Photocrosslinked Co-Assembled Amino Acid Nanoparticles for Controlled Chemo/Photothermal Combined Anticancer Therapy.

Nanostructures formed from the self-assembly of amino acids are promising materials in many fields, especially for biomedical applications. However, their low stability resulting from the weak noncovalent interactions between the amino acid building blocks limits their use. In this work, nanoparticles co-assembled by fluorenylmethoxycarbonyl (Fmoc)-protected tyrosine (Fmoc-Tyr-OH) and tryptophan (Fmoc-Trp-OH) are crosslinked by ultraviolet (UV) light irradiation. Two methods are investigated to induce the dimerization of tyrosine, irradiating at 254 nm or at 365 nm in the presence of riboflavin as a photo-initiator. For the crosslinking performed at 254 nm, both Fmoc-Tyr-OH and Fmoc-Trp-OH generate dimers. In contrast, only Fmoc-Tyr-OH participates in the riboflavin-mediated dimerization under irradiation at 365 nm. The participation of both amino acids in forming the dimers leads to more stable crosslinked nanoparticles, allowing also to perform further chemical modifications for cancer applications. The anticancer drug doxorubicin (Dox) is adsorbed onto the crosslinked nanoparticles, subsequently coated by a tannic acid-iron complex, endowing the nanoparticles with glutathione-responsiveness and photothermal properties, allowing to control the release of Dox. A remarkable anticancer efficiency is obtained in vitro and in vivo in tumor-bearing mice thanks to the combined chemo- and photothermal treatment.

Unveiling Liquid-Phase Exfoliation of Graphite and Boron Nitride Using Fluorescent Dyes Through Combined Experiments and Simulations.

Liquid-phase exfoliation (LPE) in aqueous solutions provides a simple, scalable, and green approach to produce 2D materials. By combining atomistic simulations with exfoliation experiments, the interaction between a surfactant and a 2D layer at the molecular scale can be better understood. In this work, two different dyes, corresponding to rhodamine B base (Rbb) and to a phenylboronic acid BODIPY (PBA-BODIPY) derivative, are employed as dispersants to exfoliate graphene and hexagonal boron nitride (hBN) through sonication-assisted LPE. The exfoliated 2D sheets, mostly as few-layers, exhibit good quality and high loading of dyes. Using molecular dynamics (MD) simulations, the binding free energies are calculated and the arrangement of both dyes on the layers are predicted. It has been found that the dyes show a higher affinity toward hBN than graphene, which is consistent with the higher yields of exfoliated hBN. Furthermore, it is demonstrated that the adsorption behavior of Rbb molecules on graphene and hBN is quite different compared to PBA-BODIPY.

Graphene Oxide-BODIPY Conjugates as Highly Fluorescent Materials.

Covalent functionalization of graphene oxide (GO) with boron dipyrromethenes (BODIPYs) was achieved through a facile synthesis, affording two different GO-BODIPY conjugates where the main difference lies in the nature of the spacer and the type of bonds between the two components. The use of a long but flexible spacer afforded strong electronic GO-BODIPY interactions in the ground state. This drastically altered the light absorption of the BODIPY structure and impeded its selective excitation. In contrast, the utilisation of a short, but rigid spacer based on boronic esters resulted in a perpendicular geometry of the phenyl boronic acid BODIPY (PBA-BODIPY) with respect to the GO plane, which enables only minor electronic GO-BODIPY interactions in the ground state. In this case, selective excitation of PBA-BODIPY was easily achieved, allowing to investigate the excited state interactions. A quantitative ultrafast energy transfer from PBA-BODIPY to GO was observed. Furthermore, due to the reversible dynamic nature of the covalent GO-PBA-BODIPY linkage, some PBA-BODIPY is free in solution and, hence, not quenched from GO. This resulted in a weak, but detectable fluorescence from the PBA-BODIPY that will allow to exploit GO-PBA-BODIPY for slow release and imaging purposes.

Self-assembly of amphiphilic amino acid derivatives for biomedical applications.

Amino acids are one of the simplest biomolecules and they play an essential role in many biological processes. They have been extensively used as building blocks for the synthesis of functional nanomaterials, thanks to their self-assembly capacity. In particular, amphiphilic amino acid derivatives can be designed to enrich the diversity of amino acid-based building blocks, endowing them with specific properties and/or promoting self-assembly through hydrophobic interactions, hydrogen bonding, and/or π-stacking. In this review, we focus on the design of various amphiphilic amino acid derivatives able to self-assemble into different types of nanostructures that were exploited for biomedical applications, thanks to their excellent biocompatibility and biodegradability.

Nanobiosensor Reports on CDK1 Kinase Activity in Tumor Xenografts in Mice.

Probing the dynamics and quantifying the activities of intracellular protein kinases that coordinate cell growth and division and constitute biomarkers and pharmacological targets in hyperproliferative and pathological disorders remain a challenging task. Here engineering and characterization of a nanobiosensor of the mitotic kinase CDK1, through multifunctionalization of carbon nanotubes with a CDK1-specific fluorescent peptide reporter, are described. This original reporter of CDK1 activity combines the sensitivity of a fluorescent biosensor with the unique physico-chemical and biological properties of nanotubes for multifunctionalization and efficient intracellular penetration. The functional versatility of this nanobiosensor enables implementation to quantify CDK1 activity in a sensitive and dose-dependent fashion in complex biological environments in vitro, to monitor endogenous kinase in living cells and directly within tumor xenografts in mice by fluorescence imaging, thanks to a ratiometric quantification strategy accounting for response relative to concentration in space and in time.

Strategies for the Controlled Covalent Double Functionalization of Graphene Oxide.

Graphene oxide (GO) is a versatile platform with unique properties that have found broad applications in the biomedical field. Double functionalization is a key aspect in the design of multifunctional GO with combined imaging, targeting, and therapeutic properties. Compared to noncovalent functionalization, covalent strategies lead to GO conjugates with a higher stability in biological fluids. However, only a few double covalent functionalization approaches have been developed so far. The complexity of GO makes the derivatization of the oxygenated groups difficult to control. The combination of a nucleophilic epoxide ring opening with the derivatization of the hydroxyl groups through esterification or Williamson reaction was investigated. The conditions were selective and mild, thus preserving the structure of GO. Our strategy of double functionalization holds great potential for different applications in which the derivatization of GO with different molecules is needed, especially in the biomedical field.

A Flexible Method for Covalent Double Functionalization of Graphene Oxide.

A method for the double functionalization of graphene oxide (GO) under mild alkaline conditions has been developed. Two functional groups were covalently linked to GO in two steps: the first group was attached by an epoxide ring-opening reaction and the second, bearing an amine function, was covalently conjugated to benzoquinone attached to the GO. The doubly functionalized GO was characterized by several techniques, confirming the sequential covalent modification of the GO surface with two different functional groups. This method is straightforward and the reaction conditions are mild, allowing preservation of the structure and properties of GO. This strategy could be exploited to prepare multifunctional GO conjugates with potential applications in many fields ranging from materials science to biomedicine.

Enzymatic Degradation of Graphene Quantum Dots by Human Peroxidases.

Carbon-based nanomaterials have demonstrated to be potent candidates for biomedical applications. Recently, graphene quantum dots (GQDs) have emerged as an attractive tool for bioimaging, biosensing, and therapy. Hence, studying their biodegradability in living systems is essential to speed up the translation toward real clinical innovations. Here, the enzymatic degradation of GQDs using human myeloperoxidase and eosinophil peroxidase is investigated. Transmission electron microscopy, fluorescence, and Raman spectroscopy are used to evaluate the biodegradation of GQDs. Signs of degradation by both enzymes are observed already after a few hours of incubation with each enzyme, being more evident after a couple of days of treatment. Molecular dynamics simulations show intimate interactions between the enzymes and the GQDs. The conformation of both peroxidases is slightly altered to favor the interactions, while the GQD sheets distort a little to adapt to the surface of the enzymes. The biodegradability of the GQDs ensures their real potential in the practical biomedical applications.

Fluorescent-fipronil: Design and synthesis of a stable conjugate.

Fipronil is a phenyl pyrazole molecule widely used across the world as both insecticide and veterinary drug. The main goal of this work was to synthesize a fluorescently labeled fipronil derivative for cellular imaging without affecting its intrinsic properties. We selected fluorescein as fluorescent probe and we investigated different strategies for stable chemical ligation between both entities, such as thiourea and direct peptide bond. While thiourea bond displayed low stability, direct peptide bond was difficult to achieve due to problems of steric hindrance. The best result was obtained by conjugation using click chemistry, which allowed to obtain fipronil stably labeled with the fluorescent probe.