Table I.
Summary of the latest works integrating different POC instruments to measure protein concentrations
| Tested target | Relevance of sample∗ | Detection strategy | Sensitivity/Limit of detection (LOD)† | Timeframe | Ref. |
|---|---|---|---|---|---|
| Lateral flow immunoassays | |||||
| Thyroid-stimulating hormone (TSH) and human chorionic gonadotropin (hCG) | Whole blood and plasma | Piezofilm sensor | LOD: 18 pg/mL for TSH | 5–10 min | (7) |
| C reactive protein (CRP) | Whole blood | Fluorescence (in plastic disposable cartridge) | LOD: 133 ng/mL | 10 min | (8) |
| Biotoxins ricin, Shiga toxin I and Staphylococcal enterotoxin B | Biological toxins | Fluorescence (Microfluidic with polyacrylamide electrophoresis) | LOD: 20 nM for ricin; 500 pM for Shiga toxin I; 300 pM for Staphylococcal enterotoxin B |
Incubation Ag-Ab: 30 min Electrophoresis: 3 min |
(9) |
| Matrix metalloproteinase-8 (MMP-8) | Saliva | Fluorescence (Microfluidic with polyacrylamide electrophoresis) | LOD: 130 ng/mL | 2 min | (10) |
| CRP | Serum | Chemiluminescence (Microfluidic channels) | Linear range: 2–15 μg/mL | 26 min | (15) |
| CRP | Serum and cerebrospinal fluid | Fluorescence (Microfluidic capillary system for immunoaffinity chromatography) | Calibration ranges: 0.05–3.0 μg/mL for 1:10 diluted serum 0.01–30 for undiluted cerebrospinal fluid |
10 min | (16) |
| CRP | Serum | Fluorescence (Microfluidic on PDMS) | LOD: 10 ng/mL LOD: ng/mL |
<3 min 14 min |
(17) |
| CRP | CRP-enriched human serum | Fluorescence (Microfluidic on PDMS) | LOD: 0.42 nM | 20 min | (18) |
| Vascular endothelial growth factor (VEGF) | Human plasma | Fluorescence (Elastomeric microfluidic chip) | LOD: 4 pM | ∼10 min | (19) |
| CRP and ferritin | Serum | Fluorescence (Elastomeric microfluidic chip) | LOD: 12 μg/mL for CRP Linear range: 30–300 ng/mL for ferritin |
(20) | |
| CRP, tumor necrosis factor α (TNFα), and procalcitonin (PCT) | Serum | Fluorescence (Sensor chip of PMMA) Multiplexed |
LOD: 1.265 μg/mL for CRP LOD: 10 ng/mL for TNFα LOD: 50 ng/mL for PCT |
25 min approximately | (21) |
| Prostate specific antigen (PSA) | Serum | Voltammetry (Electrochemical inmunosensor in plastic disposable cartridge) | LOD: 20 pg/mL | 20 min | 22, 23 |
| Cardiac troponin I (cTnI) | Serum | Magnetic signal (plastic disposable cartridge) | LOD: 10 pg/mL | 15 min | (24) |
| Microarrays (multiplex) | |||||
| CRP, interleukin 6 (IL-6) and PCT | Plasma | Microfluidic fluorescence | LOD: 0.35 ng/mL for CRP LOD: 0.08 ng/mL for IL-6 LOD: 1.01 ng/mL for PCT |
35 min | (25) |
| 12 tumor markers (PSA and 11 cytokines) | Plasma | Fluorescence | LOD: ∼30pM | 10 min | (26) |
| PSA, TNFα, IL-6, and IL-23 | Protein solutions | Bright white “light-emitting diode” (LED) Multiplexed |
3.4 ng/mL for PSA 0.1 ng/mL for TNFα, IL-6, and IL-23 |
(27) | |
| Tumor markers (cancer antigens CA 153, CA 125, CA199, and carcinoembryonic antigen: CEA) | Serum | Voltammetry (Electrochemical inmunosensor) | Detectable linear ranges: 0.42–80 U/mL for CA 153 0.5–65 U/mL for CA 125 0.8–75 U/mL for CA 199 0.8–46 ng/mL for CEA |
<5 min | (28) |
| Anti-hepatitis C virus (anti-HCV) antibodies (HCV core and nonstructural 4 antigen [NS4]) | Artificial targets and human serum | Fluorescence | LOD: 10 ng/mL for anti-CHV core LOD: 50 ng /mL for NS4 |
14 min | (29) |
| CRP | Saliva (1000-fold dilution) | Fluorescence | LOD: 10 pg/mL | 10 min | (30) |
| 10 cytokines | Saliva | Fluorescence | LOD: From 8 pM for IL-8 to 469 pM for (VEGF) | Incubation: 2 h Assay: 30 min approximately |
(31) |
| Other methods | |||||
| Cardiac troponin T (cTnT) | Serum | Amperometric (Electrochemical inmunosensor) | LOD: 0.2 ng/mL Linear range: 0.1–10 ng/mL |
2 h | (38) |
| Tumor markers (PSA, CEA, and AFP) | Serum | Multiplexed silicon field-transistor (Si-FET) | Detection quantitative: from 0.2 to 114 ng/mL | 20 min | (39) |
| PSA and PSA-α 1-antichymotrypsin | Serum | Quartz crystal microbalance e sensor | LOD: 0.39 ng/mL Detection range: 0.39–200 ng/mL |
8 min | (40) |
| CRP | Whole blood | Magnetic permeability inmunoassay | LOD: 3 μg/mL Linear range: 0–260 μg/mL |
5.5 min | (41) |
| CRP | Whole Blood | Noncompetitive immunoassay Fluorescence |
LOD: 160 ng/mL | 2 min | (42) |
| PSA | Serum | Homogeneous fluoroimmunoassay | LOD: 56 pg/mL | 30 min | (43) |
| No antibodies | |||||
| Thrombin | Plasma | GoldBio strip reader after aptamers binding | LOD: 2.5 nM Linear range: 5–10 nM |
10 min | (36) |
| Generation of thrombin and other coagulation activators | Whole blood and plasma | Amperometric (Substrate cleaved for coagulation activators) | LOD: 0.4 U/mL thrombin | 15–20 min | (44) |
| Albumin | Urine | Visual (Spot test with erythrosin B) | LOD: 0.5 mg/mL | 5 min | (45) |
| Albumin | Urine | Reflectance (Test strip) | LOD: 10 μg/mL | 1 min | (46) |
| α-amilase | Saliva | Reflectance with LED device (Test strip) | Linear range: 10–132 kU/L at 37°C | 0.5 min | (47) |
∗
We indicate in this column what kind of samples (actual patient samples, synthetic test oligos, etc.) were used to compare them with what could be found in an actual patient sample.
†
Some studies focus on LOD and others on sensitivity. In either case, the values may depend on specific experimental conditions, and these values should be taken as merely indicative. Samples are usually applied in volumes of a few microliters.