Nerve Growth Factor (NGF) is a pivotal member of the neurotrophin family, first identified for its role in regulating the survival, differentiation, and maintenance of peripheral and central neurons. Encoded by the NGF gene, it is synthesized as a precursor (proNGF) and processed into mature NGF. NGF exerts biological effects by binding to two distinct receptors: high-affinity TrkA (tyrosine kinase A) and low-affinity p75NTR. Binding to TrkA activates downstream signaling cascades that promote neuronal growth and survival, while p75NTR modulates diverse cellular responses including apoptosis. Beyond neurobiology, NGF is involved in immune function, inflammation, and tissue repair. Abnormal NGF expression is linked to neurodegenerative diseases, chronic pain, and cancer, making it a key target for therapeutic development in neurological and inflammatory disorders.To detect the activity of recombinant NGF , a functional ELISA assay was performed to evaluate the interaction between recombinant horse NGF and rat human GDNF.Briefly, GDNF was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to NGF-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-GDNF pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody for 1h at 37℃, wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 µL stop solution to the wells and read at 450/630nm immediately.Measured by its binding ability in a functional ELISA. When Recombinant NGF is lmmobilized at 2 µg/mL(100 uLwell), the concentration of GDNF that produces 50% optimal bindingresponse is found to be approximately 0.69949µg/mL.