Template-synthesized gold microneedle arrays for gene delivery to the Chlamydomonas reinhardtii chloroplast

Template‐Synthesized Vertical Needle Array as Injection Platform for Microalgae

“…Track‐etched Poly(ethylene terephthalate) (PET) membranes were used to prepare the NNAs for C. reinhardtii injection because the etching processes for modifying the dimensions and geometry of the template pores are already well established: cylindrical or conical pores are achieved by changing the voltage and the solvent applied during etching; the length and the diameter of the pores can be tuned by controlling the template thickness, the etching temperature, and the etching time; and the density of the needles can be varied from one to 10 9 needles/cm 2 by changing the initial density of the damage tracks . For microalgal injection, the shape, dimensions, and density of the template pores must be carefully selected to enable the resulting needles to penetrate through the cell‐wall/cell‐membrane dual barrier without breaking or bending, while also minimizing cell death.…”

“…Template synthesis is an alternative route that enables fabrication of metallic NNAs: in our studies, electroless deposition of Au was used to prepare the solid NNA . Au was a natural choice considering its non‐toxicity to cells and its established procedure in template synthesis using track‐etched polymer membranes .…”

“…Solid Au NNAs are exposed by removing the PET template membrane through chemical dissolution using organic solvents ( e. g . hexafluoroisopropanol) (Figure a) or through reactive ion etching (RIE) (Figure b) . The chemical dissolution approach is simple but leaves organic residues on the surface which can inhibit successive attachment of biomolecules.…”

“… Solid Au NNAs prepared using electroless deposition. SEM images (top) and schematic illustrations (bottom) of (a) completely exposed Au NNA by chemical dissolution, and (b) partially exposed Au NNA by RIE using the method described in reference [20]. Adapted with permission from reference [20].…”

“…Cell deposition with centrifuge was accomplished using ProPlate™ slide modules . Briefly, the NNA platform was attached to a microscope slide and inserted into the module to form a ∼350 μL well around the NNA.…”