ABSTRACT
We present a nanomechanical platform for real-time quantitative label-free detection of target biomolecules in a liquid environment with mass sensitivity down to few pg. Newly fabricated arrays of up to 18 cantilevers are integrated in a micromachined fluidic chamber, connected to software-controlled fluidic pumps for automated sample injections. We discuss two functionalization approaches to independently sensitize the interface of different cantilevers. A custom piezo-stack actuator and optical readout system enable the measurement of resonance frequencies up to 2 MHz. We implement a new measurement strategy based on a phase-locked loop (PLL), built via in-house developed software. The PLL allows us to track, within the same experiment, the evolution of resonance frequency over time of up to four modes for all the cantilevers in the array. With respect to the previous measurement technique, based on standard frequency sweep, the PLL enhances the estimated detection limit of the device by a factor of 7 (down to 2 pg in 5 min integration time) and the time resolution by more than threefold (below 15 s), being on par with commercial gold-standard techniques. The detection limit and noise of the new setup are investigated via Allan deviation and standard deviation analysis, considering different resonance modes and interface chemistries. As a proof-of-concept, we show the immobilization and label-free in situ detection of live bacterial cells (E. coli), demonstrating qualitative and quantitative agreement in the mechanical response of three different resonance modes.
Subject(s)
Escherichia coli , Biosensing Techniques , VibrationABSTRACT
Nanowire networks are promising memristive architectures for neuromorphic applications due to their connectivity and neurosynaptic-like behaviours. Here, we demonstrate a self-similar scaling of the conductance of networks and the junctions that comprise them. We show this behavior is an emergent property of any junction-dominated network. A particular class of junctions naturally leads to the emergence of conductance plateaus and a "winner-takes-all" conducting path that spans the entire network, and which we show corresponds to the lowest-energy connectivity path. The memory stored in the conductance state is distributed across the network but encoded in specific connectivity pathways, similar to that found in biological systems. These results are expected to have important implications for development of neuromorphic devices based on reservoir computing.
ABSTRACT
Liposomes have been the centre of attention in research due to their potential to act as drug delivery systems. Although its versatility and manufacturing processes are still not scalable and reproducible. In this study, the microfluidic method for liposomes preparation is presented. DMPC and DSPC liposomes containing two different lipid/cholesterol ratios (1:1 and 2:1) are prepared. Results from this preparation process were compared with the film hydration method in order to understand benefits and drawbacks of microfluidics. Liposomes characterisation was evaluated through stability studies, encapsulation efficacy and drug release profiles of hydrophilic and lipophilic compounds. Stability tests were performed during 3 weeks and the liposomes properties of the most stable formulations were determined using Infrared Microscopy and Atomic Force Microscopy. Microfluidic allows loading of drugs and assembly in a quick single step and the chosen flow ratio for liposomes formulation plays a fundamental role for particle sizes. One hydrophilic and one lipophilic compounds were incorporated showing how formulation and physic-chemical characteristics can influence the drug release profile.
