Fluorescent probe technology is a method of using the photophysical and photochemical properties of probe compounds to study the physical and chemical processes of certain systems at the molecular level and to detect the structure and physical properties of a special environmental material. This technology is not only available. It is used to study the steady-state properties of some systems, and it can also monitor the fast dynamic processes of some systems, such as the production and decay of a new species. The basic feature of this technology is that it has high sensitivity and Extremely wide dynamic time response range, with the development of science, in the process of information transmission, fluorescent molecules are subject to different environmental stimuli such as isomer interconversion, ion coordination, redox, photoelectrically controlled electron energy transfer, weak bonds, and weak bonds. Fluorescence changes occur due to the formation and breakage of fluorophores, which can realize the switching of fluorescence, which is more suitable for the identification and labeling of biological microstructures. Therefore, in recent years, fluorescent molecules have been used as probes in the fields of life science, environmental science, materials science, and information science. has been widely used.
Introduction
It is generally believed that a chemical sensor refers to a sensing device that can continuously provide its environmental chemical quantity and information, and is composed of a chemical detection layer and a physical sensing element. According to this definition, a device that can be used for one-time use or cannot be continuously sensed is called a probe (Probe). Fluorescent molecules as sensing signals have the following advantages: up to the high sensitivity of single-molecule detection, the ability to achieve switching operations, and the detection of sub-particles. It has visible sub-nanometer spatial resolution and sub-millisecond time resolution. In situ detection (fluorescence imaging technology) and long-distance detection using optical fiber, etc. Fluorescent molecules are specially designed and introduced into the system to be tested, which can convert the information of molecular recognition into fluorescent signals and transmit them to the outside world, thus making it possible to communicate between people and molecules, and building a bridge between the macro world and the micro world. Functional molecules are called fluorescent molecular probes.
Fluorophore
Fluorophore is the most basic part of fluorescent molecular probe, its function is to express molecular identification information as fluorescent signal, fluorophore in fluorescent molecular probe, by giving the enhancement and weakening of fluorescence intensity, and the shift of fluorescence peak wavelength, etc. information to reflect the role of molecular recognition in the microscopic world. However, the fluorophores currently used in fluorescent molecular probes are very limited, mainly fluorescein derivatives, polycyclic aromatic hydrocarbons, and other organic compounds and metal complexes that can emit fluorescence. They themselves or derived products have high fluorescence quantum yield, but the maximum absorption wavelength and fluorescence emission wavelength are mostly less than 600nm. Therefore, it is very important for the design of fluorescent molecular probes to find new fluorophores with high sensitivity, good selectivity, stability to light, and high quantum yield, which can be used for fluorescent molecular probes.
Recognition group
The recognition group (also called the acceptor part) in the fluorescent molecular probe is the main part that reflects the molecular recognition function of the probe, which determines the sensitivity and selectivity of the binding between the fluorescent molecular probe and the guest. The relationship between the size and the guest is the primary criterion for selective molecular recognition. In addition, the number of coordination sites contained in the recognition group and the coordination number of the guest, as well as the type of ligand, including the acidity and basicity of the ligand, also affect the selectivity. The recognition of the guest by the recognition group is not limited to Metal cations, but also anions and neutral molecules, etc., have specific requirements for the identification of different classes of chemicals. In order to achieve a high degree of specific recognition, the key to the selection and design of the recognition group is to achieve a high degree of complementarity between the recognition group and the guest, including the mutual matching of shape, size and distribution of interaction points. Therefore, designing and synthesizing a three-dimensional structural system with reasonable arrangement of action points can be considered as the highest standard in the design of fluorescent molecular probes.
Structural features
Most of the fluorescent compounds are organic aromatic compounds or their complexes with metal ions. The absorption and emission spectra of these compounds in the ultraviolet and visible regions are all caused by the electronic transitions of the compounds. It is known that in a large number of organic substances, only a small part will produce strong fluorescence, and their excitation spectrum, emission spectrum and fluorescence intensity are closely related to their structure.
Evaluation standard
Generally, four factors, such as sensitivity, selectivity, real-time and in situ detection performance, should be mainly considered when evaluating the performance of fluorescent molecular probes. There are many factors that affect the sensitivity. For example, the binding strength of the fluorescent molecular probe and the detected object is the premise of the recognition sensitivity, and the fluorescence signal conversion efficiency of the recognition information also affects the recognition sensitivity and fluorescence-enhanced probes. Fluorescence quenched probe, high sensitivity, etc. The selectivity mainly depends on the specific binding of the probe to the detected substance, and also is related to the nature of the bound object, and the specific selectivity is the best. The real-time performance mainly includes the speed of the recognition response and the reversibility. If the speed of the reversible response is faster than or matches the change speed of the detected object, it can be called a real-time response probe; the in situ detection performance mainly depends on the molecule. The compatibility of the probe and the detected system, the probe can be dispersed in the detected system in an independent molecular state and issue a recognition signal.
