Nikolay Dimov

Paper imbibition for timing of multi-step liquid handling protocols on event-triggered centrifugal microfluidic lab-on-a-disc platforms

Rotational microfluidic platforms have attracted swiftly growing interest over the last decade due to their suitability for integration and automation of sample preparation and detection. Valving is of pivotal importance on these compact “Lab-on-a-Disc” (LoaD) platforms as all liquids are exposed to the same centrifugal field. A number of valving technologies have been developed to coordinate timing of serial and/or parallel multi-step/multi-liquid assay protocols comprising of laboratory unit operations (LUOs) such as the release, metering and mixing of sample and reagents. So far these valving techniques could be broadly categorised into rotationally controlled or externally actuated schemes. Only recently a new, “event-triggered” flow control has been introduced. In this approach, a valve is opened upon arrival of a liquid at a defined destination on the disc; this innovative mechanism for the first time permits the cascading of LUOs independent of the spin rate. In one technology, dissolvable films (DFs) are configured with a pneumatic chamber to offer function akin to an electrical relay. Dissolving one DF, termed the control film (CF), results in the release of liquid at a distal location through a so-called load film (LF). In this paper, a new method for temporal control of actuating DF-based, event-triggered CFs which are serially aligned at defined distances along a paper strip is introduced. Liquids are transported through the paper strip at a given velocity, thus setting well-defined intervals between subsequent LUOs, e.g. incubation steps. As a proof-of-concept, we present a disc with integrated metering and mixing which can perform a prototypical, 4-fold serial dilution; a common function in bioanalytical protocols. Imbibition of the paper strip sequentially opens five valves for serial dilution and mixing. To illustrate an unprecedented level of on-disc automation, this is followed by a branched cascade of 17 event-triggered valves (for a total of 22 liquid handling steps) which completes the serial dilution protocol.

Biomimetic insect infochemical communication system

By exploiting recent advances in both our understanding of pheromone biosynthesis pathways and the detection of molecules in the insect nervous system, we are developing a novel communication system based on functional equivalents of the cellular, sub-cellular and molecular biological machinery. This will form the basis of a new branch of information technology employing infochemical ligands for communication over space and time. In order to achieve this objective, both chemical signal generation and reception are replicated by taking a systematic approach that implements reaction steps as biosynthetic modules, which are then hierarchically integrated as a technological solution towards realising `infochemical communication.

Mimicking Insect Communication: Release and Detection of Pheromone, Biosynthesized by an Alcohol Acetyl Transferase Immobilized in a Microreactor

Infochemical production, release and detection of (Z,E)-9,11-tetradecadienyl acetate, the major component of the pheromone of the moth Spodoptera littoralis, is achieved in a novel microfluidic system designed to mimic the final step of the pheromone biosynthesis by immobilized recombinant alcohol acetyl transferase. The microfluidic system is part of an “artificial gland”, i.e., a chemoemitter that comprises a microreactor connected to a microevaporator and is able to produce and release a pre-defined amount of the major component of the pheromone from the corresponding (Z,E)-9,11-tetradecadienol. Performance of the entire chemoemitter has been assessed in electrophysiological and behavioral experiments. Electroantennographic depolarizations of the pheromone produced by the chemoemitter were ca. 40% relative to that evoked by the synthetic pheromone. In a wind tunnel, the pheromone released from the evaporator elicited on males a similar attraction behavior as 3 virgin females in most of the parameters considered.

Formation and purification of tailored liposomes for drug delivery using a module-based micro continuous-flow system

Liposomes are lipid based bilayer vesicles that can encapsulate, deliver and release low-soluble drugs and small molecules to a specific target site in the body. They are currently exploited in several nanomedicine formulations. However, their development and application is still limited by expensive and time-consuming process development and production methods. Therefore, to exploit these systems more effectively and support the rapid translation of new liposomal nanomedicines from bench to bedside, new cost-effective and scalable production methods are needed. We present a continuous process flow system for the preparation, modification and purification of liposomes which offers lab-on-chip scale production. The system was evaluated for a range of small vesicles (below 300u2009nm) varying in lipid composition, size and charge; it offers effective and rapid nanomedicine purification with high lipid recovery (>u200998%) combined with effective removal of non-entrapped drug (propofol >95% reduction of non-entrapped drug present) or protein (ovalbumin >90% reduction of OVA present) and organic solvent (ethanol >95% reduction) in less than 4u2009minutes. The key advantages of using this bench-top, rapid, process development tool are the flexible operating conditions, interchangeable membranes and scalable high-throughput yields, thereby offering simultaneous manufacturing and purification of nanoparticles with tailored surface attributes.

Simplified immobilisation method for histidine-tagged enzymes in poly(methyl methacrylate) microfluidic devices

Graphical abstract

Centrifugally automated solid-phase purification of RNA

The purity and integrity of RNA after extraction from a biosample like blood are critical for both downstream analysis and development of on-chip diagnostics. We report for the first time on a fully centrifugally automated solidphase purification of RNA on an integrated microfluidic disc with sequential release of on-board reagents. Building on our earlier work the system successfully concatenates event-triggered valving and centrifugally controlled routing in order to collect purified RNA separately from the aqueous and organic wastes. In this article two-stage purification of RNA and sample conditioning through novel high-frequency release and hybrid event-triggered release valves is demonstrated.

Mimicking insect signaling: Artificial gland for biosynthesis and release of semiochemicals for communication

We explore the functionality of a complete chemoemitter platform mimicking the biosynthetic pathways and release of female sex pheromones of the Spodoptera littoralis moth. This artificial gland system consists of a microreactor in which the pheromone biosynthesis takes place, and a micromachined evaporator that releases ratiometrically-encoded blend into the environment. The artificial gland was implemented for the investigation and detection of patterns by highly sensitive olfaction system of male moths in electroantennographic and behavioral assays. Thus, a new information emission scheme by utilizing semiochemicals as a data carrier was demonstrated.

A Chemoemitter System Mimicking Chemical Communication in Insects

The first chemoemitter based on the concept of infochemical communication is presented emphasizing details on the microfabrication and functionality of its elements, particularly the biomicroreactor and the evaporator. The functionality of the integrated chemoemitter has been evidenced in electrophysiological assays using antennae from Spodoptera littoralis males for pheromone detection and quantification.

Author Correction: Formation and purification of tailored liposomes for drug delivery using a module-based micro continuous-flow system

A correction to this article has been published and is linked from the HTMLxa0and PDF versions of this paper. The error has not been fixed in the paper.

Manufacturing Methods Overview for Rapid Prototyping

Microfabrication is seldom in the focus of a biological studies but it influences the performance and functionality of a miniaturised fluidic platform that affects research outcomes. The scope of this chapter falls on methods, which are accessible, reproducible, and applicable for small-scale, laboratory production. However, fundamental techniques such as photo- and soft lithography are also briefly introduced with references to more detailed sources to facilitate the reader in his choice of fabrication method. It is impossible to cover all the various aspects of microfabrication with extensive details in a single chapter, instead an overview of the rapid and inexpensive methods are conveyed.