The Indian POC market has seen tremendous growth in the past five years. The entry of semi-automatic im-

immunofluorescence analyzers (IFAs) have created a new segment of customers who look for compact and easy-to-use equipment for hormone and specific protein testing. In the past three years, the availability of equipment with better CV, better ROI for customers and distributors, and the increased demand during the pandemic have increased the customer base and popularity for IFA rapidly. Even though IFA was evolving, specificity- and sensitivity-related worries were inevitable for any user. There comes the significance of time-resolved technology in IFA, where specificity and sensitivity are also taken care of.

AURA FIA is a quantitative Time-Resolved Fluorescence Immunoassay analyzer designed to provide affordable and easy diagnostic solutions for all specific protein and hormone assays. This machine truly celebrates science meeting technology with its TRFIA PRINCIPLE. It uses lanthanide chelates to label antigens or antibodies and a time-resolved technology to measure fluorescence resulting in the effective elimination of any interference from non-specific fluorescence and thus giving you the accuracy of the highest of forms. It is equipped with an 8-inch LCD screen that can be operated with touch and to ensure advanced connectivity the machine comes enabled with LIS/HIS compatibility, Wi-Fi, Ethernet, Serial Port, and USB Interface. The machine is run on Android system 5.1.1 and the smooth screen interface enables a faster and easier operation with zero complexities. Two modes of operation are available such as; Standard Test and Quick Test mode. We have about 36 parameters that can be quantitatively analyzed on this machine ranging from cardiac, thyroid, and renal tumor markers, etc.

The two main principles that govern the obtainment of quantitative results in this machine are the double antibody sandwich method and the time-resolved immunofluorescence technology. Our test cartridges are developed in such a manner that the nitrocellulose membrane strip is divided into three sections, i.e., the sample pad, conjugate pad, and absorbent pad. When the sample mixed with diluent is added into the sample well of the test card, the target antigen present in the sample forms a semi-complex with the fluorescently labeled antibodies already pre-embedded into the conjugate pad. This complex formed will move in a direction from the conjugate pad towards the absorbent pad and along the way it will pass through a test that is pre-embedded with capture antibodies. The complex is captured by this antibody forming a double antibody sandwich and held stationary at the test line itself. Both antibodies are highly specific to the respective target antigen.

Further, when the card is inserted into the machine, the LED Light source is arranged in such a way that it falls directly onto the test line providing the excitation energy (365nm) required to excite fluorescent molecules attached to the complex. Once excited, these molecules will emit their own fluorescence at a wavelength ranging from 500nm-700nm. The emitted fluorescence is then captured by a photo-sensitive diode that converts the light energy into electrical energy thereby giving us a quantitative value indicating the exact concentration of the target antigen present in the sample.

In machines that enable a time-resolved fluorescence technology, the fluorescent labels used belong to the lanthanide elements of the periodic table. These rare earth metals such as Samarium, Europium, Terbium, etc. have unique features when hydrolyzed with compounds like 4,7-bis (chlorosulfophenyl)-l, 10- phenanthroline-2,9- dicarboxylic acid (BCPDA). Such lanthanide complexes have unusually large Stokes shift (295nm) allowing an easier separation of excitation and the emission spectrum. In conventional fluorometry, the fluorescent dyes used have their emission spectrum overlapping with mainly the autofluorescence of serum. Hence fluorescence quenching and serum autofluorescence effects are reduced when BCPDA-Eu³⁺ complexes are used (Anti-interference ability).

Another characteristic feature of Europium complexes is that the fluorescence emitted is long-lived (600-1000 us for Eu³⁺ compared with 5-100 ns for conventional fluorophores) which allows the use of microsecond time-resolved fluorescence measurements, which reduce the observed background signals. Short-lived fluorescence usually dissipates to zero in <100 us. If no measurements are taken during the first 100-200 us after excitation, all short-lived fluorescence background signals and scattered excitation radiation are completely eliminated, and the long-lived fluorescence signals can be measured with very high sensitivity.