounds dissolved in it.

Zein-based nanocarriers for the oral delivery of insulin. In vivo evaluation in Caenorhabditis elegans

The aim was to evaluate the potential of nanocarriers, based on the coating of zein nanoparticles (ZNP) with a Gantrez® AN-PEG conjugate (GP), for the oral delivery of insulin. ZNP-GP displayed less negative surface charge and a 14-fold higher diffusion coefficient in pig intestinal mucus than ZNP. Both nanoparticles showed a spherical shape and an insulin load of 77.5 µg/mg. Under simulated gastric conditions, ZNP-GP released significantly lower amount of insulin than ZNP, while under simulated intestinal conditions, both types of nanoparticles displayed similar behaviour. In Caenorhabditis elegans wild-type N2, grown under high glucose conditions, insulin treatments reduced glucose and fat accumulation without altering the growth rate, the worm length, or the pumping rate. The effect was significantly greater (p < 0.001) when insulin was nanoencapsulated in ZNP-GP compared with that encapsulated in ZNP or formulated in solution. This would be related to the highest capability of ZNP-GP to diffuse in the dense peritrophic-like layer covering intestinal cells in worms. In daf-2 mutants, the effect on fat and glucose reduction by insulin treatment was suppressed, indicating a DAF-2 dependent mechanism. In summary, ZNP-GP is a promising platform that may offer new opportunities for the oral delivery of insulin and other therapeutic proteins.

Delivery of Insulin via Skin Route for the Management of Diabetes Mellitus: Approaches for Breaching the Obstacles

Insulin is used for the treatment of diabetes mellitus, which is characterized by hyperglycemia. Subcutaneous injections are the standard mode of delivery for insulin therapy; however, this procedure is very often invasive, which hinders patient compliance, particularly for individuals requiring insulin doses four times a day. Furthermore, cases have been reported of sudden hypoglycemia occurrences following multidose insulin injections. Such an invasive and intensive approach motivates the quest for alternative, more user-friendly insulin administration approaches. For example, transdermal delivery has numerous advantages, such as prolonged drug release, low variability in the drug plasma level, and improved patient compliance. In this paper, the authors summarize different approaches used in transdermal insulin delivery, including microneedles, chemical permeation enhancers, sonophoresis, patches, electroporation, iontophoresis, vesicular formulations, microemulsions, nanoparticles, and microdermabrasion. Transdermal systems for insulin delivery are still being widely researched. The conclusions presented in this paper are extracted from the literature, notably, that the transdermal route could effectively and reliably deliver insulin into the circulatory system. Consistent progress in this area will ensure that some of the aforementioned transdermal insulin delivery systems will be introduced in clinical practice and commercially available in the near future.

Potential and Applications of Nanocarriers for Efficient Delivery of Biopharmaceuticals

During the past two decades, the clinical use of biopharmaceutical products has markedly increased because of their obvious advantages over conventional small-molecule drug products. These advantages include better specificity, potency, targeting abilities, and reduced side effects. Despite the substantial clinical and commercial success, the macromolecular structure and intrinsic instability of biopharmaceuticals make their formulation and administration challenging and render parenteral delivery as the only viable option in most cases. The use of nanocarriers for efficient delivery of biopharmaceuticals is essential due to their practical benefits such as protecting from degradation in a hostile physiological environment, enhancing plasma half-life and retention time, facilitating absorption through the epithelium, providing site-specific delivery, and improving access to intracellular targets. In the current review, we highlight the clinical and commercial success of biopharmaceuticals and the overall applications and potential of nanocarriers in biopharmaceuticals delivery. Effective applications of nanocarriers for biopharmaceuticals delivery via invasive and noninvasive routes (oral, pulmonary, nasal, and skin) are presented here. The presented data undoubtedly demonstrate the great potential of combining nanocarriers with biopharmaceuticals to improve healthcare products in the future clinical landscape. In conclusion, nanocarriers are promising delivery tool for the hormones, cytokines, nucleic acids, vaccines, antibodies, enzymes, and gene- and cell-based therapeutics for the treatment of multiple pathological conditions.

Black phosphorus-based 2D materials for bone therapy

Since their discovery, Black Phosphorus (BP)-based nanomaterials have received extensive attentions in the fields of electromechanics, optics and biomedicine, due to their remarkable properties and excellent biocompatibility. The most essential feature of BP is that it is composed of a single phosphorus element, which has a high degree of homology with the inorganic components of natural bone, therefore it has a full advantage in the treatment of bone defects. This review will first introduce the source, physicochemical properties, and degradation products of BP, then introduce the remodeling process of bone, and comprehensively summarize the progress of BP-based materials for bone therapy in the form of hydrogels, polymer membranes, microspheres, and three-dimensional (3D) printed scaffolds. Finally, we discuss the challenges and prospects of BP-based implant materials in bone immune regulation and outlook the future clinical application.

Microneedles: Characteristics, Materials, Production Methods and Commercial Development

Although transdermal drug delivery systems (DDS) offer numerous benefits for patients, including the avoidance of both gastric irritation and first-pass metabolism effect, as well as improved patient compliance, only a limited number of active pharmaceutical ingredients (APIs) can be delivered accordingly. Microneedles (MNs) represent one of the most promising concepts for effective transdermal drug delivery that penetrate the protective skin barrier in a minimally invasive and painless manner. The first MNs were produced in the 90s, and since then, this field has been continually evolving. Therefore, different manufacturing methods, not only for MNs but also MN molds, are introduced, which allows for the cost-effective production of MNs for drug and vaccine delivery and even diagnostic/monitoring purposes. The focus of this review is to give a brief overview of MN characteristics, material composition, as well as the production and commercial development of MN-based systems.

Alginate Calcium Microbeads Containing Chitosan Nanoparticles for Controlled Insulin Release

Effective delivery system for oral insulin administration is a promising way for diabetes therapy. Herein, we prepared alginate microbeads containing chitosan nanoparticles (CNP) for controlled release of insulin. CNP was developed by reaction between tripolyphosphate (TPP) and chitosan. The ratio of TPP to chitosan was optimized aiming with smaller and more unified distributed CNP. TEM and DLS analysis confirmed that CNP has size around 150 nm with low PDI value and strong surface charge. Encapsulate ability for bovine serum albumin, working as model protein, was 11.45%, and the encapsulate efficiency was 23.70%. To modify the release profile of protein suitable for oral insulin delivery, sodium alginate was applied to coat on the surface of CNP by electrostatic interaction. After that, CaCl₂ was added to reinforce the alginate coating layer. FTIR analysis confirmed the interaction of alginate with chitosan and reaction with calcium ion. After reaction with Ca²⁺ ion, size measurement revealed that CNP was incorporated into alginate microbeads with mean diameter about 3.197 μm. Alginate microbeads presented irregular shape with small particles inside as revealed by optical microscope. Meanwhile, the release test demonstrated that protein release was pH-dependent. Acidic pH value retards protein release and neutral pH value promotes protein release. At last, insulin-loaded alginate microbeads were administrated to hyperglycemia model mice and blood glucose profile was monitored afterward. Insulin-loaded microbeads significantly lowered blood glucose level compared with mice treated with alginate microbeads without insulin. It is noted that insulin-loaded alginate microbeads could lower blood glucose level in much prolonged period of 96 h, indicating that insulin was released in controlled manner.

A basal-bolus insulin regimen integrated microneedle patch for intraday postprandial glucose control

Multiple daily insulin injections have been a common regimen worldwide for the management of diabetes mellitus but involved potential safety and compliance problems. In this context, a single integrated microneedle patch (IMP) with multiple release kinetics is demonstrated to provide better physiologic insulin coverage for postprandial glycemic excursion in a convenient and pain-free manner. The combination of rapid separating technique and multiple individual microneedle arrays provides the combined ability to efficiently deliver insulin into the skin within seconds and to independently control insulin release kinetics. In addition, the diabetic rats with a traditional breakfast-lunch-dinner lifestyle exhibit obvious intraday glucose fluctuations, while the hypoglycemic experiments indicate that the IMP is capable of simultaneous bolus and sustained insulin delivery to closely match the glucose rise that occurs in response to meals and efficiently minimize excessive fluctuations, suggesting the potential of this new transdermal insulin delivery system as substitutes for multiple daily injections.

Functionalization of Polymers and Nanomaterials for Biomedical Applications: Antimicrobial Platforms and Drug Carriers

The use of polymers and nanomaterials has vastly grown for industrial and biomedical sectors during last years. Before any designation or selection of polymers and their nanocomposites, it is vital to recognize the targeted applications which require these platforms to be modified. Surface functionalization to introduce the desired type and quantity of reactive functional groups to target a cell or tissue in human body is a pivotal approach to improve the physicochemical and biological properties of these materials. Herein, advances in the functionalized polymer and nanomaterials surfaces are highlighted along with their applications in biomedical fields, e.g., antimicrobial therapy and drug delivery.

Review of recently used techniques and materials to improve the efficiency of orally administered proteins/peptides

OBJECTIVES

The main objective of present review is to explore and evaluate the effectiveness of recently developed methods to improve the bioavailability of orally administered biopharmaceutical drugs.

METHODS

A systematic search of sciencedirect, tandfonline and Google Scholar databases based on various sets of keywords was performed. All results were evaluated based on their abstracts, and irrelevant studies were neglected during further evaluation.

RESULTS

At present, biopharmaceuticals are used as injectable therapies as they are not absorbed adequately from the different routes of drug administration, particularly the oral one. Their insufficient absorption is attributed to their high molecular weight, degradation by proteolytic enzymes, high hydrophilicity and rigidity of the absorptive tissues. From industrial aspect incorporation of enzyme inhibitors (EIs) and permeation enhancers (PEs) and mucoadhesive polymers into conventional dosage forms may be the easiest way of formulation of orally administered macromolecular drugs, but the effectiveness of protection and absorption enhancement here is the most questionable. Conjugation may be problematic from regulatory aspect. Encapsulation into lipid-based vesicles sufficiently protects the incorporated macromolecule and improves intestinal uptake but have considerable stability issues. In contrast, polymeric nanocarriers may provide good stability but provides lower internalization efficacy in comparison with the lipid-based carriers.

CONCLUSION

It can be concluded that the combination of the advantages of mucoadhesive polymeric and lid-based carriers in hybrid lipid/polymer nanoparticles may result in improved absorption and might represent a potential means for the oral administration of therapeutic proteins in the near future. Graphical abstract Delivery systems for oral protein daministration.

Cell-penetrating peptide enhanced insulin buccal absorption

Non-injectable delivery of peptides and proteins is not feasible due to the limitations of large molecular mass, high hydrophilic properties, and gastrointestinal degradation. Therefore, proposing a new method to solve this problem is a burning issue. The objective of this study was to propose a novel protein delivery strategy to overcome the poor efficacy and irritation of buccal insulin delivery. In this study, we applied a conjugate of cell-penetrating peptides (LMWP) and insulin (INS-PEG-LMWP) for buccal delivery. INS-PEG-LMWP was prepared using insulin solution and mixture as references. The transport behaviour, in vivo bioactivity, hypoglycaemic effect, and safety of INS-PEG-LMWP were systematically characterised. An in vitro study demonstrated that the uptake and transportation of INS-PEG-LMWP across buccal mucosal multilayers significantly increased. By comparing the effects of different endocytic inhibitors on INS-PEG-LMWP uptake, the conjugate might be delivered via an energy independent, electrostatically adsorbed pathway. INS-PEG-LMWP's relative pharmacological bioavailability was high and its relative bioavailability was up to 26.86%, demonstrating no visible mucosal irritation. Cell-penetrating peptides are likely to become a reliable and safe tool for overcoming insulin's low permeability through the epithelial multilayers, the major barrier to buccal delivery.

Non-invasive Transdermal Delivery of Human Insulin Using Ionic Liquids: In vitro Studies

In this research project, synthesis and characterization of ionic liquids and their subsequent utilization as facilitators of transdermal delivery of human insulin was pursued. Choline geranate and choline oleate ionic liquids (and their deep eutectic solvents) were produced and characterized by nuclear magnetic resonance (¹H NMR), water content, oxidative stability, cytotoxicity and genotoxicity assays, and ability to promote transdermal protein permeation. The results gathered clearly suggest that all ionic liquids were able to promote/facilitate transdermal permeation of insulin, although to various extents. In particular, choline geranate 1:2 combined with its virtually nil cyto- and geno-toxicity was chosen to be incorporated in a biopolymeric formulation making it a suitable facilitator aiming at transdermal delivery of insulin.