Recent years have confirmed the ubiquitous applicability of lateral flow assays (LFA) in point-of-care testing (POCT). To make this technology available for low abundance analytes, strategies towards lower limits of detections (LOD), while maintaining the LFA’s ease of use, are still being sought. Here, we demonstrate how liposomes can significantly improve the LOD of traditional gold nanoparticle (AuNP)–based assays while fully supporting a ready-to-use system for commercial application. We fine-tuned liposomes towards photometric and fluorescence performance on the synthesis level and applied them in an established interleukin 6 (IL-6) immunoassay normally using commercial AuNP labels. IL-6’s low abundance (< 10 pg mL−1) and increasing relevance as prognostic marker for infections make it an ideal model analyte. It was found that liposomes with a high encapsulant load (150 mmol L−1 sulforhodamine B (SRB)) easily outperform AuNPs in photometric LFAs. Specifically, liposomes with 350 nm in diameter yield a lower LOD even in complex matrices such as human serum below the clinically relevant range (7 pg mL−1) beating AuNP by over an order of magnitude (81 pg mL−1). When dehydrated on the strip, liposomes maintained their signal performance for over a year even when stored at ambient temperature and indicate extraordinary stability of up to 8 years when stored as liquid. Whereas no LOD improvement was obtained by exploiting the liposomes’ fluorescence, an extraordinary gain in signal intensity was achieved upon lysis which is a promising feature for high-resolution and low-cost detection devices. Minimizing the procedural steps by inherently fluorescent liposomes, however, is not feasible. Finally, liposomes are ready for commercial applications as they are easy to mass-produce and can simply be substituted for the ubiquitously used AuNPs in the POCT market.
Graphical abstract
Recent years have confirmed the ubiquitous applicability of lateral flow assays (LFA) in point-of-care testing (POCT). To make this technology available for low abundance analytes, strategies towards lower limits of detections (LOD), while maintaining the LFA’s ease of use, are still being sought. Here, we demonstrate how liposomes can significantly improve the LOD of traditional gold nanoparticle (AuNP)–based assays while fully supporting a ready-to-use system for commercial application. We fine-tuned liposomes towards photometric and fluorescence performance on the synthesis level and applied them in an established interleukin 6 (IL-6) immunoassay normally using commercial AuNP labels. IL-6’s low abundance (< 10 pg mL−1) and increasing relevance as prognostic marker for infections make it an ideal model analyte. It was found that liposomes with a high encapsulant load (150 mmol L−1 sulforhodamine B (SRB)) easily outperform AuNPs in photometric LFAs. Specifically, liposomes with 350 nm in diameter yield a lower LOD even in complex matrices such as human serum below the clinically relevant range (7 pg mL−1) beating AuNP by over an order of magnitude (81 pg mL−1). When dehydrated on the strip, liposomes maintained their signal performance for over a year even when stored at ambient temperature and indicate extraordinary stability of up to 8 years when stored as liquid. Whereas no LOD improvement was obtained by exploiting the liposomes’ fluorescence, an extraordinary gain in signal intensity was achieved upon lysis which is a promising feature for high-resolution and low-cost detection devices. Minimizing the procedural steps by inherently fluorescent liposomes, however, is not feasible. Finally, liposomes are ready for commercial applications as they are easy to mass-produce and can simply be substituted for the ubiquitously used AuNPs in the POCT market.
Graphical abstract
“…in the control group; O.D.mean t = mean of O.D. in the test group; SD c = standard deviation in the control group; and SD t = standard deviation in the test group (Desphande, ).…”
Section: Methodsmentioning
confidence: 99%
“…SD c = standard deviation in the control group; and SD t = standard deviation in the test group (Desphande, 1996).…”
Objective
To evaluate the effect of the periodontal treatment on Aggregatibacter actinomycetemcomitans JP2 clone, and the IgG serum levels against its outer membrane protein (Omp29) and A. actinomycetemcomitans serotypes in aggressive periodontitis (AgP).
Subjects and Methods
Seventeen patients with generalized (GAgP), 10 with localized (LAgP), and 10 healthy controls were included. AgP participants were submitted to periodontal treatment—scaling and root planing plus antibiotics (SRP+A). Periodontal parameters, for example, probing depth (PD) and clinical attachment loss (CAL), were evaluated at baseline and at 1‐year. Serum IgG against Omp29 and serotypes a, b, and c were determined by ELISA. The levels of A. actinomycetemcomitans JP2 clone were determined in subgingival biofilm samples by qPCR.
Results
Periodontal treatment resulted in significant reductions of PD, CAL, and IgG levels against Omp29, serotypes b, and c. After therapy, IgG levels against A. actinomycetemcomitans serotypes, as well as the levels of the JP2 clone in AgP, became similar to controls. The reduction in JP2 clone count was correlated with a reduction of PD and IgG response against Omp29.
Conclusion
Scaling and root planing plus antibiotics decreased IgG levels response against Omp29 and A. actinomycetemcomitans serotypes involved in the disease (b and c), while the serum response increased against tne commensal serotype (a), similar to what occurs in periodontally healthy individuals.
“…The cut‐off levels for reactivity to antigens were calculated based on Desphande′s formula [normalized O.D. − (control mean + 2 standard deviations of control)] (Desphande ). For Aa the formula was: normalized O.D.…”
Given the evidences that IgG response in AP patients correlated with bacterial infection level in GAP, but not in LAP, and that LAP patients lack a response to Tf, despite harbouring this species, our data suggest a difference in host immune defence between these two forms of aggressive periodontitis.
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