Table 2.
Synthetic polymers for BDNF modification or BDNF delivery system
| Polymer | Formulation or modification | Preparation | Results | References |
|---|---|---|---|---|
| PEG | BDNF-PEG2000, BDNF-PEG5000 | Coupled PEG to BDNF carboxyls using carbodiimide | PEG conjugation at the C-terminus of BDNF retains the biologic activity and reduces systemic clearance in vivo | [451] |
| BDNF-PEG mixtures | Covalently attached BDNF to PEG | Mixtures with one and two conjugate products maintain high bioactivity in vitro; improve half-life of BDNF in CSF; enhance the penetration into spinal cord tissue | [452] | |
| BDNF-PEG2000-biotin/SA-OX26 (BDNF chimeric peptide) | (1) Attached a hydrazide to one end of PGE and a biotin moiety to the other end; (2) Prepared OX26/SA by thiol-ether linkage; (3) Coupled PEG to BDNF via hydrazide linkers; (4) Conjugated BDNF-PEG-biotin to OX26/SA | The bioactivity of the BDNF chimeric peptide is identical to native BDNF; transported through BBB after intravenous administration; minimizes rapid clearance of BDNF; increases brain uptake of BDNF to about twofold | [453, 454] | |
| BDNF-PEG2000 | BDNF in pH 8.0 borate buffer was reacted with PEG | Enhances the diffusion of BDNF into brain tissues | [427] | |
| BDNF-PEG | N-terminal pegylated form of BDNF | Improves the penetration of BDNF into the spinal cord | [428] | |
| PLGA | BDNF-immobilized PLGA membrane | Incorporated BDNF onto the surfaces of PLGA membrane by heparin immobilization |
Controlled release of BDNF for 4 weeks; protects against cavernous nerve; improves angiogenesis in the corpus cavernosum |
[455] |
| PLA | BDNF/PLA macroporous tubular scaffolds (foams) | (1) Dissolved BDNF in BSA solution and then lyophilized to powder; (2) Dispersed BDNF/BSA powder into PLA/DMC solution | PLA tubular macroporous scaffolds with BDNF enhance cell survival and angiogenesis | [456] |
| Composite materials | PLGA-PLL-PEG microspheres | (1) Conjugated PLGA-PLL-PEG polymer; (2) Dissolved BDNF/BSA into polymer/DCM solution; (3) Fabricated microspheres by double emulsion technique | Yields greater loading and longer-term delivery of BDNF for more than 60 days; maintains the bioactivity of BDNF | [436] |
| PLGA microparticles/ PEG hydrogel | (1) Prepared BDNF-loaded PLGA microparticles via water/oil/water emulsion technique; (2) Polymerized PLGA microparticles and PEG hydrogel by UV exposure | Sustained release of BDNF over a period of 56 days; alleviates the reactive glial response; increases the recruitment of astrocytes | [434] |
BDNF brain-derived neurotrophic factor, CSF cerebrospinal fluid, BBB brain–blood barrier, HA hyaluronic acid, PEG polyethylene glycol, PLL poly-l-lysine, PLGA poly (lac-co-glycolic acid), SA streptavidin, ADSCs adipose-derived stem cells, PLA poly(d,l-lactic acid), DMC dimethylcarbonate, BSA bovine serum albumin