I. What is chemiluminescence technology, and what is its principle?

Chemiluminescence technology is an analytical method developed over the past two to three decades. Its principle involves using the free energy released by a chemical reaction to excite an intermediate, causing it to transition from an excited state back to the ground state. When the intermediate returns to the ground state, it releases photons of equivalent energy levels, which are then measured for quantitative analysis.Chemiluminescence possesses the specificity of fluorescence but does not require excitation light, thereby avoiding the interference of stray light found in fluorescence analysis and improving sensitivity. Additionally, it eliminates the environmental pollution and health hazards associated with radioactive analysis, making it an excellent quantitative analytical method.

II. What Are the Advantages of Chemiluminescence Technology?

1. Simplicity and Full Automation Potential: The appeal of chemiluminescence as an analytical tool lies in its simplicity. Since chemiluminescence is essentially self-emission of light, the analytical instruments only need to provide a method for detecting the light signal and recording the results.

2. Minimal Background Signal in Most Samples: The majority of samples do not exhibit a "background" signal, meaning they do not emit light on their own.

III. What Are the Conditions for Chemiluminescence Reactions?

The conditions for chemiluminescence reactions are: energy, pathway, and fluorophore.

1. The chemical reaction must be exothermic (release heat).

2. There must be a pathway for the formation of an electronically excited state.

3. The excited-state molecules must return to the ground state by emitting photons (light) or transfer energy to a fluorescent molecule.

IV. What Are the Classifications of Chemiluminescence Technology?

Chemiluminescence technology can be classified based on different luminescent agents as follows: indirect chemiluminescence, electrochemiluminescence, direct chemiluminescence, and light-initiated chemiluminescence.  The final characterization of these technologies involves converting optical signals into electrical signals, which are then processed and interpreted by a computer to produce experimental results.

Indirect Chemiluminescence The main process involves using enzymes to label antigens or antibodies.  During the reaction of the labeled complex, a substrate (i.e., the luminescent agent) is added, which undergoes catalysis and decomposition to produce light emission.  The advantage of indirect chemiluminescence lies in the fact that the enzyme used as the label is barely consumed during the process, resulting in strong and stable luminescent signals with a long duration.  Additionally, the detection method is simple and cost-effective.

Direct Chemiluminescence The main process involves labeling antigens or antibodies with markers such as acridinium esters.  During the reaction of the labeled complex, an oxidant (hydrogen peroxide) and sodium hydroxide are added to create an alkaline environment, leading to decomposition and light emission.  The advantages of direct chemiluminescence include excellent reagent stability and ease of storage.  The labeling molecules are small, causing minimal steric hindrance to the labeled antigens/antibodies.  It also features low background noise, high sensitivity, and stable results.

Electrochemiluminescence The main process involves labeling antigens or antibodies with electrochemiluminescent agents.  During the electrochemical reaction, electron transfer induces chemiluminescence.  The advantages of electrochemiluminescence include a controllable reaction system, rapid detection time, high precision, high sensitivity, and a broad detection range.

V. What Are the Precautions for Chemiluminescence Reactions?

1. Chemiluminescence detection is not a ratiometric assay, which distinguishes it from fluorescence, absorbance, or colorimetric tests.

2. If the sample is turbid, a portion of stray light may enter the detector.

3. It is important to ensure that the detector's spectral sensitivity aligns as closely as possible with the emission spectrum of the chemiluminescence to maximize sensitivity. Generally, photomultiplier tubes (PMTs) in luminometers respond best to blue light and are less sensitive to the red end of the spectrum. Solid-state detectors, however, exhibit better responsiveness to red light.

4. X-ray films are widely used to record chemiluminescent blotting analyses on nylon, cellulose, or PVDF membranes. However, X-ray films can only detect light signals within the ultraviolet-to-blue spectral range.