Degradation of the electrospun silica nanofiber in a biological medium for primary hippocampal neuron – effect of surface modification

Abstract

In this work, silica nanofibers (SNFs) were prepared by an electrospinning method and modified with poly-d-lysine (PDL) or (3-aminopropyl) trimethoxysilane (APTS) making biocompatible and degradable substrates for neuronal growth. The as-prepared SNF, modified SNF-PDL, and SNF-APTS were evaluated using scanning electron microscopy, nitrogen adsorption/desorption isotherms, contact angle measurements, and inductively coupled plasma atomic emission spectroscopy. Herein, the scanning electron microscopic images revealed that dissolution occurred in a corrosion-like manner by enlarging porous structures, which led to loss of structural integrity. In addition, covalently modified SNF-APTS with more hydrophobic surfaces and smaller surface areas resulted in significantly slower dissolution compared to SNF and physically modified SNF-PDL, revealing that different surface modifications can be used to tune the dissolution rate. Growth of primary hippocampal neuron on all substrates led to a slower dissolution rate. The three-dimensional SNF with larger surface area and higher surface density of the amino group promoted better cell attachment and resulted in an increased neurite density. This is the first known work addressing the degradability of SNF substrate in physiological conditions with neuron growth in vitro, suggesting a strong potential for the applications of the material in controlled drug release.

Keywords:

• silica nanofibers
• electrospinning
• dissolution
• neurite density
• surface modification

Supplementary materials

Figure S1 Representative scanning electron micrographs of SNF-PDL on Day 15.

Abbreviation: SNF-PDL, poly-d-lysine-treated silica nanofiber.

Figure S2 Confocal microscopic images of E18 primary hippocampal neurons grown on SNF-PDL.

Notes: Cells were fixed and counter stained for nucleus (DAPI, blue) (A) and immunocytochemistry against neuronal marker (MAP2, red) (B). Merged images of the two stains are shown in panel (C). Scale bars represent 50 μm.

Abbreviations: E18, embryonic day 18; SNF-PDL, poly-d-lysine-treated silica nanofiber.

Acknowledgments

The support of this research by the Branfman Family Foundation and the Sunquist Fund is gratefully acknowledged. We warmly thank URGO at Augsburg College and Quasi Endowment Fund from Concordia University, St Paul for the support provided. This work was also supported in part by the National Science Foundation through the University of Minnesota MRSEC under Award Number DMR-0819885. We also gratefully acknowledge Ministry of Science and Technology, Taiwan, Republic of China (102-2632-M-033-001-MY3), and Chung Yuan Christian University, Taiwan, Republic of China. We thank Brian Barber at the Research Analytical Laboratory, University of Minnesota, for assistance with ICP-AES analysis.

Disclosure

The authors report no conflicts of interest in this work.