Orthogonal Identification of Gunshot Residue with Complementary Detection Principles of Voltammetry, Scanning Electron Microscopy, and Energy-Dispersive X‑ray Spectroscopy: Sample, Screen, and Confirm

Field-deployable voltammetric screening coupled with complementary laboratory-based analysis to confirm the presence of gunshot residue (GSR) from the hands of a subject who has handled, loaded, or discharged a firearm is described. This protocol implements the orthogonal identification of the presence of GSR utilizing square-wave stripping voltammetry (SWSV) as a rapid screening tool along with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) to confirm the presence of the characteristic morphology and metal composition of GSR particles. This is achieved through the judicious modification of the working electrode of a carbon screen-printed electrode (CSPE) with carbon tape (used in SEM analysis) to fix and retain a sample. A comparison between a subject who has handled and loaded a firearm and a subject who has had no contact with GSR shows the significant variations in voltammetric signals and the presence or absence of GSR-consistent particles and constituent metals. This initial electrochemical screening has no effect on the integrity of the metallic particles, and SEM/EDX analysis conducted prior to and postvoltammetry show no differences in analytical output. The carbon tape is instrumental in retaining the GSR sample after electrochemical analysis, supported by comparison with orthogonal detection at a bare CSPE. This protocol shows great promise as a two-tier detection system for the presence of GSR from the hands of a subject, whereby initial screening can be conducted rapidly onsite by minimally trained operators; confirmation can follow at the same substrate to substantiate the voltammetric results

Self-Propelled Carbohydrate-Sensitive Microtransporters with Built-In Boronic Acid Recognition for Isolating Sugars and Cells

A new nanomotor-based target isolation strategy, based on a “built-in” recognition capability, is presented. The concept relies on a poly­(3-aminophenylboronic acid) (PAPBA)/Ni/Pt microtube engine coupling the selective monosaccharide recognition of the boronic acid-based outer polymeric layer with the catalytic function of the inner platinum layer. The PAPBA-based microrocket is prepared by membrane-templated electropolymerization of 3-aminophenylboronic acid monomer. The resulting boronic acid-based microengine itself provides the target recognition without the need for additional external functionalization. “On-the-fly” binding and transport of yeast cells (containing sugar residues on their wall) and glucose are illustrated. The use of the recognition polymeric layer does not hinder the efficient propulsion of the microengine in aqueous and physiological media. Release of the captured yeast cells is triggered via a competitive sugar binding involving addition of fructose. No such capture and transport are observed in control experiments involving other cells or microengines. Selective isolation of monosaccharides is illustrated using polystyrene particles loaded with different sugars. Such self-propelled nanomachines with a built-in recognition capability hold considerable promise for diverse applications

Molecularly Imprinted Polymer-Based Catalytic Micromotors for Selective Protein Transport

We demonstrate an attractive nanomachine “capture and transport” target isolation strategy based on molecularly imprinted polymers (MIPs). MIP-based catalytic microtubular engines are prepared by electropolymerization of the outer polymeric layer in the presence of the target analyte (template). Tailor-made selective artificial recognition sites are thus introduced into the tubular microtransporters through complementary nanocavities in the outer polymeric layer. The new microtransporter concept is illustrated using bilayer poly­(3,4-ethylenedioxythiophene) (PEDOT)/Pt–Ni microengines and fluorescein isothiocyanate (FITC)-labeled avidin (Av-FITC) as the template. The avidin-imprinted polymeric layer selectively concentrates the fluorescent-tagged protein target onto the moving microengine without the need for additional external functionalization, allowing “on-the-fly” extraction and isolation of Av-FITC from raw serum and saliva samples along with real-time visualization of the protein loading and transport. The new micromachine–MIP-based target isolation strategy can be extended to the capture and transport of other important target molecules, leading toward diverse biomedical and environmental applications

Molecularly Imprinted Polymer-Based Catalytic Micromotors for Selective Protein Transport

We demonstrate an attractive nanomachine “capture and transport” target isolation strategy based on molecularly imprinted polymers (MIPs). MIP-based catalytic microtubular engines are prepared by electropolymerization of the outer polymeric layer in the presence of the target analyte (template). Tailor-made selective artificial recognition sites are thus introduced into the tubular microtransporters through complementary nanocavities in the outer polymeric layer. The new microtransporter concept is illustrated using bilayer poly­(3,4-ethylenedioxythiophene) (PEDOT)/Pt–Ni microengines and fluorescein isothiocyanate (FITC)-labeled avidin (Av-FITC) as the template. The avidin-imprinted polymeric layer selectively concentrates the fluorescent-tagged protein target onto the moving microengine without the need for additional external functionalization, allowing “on-the-fly” extraction and isolation of Av-FITC from raw serum and saliva samples along with real-time visualization of the protein loading and transport. The new micromachine–MIP-based target isolation strategy can be extended to the capture and transport of other important target molecules, leading toward diverse biomedical and environmental applications

Molecularly Imprinted Polymer-Based Catalytic Micromotors for Selective Protein Transport

We demonstrate an attractive nanomachine “capture and transport” target isolation strategy based on molecularly imprinted polymers (MIPs). MIP-based catalytic microtubular engines are prepared by electropolymerization of the outer polymeric layer in the presence of the target analyte (template). Tailor-made selective artificial recognition sites are thus introduced into the tubular microtransporters through complementary nanocavities in the outer polymeric layer. The new microtransporter concept is illustrated using bilayer poly­(3,4-ethylenedioxythiophene) (PEDOT)/Pt–Ni microengines and fluorescein isothiocyanate (FITC)-labeled avidin (Av-FITC) as the template. The avidin-imprinted polymeric layer selectively concentrates the fluorescent-tagged protein target onto the moving microengine without the need for additional external functionalization, allowing “on-the-fly” extraction and isolation of Av-FITC from raw serum and saliva samples along with real-time visualization of the protein loading and transport. The new micromachine–MIP-based target isolation strategy can be extended to the capture and transport of other important target molecules, leading toward diverse biomedical and environmental applications

Molecularly Imprinted Polymer-Based Catalytic Micromotors for Selective Protein Transport

We demonstrate an attractive nanomachine “capture and transport” target isolation strategy based on molecularly imprinted polymers (MIPs). MIP-based catalytic microtubular engines are prepared by electropolymerization of the outer polymeric layer in the presence of the target analyte (template). Tailor-made selective artificial recognition sites are thus introduced into the tubular microtransporters through complementary nanocavities in the outer polymeric layer. The new microtransporter concept is illustrated using bilayer poly­(3,4-ethylenedioxythiophene) (PEDOT)/Pt–Ni microengines and fluorescein isothiocyanate (FITC)-labeled avidin (Av-FITC) as the template. The avidin-imprinted polymeric layer selectively concentrates the fluorescent-tagged protein target onto the moving microengine without the need for additional external functionalization, allowing “on-the-fly” extraction and isolation of Av-FITC from raw serum and saliva samples along with real-time visualization of the protein loading and transport. The new micromachine–MIP-based target isolation strategy can be extended to the capture and transport of other important target molecules, leading toward diverse biomedical and environmental applications

Superhydrophobic Alkanethiol-Coated Microsubmarines for Effective Removal of Oil

We demonstrate the use of artificial nanomachines for effective interaction, capture, transport, and removal of oil droplets. The simple nanomachine-enabled oil collection method is based on modifying microtube engines with a superhydrophobic layer able to adsorb oil by means of its strong adhesion to a long chain of self-assembled monolayers (SAMs) of alkanethiols created on the rough gold outer surface of the device. The resultant SAM-coated Au/Ni/PEDOT/Pt microsubmarine displays continuous interaction with large oil droplets and is capable of loading and transporting multiple small oil droplets. The influence of the alkanethiol chain length, polarity, and head functional group and hence of the surface hydrophobicity upon the oil–nanomotor interaction and the propulsion is examined. No such oil–motor interactions were observed in control experiments involving both unmodified microengines and microengines coated with SAM layers containing a polar terminal group. These results demonstrate that such SAM-Au/Ni/PEDOT/Pt micromachines can be useful for a facile, rapid, and efficient collection of oils in water samples, which can be potentially exploited for other water–oil separation systems. The integration of oil-sorption properties into self-propelled microengines holds great promise for the remediation of oil-contaminated water samples and for the isolation of other hydrophobic targets, such as drugs

Bacterial Isolation by Lectin-Modified Microengines

New template-based self-propelled gold/nickel/polyaniline/platinum (Au/Ni/PANI/Pt) microtubular engines, functionalized with the Concanavalin A (ConA) lectin bioreceptor, are shown to be extremely useful for the rapid, real-time isolation of <i>Escherichia coli</i> (<i>E. coli</i>) bacteria from fuel-enhanced environmental, food, and clinical samples. These multifunctional microtube engines combine the selective capture of <i>E. coli</i> with the uptake of polymeric drug-carrier particles to provide an attractive motion-based theranostics strategy. Triggered release of the captured bacteria is demonstrated by movement through a low-pH glycine-based dissociation solution. The smaller size of the new polymer-metal microengines offers convenient, direct, and label-free optical visualization of the captured bacteria and discrimination against nontarget cells

Bacterial Isolation by Lectin-Modified Microengines

New template-based self-propelled gold/nickel/polyaniline/platinum (Au/Ni/PANI/Pt) microtubular engines, functionalized with the Concanavalin A (ConA) lectin bioreceptor, are shown to be extremely useful for the rapid, real-time isolation of <i>Escherichia coli</i> (<i>E. coli</i>) bacteria from fuel-enhanced environmental, food, and clinical samples. These multifunctional microtube engines combine the selective capture of <i>E. coli</i> with the uptake of polymeric drug-carrier particles to provide an attractive motion-based theranostics strategy. Triggered release of the captured bacteria is demonstrated by movement through a low-pH glycine-based dissociation solution. The smaller size of the new polymer-metal microengines offers convenient, direct, and label-free optical visualization of the captured bacteria and discrimination against nontarget cells

Bacterial Isolation by Lectin-Modified Microengines

New template-based self-propelled gold/nickel/polyaniline/platinum (Au/Ni/PANI/Pt) microtubular engines, functionalized with the Concanavalin A (ConA) lectin bioreceptor, are shown to be extremely useful for the rapid, real-time isolation of <i>Escherichia coli</i> (<i>E. coli</i>) bacteria from fuel-enhanced environmental, food, and clinical samples. These multifunctional microtube engines combine the selective capture of <i>E. coli</i> with the uptake of polymeric drug-carrier particles to provide an attractive motion-based theranostics strategy. Triggered release of the captured bacteria is demonstrated by movement through a low-pH glycine-based dissociation solution. The smaller size of the new polymer-metal microengines offers convenient, direct, and label-free optical visualization of the captured bacteria and discrimination against nontarget cells