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Mammalian cells have evolved complex mechanical connections to their microenvironment, including focal adhesion clusters that physically connect the cytoskeleton and the extracellular matrix. This mechanical link is also part of the cellular machinery to transduce, sense and respond to external forces. Although methods to measure cell attachment and cellular traction forces are well established, these are not capable of quantifying force transmission through the cell body to adhesion sites. We here present a novel approach to quantify intracellular force transmission by combining microneedle shearing at the apical cell surface with traction force microscopy at the basal cell surface. The change of traction forces exerted by fibroblasts to underlying polyacrylamide substrates as a response to a known shear force exerted with a calibrated microneedle reveals that cells redistribute forces dynamically under external shearing and during sequential rupture of their adhesion sites. Our quantitative results demonstrate a transition from dipolar to monopolar traction patterns, an inhomogeneous distribution of the external shear force to the adhesion sites as well as dynamical changes in force loading prior to and after the rupture of single adhesion sites. Our strategy of combining traction force microscopy with external force application opens new perspectives for future studies of force transmission and mechanotransduction in cells.

The coating of porous scaffolds with nanoparticles is crucial in many applications, for example to generate scaffolds for catalysis or to make scaffolds bioactive. A standard and well-established method for coating surfaces with charged nanoparticles is electrophoresis, but when used on porous scaffolds, this method often leads to a blockage of the pores so that only the outermost layers of the scaffolds are coated. In this study, the electrophoretic coating process is monitored in situ and the kinetics of nanoparticle deposition are investigated. This concept can be extended to design a periodic electrophoretic deposition (PEPD) strategy, thus avoiding the typical blockage of surface pores. In the present work we demonstrate successful and homogeneous electrophoretic deposition of hydroxyapatite nanoparticles (HAn, diameter ≤200 nm) on a fibrous graphitic 3D structure (ultralightweight aerographite) using the PEPD strategy. The microfilaments of the resulting scaffold are covered with HAn both internally and on the surface. Furthermore, protein adsorption assays and cell proliferation assays were carried out and revealed that the HAn-decorated aerographite scaffolds are biocompatible. The HAn decoration of the scaffolds also significantly increases the alkaline phosphatase activity of osteoblast cells, showing that the scaffolds are able to promote their osteoblastic activity.

Nano letters 21(8), 3690 - 3697 (2021). doi:10.1021/acs.nanolett.0c04375, The fabrication of electrically conductive hydrogels is challenging as the introduction of an electrically conductive filler often changes mechanical hydrogel matrix properties. Here, we present an approach for the preparation of hydrogel composites with outstanding electrical conductivity at extremely low filler loadings (0.34 S m$^{–1}$, 0.16 vol %). Exfoliated graphene and polyacrylamide are microengineered to 3D composites such that conductive graphene pathways pervade the hydrogel matrix similar to an artificial nervous system. This makes it possible to combine both the exceptional conductivity of exfoliated graphene and the adaptable mechanical properties of polyacrylamide. The demonstrated approach is highly versatile regarding porosity, filler material, as well as hydrogel system. The important difference to other approaches is that we keep the original properties of the matrix, while ensuring conductivity through graphene-coated microchannels. This novel approach of generating conductive hydrogels is very promising, with particular applications in the fields of bioelectronics and biohybrid robotics., Published by ACS Publ., Washington, DC

Bone, nerve, and heart tissue engineering place high demands on the conductivity of three-dimensional (3D) scaffolds. Fibrous carbon-based scaffolds are excellent material candidates to fulfill these requirements. Here, we show that highly porous (up to 94%) hybrid 3D framework structures with hierarchical architecture, consisting of microfiber composites of self-entangled carbon nanotubes (CNTs) and bioactive nanoparticles are highly suitable for growing cells. The hybrid 3D structures are fabricated by infiltrating a combination of CNTs and bioactive materials into a porous (∼94%) zinc oxide (ZnO) sacrificial template, followed by the removal of the ZnO backbone via a H2 thermal reduction process. Simultaneously, the bioactive nanoparticles are sintered. In this way, conductive and mechanically stable 3D composites of free-standing CNT-based microfibers and bioactive nanoparticles are formed. The adopted strategy demonstrates great potential for implementing low-dimensional bioactive materials, such as hydroxyapatite (HA) and bioactive glass nanoparticles (BGN), into 3D carbon-based microfibrous networks. It is demonstrated that the incorporation of HA nanoparticles and BGN promotes the biomineralization ability and the protein adsorption capacity of the scaffolds significantly, as well as fibroblast and osteoblast adhesion. These results demonstrate that the developed carbon-based bioactive scaffolds are promising materials for bone tissue engineering and related applications.

The production of micrometer-sized structures comprised of nanoparticles in defined patterns and densities is highly important in many fields, ranging from nano-optics to biosensor technologies and biomaterials. A well-established method to fabricate quasi-hexagonal patterns of metal nanoparticles is block copolymer micelle nanolithography, which relies on the self-assembly of metal-loaded micelles on surfaces by a dip-coating or spin-coating process. Using this method, the spacing of the nanoparticles is controlled by the size of the micelles and by the coating conditions. Whereas block copolymer micelle nanolithography is a high-throughput method for generating well-ordered nanoparticle patterns at the nanoscale, so far it has been inefficient in generating a hierarchical overlay structure at the micrometer scale. Here, we show that by combining block copolymer micelle nanolithography with inkjet printing, hierarchical patterns of gold nanoparticles in the form of microstructures can be achieved in a high-throughput process. Inkjet printing was used to generate droplets of the micelle solution on surfaces, resulting in printed circles that contain patterns of gold nanoparticles with an interparticle spacing between 25 and 42 nm. We tested this method on different silicon and nickel–titanium surfaces and the generated patterns were found to depend on the material type and surface topography. Based on the presented strategy, we were able to achieve patterning times of a few seconds and produce quasi-hexagonal micro-nanopatterns of gold nanoparticles on smooth surfaces. Hence, this method is a high-throughput method that can be used to coat surfaces with nanoparticles in a user-defined pattern at the micrometer scale. As the nanoparticles provide a chemical contrast on the surface, they can be further functionalized and are therefore highly relevant for biological applications.

State of the art minimally invasive treatments and diagnostics of neurological and cardiovascular diseases demand for flexible instruments and implants that enable sensing and stimulation of bioelectric signals. Besides medical applications, implantable bioelectronic brain-computer interfaces are envisioned as the next step in communication and data transfer. Conventional microelectrode arrays used for these types of applications are based on polymer substrates that are not suitable for biostable, rigid and self-expanding devices. Here, we present fully integrated bioelectrodes on superelastic NiTi carriers fabricated by microsystem technology processes. The insulation between the metallic NiTi structure and the Pt electrode layer is realized by different oxide layers (SiOx, TaOx and Yttrium stabilized Zirconia YSZ). Key properties of bioelectronic implants such as dissolution in body fluids, biocompatibility, mechanical properties and bioelectrical sensing/stimulation capabilities have been investigated by in vitro methods. Particular devices with YSZ are biostable and biocompatible, enabling sensing and stimulation. The major advantage of this system is the combination of medically approved materials and novel fabrication technology that enables miniaturization and integration beyond the state-of-the-art processes. The results demonstrate that this functionalization of superelastic NiTi is an enabling technology for the development of new kinds of bioelectronic devices.

In many situations, cells migrate through tiny orifices. Examples include the extravasation of immune cells from the bloodstream for fighting infections, the infiltration of cancer cells during metastasis, and the migration of human pathogens. An extremely motile and medically relevant type of human pathogen is Acanthamoeba castellanii. In the study presented here, we investigated how a combination of microparticles and microstructured interfaces controls the migration of A. castellanii trophozoites. The microinterfaces comprised well-defined micropillar arrays, and the trophozoites easily migrated through the given constrictions by adapting the shape and size of their intracellular vacuoles and by adapting intracellular motion. After feeding the trophozoite cells in microinterfaces with synthetic, stiff microparticles of various sizes and shapes, their behavior changed drastically: if the particles were smaller than the micropillar gap, migration was still possible. If the cells incorporated particles larger than the pillar gap, they could become immobilized but could also display remarkable problem-solving capabilities. For example, they turned rod-shaped microparticles such that their short axis fit through the pillar gap or they transported the particles above the structure. As migration is a crucial contribution to A. castellanii pathogenicity and is also relevant to other biological processes in microenvironments, such as cancer metastasis, our results provide an interesting strategy for controlling the migration of cells containing intracellular particles by microstructured interfaces that serve as migration-limiting environments.

Precise movement control is a key feature for the use of superparamagnetic microbeads in medical and biological lab-on-chip applications. We demonstrate the unidirectional transport of magnetic and biological carriers along a chain of oval shaped magnetic thin film elements by in-plane rotating magnetic fields, enabling controllable manipulation and separation schemes. The same fundamental unidirectional movement is realized independent of the sense of magnetic field rotation and orientation of the magnetic pathway. The flowless directional transport of magnetically labeled rat embryonic fibroblasts is presented, validating the applicability of the structures for biological purposes. The lined up ferromagnetic structures are a critical building block for the construction of flexible pathways for biological lab-on-a-chip applications.

Objective We tested the adhesion properties of living gingival fibroblasts on three different implant abutment materials, adhesive resin used to bond bi-partite abutments, and human dentin. Methods Discs of lithium disilicate (LS), zirconium dioxide (Zr), adhesive resin cement (AR), titanium (Ti), and human dentin (HD) were fabricated with three different levels of surface roughness (rough, machined, and polished). Ra and Rz, water contact angle, and cell detachment forces were measured. Cell detachment force was measured for single cells using single-cell force spectroscopy. Data were statistically analyzed using parametric tests (ANOVA, MANOVA, Bonferroni post-hoc tests). Results Surface roughness significantly influenced the water contact angle for all materials (P ≤ 0.05). Overall, HD showed the lowest contact angle, followed by LS, Ti, Zr, and AR (P ≤ 0.05). Comparison of cell detachment forces between materials with rough and machined surfaces revealed no significant differences (P > 0.05), with the exception of Zr compared to HD with rough surfaces (P = 0.006). For polished surfaces, HD showed the highest detachment force (P ≤ 0.0001), followed by Ti, AR, and Zr, which did not significantly differ from each other (P > 0.05) and LS; Ti/AR was significantly different from LS (P ≤ 0.05). Except for HD, where polished surfaces exhibited the highest cell detachment force (P ≤ 0.002), most machined surfaces showed higher cell detachment forces than polished or rough surfaces. Significance Implant abutments should ideally be provided with a machined like surface roughness for best cell adhesion.

Scaffolds for tissue engineering enable the possibility to fabricate and form biomedical implants in vitro, which fulfill special functionality in vivo. In this study, free-standing Nickel–Titanium(NiTi) thin film mesheswere produced by means of magnetron sputter deposition.Meshes contained precisely defined rhombic holes in the size of 440 to 1309 μm2 and a strut width ranging from 5.3 to 9.2 μm. The effective mechanical properties of the microstructured superelastic NiTi thin film were examined by tensile testing. These results will be adapted for the design of the holes in the film. The influence of hole and strut dimensions on the adhesion of sheep autologous cells (CD133+) was studied after 24 h and after seven days of incubation. Optical analysis using fluorescence microscopy and scanning electron microscopy showed that cell adhesion depends on the structural parameters of the mesh. After 7 days in cell culture a large part of the mesh was covered with aligned fibrous material. Cell adhesion is particularly facilitated on meshes with small rhombic holes of 440 μm2 and a strut width of 5.3 μm. Our results demonstrate that free-standing NiTi thin film meshes have a promising potential for applicationsin cardiovascular tissue engineering, particularly for the fabrication of heart valves.

Superparamagnetic iron oxide nanoparticles (SPIONs) are an important tool for labeling cells and tissues in many therapeutic and diagnostic applications, such as magnetic resonance imaging (MRI) and magnetic particle imaging (MPI). However, these methods require large and expensive instrumentation. Here we show that our magnetic susceptibility particle mapping (MSPM) system can achieve the detection of magnetic nanoparticles in an inexpensive and small device. The system is based on magnetoelectric (ME) sensors utilizing the ΔE effect in combination with a permanent magnet that is generating a bias field for the sensor and at the same time is magnetizing the SPIONs in the sample. The permanent magnet is placed above the sensor, and the sample is rotated through the gap in between. The magnetized SPIONs in the sample generate an additional magnetic field that can be detected by the ME sensor. The clear novelty of our approach is the use of a rotating sample, generating a periodic signal, which enables an easy separation of the desired signal from the background signal and the possibility to compensate drift, which is commonly observed in ME sensor measurements. With this improvement and the use of a ME sensor that is sensitive for low frequencies the setup is able to measure significantly smaller amounts of magnetic nanoparticles than previous approaches described in the literature and we are even able to reconstruct 2D nanoparticle distributions. The noise floor, also referred to as limit of detection (LOD), of this measurement system is around 500 pT/(Hz)1/2. The detection threshold of our MSPM system is 20 μg SPIONs in a volume of 200 mm3 and the spatial resolution is in the range of a few mm. The spatial resolution is determined by reconstructing the particle distribution in the sample layer by solving the inverse problem. To demonstrate the feasibility of the method for detecting living cells, we measured the field distribution originating from SPION-labeled fibroblast cells in an alginate-gelatin matrix, thus demonstrating the potential of our method for biomaterial applications.

Carbon-based fibrous scaffolds are highly attractive for all biomaterial applications that require electrical conductivity. It is additionally advantageous if such materials resembled the structural and biochemical features of the natural extracellular environment. Here, we show a novel modular design strategy to engineer biomimetic carbon fiber-based scaffolds. Highly porous ceramic zinc oxide (ZnO) microstructures serve as three-dimensional (3D) sacrificial templates and are infiltrated with carbon nanotubes (CNTs) or graphene dispersions. Once the CNTs and graphene coat the ZnO template, the ZnO is either removed by hydrolysis or converted into carbon by chemical vapor deposition. The resulting 3D carbon scaffolds are both hierarchically ordered and free-standing. The properties of the microfibrous scaffolds were tailored with a high porosity (up to 93%), a high Young’s modulus (ca. 0.027–22 MPa), and an electrical conductivity of ca. 0.1–330 S/m, as well as different surface compositions. Cell viability, fibroblast proliferation rate and protein adsorption rate assays have shown that the generated scaffolds are biocompatible and have a high protein adsorption capacity (up to 77.32 ± 6.95 mg/cm3) so that they are able to resemble the extracellular matrix not only structurally but also biochemically. The scaffolds also allow for the successful growth and adhesion of fibroblast cells, showing that we provide a novel, highly scalable modular design strategy to generate biocompatible carbon fiber systems that mimic the extracellular matrix with the additional feature of conductivity.

Porous hydrogel scaffolds are ideal candidates for mimicking cellular microenvironments, regarding both structural and mechanical aspects. We present a novel strategy to use uniquely designed ceramic networks as templates for generating hydrogels with a network of interconnected pores in the form of microchannels. The advantages of this new approach are the high and guaranteed interconnectivity of the microchannels, as well as the possibility to produce channels with diameters smaller than 7 μm. Neither of these assets can be ensured with other established techniques. Experiments using the polyacrylamide substrates produced with our approach have shown that the migration of human pathogenic Acanthamoeba castellanii trophozoites is manipulated by the microchannel structure in the hydrogels. The parasites can even be captured inside the microchannel network and removed from their incubation medium by the porous polyacrylamide, indicating the huge potential of our new technique for medical, pharmaceutical, and tissue engineering applications.

European polymer journal 120, 109211 (2019). doi:10.1016/j.eurpolymj.2019.08.038, It is well known that amyloid beta-lactoglobulin (BLG) fibril solutions contain a heterogeneous mixture of amyloid aggregates and non-amyloid material. However, few information are available on how strongly separated fractions of different morphologies (straight fibrils at pH 2 and worm-like aggregates at pH 3.5) vary with respect to physicochemical properties and building blocks as most analyses are conducted with unfractionized solutions where superposition effects occur.The pH-value shift resulted in an altered degree of acid hydrolysis which led to dissimilar building blocks of the aggregates (peptides at pH 2, non-hydrolyzed protein at pH 3.5). The respective separated amyloid and non-amyloid fractions showed significantly different size (SAXS, SEC, AUC) and charge properties (Zeta potential) than the whole samples. Strong superposition effects were evident with common analyses such as FTIR, TRP fluorescence and Thioflavin-T. At the same time, structural differences of pH 2 and pH 3.5 aggregates could be presented more clearly., Published by Elsevier, New York, NY [u.a.]

Multimode waveguiding in the visible and near-ultraviolet spectral regime is observed and characterized in thermally grown ${\mathrm{SiO}}_{2}$ layers on silicon using photoemission electron microscopy (PEEM). Comparison with finite-element-method simulations allows identifying order and character of the attenuated modes. Real-time investigations on mode propagation support these findings and give additional evidence for the existence of radiative modes. Finally, the presented experimental results illustrate how a defined deposition of gold nanoparticles can substantially enhance the sensitivity of the PEEM technique to electromagnetic field modes supported by thin dielectric and insulating layers.

Measurements of Young's moduli are mostly evaluated using strong assumptions, such as sample homogeneity and isotropy. At the same time, descriptions of measurement parameters often lack detailed specifications. Many of these assumptions are, for soft hydrogels especially, not completely valid and the complexity of hydrogel microindentation demands more sophisticated experimental procedures in order to describe their elastic properties more accurately. We created an algorithm that automates indentation data analysis as a basis for the evaluation of large data sets with consideration of the influence of indentation depth on the measured Young's modulus. The algorithm automatically determines the Young's modulus in indentation regions where it becomes independent of the indentation depth and furthermore minimizes the error from fitting an elastic model to the data. This approach is independent of the chosen elastic fitting model and indentation device. With this, we are able to evaluate large amounts of indentation curves recorded on many different sample positions and can therefore apply statistical methods to overcome deviations due to sample inhomogeneities. To prove the applicability of our algorithm, we carried out a systematic analysis of how the indentation speed, indenter size and sample thickness affect the determination of Young's modulus from atomic force microscope (AFM) indentation curves on polyacrylamide (PAAm) samples. We chose the Hertz model as the elastic fitting model for this proof of principle of our algorithm and found that all of these parameters influence the measured Young's moduli to a certain extent. Hence, it is essential to clearly state the experimental parameters used in microindentation experiments to ensure reproducibility and comparability of data.

Living beings have an unsurpassed range of ways to manipulate objects and interact with them. They can make autonomous decisions and can heal themselves. So far, a conventional robot cannot mimic this complexity even remotely. Classical robots are often used to help with lifting and gripping and thus to alleviate the effects of menial tasks. Sensors can render robots responsive, and artificial intelligence aims at enabling autonomous responses. Inanimate soft robots are a step in this direction, but it will only be in combination with living systems that full complexity will be achievable. The field of biohybrid soft robotics provides entirely new concepts to address current challenges, for example the ability to self-heal, enable a soft touch, or to show situational versatility. Therefore, "living materials" are at the heart of this review. Similarly to biological taxonomy, there is a recent effort for taxonomy of biohybrid soft robotics. Here, an expansion is proposed to take into account not only function and origin of biohybrid soft robotic components, but also the materials. This materials taxonomy key demonstrates visually that materials science will drive the development of the field of soft biohybrid robotics.

Aerographite (AG) is a novel carbon-based material that exists as a self-supportive 3D network of interconnected hollow microtubules. It can be synthesized in a variety of architectures tailored by the growth conditions. This flexibility in creating structures presents interesting bioengineering possibilities such as the generation of an artificial extracellular matrix. Here we have explored the feasibility and potential of AG as a scaffold for 3D cell growth employing cyclic RGD (cRGD) peptides coupled to poly(ethylene glycol) (PEG) conjugated phospholipids for surface functionalization to promote specific adhesion of fibroblast cells. Successful growth and invasion of the bulk material was followed over a period of 4 days.

We report a method enabling intensity-based readout for label-free cellular assays and realize a reader device with the same footprint as a microtiter plate. For unambiguous resonance intensity measurements in resonance waveguide grating (RWG) sensors, we propose to apply resonances near the substrate cutoff wavelength. This method was validated in bulk refractive index, surface bilayer and G protein-coupled receptor (GPCR) experiments. The significantly reduced size of the reader device opens new opportunities for easy integration into incubators or liquid handling systems.

We have studied the initial phase of cell adhesion as a function of the lateral organization of individual integrin molecules with single-cell force microscopy. Nanostructures, consisting of hexagonally ordered gold dots, were prepared with diblock-copolymer micelle lithography and functionalized with arginine- glycine-aspartate peptides, thus defining integrin position with nanometer resolution. Adhesion strength was characterized with an atomic force microscope and both cell detachment forces and work of detachment showed a reinforcement of adhesion if the distance between integrin molecules was

In order to understand the variations in photocatalytic efficiencies of titania thin films prepared by different physical vapor deposition techniques, we studied the microstructure and resulting properties for the two widely used PVD methods, electron beam evaporation and reactive pulsed DC magnetron sputtering. In addition, we investigated the effect of oxygen vacancy defects induced by tempering in reducing atmospheres and the aging behavior. After deposition, several tempering series in oxygen, air, argon, and forming gas were carried out to control the amount of oxygen vacancy defects. The films were characterized with respect to crystallinity, texture, grain growth, grain structure, surface roughness, light transmission as well as band gap energy; the photocatalytic efficiency was measured via methylene blue degradation. The results show different nucleation and growth mechanisms between evaporated and sputtered titania thin films, resulting in severe influence on photocatalytic efficiency. The evaporated thin films exhibited homogeneous nucleation and growth, and stayed in the anatase structure even after tempering at 800 °C for 1 h. In contrast, the sputtered thin films started to form grains at the interface to the substrate and showed heterogeneous nucleation and growth. Moreover, the sputtered films already formed rutile when tempered at 600 °C for 1 h. The gain in surface area due to tempering, which promotes adsorption of photocatalytic reactants, was more pronounced in sputtered thin films (+29%) compared to evaporated thin films (+6%). Films with oxygen vacancy defects, preserved by tempering in argon or induced by tempering in forming gas, showed a large improvement in photocatalytic efficiency. However, aging of the samples over a period of 19 months lead to a progressive decline in efficiency, finally reaching the level of thin films tempered in air, which had remained stable over the same 19 month period. This strongly questions widely applied concepts based on improving the photocatalytic efficiency via oxygen vacancy defects.

Following a myocardial infarction (MI), cardiomyocytes are replaced by scar tissue, which decreases ventricular contractile function. Tissue engineering is a promising approach to regenerate such damaged cardiomyocyte tissue. Engineered cardiac patches can be fabricated by seeding a high density of cardiac cells onto a synthetic or natural porous polymer. In this study, nanocomposite scaffolds made of gold nanotubes/nanowires incorporated into biodegradable castor oil-based polyurethane were employed to make micro-porous scaffolds. H9C2 cardiomyocyte cells were cultured on the scaffolds for one day, and electrical stimulation was applied to improve cell communication and interaction in neighboring pores. Cells on scaffolds were examined by fluorescence microscopy and scanning electron microscopy, revealing that the combination of scaffold design and electrical stimulation significantly increased cell confluency of H9C2 cells on the scaffolds. Furthermore, we showed that the gene expression levels of Nkx2.5, atrial natriuretic peptide (ANF) and natriuretic peptide precursor B (NPPB), which are functional genes of the myocardium, were up-regulated by the incorporation of gold nanotubes/nanowires into the polyurethane scaffolds, in particular after electrical stimulation.

Rapid and reversible photoswitching of cell adhesion is achieved by c(RGDfK)-azobenzenes embedded in a poly(ethylene glycol) background on surfaces. The light-induced cis-trans-isomerization of the azobenzene enables switching of cell adhesion on the surface. Reversibility of switching over several consecutive switching cycles is demonstrated by single-cell force spectroscopy.

Diblock copolymer micelle nanolithography (BCML) is a versatile and efficient method to cover large surface areas with hexagonally ordered arrays of metal nanoparticles, in which the nanoparticles are equally spaced. However, this method falls short of providing a controlled allocation of such regular nanoparticle arrays with specific spacing into micropatterns. We present here a quick and high-throughput method to generate quasi-hexagonal nanoparticle structures with well-defined interparticle spacing on segments of nanotopographic Si substrates. The topographic height of these segments plays a dominant role in dictating the spacing between the gold nanoparticles, as the nanoparticle arrangement is controlled by immersion forces and by their self-assembly within the segments. Our novel strategy of employing a single-step BCML routine is a highly promising method for the fabrication of regular gold nanopatterns in micropatterns for a wide range of applications.

We present a handheld biosensor system for the label-free and specific multiplexed detection of several biomarkers employing a spectrometer-free imaging measurement system. A photonic crystal surface functionalized with multiple specific ligands forms the optical transducer. The photonic crystal slab is fabricated on a glass substrate by replicating a periodic grating master stamp with a period of 370 nm into a photoresist via nanoimprint lithography and deposition of a 70-nm titanium dioxide layer. Capture molecules are coupled covalently and drop-wise to the photonic crystal surface. With a simple camera and imaging optics the surface-normal transmission is detected. In the transmission spectrum guided-mode resonances are observed that shift due to protein binding. This shift is observed as an intensity change in the green color channel of the camera. Non-functionalized image sections are used for continuous elimination of background drift. In a first experiment we demonstrate the specific and time-resolved detection of 90.0 nM CD40 ligand antibody, 90.0 nM EGF antibody, and 500 nM streptavidin in parallel on one sensor chip. In a second experiment, aptamers with two different spacer lengths are used as receptor. The binding kinetics with association and dissociation of 250 nM thrombin and regeneration of the sensor surface with acidic tris-HCl-buffer (pH 5.0) is presented for two measurement cycles.

We designed and evaluated a microfluidic test chip for human blood filtration and imaging label-free detection of multiple biomarkers. The microfluidic chip has a total size of 75 mm × 25 mm × 2 mm. It is realized as an assembly of a plastic chip and a functionalized photonic crystal slab on a glass substrate. The plastic chip contains capillary channels, a filter membrane and a cavity open on one side. The photonic crystal chip is bonded with an adhesive foil to the open cavity. Human blood filtration is demonstrated. We determined that fluorescently labelled particles of diameter 3 µm or larger are filtered out by the system. Refractometric measurements are performed with the test chip in combination with a compact imaging read-out system to investigate the system response to refractive index changes. Flow dynamics in the sensor cavity are imaged for replacing water by isopropanol. Finally, the binding of 500 nm biotin dissolved in phosphate buffer saline to a photonic crystal surface locally functionalized with streptavidin is demonstrated.