Selective attachment of F-actin with controlled length for developing an intelligent nanodevice

Biotinylated Photopolymers for 3D-Printed Unibody Lab-on-a-Chip Optical Platforms

The present work reports the first demonstration of straightforward fabrication of monolithic unibody lab-on-a-chip (ULOCs) integrating bioactive micrometric 3D scaffolds by means of multimaterial stereolithography (SL). To this end, a novel biotin-conjugated photopolymer is successfully synthesized and optimally formulated to achieve high-performance SL-printing resolution, as demonstrated by the SL-fabrication of biotinylated structures smaller than 100 µm. By optimizing a multimaterial single-run SL-based 3D-printing process, such biotinylated microstructures are incorporated within perfusion microchambers whose excellent optical transparency enables real-time optical microscopy analyses. Standard biotin-binding assays confirm the existence of biotin-heads on the surfaces of the embedded 3D microstructures and allow to demonstrate that the biofunctionality of biotin is not altered during the SL-printing, thus making it exploitable for further conjugation with other biomolecules. As a step forward, an in-line optical detection system is designed, prototyped via SL-printing and serially connected to the perfusion microchambers through customized world-to-chip connectors. Such detection system is successfully employed to optically analyze the solution flowing out of the microchambers, thus enabling indirect quantification of the concentration of target interacting biomolecules. The successful application of this novel biofunctional photopolymer as SL-material enables to greatly extend the versatility of SL to directly fabricate ULOCs with intrinsic biofunctionality.

Covalent and non-covalent chemical engineering of actin for biotechnological applications

The cytoskeletal filaments are self-assembled protein polymers with 8-25nm diameters and up to several tens of micrometres length. They have a range of pivotal roles in eukaryotic cells, including transportation of intracellular cargoes (primarily microtubules with dynein and kinesin motors) and cell motility (primarily actin and myosin) where muscle contraction is one example. For two decades, the cytoskeletal filaments and their associated motor systems have been explored for nanotechnological applications including miniaturized sensor systems and lab-on-a-chip devices. Several developments have also revolved around possible exploitation of the filaments alone without their motor partners. Efforts to use the cytoskeletal filaments for applications often require chemical or genetic engineering of the filaments such as specific conjugation with fluorophores, antibodies, oligonucleotides or various macromolecular complexes e.g. nanoparticles. Similar conjugation methods are also instrumental for a range of fundamental biophysical studies. Here we review methods for non-covalent and covalent chemical modifications of actin filaments with focus on critical advantages and challenges of different methods as well as critical steps in the conjugation procedures. We also review potential uses of the engineered actin filaments in nanotechnological applications and in some key fundamental studies of actin and myosin function. Finally, we consider possible future lines of investigation that may be addressed by applying chemical conjugation of actin in new ways.

Heparin micropatterning onto fouling-release perfluoropolyether-based polymers via photobiotin activation

A simple method for constructing versatile ordered biotin/avidin arrays on UV-curable perfluoropolyethers (PFPEs) is presented. The goal is the realization of a versatile platform where any biotinylated biological ligands can be further linked to the underlying biotin/avidin array. To this end, microcontact arrayer and microcontact printing technologies were developed for photobiotin direct printing on PFPEs. As attested by fluorescence images, we demonstrate that this photoactive form of biotin is capable of grafting onto PFPEs surfaces during irradiation. Bioaffinity conjugation of the biotin/avidin system was subsequently exploited for further self-assembly avidin family proteins onto photobiotin arrays. The excellent fouling release PFPEs surface properties enable performing avidin assembly step simply by arrays incubation without PFPEs surface passivation or chemical modification to avoid unspecific biomolecule adsorption. Finally, as a proof of principle biotinylated heparin was successfully grafted onto photobiotin/avidin arrays.

The influence of gold surface texture on microglia morphology and activation

Microglial cells play a critical role in the propagation of neuroinflammation in the central nervous system. Microglia sense and respond to environmental signals including chemical, physical and biological cues from the surrounding cell/tissue components. In this project, our goal was to examine the effects of surface texture on BV-2 microglia morphology and function by comparing flat and nanoporous gold (np-Au) surfaces to the more conventional glass. The biocompatibility of np-Au with microglia was evaluated using functional cell assays and high resolution imaging with scanning electron microscopy (SEM). Microglia seeded on glass, ultra-flat gold (UF-Au), ultra-thin (UT) np-Au and np-Au monolith were adherent to all surfaces and their viability was not compromised as assessed by multiple toxicity assays. SEM revealed detailed morphological characteristics of adherent microglia and indicated few dramatic changes as a result of the different surfaces. Microglia proliferation was hampered by np-Au monolith but less by UT np-Au and not at all on UF-Au or glass. Microglial activation, measured by tumor necrosis factor α (TNFα) production, was fully functional (and equivalent) on all gold surfaces compared to glass. The present findings should help further the understanding of basic microglia biology on textured surfaces and more fully evaluate np-Au as a multi-functional biocompatible material. The knowledge obtained and technology developed will have a significant impact in the fabrication of nanoelectronic devices, chemical sensor development, porous nanostructured materials for BioMEMs/NEMs integration, and functional biomaterial coatings for drug delivery.

Orienting actin filaments for directional motility of processive myosin motors

To utilize molecular motors in manmade systems, it is necessary to control the motors' motion. We describe a technique to orient actin filaments so that their barbed ends point in the same direction, enabling same-type motors to travel unidirectionally. Myosin-V and myosin-VI were observed to travel, respectively, toward and away from the filaments' barbed ends. When both motors were present, they occasionally passed each other while "walking" in opposite directions along single actin filaments.

Transport of actin-decorated liposomes along myosin molecules in vitro

We examined whether actin filaments bound to positively charged liposomes could interact with myosin molecules and induce liposome motility. When liposomes were constructed from the mixture of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and cationic N-[1-(2,3-Dioleoyloxy)propyl]-N,N,N-trimethylammonium (DOTAP), actin filaments bound to the liposomes. The actin-bound liposomes exhibited movement on myosin molecules in the presence of adenosine-5'-triphosphate (ATP). The displacement was almost linearly increased with time and the behavior differed from that of Brownian motion. Furthermore, the presence of 30% DOTAP in liposomes was most effective for transport. These data show that the actomyosin system was successfully integrated into the liposomes and possesses the ability to actively transport useful agents enclosed within the liposomes.

Preliminary study on the effects of ageing cold oxygen plasma treated PET/PP with respect to protein adsorption

Surfaces of polyethylene terephthalate (PET) and polypropylene (PP) have been modified by oxygen plasma. The surface hydrophilicity and changes in topography during up to 90 days storage in water and in dry air in a desiccator were analysed by dynamic contact angle test and atomic force microscopy (AFM). Clear ageing effects on the plasma treated surface were observed as increases in contact angle and changes in roughness as functions of increasing storage time. However, the effect of oxygen plasma treatment to increase the hydrophilicity of surface was still evident on the treated surfaces even after 90 days storage either in dry air or in water. In protein adsorption experiments, human serum albumin (HSA) and fibrinogen (Fg) were adsorbed on untreated and oxygen plasma treated PET and PP surfaces. The quantified ATR-FTIR results showed that both HSA and Fg adsorption on PET and PP surfaces decreased after oxygen plasma treatment, with the effect most evident for HSA. Although for both proteins adsorption increased with ageing, the amount of adsorbed proteins was still lower than untreated surface at 30 days. This suggests the shelf life of oxygen plasma treated samples could be as long as 30 days.