RESUMEN
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.
Asunto(s)
Ácidos Borónicos/química , Carbohidratos/química , Carbohidratos/aislamiento & purificaciónRESUMEN
The influence of the composition and electropolymerization conditions upon the propulsion of new template-prepared polymer-based bilayer microtubular microbots is described. The effects of different electropolymerized outer layers, including polypyrrole (PPy), poly(3,4-ethylenedioxythiophene) (PEDOT), polyaniline (PANI), and of various inner catalytic metal surfaces (Ag, Pt, Au, Ni-Pt alloy), upon the movement of such bilayer microtubes are evaluated and compared. Electropolymerization conditions, such as the monomer concentration and medium (e.g. surfactant, electrolyte), have a profound effect upon the morphology and locomotion of the resulting microtubes. The most efficient propulsion is observed using PEDOT/Pt microbots that offer a record-breaking speed of over 1400 body lengths s(-1) at physiological temperature, which is the fastest relative speed reported to date for all artificial micro/nanomotors. An inner Pt-Ni alloy surface is shown useful for combining magnetic control and catalytic fuel decomposition within one layer, thus greatly simplifying the preparation of magnetically-guided microbots. Polymer-based microbots with an inner gold layer offer efficient biocatalytic propulsion in low peroxide level in connection to an immobilized catalase enzyme. Metallic Au/Pt bilayer microbots can also be prepared electrochemically to offer high speed propulsion towards potential biomedical applications through functionalization of the outer gold surface. Such rational template preparation and systematic optimization of highly efficient microbots hold considerable promise for diverse practical applications.
Asunto(s)
Microtecnología/métodos , Nanotubos/química , Polímeros/química , Polímeros/síntesis química , Robótica/instrumentación , Compuestos de Anilina/química , Compuestos Bicíclicos Heterocíclicos con Puentes/química , Oro/química , Microscopía Electrónica de Rastreo , Modelos Biológicos , Platino (Metal)/química , Polimerizacion , Pirroles/química , Tiofenos/químicaRESUMEN
Tubular polyaniline (PANI)/Zn microrockets are described that display effective autonomous motion in extreme acidic environments, without any additional chemical fuel. These acid-driven hydrogen-bubble-propelled microrockets have been electrosynthesized using the conical polycarbonate template. The effective propulsion in acidic media reflects the continuous thrust of hydrogen bubbles generated by the spontaneous redox reaction occurring at the inner Zn surface. The propulsion characteristics of PANI/Zn microrockets in different acids and in human serum are described. The observed speed-pH dependence holds promise for sensitive pH measurements in extreme acidic environments. The new microrockets display an ultrafast propulsion (as high as 100 body lengths/s) along with attractive capabilities including guided movement and directed cargo transport. Such acid-driven microtubular rockets offer considerable potential for diverse biomedical and industrial applications.
RESUMEN
Substituted polyaniline/chitosan (sPANI/Ch) composites were chemically synthesized in H(2)SO(4) and CH(3)COOH synthesis media. Structural and physical properties of the composites were characterized by using FTIR, SEM, TGA, UV-vis, XRD techniques, and conductivity measurements. The effect of synthesis media on morphology, thermal stability, conductivity, and crystalline properties was investigated. Chemical interactions between substituted polyanilines and chitosan were explained using FTIR spectra results. The different morphological surfaces were observed in SEM images of the composites. The size of the substituted polyaniline/chitosan (sPANI/Ch) composites was in nanoscale, and the composites synthesized in acetic acid media showed smaller structures than those of H(2)SO(4) media and pure chitosan. It was interpreted from XRD results that the composites have amorphous structure and the PNEANI/Ch-CH(3)COOH composite has the highest crystallinity.
Asunto(s)
Compuestos de Anilina/química , Técnicas de Química Sintética/métodos , Quitosano/química , Acetatos/química , Microscopía Electrónica de Rastreo , Espectrofotometría Ultravioleta , Espectroscopía Infrarroja por Transformada de Fourier , Ácidos Sulfúricos/química , Temperatura , Termogravimetría , Difracción de Rayos XRESUMEN
Chitosan nano powders were modified using RF hydrazine plasma produced at low pressure (26.66Pa) with 13.56MHz frequency at a power of 100W for 30min. Characterization and investigation of the properties of plasma-modified chitosan (PMCh) and non-modified chitosan (Ch) were carried out using an optical monochromator, FTIR, florescence analysis, TGA, SEM, and X-ray techniques. FTIR spectra of PMCh indicated a band broadening at 3436cm(-1) that confirmed increasing functional groups based on H-bonding. The number of NH(2) groups was determined from fluorescence analysis. TGA analysis shows that the moisture absorption is three times higher in the PMCh structure. Ch and PMCh in PVA solutions were used to produce nanofibers by the electrospinning method; average fiber diameters were 480 and 280nm for Ch and PMCh, respectively. It was found that the antibacterial effect of PMCh is better than the Ch for Gram-positive strains.
Asunto(s)
Antibacterianos/química , Quitosano/química , Hidrazinas/química , Nanofibras/química , Gases em Plasma/química , Antibacterianos/farmacología , Bacterias/efectos de los fármacos , Quitosano/farmacología , Fluorescencia , Hidrazinas/farmacología , Espectroscopía Infrarroja por Transformada de FourierRESUMEN
A simple and label-free electrochemical sensor for recognition of the DNA sensor event was prepared by electrochemical polymerization of 4-hydroxyphenyl thiophene-3-carboxylate. Poly(4-hydroxyphenyl thiophene-3-carboxylate) (PHPT) was synthesized electrochemically onto glassy carbon electrode and characterized by cyclic voltammetry, FTIR and AFM measurements. An ODN-probe was physisorbed onto PHPT film and tested on hybridization with complementary ODN segments. A biological recognition can be monitored by comparison with electrochemical signal (cyclic voltammogram) of single and double strand state oligonucleotide. The oxidation current of double strand state oligonucleotide is lower than that of single strand, that is corresponding to the decrease of electroactivity of PHPT with the increase of stiffness of polymer structure. Physisorbed ODN-probe and its hybridization were observed morphologically onto ITO electrodes using AFM. The sensitivity of the electrochemical sensor is 0.02 microA/nmol, detection limit is 1.49 nmol and it has good selectivity.