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Printing biology is our way to define a novel field employing material printing techniques generally used in plastic electronics to solve important issues of biology by miniaturized and high-throughput platforms. In this field, we already showed the possibility to use Dip Pen Lithography to fabricate single-cell biochips [1]. Also,we employed non-contact patterning methods such as inkjet printing methods to fabricate microarrays for drug screening at solid-liquid interfaces [2] or in picoliter-scale liquid droplets [3] so enabling high-throughput screening of chemical libraries onto disease-based targets. In this regard, printing methods would greatly reduce times and costs of standard drug screening campaigns which are commonly based on complex liquid handling robotics and are time and reagent consuming (micro-, nanoliter scale). In this work, we show a low-cost, general and miniaturized printing biology approach for drug screening, by combining Inkjet Printing and Dip Pen Lithography to develop the biochip. We show the possibility to precisely deliver femtoliter scale droplets of protein targets by Dip Pen Lithography by finely tuning the deposition parameters and ink formulation. Protein solutions are spiked with glycerol at 30 % v/v and are deposited at defined values of humidity (50 % -70 % R.H.). This permits to obtain microscale droplet arrays where picoliter volumes of drug candidates solutions are readily deposited by inkjet printing. In this way, it is possible to produce different drug targets concentration directly on-chip. Fluorescence confocal microscopy is here used to quantify drug-ligand interaction by means of standard intensity based imaging and fluctuation techniques that permit mapping concentration and important biophysical parameters including diffusion coefficients of fluorolabeled (or intrinsically fluorescent) ligands at nanomolar concentration. Outputs obtained on different systems by means of such a miniaturized approach are compared with the ones obtained on standard microliters volumes samples, confirming the ability of our biochip printing methodology to discriminate ligand-target interactions in different compounds. MiUR and the PRIN2012 program are acknowledged for fudings.

Our studies in the field of printing nanobiology in aqueous solution are proposed to highlight the role of water in the processes of interaction between biomolecules in drug- screening devices fabricated by bioprinting technologies and to emphasize the influence of water evaporation on the diffusion of molecules in droplets of picoliter-scale.

The wet chemical synthesis of nanostructures has many crucial advantages over high-temperature methods, including simplicity, low-cost, and deposition on almost arbitrary substrates. Nevertheless, the density-controlled solution growth of nanowires still remains a challenge, especially at the low densities (e.g. 1 to 10 nanowires/100 μm(2)) required, as an example, for intracellular analyses. Here, we demonstrate the solution-growth of ZnO nanowires using a thin chromium film as a nucleation inhibitor and Au size-selected nanoclusters (SSNCs) as catalytic particles for which the density and, in contrast with previous reports, size can be accurately controlled. Our results also provide evidence that the enhanced ZnO hetero-nucleation is dominated by Au SSNCs catalysis rather than by layer adaptation. The proposed approach only uses low temperatures (≤70 °C) and is therefore suitable for any substrate, including printed circuit boards (PCBs) and the plastic substrates which are routinely used for cell cultures. As a proof-of-concept we report the density-controlled synthesis of ZnO nanowires on flexible PCBs, thus opening the way to assembling compact intracellular-analysis systems, including nanowires, electronics, and microfluidics, on a single substrate.

The multiplexed, high-throughput fabrication of microarrays is of vital importance for many applications in life sciences, including drug screening, medical diagnostics and cell biology. In single cell investigations, features smaller than 10 μm are needed for functional manipulation of sub-cellular structures. Several top-down methodologies like electron beam lithography and microcontact printing can be employed for indirect surface patterning at this scale, however those approaches often require clean rooms and multiplexing of several different biomolecules on the same surface is limited [1]. To overcome these obstacles, we combined Dip-pen nanolithography (DPN) and DNA-directed immobilization (DDI) of proteins to fabricate cell-compatible functionalized glass surfaces [2]. We optimized ink formulation for ssDNA printing and the produced arrays were then functionalized with epidermal growth factor (EGF) taking advantage of covalent ssDNA-streptavidin conjugates as adaptor molecules. The surface-immobilized EGF was used for recruiting EGFR in the plasma membrane of MCF7 cells. Via this bottom-up structuring approach, we were able to analyse multiple protein-protein interactions simultaneously in individual living cells [3]. To improve the efficiency of multiplexed surface patterning, we developed a prototype of a robust custom plotter based on 2D polymer-pen lithography (2D-PPL) [4]. This device enables rapid fabrication of microarrays at ambient conditions in a multiplexed direct-writing mode. The printing process was carried out by polymeric pyramidal pens onto which multiple (up to 36) ssDNA solutions can be loaded through a microfluidic inkwell device. Subsequent to optimization of ink viscosity and surface tension by glycerol and tween-20, DNA arrays were plotted and used for DDI of EGF-bearing ssDNA-streptavidin conjugates. The resulting microarrays covered areas of about 0.5 cm2, and were capable of recruiting and activating EGF receptors in sub-cellular regions within human MCF7 cells [4]. References [1] G. Arrabito, B. Pignataro. 2012. Solution Processed Micro- and Nano- Bioarrays for Multiplexed Biosensing. Anal. Chem. 84:5450–5462. [2] G. Arrabito et al. 2013. Biochips for Cell Biology by Combined Dip-Pen Nanolithography and DNA-Directed Protein Immobilization. Small. 9:4243-4249. [3] S. Gandor et al. 2013. A Protein-Interaction Array Inside a Living Cell. Angew. Chem. Int. Ed. Engl. 52:4790–4794. [4] G. Arrabito, et al. 2014. Low-cost Plotter Device for Sub-Cellular Scale Microarray Fabrication. Small. DOI: 10.1002/smll.201303390.

In this thesis work, solution dispensing techniques have been employed for the realization of complex biological arrays. Inkjet printing techniques were employed for the generation of drug screening platforms. This approach was initially proved with a model enzyme system like Glucose Oxidase substrate covalently linked to a functionalized silicon oxide support. On this support an enzymatic substrate (D-glucose)/inhibitor (D-glucal) couple was accurately dispensed. A simple optical detection method was used to prove the screening capability of the microarray with the possibility to assay with high reproducibility at the single spot level. Afterwards, this methodology has been extended to CYP450 enzymes like CYP3A4, one of the main targets for the phase I drug metabolism via a droplet microreactors arrays containing CYP3A4 enzyme mixed with model inhibitors (erythromycin) and enzymatic chemiluminescent substrates (Luciferin-Isopropylacetate). The enzymatic activity was detected by using easy and low cost optical measurements of spot brightness. As a second main objective, high-throughput and multiplexed Dip Pen Nanopatterning methodologies in liquid format were combined with Proteic Ligand DNA-Directed Immobilization for the creation of complex protein biochips on modified glass surfaces displaying spots of cell-specific ligands with lateral dimensions minor than one single cell. In a first application the epidermal growth factor (EFG) protein arrays were realized to display specific single cell adhesion activity. As a second application, immobilized proteic ligands were used to recruit designed cellular receptors which presented intracellular protein domain whose interaction with a cytosolic binding partner was monitored and perturbated.