The majority of medical products manufactured worldwide are made of plastic. These include in particular catheters, surgical instruments or syringes. But even beyond these disposables, polymer-based materials are a rapidly growing market in medical technology. Current research focuses on the use of alternative or new materials to prevent microbial contamination of surfaces. One potential solution is dendritic chelating polymeric structures (e.g. PEI) for immobilising metal ions (e.g. Ag, Zn, and Cu) with antimicrobial properties in the form of PEImX hybrids in polymeric materials. The aim of this project was to develop an analytical method for the reliable, quantitative determination of PEI and PEI derivatives in polymer extracts. This was to be investigated by adsorption experiments with variable experimental parameters in the presence of metal ions on a cellulosic matrix. ICP-OES was used as an analytical tool for the indirect determination of PEI content by means of metal ions. The aim was to assess process-relevant parameters such as saturation concentrations, the influence of different solvents on the adsorption capacity of PEI derivatives and to develop an analysis kit for the quantification of PEI derivatives.
The project to develop an analytical kit for the quantification of PEI derivatives by means of adsorption on cellulose fibres and subsequent complexation with copper(II) ions was successfully implemented using an alternative approach despite difficulties encountered. The main problem is the strong competitive reaction of cellulose with copper. A clear determination of the copper content before the reaction with PEI derivatives in comparison to the reduced content in the filtrate, which is mainly caused by the adsorption on the cellulose and to a lesser extent by the adsorption of PEI, can therefore not provide any conclusions on the actual content of PEI derivatives. Further problematic are the parameters that are difficult to control, such as the texture and packing density of the cellulose, which led to non-reproducible residence times in the potential experimental setup.
As an alternative approach, the quantitative precipitation of PEI derivatives from methanolic solution with copper(II) ions and downstream analysis by ICP-OES was worked out. This concept does not make any special demands on the necessary experimental setup and avoids the complicated mechanisms of adsorption and desorption. The results obtained have great potential as a simple and robust analytical kit for the quantification of alkyl-modified PEI derivatives.