Biology subjects

Pappone, C.

Publications and source records attributed to Pappone, C..

3 recordsLinked to original sources

bioRxiv2026

Real-time mass-resolved label-free single-molecule immunoassay

Protein-protein interactions govern the biomolecular logic of immunity, signalling, and disease. Elementary rates of association, dissociation, and inhibition underpin our understanding of life processes and remain a limiting factor at the frontier of therapeutic discovery. Yet existing assays infer these processes indirectly through ensemble-averaged signals or molecular labels that obscure native dynamics. Here, we introduce a label-free, real-time, mass-resolved single-molecule immunoassay based on interferometric scattering microscopy (iSCAT) that directly observes individual protein-protein binding events in complex biological samples. By detecting light scattered from single proteins as they bind to an antibody-functionalized surface, we resolve discrete antibody-antigen interactions with single-molecule sensitivity and molecular-weight discrimination. Using IgM as a model system, we demonstrate real-time detection of individual binding events, with measured association rates that scale linearly with concentration over three orders of magnitude. Direct counts of IgM binding events in human serum yield quantitative concentrations that agree with bulk measurements obtained by enzyme-linked immunosorbent assay (ELISA). This bioaffinity iSCAT platform unifies molecular specificity, label-free detection, real-time kinetics, and mass-resolved single-molecule sensitivity, enabling direct access to protein-protein recognition processes and establishing a general framework for quantitative, single-molecule immunoassays.

biophysics↗

bioRxiv2025

Exploring light chain cardiotoxicity in AL amyloidosis: Impact on hiPSC-derived Cardiomyocyte Activity

AimsImmunoglobulin light chain (AL) amyloidosis is a protein misfolding disease characterized by the systemic deposition of amyloid fibrils derived from monoclonal light chains (LCs). Cardiac involvement is the major determinant of prognosis and mortality, and beyond fibril accumulation, soluble cardiotoxic LCs play a critical role in disease progression. While current in vivo models like C. elegans and murine systems have demonstrated LC toxicity, they lack human relevance or fail to capture soluble LC-induced cardiotoxicity. This study aimed to characterize the electrophysiological effects of cardiotoxic LCs on a human-relevant model using human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Methods and ResultsTwo amyloidogenic cardiotoxic LCs (H3 and H6) from AL patients and one non-cardiotoxic LC (M10) from a multiple myeloma patient were biophysically characterized and tested in hiPSC-CMs at clinically relevant concentrations. Electrophysiological recordings revealed that H3 and H6 significantly reduced spontaneous action potential (AP) firing frequency and maximal upstroke velocity (dV/dt) in hiPSC-CMs, indicating impaired excitability. H6 also shortened AP duration. H3 exposure led to a [~]40% reduction in peak sodium current density and altered inactivation kinetics of the L-type calcium current, without affecting major pacemaker or repolarizing potassium (IKr or IKs) currents. In contrast, M10 had no effect on any measured parameter, validating the models ability to discriminate toxic from non-toxic LCs. ConclusionThis study demonstrates that hiPSC-CMs provide a clinically relevant human model to investigate LC-induced cardiotoxicity. Cardiotoxic LCs exert distinct but converging electrophysiological impairments, including disruption of sodium and L-type calcium currents, contributing to reduced excitability and altered AP morphology. These findings provide mechanistic insights into AL amyloidosis-related cardiac dysfunction and establish a foundation for future therapeutic screening targeting soluble LC toxicity in a human context.

pathology↗

bioRxiv2023

Nanobodies counteract the toxicity of an amyloidogenic light chain by stabilizing a partially open dimeric conformation

Light chain amyloidosis (AL) is a systemic disease where fibrillar deposition of misfolded immunoglobulin light chains (LCs) severely affects organ function and results in poor prognosis for patients, especially when heart involvement is severe. Particularly relevant in this context is the cardiotoxicity exerted by still uncharacterized soluble LC species. Here, with the final goal of identifying alternative therapeutic strategies to tackle AL amyloidosis, we produced five llama-derived nanobodies (Nbs) specific against H3, a well-characterized amyloidogenic and cardiotoxic LC from an AL patient with severe cardiac involvement. We found that Nbs are specific and potent agents capable of abolishing H3 soluble toxicity in C. elegans in vivo model. Structural characterization of H3-Nb complexes revealed that the protective effect of Nbs is related to their ability to bind to the H3 VL domain and stabilise an unexpected partially open LC dimer in which the two VL domains no longer interact with each other. Thus, while identifying potent inhibitors of LC soluble toxicity, we also describe the first non-native structure of an amyloidogenic LC that may represent a crucial step in toxicity and aggregation mechanisms.

biophysics↗