Journal: Analytical and Bioanalytical Chemistry
Article Title: A homogeneous immunoassay technology based on liposomes and the complement system enables one-step, no-wash, rapid diagnostics directly in serum
doi: 10.1007/s00216-025-05882-4
Figure Lengend Snippet: Optimization of the liposome composition to generate stealth liposomes. a Homogeneous complement assay of 10 mM SRB-encapsulating liposomes (10 µM total lipids; batches –6) showing the cholesterol dependency of liposome stealthiness in active serum (10 vol% PHS). Statistical analysis (two-sample independent t-test) revealed a significant difference between active and inactive serum samples at a cholesterol content of 10 mol% (p = 0.026) and above (p < 0.001). In contrast, no significant difference was observed at a cholesterol content of 5 mol% (p = 0.881). b Liposome stealthiness in active serum depending on SRB and cholesterol content (batches –10). 10 vol% human serum was used as a complement source (IRS41174). Statistical analysis (two-sample independent t-test) showed no significant difference between active and inactive serum samples of liposomes containing 10 mM SRB and 5 mol% cholesterol (p = 0.714), while in the other cases either a statistically significant amount of complement lysis (p < 0.001) or general serum stability was observed. Fluorescence measurements were carried out for 1 h at 37 °C in LCB, iaS, aS, and 30 mM OG + aS. Fluorescence intensities were normalized to the endpoint fluorescence of the positive control. λ Ex = 565(5 or 8) nm and λ Em = 585(5 or 8) nm; gain 150. T = 37 °C. n = 3. c Heterogeneous complement assay of biotin-modified chemiluminescence liposomes (30 mM m -carboxy luminol; batches CL1–2). Statistical analysis (two-sample independent t-test) showed a significant difference between active and inactive serum samples of high-cholesterol liposomes. Low-cholesterol liposomes remained stealth and showed no statistical difference in 5 and 10 vol% serum, whereas 25 vol% led to minor lysis in active serum. Liposomes (50 μM total lipids) were immobilized overnight on a streptavidin-coated MTP and incubated for 1 h at 37 °C in either inactive serum or active serum (5, 10, or 25 vol% PHS in LCB). Chemiluminescence measurements were performed by adding 50 μL of 4 μM hemin and 50 μL 40 mM H 2 O 2 in 0.01 M CBS, pH 10.5, 2 s integration time, gain 80, RH 1 mm, T = 25 °C, n = 3. d Flow chart of the homogeneous complement assay procedure for SRB-encapsulating liposomes
Article Snippet: Pooled human complement sera (batches 31,758, 33,478, 35,577, 41,174 and 45,270) were purchased from Innovative Research (Novi, MI, USA); ARMS peptide (peptide sequence: IHTELCLPAFFSPAGTQRRFQQPQHHLTLSIIHTAAR) was purchased from ProteoGenix (France).
Techniques: Liposomes, Complement Assay, Lysis, Fluorescence, Positive Control, Modification, Incubation