Maria Antonieta Daza Millone

The adsorption of serum albumins onto nanoparticle surfaces governs protein corona formation, which modulates nano-bio interfaces and can interfere with targeted cellular interactions. We employ a molecular theory to study the adsorption of human and bovine serum albumin (HSA and BSA) on silica nanoparticles by systematically varying pH, salt concentration, and nanoparticle size. Albumin adsorption peaks near the isoelectric point and is largely insensitive to salt concentration. Below a radius of approximately 10 nm, surface curvature triggers a marked transition: adsorption per unit area increases, and proteins adopt a wider range of orientations, resulting in a more heterogeneous adsorbed layer. Despite similar adsorption profiles, HSA and BSA exhibit distinct interfacial organizations on both small and large nanoparticles. These findings challenge the common use of BSA as a surrogate for HSA and establish nanoparticle curvature as a key determinant of interfacial organization. Competition with cytokines reveals that corona composition depends on nanoparticle size and pH, highlighting how environmental and design parameters govern bio-nano interactions.

Immunocastration, a non-surgical strategy based on active immunization against gonadotropin-releasing hormone (GnRH), effectively suppresses steroidogenesis and spermatogenesis. However, peptide vaccines targeting poorly immunogenic antigens such as GnRH often fail to elicit robust adaptive immune responses, requiring adjuvants or carrier proteins. Previously, we introduced Coated Bacterial Vaccines (CBVs), a platform that uses chemically inactivated Gram-positive bacteria to display recombinant antigens fused to the SlpA carboxy-terminal domain (dSLPA) on their surface. This system leverages natural pathogen-associated molecular patterns (PAMPs) to enhance immunogenicity without additional adjuvants. In this work, we extended the application of the CBVs platform to enhance the immune response against a poorly immunogenic GnRH-based peptide vaccine. GnRH-CBVs were formulated using inactivated Bacillus subtilis var. natto coated with a recombinant GnRH tandem-repeat–dSLPA fusion protein and administered to male BALB/c mice. A chitosan-adjuvanted GnRH-dSLPA formulation served as a positive control. GnRH-CBVs induced a strong Th2-biased humoral response, characterized by predominant IgG1 levels comparable to those achieved with chitosan. The resulting antibodies effectively neutralized endogenous GnRH, reducing steroidogenesis and spermatogenesis and inducing marked testicular histological alterations. These findings support CBVs as a promising strategy to enhance peptide vaccine immunogenicity for veterinary immunocastration.

The perivitellin-2 (PV2) from snails is an unusual neuro and enterotoxin comprising a pore-forming domain of the Membrane Attack Complex and Perforin Family (MACPF) linked to a lectin. While both domains have membrane binding capabilities, PV2’s mechanism of action remains unclear. We studied the apple snail Pomacea maculata PV2’s (PmPV2’s) interaction with lipid membranes using various biophysical and cell biology approaches. In vitro studies showed that PmPV2 toxicity decreased when cholesterol (Chol) was diminished from enterocyte cell membranes. Chol enhanced PmPV2 association with phosphatidylcholine membranes but did not induce pore formation. In contrast, using rat brain lipid models, rich in glycolipids, PmPV2 exhibited high affinity and induced vesicle permeabilization. Negative stain electron microscopy and atomic force microscopy confirmed the formation of pore-like structures in brain lipid vesicles. Our findings suggest that Chol is a necessary lipid component and point to PmPV2–glycolipid interactions as potential activators critical to triggering PmPV2’s pore-forming activity, providing insights into this novel toxin’s mechanism.

Graphene oxide has been widely deployed in electricalsensors formonitoring physical, chemical, and biological processes. The presenceof abundant oxygen functional groups makes it an ideal substrate forintegrating biological functional units to assemblies. However, theintroduction of this type of defects on the surface of graphene hasa deleterious effect on its electrical properties. Therefore, adjustingthe surface chemistry of graphene oxide is of utmost relevance foraddressing the immobilization of biomolecules, while preserving itselectrochemical integrity. Herein, we describe the direct immobilizationof glucose oxidase onto graphene oxide-based electrodes prepared byLangmuir-Blodgett assembly. Electrochemical reduction of grapheneoxide allowed to control its surface chemistry and, by this, regulatethe nature and density of binding sites for the enzyme and the overallresponsiveness of the Langmuir-Blodgett biofilm. X-ray photoelectronspectroscopy, surface plasmon resonance, and electrochemical measurementswere used to characterize the compositional and functional featuresof these biointerfaces. Covalent binding between amine groups on glucoseoxidase and epoxy and carbonyl groups on the surface of graphene oxidewas successfully used to build up stable and active enzymatic assemblies.This approach constitutes a simple, quick, and efficient route tolocally address functional proteins at interfaces without the needfor additives or complex modifiers to direct the adsorption process.

Alpha hemolysin of Escherichia coli (HlyA) is a pore-forming protein, which is a prototype of the "Repeat in Toxins" (RTX) family. It was demonstrated that HlyA-cholesterol interaction facilitates the insertion of the toxin into membranes. Putative cholesterol-binding sites, called cholesterol recognition/amino acid consensus (CRAC), and CARC (analogous to CRAC but with the opposite orientation) were identified in the HlyA sequence. In this context, two peptides were synthesized, one derived from a CARC site from the insertion domain of the toxin (residues 341-353) (PEP 1) and the other one from a CRAC site from the domain between the acylated lysines (residues 639-644) (PEP 2), to study their role in the interaction of HlyA with membranes. The interaction of peptides with membranes of different lipid compositions (pure POPC and POPC/Cho of 4:1 and 2:1 molar ratios) was analyzed by surface plasmon resonance and molecular dynamics simulations. Results demonstrate that both peptides interact preferentially with Cho-containing membranes, although PEP 2 presents a lower K_D than PEP 1. Molecular dynamics simulation results indicate that the insertion and interaction of PEP 2 with Cho-containing membranes are more prominent than those caused by PEP 1. The hemolytic activity of HlyA in the presence of peptides indicates that PEP 2 was the only one that inhibits HlyA activity, interfering in the binding between the toxin and cholesterol.

Sra. editora: A propósito del editorial publicado en esta revista (1), quisimos dirigirnos a usted, con la convicción de que tanto la medicina como las ciencias de las cuales se nutre y, especialmente, la investigación como práctica vinculante deben comenzar a establecer un diálogo con otros tipos de saberes que permitan la generación de cambios que impacten de forma profunda a las poblaciones.

Cationic amino acid-based surfactants are known to interact with the lipid bilayer of microorganism resulting in cell death through a disruption of the membrane topology. To elucidate the interaction of a cationic surfactant synthesized in our lab, investigations involving N^α-benzoyl-arginine decyl amide (Bz-Arg-NHC₁₀), and model membranes composed by 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) were done. Bz-Arg-NHC₁₀was able to penetrate into DPPC monolayers up to a critical pressure of 59.6 mN m⁻¹. Differential scanning calorimetry revealed that as the concentration of Bz-Arg-NHC₁₀ increased, the main transition temperature of DPPC slightly decreased. Atomic force microscopy (AFM) in situ experiments performed on supported DPPC bilayers on mica allowed monitoring the changes induced by Bz-Arg-NHC₁₀. DPPC bilayer patches were partially removed, mainly in borders and bilayer defects for 50 µM Bz-Arg-NHC₁₀ solution. Increasing the concentration to 100 µM resulted in a complete depletion of the supported bilayers. Surface plasmon resonance (SPR) experiments, carried out with fully DPPC bilayers covered chips, showed a net increase of the SPR signal, which can be explained by Bz-Arg-NHC₁₀ adsorption. When patchy DPPC bilayers were formed on the substrate, a SPR signal net decrease was obtained, which is consistent with the phospholipids’ removal observed in the AFM images. The results obtained suggest that the presence of the benzoyl group attached to the polar head of our compound would be the responsible of the increased antimicrobial activity against gram-negative bacteria when compared with other arginine-based surfactants.

The development of drug carriers based in lipid nanoparticles (LNPs) aims toward the synthesis of non-toxic multifunctional nanovehicles that can bypass the immune system and allow specific site targeting, controlled release and complete degradation of the carrier components. Among label free techniques, Surface Plasmon Resonance (SPR) biosensing is a versatile tool to study LNPs in the field of nanotherapeutics research. SPR, widely used for the analysis of molecular interactions, is based on the immobilization of one of the interacting partners to the sensor surface, which can be easily achieved in the case of LNPs by hydrophobic attachment onto commercial lipid- capture sensor chips. In the last years SPR technology has emerged as an interesting strategy for studying molecular aspects of drug delivery that determines the efficacy of the nanotherapeutical such as LNPs' interactions with biological targets, with serum proteins and with tumor extracelullar matrix. Moreover, SPR has contributed to the obtention and characterization of LNPs, gathering information about the interplay between components of the formulations, their response to organic molecules and, more recently, the quantification and molecular characterization of exosomes. By the combination of available sensor platforms, assay quickness and straight forward platform adaptation for new carrier systems, SPR is becoming a high throughput technique for LNPs' characterization and analysis.

trans-Sialidase and cruzipain are important virulence factors from Trypanosoma cruzi, the etiological agent of Chagas disease, that have highly antigenic domains in their structure and were reported as potential tools for diagnosis of the illness. The aim of the present study is to assess the possibility of using cruzipain and the catalytic domain of trans-sialidase in a Surface Plasmon Resonance-based immunosensor for the diagnosis of chronic Chagas disease. Immunoassays carried out with canine sera verified that cruzipain allows the detection of anti-Trypanosoma cruzi antibodies whereas recombinant trans-sialidase did not yield specific detections, due to the high dilutions of serum used in the immunoassays that hinder the possibility to sense the specific low titer antibodies. The developed cruzipain-based biosensor, whose price per assay is comparable to a commercial enzyme-linked immunosorbent assay (ELISA), was successfully applied for the rapid quantification of specific antibodies against Trypanosoma cruzi in fresh human sera showing an excellent agreement with ELISA.