Table 1.

Comparison of common BCA signal amplification methods.

Method	Target	Year	Country	Sensitivity	Time	Principle	Advantages	Disadvantages	References
Chip methods	Anthrax	2004	USA	5 × 10−15 mol/L	3–4 h	A chip with a surface-fixed capture probe is hybridized with AuNP labelled with the complementary DNA sequence barcode, and silver staining is performed for scanning analysis.	Small, portable, fast. The barcode DNA is highly concentrated on the surface of the chip, and the silver staining method can further amplify the detection signal with high sensitivity.	It is sometimes inconvenient to amplify and detect non-nucleic acid macromolecules.	[25]
	Human Immunodeficiency Type 1 Capsid (p24) Antigen	2007	USA	100 fg/mL	2–3 h				[27]
	Hepatitis B Virus Deoxyribonucleic Acid	2010	China	10−15 mol/L	1.5 h				[26]
	Human IgG	2013	China	1 pg/mL	14 h				[24]
Fluorescent labelling	Salmonella enterica serovar Enteritidis	2009	USA	1 ng/mL	4 h	Barcode DNA is labelled with fluorescent dyes and detected by collecting signals using a fluorescence scanner.	Wide application range, improved sensitivity, short detection time.	This combination of technologies is not yet mature, and it is necessary to further optimize the experimental steps and conditions to reduce the cost of testing.	[30]
	Bluetongue virus	2012	China	10−2 fg/mL	3 h				[28]
	Ricin toxin	2012	China	1 fg/mL	3 h				[29]
	Multiple DNAs (HCV and HIV)	2017	China	5 × 10−12 mol/L	2 h				[31]
Colorimetric methods	Cytokines-IL-2	2005	USA	30 × 10−18 mol/L	3 h	The sequence is hybridized with the labelled AuNP, and the experimental results are determined according to the change in the colour of the solution.	Simple, portable, low cost. The experimental results can be observed more intuitively through colour changes.	The experimental steps are complicated. Reproducibility and sensitivity need to be further improved.	[32]
	Cytokines-IL-2	2007	USA	10−18 mol/L	3 h				[33]
	Pesticide triazophos	2017	China	14 ng/L	1 h				[34]
Biosensor methods	HTLV-I and HTLV-II	2009	China	1.71 × 10−12 mol/L; 1.5 × 10−12 mol/L	1.5 h	The AuNP is used as a signal amplifier, and the magnetic probe is used as a splitter. The signal amplification and silver staining form a complex structure, and other techniques are used for detection.	Variety of sensors, simple operation, good portability, short response time, high sensitivity, low background signal.	The detection sensitivity cannot meet the practical requirements for large-scale applications. Experimental steps are complicated.	[38]
	Human platelet antigen	2010	Germany	2 × 10−12 mol/L	150 s				[35]
	The protective antigen A (pagA) gene of Bacillus anthracis and the insertion element (Iel) gene of Salmonella enteritidis	2010	USA	0.5 ng/mL; 50 pg/mL	1 h				[36]
	Escherichia coli O157:H7	2018	China	50 CFU/mL	1 h				[37]
IPCR	Hantaan virus nucleocapsid protein HCV core antigen	2009	China	10 fg/mL	1.5 h	Detection of target by antigen-antibody specificity and PCR amplification technology. Sometimes used in conjunction with fluorescence PCR technology.	High sensitivity and specificity and rapid detection Can be applied in the diagnosis of cancer, Salmonella, and animal diseases and in food safety testing.	Separate IPCR technology, quantitative uncertainty. The instrument is expensive, and the results cannot be stored for a long time.	[39]
	Polychlorinated biphenyls (PCBs) 77	2014	China	1.72 pg/L	10 h				[40]
	PCBs-Aroclor 1248	2015	China	2.55 pg/L	10 h				[41]
	Staphylococcal enterotoxin B	2019	China	0.269 pg/mL	3 h				[42]