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Not only bacteria but also fungal pathogens, particularly Candida species, can lead to biofilm infections on biomedical devices. By covalent grafting of the antifungal drug caspofungin, which targets the fungal cell wall, onto solid biomaterials, a surface layer can be created that might be able to provide long-term protection against fungal biofilm formation. Plasma polymerization of propionaldehyde (propanal) was used to deposit a thin (∼20 nm) interfacial bonding layer bearing aldehyde surface groups that can react with amine groups of caspofungin to form covalent interfacial bonds for immobilization. Surface analyses by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry confirmed the intended grafting and uniformity of the coatings, and durability upon extended washing. Testing for fungal cell attachment and ensuing biofilm formation showed that caspofungin retained activity when covalently bound onto surfaces, disrupting colonizing Candida cells. Mammalian cytotoxicity studies using human primary fibroblasts indicated that the caspofungin-grafted surfaces were selective in eliminating fungal cells while allowing attachment and spreading of mammalian cells. These in vitro data suggest promise for use as antifungal coatings, for example, on catheters, and the use of a plasma polymer interlayer enables facile transfer of the coating method onto a wide variety of biomaterials and biomedical devices.

Stimuli-responsive materials show considerable promise for applications that require control over biomolecule interactions at solid material interfaces. Graft coatings of poly(N-isopropylacrylamide) (pNIPAM) are of interest for biomedical and biotechnological applications due to their temperature-dependent switching of surface properties between adhesive and nonadhesive states for cells and proteins. The characterization of protein adsorption to these switchable coatings is a formidable task since switching not only influences the affinity for proteins but at the same time induces a significant change in the coating. Here, the highly sensitive analytical technique of time-of-flight-secondary ion mass spectrometry (TOF-SIMS) combined with principal component analysis (PCA) was used for the characterization of protein adsorption onto pNIPAM coatings prepared by free radical polymerization onto surface-bound polymerizable groups. Adsorption of bovine serum albumin and lysozyme onto pNIPAM coatings from phosphate buffered solutions was investigated at temperatures above and below the polymer's lower critical solution temperature (LCST). Below the LCST, no adsorbed proteins could be detected even with this ultrasensitive method. Whereas above the LCST, adsorbed protein was detected in amounts corresponding at less than the monolayer. PCA loadings plots showed that adventitious contaminants, which might lead to confounding or misleading spectral changes upon protein exposure, were not observed.

A block copolymer consisting of a phosphate-containing moiety (poly[2-(methacryloyloxy)ethyl phosphate], PMOEP) and a keto-containing moiety (poly[2-(acetoacetoxy)ethyl methacrylate], PAAEMA) showed good stability after attachment to an APS amine-modified glass slide, as did both of the respective homopolymers. The PAAEMA homopolymer can attach to the APS amine groups via covalent linkages, while the PMOEP homopolymer most likely attaches through electrostatic interactions involving deprotonated phosphate and protonated amine groups. To elucidate the conformation of the block copolymer after attachment, particularly with respect to the PMOEP segment orientation, principal component analysis (PCA) of time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra of the surface-attached polymer layers was performed. Comparison with the pure homopolymer spectra and interpretation after PCA indicate that the adsorbed conformation is not random. Rather, the copolymer is adsorbed in a conformation that preferentially exposes the PMOEP block toward the outer surface. We thus conclude that the most likely conformation of PMOEP-b-PAAEMA immobilized onto the APS-modified glass slide is via covalent interfacial linkages involving the PAAEMA block with the result that the surface is enriched in PMOEP tails. This in turn implies that under the conditions applied (dry DMF) the covalent coupling of keto groups to the amine groups of the aminated slide is more efficient than the proton transfer required for the generation of electrostatic attractions. This (partially) preferential orientation of the PMOEP-b-PAAEMA copolymer could have significant implications on interfacial interactions such as those involved in nucleation and the subsequent mineralization sequence of events in hydroxyapatite formation. The present study demonstrates that ToF-SIMS is a powerful tool not only for the investigation of the surface composition of adsorbed layers, but also for probing the molecular conformation of such adsorbed block copolymers, though care is required in the PCA analysis of multiple spectra.

Plasma polymers from glycidol vapors are of interest for direct covalent grafting of molecules bearing amine or thiol groups. The question of whether pulsed plasma operation might lead to a higher surface density of epoxide groups and a higher density of grafted molecules is studied using the antifungal drug caspofungin. X‐ray photoelectron spectroscopy and Time of flight‐secondary ions mass spectrometry analysis followed by caspofungin grafting revealed that both continuous wave and pulsed plasmas led to surface epoxides but with higher densities upon pulsing. Investigations into stability suggested that glycidol plasma polymer coatings were still able to immobilize caspofungin after 2 years of storage, making them suitable for applications where grafting of molecules needs to be done immediately before usage of a device. [ABSTRACT FROM AUTHOR]

To combat infections on biomedical devices, antimicrobial coatings have attracted considerable attention, including coatings comprising naturally occurring antimicrobial peptides (AMPs). In this study the aim was to explore performance upon extended challenge by bacteria growing in media above samples. The AMPs LL37, Magainin 2, and Parasin 1 were selected on the basis of well-known membrane disruption activity in solution and were covalently grafted onto a plasma polymer platform, which enables application of this multilayer coating strategy to a wide range of biomaterials. Detailed surface analyses were performed to verify the intended outcomes of the coating sequence. Samples were challenged by incubation in bacterial growth media for 5 and 20 h. Compared with the control plasma polymer surface, all three grafted AMP coatings showed considerable reductions in bacterial colonization even at the high bacterial challenge of initial seeding at 1 × 107 CFU, but there were increasing numbers of dead bacteria attached to the surface. All three grafted AMP coatings were found to be non-toxic to primary fibroblasts. These coatings thus could be useful to produce antibacterial surface coatings for biomaterials, though possible consequences arising from the presence of dead bacteria need to be studied further, and compared to non-fouling coatings that avoid attachment of dead bacteria. [ABSTRACT FROM AUTHOR]

A study of polyaniline (PANI), poly-o-toluidine (POT) and poly-o-anisidine (POA) cobalt supported catalysts has been presented. The catalysts were prepared by depositing cobalt species onto the polymers surfaces. Cobalt(II) acetate and N,N′-ethylene-bis(salicylideneimine) cobalt(II) (Co(II)Salen) were used in the syntheses. The catalysts performance was examined in epoxidation of trans-stilbene by molecular oxygen and they turned out to be very efficient under mild conditions. The relationship between the surface exposure of cobalt species and the activity of these polymeric catalysts has been established. [Copyright &y& Elsevier]