Molecular recognition of cyclophanes in water

Molecular recognition in water,the biological solvent,always receives significant research focus in supramolecular chemistry.The mechanisms of molecular recognition in water is key to comprehending biological processes at the molecular level.Over the past five decades,supramolecular chemists have developed a vast array of synthetic receptors with highly diverse structures and recognition properties.Among them,cyclophanes represent an important family of macrocyclic receptors that have been extensively explored.The aromatic moieties in cyclophanes not only facilitate chemical modifications to impart water solubility but also enable forming hydrophobic cavities for guest inclusion in aqueous environments.Pioneered by Koga et al.,who reported the first inclusion complex of cyclophanes in water and solid state,numerous water-soluble cyclophanes,including derivatives of blue box,calixarenes,resorcinarenes,pillararenes,octopusarenes,biphenarenes,coronarenes,and naphthotubes,etc.,have been synthesized and subjected to investigation of the recognition capabilities in aqueous solutions.This review provides an overview of cyclophane receptors designed to bind organic guests in water.We categorize them into two classes based on the modifications made to their hydrophobic cavities:those with“exo-functionalized hydrophobic cavities”and those with“endo-functionalized hydrophobic cavities”.We introduce their distinctive features and discuss strategies to enhance recognition affinity and selectivity.This review aims to inspire the development of novel synthetic receptors with intriguing properties and foster practical applications of cyclophanes.

Azocalixarenes: a scaffold of universal excipients with high efficiency

Excipients are important components of pharmaceutical preparations that affect their quality, safety, and efficacy. Macrocyclic receptors are a family of supramolecular excipients with several advantages, including molecular-level protection, small sizes,fast kinetics of host-guest recognition, and modular construction. With the continuous advances in the medical field, personalized and precision medicine requires the development of excipients with low dosages, integrated modifying effects, universality,and controlled release. To meet these requirements, we have developed a new family of macrocyclic excipients based on calixarenes by integrating their covalent(broad chemical design space) and noncovalent(wide range of substrates) advantages.Accordingly, azocalixarenes(Azo CAs) were designed, showing high binding affinities to a broad spectrum of active pharmaceutical ingredients(APIs), selectivity to interferents, and responsiveness to hypoxic microenvironments. Due to their highly efficient and controllable recognition, Azo CAs serve as low-dose excipients for 30 APIs. Molecular encapsulation by Azo CAs results in the integrated modification of the physicochemical properties of APIs, including solubility, stability, bioavailability,and biocompatibility. Moreover, Azo CAs can be reduced by azoreductases overexpressed in hypoxic microenvironments,leading to the controlled release of APIs. Collectively, Azo CA excipients have broad application prospects for a series of diseases such as enteritis, arthritis, stroke, cancer, bacterial infection and kidney injury, with diverse therapeutic modalities,including chemotherapy, photodynamic therapy, photothermal therapy, immunotherapy, boron neutron capture therapy, radiotherapy, fluorescence imaging, and their combinations.

CASTING: A Potent Supramolecular Strategy to Cytosolically Deliver STING Agonist for Cancer Immunotherapy and SARS-CoV-2 Vaccination

Stimulator of interferon genes,namely STING,an adaptor protein located in the endoplasmic reticulum,has been recognized as a shining target for cancer and infection research.However,STING agonists cyclic dinucleotides(CDNs)have shown almost zero efficacy in phase I clinical trials as a monotherapy,likely due to poor cellular permeability and rapid diffusion despite intratumoral injection.These deficiencies further affect other applications of CDNs,such as pandemic SARS-CoV-2 prevention and therapy.Here,we rationally design a supramolecular cytosolic delivery system based on controllable recognition of calixarene,namely CASTING(CAlixarene-STING),to improve CDN druggability,including degradation stability,cellular permeability,and tissue retention.CASTING efficiently enhances the immunostimulatory potency of CDGSF[a chemically modified cyclic di-GMP(CDG)]to generate an immunogenic microenvironment for melanoma regression,anti-PD-1 response rate increase,and durable memory formation against tumor recurrence.More importantly,CASTING displays a superior adjuvant activity on SARSCoV-2 recombinant spike/receptor binding domain vaccines,inducing robust and coordinated T-cell and antibody responses against SARS-CoV-2 infection in vivo.Collectively,the CASTING design represents an innovative advancement to facilitate the clinical translational capability of STING agonists.