The main protease (Mpro or 3CLpro) is an enzyme that is evolutionarily conserved among different genera of coronaviruses. As it is essential for processing and maturing viral polyproteins, Mpro has been identified as a promising target for the development of broad-spectrum drugs against coronaviruses. Like SARS-CoV and MERS-CoV, the mature and active form of SARS-CoV-2 Mpro is a dimer composed of identical subunits, each with a single active site. Individual monomers, however, have very low or no catalytic activity. As such, inhibition of Mpro can be achieved by molecules that target the substrate binding pocket to block catalytic activity or target the dimerization process. In this study, we investigated GC376, a transition-state analog inhibitor of the main protease of feline infectious peritonitis coronavirus, and Nirmatrelvir (NMV), an oral, bioavailable SARS-CoV-2 Mpro inhibitor with pan-human coronavirus antiviral activity. Our results show that both GC376 and NMV are capable of strongly binding to SARS-CoV-2 Mpro and altering the monomer-dimer equilibrium by stabilizing the dimeric state. This behavior is proposed to be related to a structured hydrogen-bond network established at the Mpro active site, where hydrogen bonds between Ser1’ and Glu166/Phe140 are formed in addition to those achieved by the latter residues with GC376 or NMV.

The uncontrolled release of pharmaceutical drugs into the environment raised serious concerns in the last decades as they can potentially exert adverse effects on living organisms even at the low concentrations at which they are typically found. Among them, platinum based cytostatic drugs (Pt CDs) are among the most used drugs in cancer treatments which are administered via intravenous infusion and released partially intact or as transformation products. In this review, the studies on environmental occurrence, transformation, potential ecotoxicity, and possible treatment for the removal of platinum cytostatic compounds are revised. The analysis of the literature highlighted the generally low total platinum concentration values (from a few tens of ng L⁻¹ to a few hundred μg L⁻¹) found in hospital effluents. Additionally, several studies highlighted how hospitals are sources of a minor fraction of the total Pt CDs found in the environment due to the slow excretion rate which is longer than the usual treatment durations. Only some data about the impact of the exposure to low levels of Pt CDs on the health of flora and fauna are present in literature. In some cases, adverse effects have been shown to occur in living organisms, even at low concentrations. Further ecotoxicity data are needed to support or exclude their chronic effects on the ecosystem. Finally, fundamental understanding is required on the platinum drugs removal by MBR, AOPs, technologies, and adsorption.

CIDEM-501 is a hybrid antimicrobial peptide rationally designed based on the structure of panusin and panulirin template peptides. The new peptide exhibits significant antibacterial activity against multidrug-resistant pathogens (MIC = 2–4 μM) while conserving no toxicity in human cell lines. We conducted molecular dynamics (MD) simulations using the CHARMM-36 force field to explore the CIDEM-501 adsorption mechanism with different membrane compositions. Several parameters that characterize these interactions were analyzed to elucidate individual residues’ structural and thermodynamic contributions. The membrane models were constructed using CHARMM-GUI, mimicking the bacterial and eukaryotic phospholipid compositions. Molecular dynamics simulations were conducted over 500 ns, showing rapid and highly stable peptide adsorption to bacterial lipids components rather than the zwitterionic eucaryotic model membrane. A predominant peptide orientation was observed in all models dominated by an electric dipole. The peptide remained parallel to the membrane surface with the center loop oriented to the lipids. Our findings shed light on the antibacterial activity of CIDEM-501 on bacterial membranes and yield insights valuable for designing potent antimicrobial peptides targeting multi- and extreme drug-resistant bacteria.

The polyallylamine hydrochloride (PAH) polymer is here functionalized with branched and biocompatible polysaccharide dextran (DEX) molecules. Covalent conjugation of DEX to PAH has been achieved through a straightforward reductive amination approach, allowing for a controlled number of DEX chains per PAH polymer (PAH:DEX_n, n = 0.1, 0.5, 1, 2, 5, 10). When exposed to phosphate buffer, PAH:DEX_n polymers form supramolecular assemblies. Physico chemical characteristics and pH responsiveness of the assemblies are correlated with the number of dextran chains per PAH molecule. Nanocapsules (NCs) are formed when PAH:DEX ratio is 1. Capsule formation is explained by the branched nature of DEX and steric consideration ruling the organization of polyamine chains in phosphate buffer. NCs and glyconanoparticles formed with n < 1 are responsive to pH changes, being disassembled at endosomal pH < 6 and reassembled when 6 < pH < 9. Dynamic light Scattering (DLS), ζ-potential measurements, cryo-Electron Microscopy and Small Angle X-ray Scattering (SAXS) provided key information about their structure, morphology, size, polydispersity, surface charge, and stability over time. Protein entrapment into the NCs and pH-dependent release is demonstrated with bovine serum albumin (BSA) as model protein by diffusion measurements in fluorescence correlation spectroscopy (FCS), following changes in BSA conformation before and after triggering NC disassembly by circular dichroism (CD), and comparing NCs SAXS fingerprints with and without BSA. Our results show novel assemblies based on polyamine phosphate interactions with capacity of loading large molecules through the formation of capsules, which may find applications in the endosomal delivery of therapeutic proteins and enzymes.