Complex bioactive nanofibrous dura mater repairs traumatic brain injury

TL;DR

The paper reports a three-layer nanofibrous dura mater (MNDM) with a dual core-shell inner layer that rapidly releases minocycline hydrochloride (MH) and sustainably releases IGF-1. In vitro and rat TBI models, the MH+IGF-MNDM promoted damaged neural cell survival and neurite regeneration, modulated microglial polarization, and showed antibacterial, anti-adhesive, barrier, anti-leakage, and biocompatibility properties.

Key findings

• The MNDM was successfully fabricated with an outer PCL/HA-NDM, middle PCL-NDM, and inner MH+IGF-NDM layer; thickness was approximately 180–250 μm, fiber diameters were about 300–550 nm for PCL/HA-NDM and PCL-NDM and 450–700 nm for MH+IGF-NDM. The MH+IGF-MNDM had tensile strength 9.88 ± 0.6 MPa and maximum strain 53.99% ± 6.5%, versus 10.27 ± 0.73 MPa and 27.95% ± 3.6% for MH+IGF-NDM; normal human dura mater was reported as 7.2 ± 0.4 MPa. At 180 days degradation, MH+IGF-MNDM retained 84% ± 2% of initial mass and pH remained 7.25–7.5.
• Drug release was differential: MH cumulative release reached 51.81% ± 2.08% within 1 hour, 68.32% ± 2.4% from 1–12 hours, and 76.59% ± 0.46% by day 3. The core-layer model drug rhodamine B released over up to 42 days, increasing from 29.2% ± 6.7% to 44.91% ± 8% over days 1–5, to 63.6% ± 5.8% over days 5–14, and to 94.2% ± 2.9% over days 14–42.
• In SH-SY5Y neurite transection, oxidative stress, and OGD injury models, MH+IGF-NDM and IGF-NDM groups showed significantly longer average and longest neurites and higher cell viability than other groups, with apoptosis after OGD significantly lower in MH+IGF-NDM and IGF-NDM groups (P < 0.01). MH-NDM/MH groups showed lower iNOS and higher arginase-1 than LPS and NDM groups (P < 0.001), and MH-NDM reduced NO release (P < 0.001). In TBI rats, TNF-α and IL-1β were lower in TBI+MH+IGF-MNDM than TBI (P < 0.01) and not significantly different from sham (P > 0.05).
• MH+IGF-NDM and MH-NDM had significantly higher antibacterial rates against S. aureus and E. coli than IGF-NDM and NDM (P < 0.001). PCL/HA-NDM reduced NIH3T3 adhesion at 6 and 12 hours (P < 0.001), reduced viability over days 1–5 (P < 0.01), and lowered Ki67 expression (P < 0.05). MH+IGF-MNDM blocked fibroblast penetration and showed no rhodamine B fluorescence penetration at 5, 10, 30, or 60 minutes; >95% SH-SY5Y and NIH3T3 cells survived in biocompatibility tests, and in vivo implantation showed reduced inflammation from 3 to 7 days.

Methods

• Fabrication: three nanofibrous layers were prepared by electrospinning. The outer layer was PCL/HA, the middle layer was PCL, and the inner layer was a coaxial/emulsion electrospun MH+IGF-NDM with MH in the shell and IGF-1 in the core; scaffolds were crosslinked by glutaraldehyde fumigation.
• In vitro characterization and assays: SEM, contact angle, fluorescence microscopy, TEM, drug release, mechanical testing, and degradation were performed. Nerve injury used SH-SY5Y cells in neurite transection, OGD, and H2O2 oxidative stress models; inflammation used LPS-stimulated BV2 cells; anti-adhesion and barrier assays used NIH3T3 cells; antibacterial testing used S. aureus and E. coli; anti-leakage used rhodamine B; biocompatibility used live/dead staining and CCK-8.
• In vivo: subcutaneous implantation used six male Sprague–Dawley rats with n = 3 per group/time point at 3 and 7 days. TBI used 18 male Sprague–Dawley rats divided into sham, TBI, and TBI + MH + IGF-MNDM groups (n = 6 each), with a controlled impact injury and ELISA for TNF-α and IL-1β at postoperative day 3. Statistical analysis used independent t-tests or one-way ANOVA with Tukey’s test, P < 0.05.

Limitations

• Stated: rhodamine B was used as a model drug for the core layer, but it does not directly reflect IGF-1 release behavior; the authors plan further IGF-1 release studies.
• Stated: the study did not systematically investigate the specific signaling mechanisms, such as nuclear factor kappa-B and IGF-1/PI3K/AKT pathways, by which the MNDM regulates the inflammatory microenvironment and neuroprotection.
• Evident from the text: the in vivo TBI experiment assessed only TNF-α and IL-1β at day 3, with no long-term functional, behavioral, or histological brain-repair outcomes reported; antibacterial testing was limited to S. aureus and E. coli, and barrier/anti-leakage evaluations were largely in vitro.