Prof. Gabriel Luna Bárcenas

 

Nanocomposites for biomedical & environmental applications

Prof. Gabriel Luna-Barcenas

Center for Advanced Studies (CINVESTAV)

Querétaro, MEXICO

 

In this talk I will discuss some applications in which the proper combination of synthesis and characterization methods help fine-tune the performance of a nanocomposite. In this regard, the extensive use of polysaccharides and proteins has triggered many interested applications due to the presence of amine, carboxyl and hydroxyl groups. In acidic aqueous media, the primary amine protonates giving rise to hydrogen abstraction, chelation, and other bonding forces when in the presence of an “appropriate” substrate. In this regard, I will present three investigations that our group has developed:

1.    Antibacterial Skin Patch.Chitosan–silver (CS/Ag), Chitosa-cooper (CS-Cu), CS/Ag-halloysite nanocomposites either in the form of nanoparticles (AgNP) or as ionic dendritic structures (Ag+). The antibacterial activity of the resulting nanocomposites in the form of films is studied against two bacteria, Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. The collective action of AgNP and Ag+ions/halloysite facilitate the enhancement and synergetic antibacterial activity below certain critical concentration. The nanocomposites containing 1 wt.% of silver nanoparticles and about of 2 wt.% of silver ions exhibit a maximum antibacterial activity, which is close to their electrical percolation threshold.

2.    Cu++Detection Electrode.We developed electrodes with chitosan-gold nanoparticle (CS-AuNPs) based membranes. Adsorption of the positively charged Cu++is related to its interaction with the complex formed by the protonated amino groups of CS with the carboxylate groups that adsorbs onto AuNPs and with the C=O group of amide I groups of CS. For the first time, the relation between percolation threshold and detection limit of copper ions has been established. Impedimetric method shows superior properties; detection limit ca. 10-7M, linear response range 10-7-10-3M of Cu++.

Protein-coated magnetic nanowires as highly detectable optical labels. This work proposes the elaboration of magnetic nickel nanowires (NiNWs) coated with a protein as highly optical detection labels. Incorporation of silver nanoparticles (AgNPs) into the protein matrix helps amplify detection limits.Our approach takes advantage of the use of NiNWs that act as preferential light dispersant and the use of an inexpensive protein coating; this coating helps impregnate AgNPs by simultaneously increasing the composite plasmonic contrast and as an antimicrobial protector. Synthesized nanocomposiste exhibits superior detection performance in the pico-g/mL range when compared with light scattering techniques; the best detection limit of our optical label is ca.140 pg/mL (0.14 ppb). Obtained detectability compares with sophisticated expensive state-of-art detection levels suggesting that our nanocomposite may be used in many fields of study including medicine, microbiology and chemistry of materials.