Promises of anionic calix[n]arenes in life science: State of the art in 2023.

Because they hold together molecules by means of non-covalent interactions - relatively weak and thus, potentially reversible - the anionic calixarenes have become an interesting tool for efficiently binding a large range of ligands - from gases to large organic molecules. Being highly water soluble and conveniently biocompatible, they showed growing interest for many interdisciplinary fields, particularly in biology and medicine. Thanks to their intrinsic conical shape, they provide suitable platforms, from vesicles to bilayers. This is a valuable characteristic, as so they mimic the biologically functional architectures. The anionic calixarenes propose efficient alternatives for overcoming the limitations linked to drug delivery and bioavailability, as well as drug resistance along with limiting the undesirable side effects. Moreover, the dynamic non-covalent binding with the drugs enables predictable and on demand drug release, controlled by the stimuli present in the targeted environment. This particular feature instigated the use of these versatile, stimuli-responsive compounds for sensing biomarkers of diverse pathologies. The present review describes the recent achievements of the anionic calixarenes in the field of life science, from drug carriers to biomedical engineering, with a particular outlook on their applications for the diagnosis and treatment of different pathologies.

One-Step Photochemical Green Synthesis of Water-Dispersible Ag, Au, and Au@Ag Core-Shell Nanoparticles.

A simple and green synthetic protocol for the rapid and effective preparation of Ag, Au and Au@Ag core-shell nanoparticles (NPs) is reported based on the light irradiation of a biocompatible, water-soluble dextran functionalized with benzophenone (BP) in the presence of AgNO3 , HAuCl4 , or both. Photoactivation of the BP moiety produces the highly reducing ketyl radicals through fast (<50 ns) intramolecular H-abstraction from the dextran scaffold, which, in turn, ensures excellent dispersibility of the obtained metal NPs in water. The antibacterial activity of the AgNPs and the photothermal action of the Au@Ag core-shell are also shown.

A multifunctional ß-cyclodextrin-conjugate photodelivering nitric oxide with fluorescence reporting.

This contribution reports the design, synthesis and photochemical properties of a novel cationic, water soluble, ß-cyclodextrin (ßCD) conjugate integrating an anthracene moiety and a nitroaniline derivative within the primary side of the ßCD scaffold. Photoinduced energy transfer between the anthracene and the nitroaniline chromophores effectively suppresses the fluorescence of the anthracene unit. Excitation with visible light triggers the release of nitric oxide (NO) from the nitroaniline chromophore, accompanied to the concomitant revival of the anthracene fluorescence, which acts as an optical reporter for detecting the amount of the NO released. Furthermore, the anthracene moiety photogenerates singlet oxygen (1O2) sequentially to NO release. The conjugate is also able to accommodate hydrophobic guests within the ßCD cavity, as proven by using naphthalene as a model compound. In view of the key role NO and 1O2 play as anticancer and antibacterial species, the present ßCD derivative represents an intriguing candidate for further studies in biopharmaceutical research addressed to multimodal therapeutic applications.

Photo-antimicrobial polymeric films releasing nitric oxide with fluorescence reporting under visible light.

A novel photoresponsive molecular hybrid has been embedded in poly(lactic-co-glycolic acid) (PLGA) to give an antibacterial polymeric film generating nitric oxide (NO) under visible light, with concomitant fluorescence reporting of NO release. The molecular hybrid integrates a nitroaniline NO photodonor and a coumarin latent fluorophore in the same molecular skeleton and results in quite homogeneous distribution in the polymer matrix where it preserves well the photobehavior exhibited in solution. The doped PLGA film shows an excellent optical transparency and can be excited by visible light leading to the production of NO and the parallel fluorescence revival of the coumarin fluorophore, which acts as an optical NO reporter. Photogenerated NO diffuses out of the polymer film, can be transferred to a biological milieu and induces remarkable antibacterial activity against Escherichia coli.

Graphene oxide nanohybrid that photoreleases nitric oxide.

We report herein a photoresponsive nanoplatform that delivers nitric oxide (NO) on demand, achieved by the covalent functionalization of graphene oxide (GO) with an amino-terminated nitric oxide (NO) photodonor (NOP1). The resulting GO-NOP1 hybrid nanomaterial is dispersible in water, is very stable in the dark and has been thoroughly characterized by SEM, TEM, AFM, XRD, FTIR and UV-Vis absorption spectroscopy. Photolysis experiments demonstrate that the photodecomposition of the NO photoreleaser integrated into the GO scaffold occurs with an efficiency similar to that observed for a free model compound, ruling out any significant quenching effect (i.e. photoinduced energy/electron transfer) and accounting for the excellent preservation of its photochemical properties upon grafting. A combination of direct amperometric detection and indirect measurements based on a fluorometric assay prove that the remote-controlled release of NO from the GO-NOP1 nanoplatform is exclusively regulated by visible light stimuli.