PMC

(A) Significantly more cells attach to nanoneedle-containing surfaces and (B) cell viability is unaffected. (C–D) Cell spreading (area, perimeter) are increased on nanoneedle-containing substrates.

(A–B) Flat surfaces promote the formation of large, unorganized cell aggregates. (C–D) Cells interact directly with the nanoneedles and only small cell aggregates, if any, are able to form. (E) Parallel rows of tightly spaced nanoneedles sequester cells between them. (F) Few, if any, cells are able to attach in areas of densely packed nanoneedles, but attachment improves as spacing becomes sparser. Nanoneedle locations are indicated by X’s in each image. A: calcein, green; B–C: αSMA, green; Hoechst, blue; D–F: actin, red; Hoechst, blue.

(A) A schematic of the pattern displaying the 2D gradient in nanohole spacing (nanohole density reduced for visual clarity). The pattern is a 2×2 matrix of four quadrants, each formed by increasing the spacing between successive nanoholes by 1 μm starting from 10 μm in the densest location (edge) to 50 μm in the sparsest location (middle of the quadrant) and then decreasing from 50 μm to 10 μm at 1 μm decrements in both x and y directions. A quadrant is a matrix of 84×84 nanoholes, and a 2×2 matrix of these quadrants forms the pattern with 168×168 nanoholes. Each black dot in the schematic represents a nanohole made by focusing a single laser pulse. (B) An SEM image of the nanoholes from one edge of the pattern.

(A) Schematic of the fabrication of silica nanoneedles starting from cellulose acetate (CA) replication of the laser patterned fused silica template (steps I and II). The replica with CA nanoneedles is then peeled off from the template and glued to a 170 μm glass coverslip with uncured PDMS, and cured at room temperature for 24 hours (steps III and IV). The glass coverslip with CA nanoneedles is then affixed to an aluminum SEM peg (step V) and subjected to silica deposition to form silica nanoneedles. The glass coverslip with silica nanoneedles is then detached from the SEM peg by selectively dissolving the sticky tab adhesive in toluene. (B) SEM image of silica pattern in a specific location where nanoneedles are densely spaced in one direction and sparsely spaced in the orthogonal direction. (C) SEM images of silica nanoneedles (taken at 45° stage tilt) from a section of the 2D gradient pattern at one edge illustrating the x and y increment of 1 μm every successive nanohole.