Printing Biology: engineering analytical platforms by molecular inks

Abstract

The assembly of life-like artificial biosystems allows understanding the molecular origins of life, whilst guiding the nature-inspired development of analytical platforms for biotechnologies (e.g. molecular sensing, lab-on-chip, Point-of-care) [1]. These systems mimic and even improve the functional features of biological systems, reproducing their collective behaviors, fine organization, adaptivity to environmental stimuli [2]. This work shows the possibility to readily produce these systems by an integrative approach we herein define as Printing Biology [3], a new research field which stems from the emerging world of additive manufacturing and the bottom up Synthetic Biology fabrication. This work shows the adaptability of Printing Biology to fabricate artificial biosystems at different scales (from nanometers up to millimeters) and variable chemical composition (DNA, proteins, phospholipids), showing functionalities allowing the determination of molecular interactions and features in conditions mimicking living systems. This work shows two different analytical platforms by inkjet printing (IJP) and microcantilever spotting (ȝCS). The molecular inks are dispensed in the form of aqueous or non-aqueous compartments, whose volume typically spans from femtoliter (10-15 L) up to picoliter (10-12 L) scales. The coefficient of variation of the dispensed droplets is typically below the 3%, allowing for excellent reproducibility in the deposition process. The dispensed droplet spacing can be tuned in order to obtain a final sessile droplet with a volume at higher scales (up to nanoliter or event microliter scale). The formulation of molecular inks will be in particular analyzed, taking into consideration all the most relevant parameters (e.g. viscosity, ionic force, surface tension, solute-solvent interactions) which guide the deposition process and the activity retaining of the dispensed biomolecules [4]. The analytical determination of the dispensed molecules will be carried out by employing optical detection, in particular fluorescence intensity and fluorescence lifetime. Three different ink printable formulations will be employed, including DNA, proteins and phospholipids. The dispensed systems will be determined by analyzing their molecular content (down to few zeptomoles) and molecular conformation within the dispensed droplet. Three representative examples will be shown. The first is the formulation of DNA oligonucleotides fL-scale ink imbibition by ȝCS into nylon to realize a flexible sensor for DNA detection [5]. The second is the realization of stable pL- or fL-scale aqueous compartments stabilized in mineral oil to study molecular interactions in restricted volumes, permitting to highlight the effect of molecular crowding in compartments mimicking subcellular scale systems [6]. Finally, the fabrication of phospholipids by ȝCS onto glass surface are reported, allowing for membrane-protein interaction studies at solid-liquid interfaces.