What are the most common methods for modifying biomaterial surfaces?

Plasma-surface modification is an effective and economical surface treatment technique for many materials and of growing interests in biomedical engineering. It is possible to change in continuum the chemical composition and properties such as wettability, metal adhesion, dyeability, refractive index, hardness, chemical inertness, lubricity, and biocompatibility of materials surfaces. The application of plasma-based techniques is quite diverse and can be customized.

A combination of methods, researchers have been able to achieve remarkable outcomes in biomaterial surface modification. For example, a plasma treatment can activate the surface, making it more receptive to subsequent chemical or biological modifications. This can be particularly beneficial in enhancing cell adhesion, proliferation, and overall biocompatibility. While biological methods utilize enzymes or proteins to enhance biocompatibility, physical methods employ physical forces to alter surface characteristics. Combination methods, on the other hand, involve the utilization of multiple techniques to achieve synergistic effects and optimal surface modifications.

There are several surface modification strategies widely used in the modification of biomaterials. Surface functionalization, grafting, plasma treatment, etc., are used to modify biomaterial surfaces.

We are actively engaged in pioneering research focused on the formation of nanoparticles from plant waste materials. Our findings highlight the effectiveness of employing organic acids as a means to achieve reliable, economical, and sustainable solutions for altering the surface characteristics of biomaterials. This innovative approach holds immense promise in the realm of chemical methods for biomaterial surface modification. It allows us to fine-tune surface charge, polarity, hydrophilicity, and functionality, paving the way for enhanced specificity, recognition, and delivery of biomolecules like proteins, peptides, carbohydrates, and drugs.

One great example of biological / chemical modification of material surfaces is the formation of protein corona, i.e. adsorption of a layer of protein molecules on the surface of material. This is particularly of great significance when it comes to the nano scale and nano-biomaterials, where the protein corona pretty much dictates how cells/living tissues interact with the nanomaterial (e.g., nanoparticles).

Another way to modify the surfaces of biomaterials is by drying them on patterned PDMS molds. These patterns in the PDMS can be tailored to have different hydrophobic or hydrophilic contents.

3D-printed porous PCL/β-TCP composite scaffolds are commonly used for bone tissue regeneration due to their versatility and mechanical properties. However, a recurring issue plagues these scaffolds - poor initial cell attachment. The porosities in the scaffold structure allow many cells to escape during in vitro cell seeding, limiting their effectiveness. By combining plasma treatment and collagen coating, we can achieve optimal results in enhancing cell attachment and biocompatibility. The plasma treatment activates the scaffold's surface, making it more receptive to collagen grafting, resulting in a multi-functional surface that significantly improves cell proliferation, hydrophilicity, protein absorption, and bioactivity.

While changing the surface chemistry is the most common method, biocompatibility depends strongly on surface topography. We showed in some recent work that neural probes are far more bioactive, even for the same surface chemistry, when their surfaces were roughened up. [Ding, R., Miller, N. C., Woeppel, K. M., Cui, X. T., & Jacobs, T. D. (2022). Surface area and local curvature: Why roughness improves the bioactivity of neural implants. Langmuir, 38(24), 7512-7521.]

A key challenge is the risk of infection in vivo. For example, bacterial growth on hip replacements, and these are very difficult to treat, or even to detect at an early stage when treatment could be possible.

My first priority is Chemical Methods such as self assembly, monolayer modification, grafting etc. People may have difference of opinion on biological methods. Though it is bio systems, it's the Chemical reactions that proceeds the modification. Physical methods such as plasma coupled with Chemical methods will work better on the biomaterials surfaces.

Biocompatibility is also important for materials that have applications in biotechnological field, such as biological sensors or bioseparation media used in bioprocessing purification. Biocompatibility of these tools surface is essential to reduces biofouling, a phenomenon that can impact the performance of biological surfaces or the separation performance of membranes or resins used in separating biological therapeutics. Surface modification can greatly enhance the biocompatibility by reducing irreversible adsorption of proteins, DNA, and HCP on membrane or resins, increasing the cycling span of the media, and improving overall the purification efficiency.

One of the key challenges lies in optimizing the parameters and conditions of the various methods available. It is crucial to find the right balance to ensure effective modification without causing adverse effects or complications. Another challenge is to ensure the stability and durability of the surface modification. This is particularly important in biomedical applications. Furthermore, compliance with regulatory and ethical standards is of utmost importance in the field of biomaterials. Cost and complexity reduction is also a significant challenge in surface modification. Simplifying the processes and reducing associated costs would make these methods more accessible and feasible for a wider range of applications.