Alicia Megia-Fernandez

Although some organic selenocompounds exhibit significant therapeutic potential, synthetic access to selenopeptides remains severely limited due to complex postassembly functionalizations strategies. To overcome these limitations, we developed a stable, ebselen-derived lysine compatible with standard Fmoc/tBu solid-phase peptide synthesis (SPPS). We synthesized the Fmoc-Lys(Ebs)-OH building block in five steps, characterizing it by HRMS and NMR spectroscopy. We then evaluated its chemical stability in standard SPPS conditions by assembling a test tripeptide and a diverse tetrapeptide library containing a variety of aminoacids. The novel Fmoc-Lys(Ebs)-OH demonstrated excellent coupling efficiency and high stability, tolerating repeated basic deprotections, couplings and strong acid cleavage to yield selenopeptides without degradation or byproducts. This novel building block enables the direct, site-specific incorporation of ebselen during SPPS, avoiding labor-intensive post-synthetic modifications to access to complex organoselenium peptides for biological and structure-activity relationship studies.

“Clicking” three Gram-negative-targeting polymyxin ligands onto an NBD fluorogenic dye yielded a diagnostic probe with stronger bacterial binding and fluorescence switch-on for enhanced detection.

Water recycling and reuse are cornerstones of water management, which can be compromised by the presence of pollutants. Among these, pharmaceuticals can overcome standard water treatments and require sophisticated approaches to remove them. Sorption is an economically viable alternative limited by the need for sorbents with a sorption coefficient (Kd) higher than 500 L/kg. The cross-linking of dextrin (Dx) with divinyl sulfone (DVS) in the presence of 1 mmol or 5 mmol of ibuprofen (IBU) yields the insoluble polymers pDx1 and pDx5 with improved affinity for IBU and high selectivity towards erythromycin (ERY) and ERY Kd higher than 4 × 10³ L/kg, when tested against a cocktail of six drugs. Characterization of the polymers shows that both pDx1 and pDx5 have similar properties, fast sorption kinetics, and ERY Kd of 13.3 × 10³ for pDx1 and 6.4 × 10³ for pDx5, representing 26.6 and 12.0 times the 500 L/kg threshold. The fact that new affinities and improvements in Kd can be achieved by cross-linking Dx in the presence of other molecules that promote pre-organization expands the applications of DVS cross-linked polysaccharides as sustainable, scalable, and environmentally friendly sorbents with a potential application in wastewater treatment plants (WTPs).

Water recycling and reuse are corner stones in the water management that may be compromised by the presence of pollutants. Among them, pharmaceuticals can overcome the standard water treatments and require sophisticated approaches to remove them. Sorption is an economically affordable alternative limited by the need of sorbents that exhibit sorption coefficient (Kd) higher than 500 L/kg to be useful in wastewater treatment plants (WWTPs). We report that th cross-linking of dextrin (Dx) with divinyl sulfone (DVS) in presence of 1 mmol or 5 mmol of ibuprofen (IBU) yields the insoluble polymers pDx1 and pDx5 with improved affinity for IBU, Kd higher than 600 L/kg for ciprofloxacin (CIP) and ofloxacin and an outstanding Kd higher than 4000 L/kg for erythromycin (ERY), when assayed against a cocktail of 6 drugs. The characterization of the polymers by XRPD, TGA and SEM reveals that both pDx1 and pDx5 share similar features, with an ERY Kd of 13 x 103 for pDx1 and 6.4 x 103 for pDx5. The facts that new affinities and improvements in Kd can be achieved by cross-linking Dx in presence of other molecules that promote a pre-organization, broaden the applications of DVS cross-linked polysaccharide as sustainable and eco-friendly sorbents.

Cathepsin D is a protease that is an effector in the immune response of macrophages, yet to date, only a limited number of probes have been developed for its detection. Herein, we report a water soluble, highly sensitive, pH insensitive fluorescent probe for the detection of Cathepsin D activity that provides a strong OFF/ON signal upon activation and with bright emission at 515 nm. The probe was synthesised using a combination of solid and solution-phase chemistries, with probe optimisation to increase its water solubility and activation kinetics by addition of a long PEG chain (5 kDa) at the C-terminus. A BODIPY fluorophore allowed detection of Cathepsin D across a wide pH range, important as the protease is active both at the low pH found in lysosomes and also in higher pH phagolysosomes, and in the cytosol. The probe was successfully used to detect Cathepsin D activity in macrophages challenged by exposure to bacteria.

Water use has been increasing globally by 1% per year, and recycling and re-use are critical issues compromised by the presence of pollutants. In this context, the design of novel materials and/or procedures for the large scale-removal of pollutants must be economically and environmentally feasible in order to be considered as part of the solution by emerging economies. We demonstrate that the cross-linking of biodegradable polysaccharides such as starch, dextrin, or dextrin and β-cyclodextrin with divinyl sulfone is an innovative strategy for synthesizing insoluble and eco-friendly sorbent polymers, including pSt, pDx and pCD-Dx. The evaluation of these polymers’ ability to remove ciprofloxacin (CIP), a prime example of antibiotic pollution, revealed that pSt, with a Kd of 1469 L/kg and a removal rate higher than 92%, is a favorable material. Its sorption is pH-dependent and enhanced at a mildly alkaline pH, allowing for the desorption (i.e., cleaning) and reuse of pSt through an environmentally friendly treatment with 20 mM AcONa pH 4.6. The facts that pSt (i) shows a high affinity for CIP even at high NaCl concentrations, (ii) can be obtained from affordable starting materials, and (iii) is synthesized and regenerated through organic, solvent-free procedures make pSt a novel sustainable material for inland water and seawater remediation, especially in less developed countries, due to its simplicity and low cost.

The optimization of an undergraduate experiment for Organic Chemistry students is described to explore the concept of click chemistry. The preparation of a terminal fluorescent alkyne and an organic azide is reported consisting of simple steps. These are employed in the Cu(I)-catalized azide-alkyne cycloaddition to obtain a novel molecule containing a triazole ring whose characterization allows the students to practice a variety of techniques: NMR (¹H, ¹³C, COSY and HSQC), melting point, thin layer chromatography, IR, fluorescence spectroscopy and mass spectrometry to confirm the structure of their obtained product. An alternative methodology in a one-pot reaction is also explored and a full laboratory manual provided.

The optimization of an undergraduate experiment for Organic Chemistry students is described to explore the concept of click chemistry. The preparation of a terminal fluorescent alkyne and an organic azide is reported consisting of simple steps. These are employed in the Cu(I)-catalized azide-alkyne cycloaddition to obtain a novel molecule containing a triazole ring whose characterization allows the students to practice a variety of techniques: NMR (1H, 13C, COSY and HSQC), melting point, thin layer chromatography, IR, MS and fluorescence spectroscopy to confirm the structure of their obtained product. An alternative methodology in a one-pot reaction is also explored and a full laboratory manual provided.

From a chemistry-based perspective, this review discusses the most recent advances in the field of substrate-based probes for the detection and analysis of proteolytic activity bothin vitroandin vivo.