6.1. Interactions with blood and proteins

The implantation of a biomaterial often creates a wound, and bleeding generally ensues. Blood thus typically makes a first contact with the implanted biomaterial. Proteins are building blocks of the supporting extracellular matrix (ECM) of many tissues.

Changes in the levels of proteins or the structure of proteins can lead to altered function and are responsible for many diseases. This paved the way for blood screening for certain proteins indicating a diseased or cancer state.

Thus, protein plays a major role in determining the final nature of the tissue–implant interface.

Biomaterials can promote cell/tissue attachment and activity by allowing selective protein absorption or can inhibit tissue interactions by repelling protein.

pH and ionic strength of the biomaterial can alter confirmation of nearby proteins and its functions.

In fact, proteins also experience the structural alterations during interaction with the solid surface of biomaterials and lose some of their activity as the functions get altered (Enderle and Bronzino 2012).

A special protein known as fibrinogen has greater affinity for the biomaterial surface.

6.2. Wound healing response after biomaterial implantation

Disruption of the anatomic continuity of the tissue occurs after implantation, which creates a wound. There are four overlapping phases of wound healing:

1. Hemostasis.
   
2. Inflammation.
   
3. Proliferation.
   
4. Remodeling (Palani et al. 2024).

Figure 6.1 represents the stages (Palani et al. 2024).

Recent advances in wound dressing and the material and skin interaction are vital for in-depth knowledge about skin–material interaction. Metal nanoparticles and biomaterials have recently started playing a pivotal role in encouraging effective wound healing and averting secondary infections or any concern regarding immunogenicity. The tiny size of the healing materials, wound dressing or even the materials inserted topographically onto skin or in vitro have a high surface area, which facilitates enhanced biological interaction. Thus, the materials need to be specifically designed with respect to topography, size, material and biocompatibility. The material used for the therapy/assessment should have an optimal cell-to-cell interaction, fostering an effective purpose (Palani et al. 2024).

Chapter 5 emphasized the type of biomaterial used in the current medical scenario. The targeted approach of this chapter is to emphasize the problems of interaction of the biomaterials commonly encountered in the medical field, especially in physiotherapy subjects. The biomaterials are specially designed to mimic the ECM and the tissue topographically and hence are biocompatible. The type of materials studied in recent evidence are nano-metallic particles and biodegradable materials. The metallic substances are generally known to have a major disadvantage; this is metallic corrosion.

6.3. Effect of tissue biomaterial interaction on physiotherapy

Tissue biomaterial interactions can significantly affect physiotherapy, influencing both the rehabilitation process and the outcomes of treatment. The way a biomaterial interacts with the surrounding tissue – whether it is bone, cartilage, muscle or skin – can determine the success of the implant and the effectiveness of physiotherapy interventions (Pramanik 2024).

1. Healing and tissue integration: if the biomaterial integrates well with the surrounding tissue, physiotherapy can proceed more smoothly, as the tissue is able to heal around the implant without complications. However, if the interaction is poor – such as in cases of inflammation, infection or insufficient cellular growth – the healing process can be delayed, and physiotherapy may need to be adjusted. Physiotherapists must be aware of these interactions to tailor exercises and techniques that support tissue healing and promote successful integration.
   
2. Impact on movement and function: the way a biomaterial affects the biomechanics of the body can influence the types of exercises and movements that are safe and beneficial during rehabilitation. For instance, an implant that does not fit properly or causes discomfort may require physiotherapists to modify rehabilitation plans, taking into account the potential for mechanical failure or incorrect loading patterns. Conversely, biomaterials designed to mimic the natural function of tissues – such as joint replacements – may facilitate more traditional therapy techniques aimed at improving strength and mobility.
   
3. Risk of complications: poor biomaterial interactions, such as stress shielding, improper alignment or rejection, can lead to complications such as pain, instability or re-injury, which would affect physiotherapy. For example, in cases where a bone implant fails to integrate properly with the bone, excessive strain could occur during rehabilitation, which could compromise both the healing process and the longevity of the implant. Physiotherapists must adjust their approaches to account for such risks, ensuring exercises are not too strenuous on areas with biomaterial implants.
   
4. Adaptation of therapy plans: the type of biomaterial used (e.g. metal, polymer and ceramic) will influence how physiotherapists approach rehabilitation. For example, a metal implant in a joint may require different mobilization techniques and loading exercises compared to a soft tissue scaffold used in cartilage repair. The physiotherapy plan needs to be dynamic and responsive to how the biomaterial interacts with the surrounding tissue during healing, requiring personalized modifications to ensure the patient’s recovery progresses effectively.
   
5. Chronic effects and long-term management: over time, the interaction between biomaterials and tissue may evolve, especially in weight-bearing joints or areas subjected to high levels of stress. Physiotherapists must be aware of the potential for long-term complications, such as wear and tear on the implant or surrounding tissue degeneration, and adjust therapy plans to maintain function and prevent future issues.

In summary, tissue biomaterial interactions play a significant role in determining how effective physiotherapy will be during rehabilitation. Physiotherapists must continuously assess and adapt their approaches based on the type of biomaterial used, the patient’s healing progress and the potential challenges presented by tissue–implant interactions.

6.4. Metallic corrosions

Several mechanisms can lead to metallic corrosion; thus, its property, which is corrosive resistance, is one of the important properties of metals used for implants. There are many types of corrosion (Manam et al. 2017):

• Galvanic (mixed metal) corrosion: this results when two dissimilar metals in electrical contact are immersed in an electrolyte. There are four important components that must exist for galvanic current to occur: an anode, a cathode, an electrolyte and an external electrical conductor. For example, a patient with two Total Hip Replacements (THRs) made of different alloys is not subject to mixed metal corrosion due to the absence of electrical connection. However, a THR made of two alloys or a fracture plate of one metal fixed with screws of another metal may be susceptible to a mixed metal corrosion (Kumar et al. 2025a).
  
• Crevice corrosion: this can occur in a confined space that is exposed to a chloride solution. The space can be a kind of gasket-type connection between a metal and a nonmetal or between two pieces of metal bolted or clamped together. This is observed in some types of implants where metals come into contact with another metal such as THR devices, screws and plates used in fracture fixation and some orthodontic appliances (Kumar et al. 2025a).