Table 3 Natural polymers and drug delivery systems for BDNF

Collagen

Collagen scaffold-BDNF complex

(1) Prepared LOCS from bovine aponeurosis; (2) Fused CBD to BDNF; (3) Linked CBD-BDNF to LOCS

CBD-BDNF can bind to collagen and concentrate at the injury site; promotes neuronal regeneration and locomotion recovery

[457]

Reduces cell loss and decreases apoptosis

[438]

Promotes axonal regeneration; Increases functional nerve growth; Enhances neuronal re-myelination

[458]

Chitosan

Chitosan scaffolds

Cross-linked BDNF to chitosan scaffolds by genipin

Maintains a 30-day-period release; Induces tissue regeneration after traumatic brain injury

[459]

Alginate

Calcium alginate hydrogel

(1) Mixed BDNF into sodium alginate; (2) Dropped CaCl₂ to form hydrogel microbeads or microspheres

Sustained release of BDNF over 48 days; Promotes axonal regeneration in vivo; Alleviates neuropathic pain

[460]

Controlled release of BDNF for more than 7 days; Improves depressive-like behavior

[461]

Cell-seeded alginate hydrogel scaffold

(1) Placed sodium alginate solution in a cylindrical aluminum mold; (2) Cross-linked with Sr²⁺ or Zn²⁺; (3) Socked BMSCs-BDNF suspensions into the hydrogel scaffolds

Releases BDNF from the scaffolds; BMSCs survive in the alginate hydrogel channels; Guides axons to orient parallel to the hydrogel channel and promoted axons growth

[462]

Agarose

Agarose scaffolds

(1) Loaded BDNF into lipid microtubules and mixed with agarose solution; (2) Prepared agarose in situ gel via cooled nitrogen gas

Encourages neurite growth into the scaffolds; Reduces inflammatory response induced by agarose; Enhances regeneration after spinal cord injury in vivo

[463, 464]

Fabricated scaffolds by freeze-dry processing

Maintains high stability and biocompatibility for at least 1 month in vivo; Supports the growth of injured axons

[465]

Cell-seeded agarose scaffolds

(1) Fabricated agarose scaffolds and PS fibers to form multi-channels; (2) Filled BMSCs into scaffolds

Secretes BDNF from the scaffolds; Supports host axon regeneration across the lesion gap

[366]