58 Textile care
Adsorption processes play a signifi cant role in textile care, particularly in the context of cleaning and stain removal, the application of fabric softeners or the adsorption of specifi c functionalising materials.
Detergents and stain removers contain surfactants and other chemicals that facilitate the desorption of dirt, oils, and other stain components. The cleaning agents surround the stain particles, making them more water-soluble and allow for easier removal during the washing process. Fabric softeners use cationic surfactants that adsorb onto the fabric’s surface. These positively charged molecules reduce the friction between fi bres, making the fabric feel softer and smoother. Additionally, they can provide antistatic properties and improve the overall feel of the textile.
The adsorption of proteins onto surfaces is a dynamic and complex process infl uenced by various factors, including the physicochemical properties of the material, the nature of the proteins, and the surrounding environment. Proteins can undergo conformational changes upon adsorption, and the extent and pattern of adsorption can impact the performance and biocompatibility of the material.
In medical applications, understanding protein adsorption is crucial for the development of biomaterials, implants, and medical devices. The interaction between proteins and surfaces can infl uence cell adhesion, tissue response, and the overall biocompatibility of the material.
In the adsorption study shown in Figure 4, the process of bovine serum albumin (BSA) adsorption onto a titanium dental implant surface was evaluated. [3] Initially, the surface’s zeta potential was recorded at -80 mV. As BSA began to adsorb, there was a noticeable decrease in the net charge, leading to a shift in the zeta potential towards less negative values, reaching -52 mV after 20 min.
Figure 4.
Time-dependent assessment of the streaming potential of BSA adsorbing onto a titanium dental implant
Figure 3: Dynamic streaming potential of cotton/modacrylic fabric during adsorption of fabric softener and subsequent desorption with detergent.
In the specifi c application shown in Figure 3, the adsorption of the fabric softener and the consecutive desorption process using an anionic surfactant is investigated by measuring the change of the streaming potential over time. [2] A plug-shaped sample of a cotton-modacrylic fabric was fi rst rinsed with an aqueous buffer solution before exposure to a dilute emulsion of a fabric softener (at t = 2 min). The cationic active in this softener formulation adsorbs on the fabric surface, reverses the sign of the streaming potential and approaches adsorption equilibrium after approx. 2 min. Rinsing the softener-treated fabric with the initial buffer solution removes reversibly-bound cationic compounds, thus lowering the positive charge. The desorption of softener is enhanced by treating the fabric with an anionic surfactant. The fi nal streaming potential is negative but at a lower magnitude than the initial value for the untreated fabric. This may indicate some remaining active softener or an adsorbed layer of the anionic surfactant.
Protein adsorption
The research fi eld of protein adsorption on surfaces appears to be as popular as ever. It refers to the process by which proteins adhere to the surface of a material. This phenomenon is signifi cant in various fi elds, including biology, medicine, and materials science. When a material comes into contact with a biological fl uid, such as blood or saliva, proteins in the fl uid can bind to the material’s surface.
The compatibility of implant materials like stainless steel or titanium with the human body relies on the implant surface’s biocompatibility. The biocompatibility is infl uenced by various surface attributes. The charge on the surface governs the electrostatic attractions that are crucial for binding proteins, necessary for integrating materials like dental implants into bone, the so-called ‘osseo-integration’. Thus, a deep understanding of these surface characteristics is essential in creating and evaluating biomaterials for implants.
Conclusion
In this article, we introduce the measurement of the dynamic streaming potential. The combination with the classic streaming potential method for the zeta potential analysis and the recording of adsorption isotherms gives a better understanding of adsorption phenomena at the solid-water interface. The applications detailed in this report demonstrate that the dynamic streaming potential analysis offers valuable insights into various systems, such as those related to detergents and textiles, or hair care products. The user gains a comprehensive understanding about what happens during practical application and related interactions. This approach facilitates a comprehensive understanding of the entire system and its interplay, enabling optimisation of products within these contexts.
References
Luxbacher, T., The ZETA Guide. Principles of the streaming potential technique. Anton Paar GmbH, 2014
Luxbacher, T., et al., Proceedings of the 7th International Textile, Clothing and Design Conference, ed. Dragcevic Z., University of Zagreb, 2014 Lorenzetti, M., et al., Biomed. Mater. 10 (2015) 045012
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