Peak-less hypoglycemic effect of insulin glargine by complexation with maltosyl-β-cyclodextrin

Cyclodextrin-based delivery systems in parenteral formulations: a critical update review

Parenteral formulations are indispensable in clinical practice and often are the only option to administer drugs that cannot be administrated through other routes, such as proteins and certain anticancer drugs - which are indispensable to treat some of the most prevailing chronic diseases worldwide (like diabetes and cancer). Additionally, parenteral formulations play a relevant role in emergency care since they are the only ones that provide an immediate action of the drug after its administration. However, the development of parenteral formulations is a complex task owing to the specific quality and safety requirements set for these preparations and the intrinsic properties of the drugs. Amongst all the strategies that can be useful in the development of parenteral formulations, the formation of water-soluble host-guest inclusion complexes with cyclodextrins (CDs) has proven to be one of the most advantageous. CDs are multifunctional pharmaceutical excipients able to form water-soluble host-guest inclusion complexes with a wide variety of molecules, particularly drugs, and thus improve their apparent water-solubility, chemical stability, and bioavailability, to make them suitable for parenteral administration. Besides, CDs can be employed as building blocks of more complex injectable drug delivery systems with enhanced characteristics, such as nanoparticles and supramolecular hydrogels, that has been found particularly beneficial for the delivery of anticancer drugs. However, only a few CDs are considered safe when parenterally administered, and some of these types are already approved to be used in parenteral dosage forms. Therefore, the application of CDs in the development of parenteral formulations has been a more common practice in the last few years, due to their significant worldwide acceptance by the health authorities, promoting the development of safer and more efficient injectable drug delivery systems.

Morphologic design of sugar-based polymer nanoparticles for delivery of antidiabetic peptides

Zwitterionic polymer nanoparticles of diverse morphologies (spherical, cylindrical, and platelet-like) constructed from biocompatible sugar-based polymers are designed to extend the pharmacological activities of short- and long-acting insulin peptides, thereby providing potential for therapeutic systems capable of reducing the frequency of administration and improving patient compliance. Amphiphilic block copolymers composed of zwitterionic poly(d-glucose carbonate) and semicrystalline polylactide segments were synthesized, and the respective block length ratios were tuned to allow formation of nanoscopic assemblies having different morphologies. Insulin-loaded nanoparticles had similar sizes and morphologies to the unloaded nanoparticle counterparts. Laser scanning confocal microscopy imaging of three-dimensional spheroids of vascular smooth muscle cells and fibroblasts after treatment with LIVE/DEAD® stain and FITC-insulin-loaded nanoparticles demonstrated high biocompatibility for the nanoconstructs of the various morphologies and significant intracellular uptake of insulin in both cell lines, respectively. Binding of short-acting insulin and long-acting insulin glargine to nanoparticles resulted in extended hypoglycemic activities in rat models of diabetes. Following subcutaneous injection in diabetic rats, insulin- and insulin glargine-loaded nanoparticles of diverse morphologies had demonstrated up to 2.6-fold and 1.7-fold increase in pharmacological availability, in comparison to free insulin and insulin glargine, respectively. All together, the negligible cytotoxicity, immunotoxicity, and minimal cytokine adsorption onto nanoparticles (as have been demonstrated in our previous studies) provide exciting and promising evidence of biocompatible nanoconstructs that are poised for further development toward the management of diabetes.

Cyclodextrins based delivery systems for macro biomolecules

Macro biomolecules are of vital importance in regulating the biofunctions in organisms, in which proteins (including peptides when mentioned below) and nucleic acids (NAs) are the most important. Therefore, these proteins and NAs can be applied as "drugs" to regulate the biofunctions from abnormal to normal. Either for proteins and NAs, the most challenging thing is to avoid the biodegradation or physicochemical degradation before they reach the targeted location, and then functions as complete functional structures. Hence, appropriate delivery systems are very important which can protect them from these degradations. Cyclodextrins (CDs) based delivery systems achieved mega successes due to their outstanding pharmaceutical properties and there have been several reviews on CDs based small molecule drug delivery systems recently. But for biomolecules, which are getting more and more important for modern therapies, however, there are very few reviews to systematically summarize and analyze the CDs-based macro biomolecules delivery systems, especially for proteins. In this review, there were some of the notable examples were summarized for the macro biomolecules (proteins and NAs) delivery based on CDs. For proteins, this review included insulin, lysozyme, bovine serum albumin (BSA), green fluorescent protein (GFP) and IgG's, etc. deliveries in slow release, stimulating responsive release or targeting release manners. For NAs, this review summarized cationic CD-polymers and CD-cluster monomers as NAs carriers, notably, including the multicomponents targeting CD-based carriers and the virus-like RNA assembly method siRNA carriers.

Protein–polymer conjugates prepared via host–guest interactions: effects of the conjugation site, polymer type and molecular weight on protein activity

Protein–polymer conjugates are prepared via host–guest interactions and the effects of various parameters on protein activity are investigated.

Experimental and Theoretical Investigations on the Supermolecular Structure of Isoliquiritigenin and 6-O-α-D-Maltosyl-β-cyclodextrin Inclusion Complex

Isoliquiritigenin (ILTG) possesses many pharmacological properties. However, its poor solubility and stability in water hinders its wide applications. The solubility of bioactive compounds can often be enhanced through preparation and delivery of various cyclodextrin (CD) inclusion complexes. The 6-O-α-d-maltosyl-β-CD (G₂-β-CD), as one of the newest developments of CDs, has high aqueous solubility and low toxicity, especially stable inclusion characteristics with bioactive compounds. In this work, we for the first time construct and characterize the supermolecular structure of ILTG/G₂-β-CD by scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffractometry (XRD). The solubility of ILTG in water at 25 °C rises from 0.003 to 0.717 mg/mL by the encapsulation with G₂-β-CD. Our experimental observations on the presence of the ILTG/G₂-β-CD inclusion complex are further supported by the ONIOM(our Own N-layer Integrated Orbital molecular Mechanics)-based QM/MM (Quantum Mechanics/Molecular Mechanics) calculations, typically substantiating these supermolecular characteristics, such as detailed structural assignments, preferred binding orientations, selectivity, solvent effects, interaction energies and forces of the ILTG/G₂-β-CD inclusion complex. Our results have elucidated how ILTG interacts with G₂-β-CD, demonstrating the primary host-guest interactions between ILTG and G₂-β-CD, characterized by hydrogen bonds, hydrophobic interactions, electrostatic forces, and conformational effects, are favored for the formation of the ILTG/G₂-β-CD inclusion.

Inhibition of insulin amyloid fibril formation by cyclodextrins

Localized insulin-derived amyloid masses occasionally form at the site of repeated insulin injections in patients with insulin-dependent diabetes and cause subcutaneous insulin resistance. Various kinds of insulin including porcine insulin, human insulin, and insulin analogues reportedly formed amyloid fibrils in vitro and in vivo, but the impact of the amino acid replacement in insulin molecules on amyloidogenicity is largely unknown. In the present study, we demonstrated the difference in amyloid fibril formation kinetics of human insulin and insulin analogues, which suggests an important role of the C-terminal domain of the insulin B chain in nuclear formation of amyloid fibrils. Furthermore, we determined that cyclodextrins, which are widely used as drug carriers in the pharmaceutical field, had an inhibitory effect on the nuclear formation of insulin amyloid fibrils. These findings have significant implications for the mechanism underlying insulin amyloid fibril formation and for developing optimal additives to prevent this subcutaneous adverse effect.

Emerging micro- and nanotechnology based synthetic approaches for insulin delivery

Insulin is essential for type 1 and advanced type 2 diabetics to maintain blood glucose levels and prolong lives. The traditional administration requires frequent subcutaneous insulin injections that are associated with poor patient compliance, including pain, local tissue necrosis, infection, and nerve damage. Taking advantage of emerging micro- and nanotechnologies, numerous alternative strategies integrated with chemical approaches for insulin delivery have been investigated. This review outlines recent developments in the controlled delivery of insulin, including oral, nasal, pulmonary, transdermal, subcutaneous and closed-loop insulin delivery. Perspectives from new materials, formulations and devices at the micro- or nano-scales are specifically surveyed. Advantages and limitations of current delivery methods, as well as future opportunities and challenges are also discussed.