Within biomaterials research and development, hydroxyapatite (HA) is well known for its biocompatible properties, particularly in bone bonding, and for its potency of rapid integration into the human body. Orthopaedic and dental devices are often coated with HA to facilitate integration and acceptance by human tissue.
To help out in the seek for better understanding of protein adsorption and behavior in human tissue/implant applications, Q-Sense has developed ready-to-use sensors coated with a thin, stable, and uniform crystalline Hydroxyapatite film. The coating has also drawn attention from toothpaste manufacturers.
An interesting example of studies on protein behavior onto HA using QCM-D, is the work carried out by a group of researchers in Japan and Sweden. They found that using QCM-D with a HA coated sensor was particularly useful for analysis of liquid phase changes of proteins on the surface. Liquid phase protein adsorption behavior affect biocompatibility of biomaterials and medical devices, and is therefore of biological, medical and industrial Importance. In all, six different proteins (HSA, Catalase, IgG, Hemoglobin, Lysozyme and Cytochrome c) were investigated and the results of this work has been published in the paper "Protein Adsorption on Hydroxyapatite Nano-crystals with Quartz Crystal Microbalance Technique" (Key Engineering Materials, Vols 361-363 (2008) pp 1119-1122).
The proteins exhibited very different behavior patterns in relation to adsorption. The acidic proteins (HAS and Catalase) adsorbed as a monolayer, where the internal structure remained unchanged. This is seen as a straight line in the Q-Sense-unique ΔD/Δf plots. For the neutral and basic proteins, notably Hemoglobin, the same plot clearly showed two distinct adsorption phases. This is because the neutral and basic proteins could cause conformational changes with the adsorbed amount of proteins. Different regions identified in the ΔD/Δf plot reflect different rigidity of the protein film during adsorption, usually caused by changes in water content and/or structural properties.
The researchers concluded that the QCM-D technique plays an important role in understanding the interaction between proteins and the HA surface.
Q-Sense HA Sensors
The development of a standard ready-to-use HA sensor has a major step forward for Q-Sense and its customers, particularly in the orthopaedics, dental and pharmaceutical industries. Q-Sense worked with Promimic, a leading company in the development of HA coatings. The coating technique avoids the use of conventional high temperature processes yet create HA sensors that have a uniform and stable coating. As well as these attributes, the sensor package saves customers time and effort.
The HA sensor is one of a range of sensor substrates coated with realistic surface chemistry including titanium, stainless steel, polystyrene and PMMA. Apart from these standard coatings, Q-Sense is able to provide some 40 different sensor coatings and encourage customers to inquire for their own coating needs. Custom-made sensors coatings are possible as long as they can be applied as thin homogenous films.
Q-Sense has a large knowledge of making modified surfaces user specific materials such as different polymers. Many of our biomaterial users also make their own specific coatings, such as functionalized peptide/protein, polymers or hydrogel coatings. Q-Sense can advise users on specific coating procedures.
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