Nerve Growth Factor - The Liposomes Through The Blood-brain Barrier

Neurotrophic factor are secreted peptides that act as growth factors for the phenotypic development and maintenance of specific neuronal populations in developing and adult vertebrate nervous system. They promote the growth, survival, and differentiation of neurons. The NGF-superfamily, originally called the neurotrophins, includes nerve growth factor (NGF) brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), neurotrophin-4 (NT-4), neurotrophin-5 (NT-5), and neurotrophin-6 (NT-6). NGF was the first to be discovered by Levi-Montalcini et al.Nerve growth factor (NGF) belongs to the kind of classic molecular peptide which is produced by nerve and target cell managed by nerve and cell divide, growth in order to cure nerve system disease. NGF is ready to lose biological activity quickly in water solution and is sensitive to many conditions such as pH, high temperature, and so on. The use of NGF is limited, as it can't cross the BBB freely. The NGF consists of a dimmer of 13-kDa polypeptide chains, pH 9.6, isoelectric point 9.3, each of which has three intrachain disulfide bridges. But the NGF can't cross the blood brain barrier (BBB) freely, we use the liposome to pack NGF to penetrate into it.Liposome (LIPO), which can encapsulate solutes, thereby sequestering them from the surrounding medium, have the potential for site-specific drug delivery in vivo. This has stimulated interest in their use as drug carders to enhance the therapeutic indexes of various biologically active materials, including those of drugs that affect the central nervous system. Liposome can also protect the drug from enviroment to prolong its metabolism time. To enhance the ability of penetration into BBB, we have adjusted proportion between Phospholipid and Cholesterol. In addition, we add accessories of P Glycoprotein and extended circulation substance and so on to the liposome to enhance behavior penetrating the BBB.The highly purified and bioactive NGF was obtained from submandibular gland in mice. Establish the analynatic method of encapsulation efficiency (EE) through DEAE-sephadex A50 minicolumn centrifuge; Select the EE as the parameter and make the single factor experiment. With the optimal formulation, the EE of the liposome is 33.11%. Use the 0.22um micropore sterilization on account of the specific nature of the NGF. In order to enhance the NGFs stability, prepare the lyophilized liposome. Select the optimal formulation according to EE, appearance, rehydration.Discuss the physical and chemical stability of the NGF and lyophilized liposome. Under high temperature or intense light, the liposome suspension and lyophilized liposome both have feeble stability, but the lyophilized liposome is stronger than the suspension. The accelerated stability experiment indicates the shelf life of lyophilized liposome is about two years. On the basis of physical and chemical character, discuss the biological stability by means of outgrowth of chicken embryo dorsal ganglia.The safety experiments of rehydrated liposome such as vessel irritation and hemolysis, were tested for intravenous administration. It was showed that lyophilized liposome was safe formulation and nonirritant.The preliminary studies about crossing BBB were evaluated in rabbits. The NGF concentration in BBB was determined by labeling with 99mTC with EL1SA and SPECT. The preliminary studies of brain tissue distribution were determined by SPECT. ELISA was used to quantify the NGF in cerebrospinal fluid.In this study, we have examined the stability of NGF packed with liposome, confirmed its bioassay with DRG. SPECT was used to detect the distribution of NGF in Rabbit. ELISA was used to quantify the NGF in cerebrospinal fluid. Our results suggest that NGF packed with liposome can penetrate partly into the BBB and posses controlled release function. The results are exciting.