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Although soft contact lenses are more widespread, rigid contact lenses have been around for decades and their materials have been greatly improved, especially in terms of oxygen permeability. Protein adsorption and wettability are, however, complex challenges still faced by both soft and rigid contact lenses (CLs). This study aims at improving these two major attributes by means of a low-pressure magnetron enhanced 15 kHz plasma polymerization process. The wide parameter range of the process allowed the tailoring of the surface properties and delivered stable, reproducible plasma coatings. The XPS, FT-IR, WCA, and QCM surface analysis methods were used to study the nanofilms. A contact angle of down to 18° and a protein (lysozyme) adsorption of only 0.2 µg cm−2 were achieved. Some correlations with the more commonly used 'PEO-like' coatings helped to explain the measurement results. [ABSTRACT FROM AUTHOR]

This work deals with the water uptake and swelling behavior of magnetron-enhanced plasma-polymerized nanofilms in an aqueous medium. Those coatings are used in biomedical applications such as implants or contact lenses. The role of water in biomaterial surface science is considered to be of great importance. Water is not only the major molecule in most living organisms (70%) and the carrier of cells but it is also the medium in which biochemical processes take place. Because of its small size and mobility, water is the first molecule to come in contact with a biomaterial in any clinical application. It is believed, that the degree of polymer swelling strongly affects the interaction of proteins with the surface of the polymer, which determines its biocompatibility. Polymers with a high swelling degree show weak enthalpic interactions with proteins, resulting in a protein-repellency. A new approach is applied, which combines three characterization techniques: dynamic contact angle measurements, optical waveguide spectroscopy, and electrochemical impedance spectroscopy. A relation between the composition of the films and the water and salt transport phenomena through the nanofilm was observed. A higher amount of oxygen in the precursor gas ratio in the polymerization process leads to a higher wettability as well as a higher water and salt intrusion. Based on this observation an electrical model was introduced and helped to interpret the experimental results. [ABSTRACT FROM AUTHOR]

Summary Nitrogen starvation and blue light are the two environmental cues that control sexual differentiation in Chlamydomonas reinhardtii . Insertional mutagenesis was applied to generate mutants that still require nitrogen starvation as the initiating signal for gametogenesis but were no longer dependent on irradiation. In one mutant analysed, sequences adjacent to the site of insertion were cloned and used for the isolation of a genomic clone that, upon transformation, could complement the mutant phenotype. The gene identified (LRG6 ) encodes two mRNAs that appear to be the products of differential splicing. The two putative gene products derived from these mRNAs differ in their C-terminal ends. Both predicted gene products exhibit multiple hydrophobic domains with α-helical secondary structure typical for integral membrane proteins. These proteins may form pores, and may function as transporters of as-yet unknown substrates. Since rendering the LRG6 gene non-functional resulted in light-independence of gamete formation, it is suggested that this transporter may inhibit signal flux from the photoreceptor to target genes – either directly by its activity or indirectly by serving as a scaffold for signalling proteins. Shutting off this transporter may be required for the activation of signal flux in this pathway. This concept is supported by the observed reduction in LRG6 mRNA levels during the first phase of gametic differentiation. [ABSTRACT FROM AUTHOR]