Biomaterial-Tissue Interaction Overview

Study Notes

Initial biological reaction involves protein adsorption on biomaterial surfaces occurring within seconds.
This reaction determines the biocompatibility journey of the biomaterial.
Protein bonding can be classified as reversible (low affinity) or irreversible (high affinity) and may happen via unspecific or specific interactions.
Usually, proteins adsorb in an unspecific manner with high affinity, leading to loss of their native structure and functionality.

Once proteins are adsorbed, cell populations such as macrophages, granulocytes, immunocytes, and fibroblasts adhere to the surface via integrins that recognize adsorbed proteins.
Conformational changes in adsorbed proteins may serve as cues for cell behavior, while some fragments can be released dynamically.
An adsorptive protein layer can potentially trigger inflammatory responses if it acts unspecifically.

Proteins that are released can attract tissue cell precursors by releasing morphogenetic proteins and growth factors.
Successful integration of an implant relies on biocompatibility facilitating cellular adhesion to the surface.

Biofunctionalization of biomaterials aims to enhance cell growth and differentiation, speeding up wound healing and promoting permanent integration.
Possible strategies include coating implants with bioactive materials or directly attaching signaling molecules.

Implants can be coated with a bioactive film to enhance properties, requiring careful control of thickness (ideally a few angstroms to tens of nanometers).
Stability is crucial; coatings must resist delamination and microcracking under challenging conditions.

Bioceramics are categorized into bioinert (e.g., Al2O3, TiO2), bioactive (e.g., bioactive glasses), and resorbable (e.g., tricalcium phosphate).
Bioactive materials prompt a specific response, forming interfacial bonds with living tissues.

Hydroxy-carbonate-apatite (HCA) forms on the surface of bioactive materials by migrating calcium and phosphate ions through silicon dioxide layers.

The interface stiffness varies, and surface structuring can improve bonding to bone through the effect of surface roughness.

Bioglass surfaces can undergo silanization and glutaraldehyde treatment for protein coupling, facilitating controlled release of growth factors.

Non-covalent (physical) modifications involve techniques like physisorption and layering organic films.
Covalent modifications can be achieved through grafting, photoreactions, plasma treatments, and silanization to enhance protein attachment.

Hydrophilic areas on surfaces generally favor protein and cell attachment, while extremely hydrophobic or overly soft surfaces may be unattractive.
Surface charge influences how effectively proteins and cells adhere to biomaterials.

Potential immobilization strategies include integrating biologically active proteins within polymer matrices, allowing for higher loading compared to physical adsorption.
Techniques for surface treatment can include deposition of hydroxyapatite on collagen networks for enhanced biocompatibility.