Drug nanoclusters formed in confined nano-cages of CD-MOF: dramatic enhancement of solubility and bioavailability of azilsartan

Tremendous efforts have been devoted to the enhancement of drug solubility using nanotechnologies, but few of them are capable to produce drug particles with sizes less than a few nanometers. This challenge has been addressed here by using biocompatible versatile γ-cyclodextrin(γ-CD) metal-organic framework(CD-MOF) large molecular cages in which azilsartan(AZL) was successfully confined producing clusters in the nanometer range. This strategy allowed to improve the bioavailability of AZL in Sprague–Dawley rats by 9.7-fold after loading into CD-MOF. The apparent solubility of AZL/CD-MOF was enhanced by 340-fold when compared to the pure drug. Based on molecular modeling, a dual molecular mechanism of nanoclusterization and complexation of AZL inside the CD-MOF cages was proposed, which was confirmed by small angle X-ray scattering(SAXS) and synchrotron radiation-Fourier transform infrared spectroscopy(SR-FTIR) techniques. In a typical cage-like unit of CD-MOF, three molecules of AZL were included by the γ-CD pairs, whilst other three AZL molecules formed a nanocluster inside the 1.7 nm sized cavity surrounded by six γ-CDs. This research demonstrates a dual molecular mechanism of complexation and nanoclusterization in CD-MOF leading to significant improvement in the bioavailability of insoluble drugs.

Metal-organic frameworks for advanced drug delivery

Metal-organic frameworks(MOFs),comprised of organic ligands and metal ions/metal clusters via coordinative bonds are highly porous,crystalline materials.Their tunable porosity,chemical composition,size and shape,and easy surface functionalization make this large family more and more popular for drug delivery.There is a growing interest over the last decades in the design of engineered MOFs with controlled sizes for a variety of biomedical applications.This article presents an overall review and perspectives of MOFs-based drug delivery systems(DDSs),starting with the MOFs classification adapted for DDSs based on the types of constituting metals and ligands.Then,the synthesis and characterization of MOFs for DDSs are developed,followed by the drug loading strategies,applications,biopharmaceutics and quality control.Importantly,a variety of representative applications of MOFs are detailed from a point of view of applications in pharmaceutics,diseases therapy and advanced DDSs.In particular,the biopharmaceutics and quality control of MOFs-based DDSs are summarized with critical issues to be addressed.Finally,challenges in MOFs development for DDSs are discussed,such as biostability,biosafety,biopharmaceutics and nomenclature.

Poly(β-cyclodextrin)-mediated Polylactide-cholesterol Stereocomplex Micelles for Controlled Drug Delivery

A series of host-guest interaction-adjusted polylactide stereocomplex micelles was prepared via the self-assembly of 4-armed poly（ethylene glycol）-block-poly（L-lactide/D-lactide）-cholesterol （4-armed PEG-b-PLLA/PDLA-CHOL） and poly（β-cyclodextrin） （PCD） with the molar ratios of CHOL/β-CD at 1：0.5, 1 ：l, and 1：2 in an aqueous environment. The hydrodynamic diameters of the micelles ranged from 84.1 nm to 107 nm depending on the molar ratio of CHOL/β-CD. It was shown that the micelle with the largest proportion of PCD possessed excellent abilities in drug release, cell internalization as well as proliferation inhibitory effect toward human A549 lung cancer cells. The results demonstrated that the stereocomplex and host-guest interactions-mediated PLA micelles exhibited great potential in sustained drug delivery.

Glycoside scutellarin enhanced CD-MOF anchoring for laryngeal delivery

It is essential to develop new carriers for laryngeal drug delivery in light of the lack of therapy in laryngeal related diseases.When the inhalable micron-sized crystals ofγ-cyclodextrin metal-organic framework(CD-MOF)was utilized as dry powder inhalers(DPIs)carrier with high fine particle fraction(FPF),it was found in this research that the encapsulation of a glycoside compound,namely,scutellarin(SCU)in CD-MOF could significantly enhance its laryngeal deposition.Firstly,SCU loading into CD-MOF was optimized by incubation.Then,a series of characterizations were carried out to elucidate the mechanisms of drug loading.Finally,the laryngeal deposition rate of CD-MOF was 57.72±2.19%improved by SCU,about two times higher than that of CD-MOF,when it was determined by Next Generation Impactor(NGI)at 65 L/min.As a proof of concept,pharyngolaryngitis therapeutic agent dexamethasone(DEX)had improved laryngeal deposition after being co-encapsulated with SCU in CDMOF.The molecular simulation demonstrated the configuration of SCU in CD-MOF and its contribution to the free energy of the SCU@CD-MOF,which defined the enhanced laryngeal anchoring.In conclusion,the glycosides-like SCU could effectively enhance the anchoring of CD-MOF particles to the larynx to facilitate the treatment of laryngeal diseases.

Nanoparticles with high payloads of pipemidic acid, a poorly soluble crystalline drug: drug-initiated polymerization and self-assembly approach

Nowadays, biodegradable polymers such as poly(lactic acid)(PLA), poly(D,L-lactic-coglycolic acid)(PLGA) and poly(ε-caprolactone)(PCL) remain the most common biomaterials to produce drug-loaded nanoparticles(NPs). Pipemidic acid(PIP) is a poorly soluble antibiotic with a strong tendency to crystallize. PIP incorporation in PLA/PLGA NPs was challenging because of PIP crystals formation and burst release. As PIP had a poor affinity for the NPs, an alternative approach to encapsulation was used, consisting in coupling PIP to PCL. Thus, a PCL–PIP conjugate was successfully synthesized by an original drug-initiated polymerization in a single step without the need of catalyst.PCL–PIP was characterized by NMR, IR, SEC and mass spectrometry. PCL–PIP was used to prepare selfassembled NPs with PIP contents as high as 27%(w/w). The NPs were characterized by microscopy,DLS, NTA and TRPS. This study paves the way towards the production of NPs with high antibiotic payloads by drug-initiated polymerization. Further studies will deal with the synthesis of novel polymer–PIP conjugates with ester bonds between the drug and PCL. PIP can be considered as a model drug and the strategy developed here could be extended to other challenging antibiotics or anticancer drugs and employed to efficiently incorporate them in NPs.