Table 4 Summary of the impact of micro-patterns on peripheral nerve organization

Groove

M: PLCL-GN

P: 20 µm size and 20.96 ± 1.26 MPa tensile strength

Model: In vitro/In vivo, Period: 12 weeks, Damage length: 10 mm, Outcome: Promoted cell migration, adhesion, and elongation, and the directional growth of neurites/axons. Its induce the myelin sheath, faster nerve regeneration and a 20-fold functional recovery

[78]

M: CS-AS

P: 46/18 μm groove/ridge sizes

Model: In vitro, Period: 3 days, Outcome: Increasing axon length by 80% and neurite length by 20%, reducing axon winding and promoting directional growth of neurites/axons, and enhancing cell orientation

[79]

M: Silk fibroin

P: 10, 30, and 50 µm size

Model: In vitro, Period: 3 days, Outcome: Enhancing cell orientation and directional growth of neurites/axons within a width of 30 µm, regulating cone growth along grooves

[80]

M: PCL-PLA

P: Sharp and wide ridges with 5 µm depth and groove of 15–20 µm

Model: In vitro/In vivo, Period: 16 weeks, Damage length: 10 mm, Outcome: Enhanced adhesion in wide ridges, increased directional growth of neurites/axons and cell orientation in short ridges, increased axon numbers, and cross-sectional area of axon in wide ridges

[81]

M: CS

P: Shapes of grating and isosceles triangle with 4 µm ridges, 6 µm groove, ~ 1.6 µm depth

Model: In vitro, Period: 3 days, Outcome: Despite the equal distribution among all platforms, the grating increased the directional growth of neurites/axons and cell orientation. It also reduced actin dispersion and increased cell polarization compared to other groups. However, cells on the scalene triangle platform exhibited the most displacement

[82]

M: Gelatin-coated PLCL

P: Groove/ridge/depth: 3/3/4 µm or 10/10/4 µm

Model: In vitro, Period: 24 h, Outcome: Grooves 3/3/4 μm had a greater impact than other groups, leading to increased migration, cell orientation, directional growth of neurites/axons, vinculin expression and adhesion by enhancing β1 integrin, Rac1, RhoA, and Cdc42

[83]

M: PLLA-MTMC

P: Groove/ridge/depth: 40/20/10 µm or 20/20/10 µm

Model: In vitro, Period: 5 days, Outcome: The 40/20 µm groove enhanced adhesion by cadherin, neurocan, and vinculin, leading to increased directional growth of neurites/axons, improved cell orientation, and well-organized filopodia and lamillopodia

[84]

Channel

M: PLATMC

P: 4 channels: dimensions from 400 to 1400 nm

Model: In vitro/In vivo, Period: 12 weeks, Damage length: 10 mm, Outcome: Improved directional growth of neurites/axons, axon length, cell orientation, NCV (up to ~ 15%), and DCMAP (up to ~ 40%), coupled with enhanced cell number (~ 61%), myelin thickness (~ 50%) and vessels within the channels (~ 25%)

[85]

M: Silk fibroin

P: 5 channels: dimension ~ 570 µm

Model: In vitro/In vivo, Period: 12 weeks, Damage length: 20 mm, Outcome: By enhancing neurite/axon directional growth and improving cell orientation, the channels facilitated rapid recovery of the damaged tissue by increasing the number of nerve fibers

[86]

M: Chitosan/N-succinyl-chitosan

P: Conduit with internal fibers and holes of 66 µm

Model: In vitro/In vivo, Period: 12 weeks, Damage length: 10 mm, Outcome: Enhanced cell migration, directional neurites/axons length, myelin membrane, SFI, NCV, and gastrocnemius muscle, as well as improved cell adhesion and nerve cell viability

[87]

M: gelatin methacrylate

P: 4 channels with internal diameter of 1.2–2 mm

Model: In vitro, Period: 7 days, Outcome: Cell migration increased, especially in larger diameter, enhanced directional growth of neurites/axons, improved cell orientation, increased nerve buds, and enhanced cell junctions with each other

[88]

Pillar

M: PMMA

P: Cylindrical shape, 6.5 µm pitch, 1 µm height

Model: In vitro, Period: 7 days, Outcome: Improving cell differentiation, increasing the length of axons and directional growth of neurites and axons

[89]

M: PDMS@PEDOT:PSS

P: 2.9–3.1 µm height and distance of 15 or 30 µm

Model: In vitro, Period: 24 h, Outcome: Increased adhesion, increased directional growth of neurites/axons, increased cell differentiation and enhanced cell orientation

[90]

M: SU-8

P: 812–853 nm height, 430 nm diameter and distance of 1.2–1.22 µm

Model: In vitro, Period: 3 days, Outcome: Despite cell orientation and improved filopodia, pillars hinder the directional growth of neurites/axons, cell soma, and the differentiation of nerve cells. The combination of pillars with grooves further amplified these effects

[91]

M: Silicon

P: 5 µm height, 400 nm diameter and 0.8–5 µm distance

Model: In vitro, Period: 24 h, Outcome: Enhancing cell polarization, aligning neurites, and strengthening cell orientation to improve directional growth of neurites/axons and increase filopodia at 2 µm intervals

[92]

Pit

M: PCL, PLA, PCL-PLA

P: the surface size ranged from 0.5–30 µm² with 0.8 to 6.2 µm in diameter

Model: In vitro, Period: 6 days, Outcome: Despite the increased proliferation and differentiation of cells in the PCL and PCL + PLA groups, the directional growth of neurites/axons and the length of neurites showed greater increases in the PLA and PCL + PLA groups

[93]