Colorimetric Detection of Sepsis-Derived Hyperdegranulation with Plasmonic Nanosensors

Abstract

Hyperdegranulation of neutrophilic granulocytes is a common finding in sepsis that directly contributes to the heightened immune response leading to organ dysfunction. Currently, cell degranulation is detected by flow cytometry, which requires large infrastructure that is not always available at the point of care. Here, we propose a plasmonic assay for detecting the degranulation status of septic cells colorimetrically. It is based on triggering the aggregation of gold nanoparticles with cationic granule proteins. Cells from septic patients contain fewer granules and therefore release less cationic proteins than healthy cells. This results in red-colored assays than can be easily detected by eye. The assay can selectively detect cationic granule proteins even in the presence of an excess of unrelated proteins, which is key to detect degranulation with high specificity. Coupling this signal generation mechanism with a magnetic purification step enabled the identification of septic cells with the same performance as flow cytometry. This makes the proposed method a promising alternative for diagnosing sepsis in decentralized healthcare schemes.

Plasma-induced nanoparticle aggregation for stratifying COVID-19 patients according to disease severity

“… [21] Critical patients often show higher lactic acid levels that could lead to small differences in pH, [22] which is known to modulate nanoparticle aggregation. [7] , [23] To demonstrate that proteins, and not other solutes in plasma, are the key to the observed changes in aggregation behavior, we repeated the same experiments with deproteinized plasma samples from 3 ICU and 3 ward patients. Under this condition, no aggregation was observed in the whole range of dilutions proposed, which demonstrates that proteins are essential in order to aggregate nanoparticles in Fig.…”

“…Citrate-capped gold nanoparticles with a diameter around 40 nm were synthetized using the Turkevich method. [7] Briefly, 49 mg gold(III) chloride trihydrate dissolved in 1 mL of Milli-Q water was added to 250 mL boiling Milli-Q water (final gold concentration 0.5 mM) and then sodium citrate was added to a final concentration of 0.75 mM for 15 min while vigorously stirring. The resulting gold nanoparticles were let to cool down at room temperature and then stored at 4 ºC until used.…”

“… [3] The presence of biomolecules in these solutions may stabilize or destabilize the colloids depending on their concentration, and may also be modulated by other factors such as the pH or the presence of multivalent ions. [4] , [5] For instance, proteins may aggregate nanoparticles or protect them from aggregation depending on their concentration and isoelectric point, among other factors [6] , [7] , [8] These observations have paved the way to develop a new family of sensors that detect changes in the composition of human plasma, which contains proteins and other solutes, using nanoparticle aggregation assays. ‘ [9] For example, it has been shown that plasma samples from patients with acute COVID-19 have a different composition compared to samples from patients with less severe symptoms.…”

Micro- and nanosensors for detecting blood pathogens and biomarkers at different points of sepsis care

“…The biochip shows an excellent diagnostic and prognostic accuracy when tested with patients at different times since hospital admission, which makes it promising for patient stratification. Finally, it has been proposed that plasmonic nanoparticles could be used to detect excessive degranulation in neutrophils isolated from septic patients [72]. In this approach, cationic proteins from neutrophil granules aggregate gold nanoparticles, which changes the color of the colloidal suspension.…”

Sensitive NIR Fluorescence Identification of Bacteria in Whole Blood with Bioorthogonal Nanoprobes for Early Sepsis Diagnosis

“…In early sepsis, bacteria concentration may not exceed 10 CFU/mL . Also, there are billions of blood cells and proteins in every milliliter of blood . Thus, bacteria enrichment is crucial for sepsis detection.…”