Characterization and application of a surface modification designed for QCM-D studies of biotinylated biomolecules

The rapid development of surface sensitive biosensor technologies, especially towards nanoscale devices, requires increasing control of surface chemistry to provide reliable and reproducible results, but also to take full advantage of the sensing opportunities. Here, we present a surface modification strategy to allow biotinylated biomolecules to be immobilized to gold coated sensor crystals for quartz crystal microbalance with dissipation monitoring (QCM-D) sensing. The unique feature of QCM-D is its sensitivity to nanomechanical (viscoelastic) properties at the sensing interface. The surface modification was based on mixed monolayers of oligo(ethylene glycol) (OEG) disulfides, with terminal -OH or biotin groups, on gold. Mixtures containing 1% of the biotin disulfide were concluded to be the most appropriate based on the performance when streptavidin was immobilized to biotinylated sensors and the subsequent biotinylated bovine serum albumin (BSA) interaction was studied. The OEG background kept the unspecific protein binding to a minimum, even when subjected to serum solutions with a high protein concentration. Based on characterization by contact angle goniometry, ellipsometry, and infrared spectroscopy, the monolayers were shown to be well-ordered, with the OEG chains predominantly adopting a helical conformation but also partly an amorphous structure. Storage stability was concluded to depend mainly on light exposure while almost all streptavidin binding activity was retained when storing the sensors cold and dark for 8 weeks. The surface modification was also tested for repeated antibody-antigen interactions between BSA and anti-BSA (immobilized to biotinylated protein A) in QCM-D measurements lasting for >10 h with intermediate basic regeneration. This proved an excellent stability of the coating and good reproducibility was obtained for 5 interaction cycles. With this kind of generic surface modification QCM-D can be used in a variety of biosensing applications to provide not only mass but also relevant information of the structural properties of adlayers

Thermal characterization of self-assembled monolayers of dialkyl disulfides containing the urea moiety

Thermal behaviors of urea-containing dialkyl disulfides 4-(3-octadecylureido)phenyl disulfide (ODPD) and 3-(octadecylureido)ethane disulfide (ODED) and octadecyl disulfide (ODDS) self-assembled monolayers (SAMs) were investigated by infrared reflection−absorption spectroscopy (IRRAS). Among the SAMs, the alkyl chain of ODPD is thermally reversible in the temperature region between 30 and 138 ??C, whereas alkyl chains of ODED and ODDS are irreversible. With regard to the thermal stability of alkyl chains, ODED is superior to ODPD and ODDS. It is considered that the good thermal reversibility of the ODPD SAM is due to the rigid phenyl ring and the good thermal stability of the ODED SAM is due to the flexible ethylene linker. Moreover, 2D correlation analysis provides an enhancement of spectral resolution in amide II and CH2 antisymmetric stretching bands and suggests from the comparison of sequences of spectral events of ODPD and ODED SAMs that the last reorientation of the phenyl ring in the ODPD SAM is responsible for the good thermal reversibility.close2

Protein adsorption to oligo (Ethylene Glycol) self assembled monolayers with amide linkage experiments with fibrinogen, heparinised plasma and serum

Low protein adsorption is believed advantageous for blood-contacting materials and ethylene glycols (EG)-based polymeric compounds are often attached to surfaces for this purpose. In the present study, the adsorption of brinogen, serum, and plasma were studied by ellipsometry on a series of well-de ned oligo(EG) terminated alkane-thiols self-assembled on gold. The layers were prepared with compounds of the general structure HS-(CH2)15-CONH-EGn, where n D 2, 4, and 6. Methoxy-terminated tri(EG) undecanethiol and hydroxyl-terminated hexadecanethiol self-assembled monolayers (SAMs) were used as references. The results clearly demonstrate that the adsorption depends on the experimental conditions with small amounts of brinogen adsorbing from a single protein solution, but larger amounts of proteins from serum and plasma. The adsorption of brinogen and blood plasma decreased with an increasing number of EG repeats and was temperature-dependent. Signi cantly less serum adsorbed to methoxy tri(EG) than to hexa(EG) and more proteins remained on the latter surface after incubation in a sodiumdodecyl sulfate (SDS) solution, indicating a looser protein binding to the methoxy-terminated surface. All surfaces adsorbed complement factor 3 (C3) from serum and plasma, although no surfacemediated complement activationwas observed. The present study points to the importance of a careful choice of the proteinmodel system before general statements regardingthe protein repellantproperties of potential surfaces can be made

Extracellular matrix mimetics by crosslinked peptide hydrogels: application to neural 3D cell cultures

Self-supporting, shapeable hydrogels that consist of self-assembling synthetic peptides mimic the structural blocks of the extracellular matrix (ECM). Although they have been developed for regenerative medicine purposes, with a potential of grafting into patients without transplantation from organ donors, this class of materials are attractive as scaffolds for advanced cell culture/ in vitro tissue applications. In the present study, we have combined a series of peptides with functional motives (collagen, fibronectin, and laminin-like) for promoting granule layer-like organization of primary cerebellar cells and for controlling the cell attachment, neuritogenesis, cluster size and organization. We show that the micro/nanofabricated hydrogel scaffolds are applicable as multiwell plate inserts helping to analyse cell migration, differentiation, proliferation, adhesion, ultimately forming organotypic cell culture and artificial tissue structures

Extracellular matrix mimetics by crosslinked peptide hydrogels: application to neural 3D cell cultures

Self-supporting, shapeable hydrogels that consist of self-assembling synthetic peptides mimic the structural blocks of the extracellular matrix (ECM). Although they have been developed for regenerative medicine purposes, with a potential of grafting into patients without transplantation from organ donors, this class of materials are attractive as scaffolds for advanced cell culture/ in vitro tissue applications. In the present study, we have combined a series of peptides with functional motives (collagen, fibronectin, and laminin-like) for promoting granule layer-like organization of primary cerebellar cells and for controlling the cell attachment, neuritogenesis, cluster size and organization. We show that the micro/nanofabricated hydrogel scaffolds are applicable as multiwell plate inserts helping to analyse cell migration, differentiation, proliferation, adhesion, ultimately forming organotypic cell culture and artificial tissue structures

Extracellular matrix mimetics by crosslinked peptide hydrogels: application to neural 3D cell cultures

Self-supporting, shapeable hydrogels that consist of self-assembling synthetic peptides mimic the structural blocks of the extracellular matrix (ECM). Although they have been developed for regenerative medicine purposes, with a potential of grafting into patients without transplantation from organ donors, this class of materials are attractive as scaffolds for advanced cell culture/ in vitro tissue applications. In the present study, we have combined a series of peptides with functional motives (collagen, fibronectin, and laminin-like) for promoting granule layer-like organization of primary cerebellar cells and for controlling the cell attachment, neuritogenesis, cluster size and organization. We show that the micro/nanofabricated hydrogel scaffolds are applicable as multiwell plate inserts helping to analyse cell migration, differentiation, proliferation, adhesion, ultimately forming organotypic cell culture and artificial tissue structures