Improving Biocompatibility with Parylene

As a biomaterial, Parylene offers numerous possibilities in the fields of biomedical implants, biophysical studies, biosensors and tissue engineering. For instance, biological microelectromechanical systems (BioMEMS) offer accurate, rapid medical diagnoses, copying standard laboratory services onto miniaturized devices that can be inserted safely into the human body.

A problem limiting greater effective miniaturization has been finding reliable coating materials that sustain biocompatibility, while providing coating thicknesses suitably thin and strong to maintain ongoing functioning. Parylene provides biocompatible conformal coatings for these purposes that are pinhole free, chemically inert, with low cytotoxicity and resistance to swelling in liquid environments. It has proven useful for such practical BioMEMS’ devices as bacterial and viral diagnostic platforms, low-volume blood analysis cartridge systems and home pregnancy tests. In addition, Parylene’s elastomeric properties sustain long-term implant usage within the body. A coating thickness of 5 µm to 8 µm has been demonstrated to generate sufficient protection from corrosive elements and debris.

The Possibilities of High Aspect Ratio Microstructures (HARMS) and Surface Modification/Functionalization (SM/F).

Persistent demand for greater functionality and improved performance include calls for faster delivery of treatment and enhanced diagnostic accuracy. In this respect, these developing technologies show considerable promise:

• High Aspect Ratio Microstructures (HARMS) generates a larger range of performance functionalities, more efficiently and with higher throughput.
• Surface Modification/Functionalization (SM/F) processes have been helpful for spinal interbody implants; applied in conjunction with HARMS, they functionalize implants, customizing its operational parameters to prevent or promote the adhesion of cells and proteins, as required by the treatment.

Moreover, if the objective of developing these technologies is to further reduce the sizes of BioMEMS devices, Parylene provides the best available conformal coating. It generates exceptionally durable, yet ultra-thin, biocompatible, pinhole-free coatings, uniformly deposited on HARMS; highly resistant to surface corrosion, Parylene prevents bodily fluids or substances from penetrating the medical device, allowing it to function as designed. Parylene’s other advantageous properties — chemical inertness, high dielectric strength, lightweightness and visible transparency further benefit BioMEMS applications.

In addition, Parylene coatings offer pinhole free conformal protection for microfluidic structures with film-thicknesses less than 1 µm and aspect ratios exceeding 10. Parylene C is particularly useful for promoting minimal cell adhesion. The additional benefit of non-cytotoxicity is apparent for MEMS’ devices used in cell applications; Parylene films diminish blockages within microfluidic channels by limiting the incidence of cell agglomeration around devices. Then too, surface modification (SM/F) using O₂ plasma promotes HeLa cell adhesion by at least twofold, suggesting local activation in reaction chambers increases cell-capture, further demonstrating the extent of Parylene’s biocompatible properties.

For instance, SM/F procedures support precise management of cell behavior and bio-molecular spatial location. Parylene’s versatile, bio-compatible and pinhole-free conformal coatings are useful to instruments studying and mapping multi-component combinations of molecules and receptor-ligand interactions occurring in the body. Parylene allows biocompatible surface modification of virtually any implant material. Micropatterning with Parylene “peel-off” stencils offers the advantages of patterning biomolecules in hydrated environments, with high uniformity over a large area, and a minimal sub-100 nm nanoscale resolution. This approach is particularly useful for patterning chemically and biologically sensitive molecules and helping to preserve their conformation and bioactivity.

Conclusion

Parylene polymers provide conformal, protective coatings for advanced medical technologies. Due to such properties as exceptional biocompatibility, hydrophobicity, reliable mechanical performance, and functional stability in bodily fluids. To this end, Parylene demonstrates adequate elastomeric properties, essential to sustaining strains during surgical implantation and long-term usage in the body. Its vapor deposition process promotes application of a reliably conformal and durable film on complex implant shapes, through a wide range of substrate/product materials, including ceramic, composite and metallic substance. In particular, Parylene C has demonstrated considerable versatility for biomedical applications, although Parylene N has also been successfully adapted for numerous uses. Parylene’s biocompatible films homogeneously coat BioMEMS structures designed to stimulate and monitor critical bodily functions, without interfering with the actual processes themselves, generating exceptionally dependable process compatibility.