Introduction:
The widespread use of antibiotics and the associated health risks necessitate the need to control these compounds throughout their circulation chains. Immunoassays, especially lateral flow immunoassay (LFIA), allow for simple, rapid and productive testing. However, due to the large number of structurally related antibiotics, integral LFIA results have limited output in terms of concentrations for specific compounds. In addition, traditional LFIA is usually inferior to alternative methods in sensitivity. The report presents our developments to improve LFIA tests for antibiotics.

Methods:
Synthesized gold nanoparticles – spherical and with a branched surface, nanoflowers, as well as commercial fluorescent nanoparticles, quantum dots – were used as markers in the LFIA tests. The test systems implemented the principle of competitive immunoassay with direct or indirect antibody labeling. The degree of marker binding in the test zone was registered photo- or fluorimetrically to calculate the concentration of the analyte in the sample.

Results:
To reach desirable detection limit and working range of LFIA, such parameters as size and shape of nanoparticles, antibody nanoparticle and hapten protein ratios can be efficiently varied. Using QSAR analysis, the structural components of antibiotics that make the main contribution to their immune recognition were characterized. Shifting the reactant ratio has been shown to affect cross-reactivity levels, thereby increasing individual or group selectivity. For LFIAs with fluorescent detection or complexation of several functionalized nanoparticles, detection limits decreased from 10 to 100 times. LFIA tests have been developed for antibiotics from the groups of beta-lactams, fluoroquinolones, aminoglycosides, lincosamines; their effectiveness for food (milk, meat) control has been shown.

Conclusions:
Varying the composition of immunoreagents and the conditions of their interaction, the use of new nanodispersed markers and self-assembling complexes of nanoparticles are effective tools to modulate both sensitivity and selectivity of LFIA for antibiotics.

Conflicts of interest:
The authors declare that they have no conflict of interest in the publication of this article. The authors have no conflicts of interest to report in this work. Abstract was not submitted elsewhere and was first published here.

Funding:
The study was supported by the Russian Science Foundation; grant # 24-16-00273 (https://rscf.ru/project/24-16-00273/).