Layer-by-layer polyelectrolyte encapsulation of Mycoplasma pneumoniae for enhanced Raman detection
Mycoplasma pneumonia is a major cause of respiratory disease in humans and accounts for as much as 20% of all community-acquired pneumonia. Existing mycoplasma diagnosis is primarily limited by the poor success rate at culturing the bacteria from clinical samples. There is a critical need to develop a new platform for mycoplasma detection that has high sensitivity, specificity, and expediency. Here we report the layer-by-layer (LBL) encapsulation of M. pneumoniae and mycoplasma commensal cells with Ag nanoparticles in two different polyelectrolyte matrixes; one matrix is the combination poly(allylamine hydrochloride) (PAH) with poly(styrene sulfonate) (PSS) and the other is poly(diallyldimethylammonium chloride) (PDADMAC) with PSS. We evaluated nanoparticle encapsulated mycoplasma cells as a platform for the differentiation of M. pneumoniae from mycoplasma commensal strains using surface enhanced Raman scattering (SERS) combined with multivariate statistical analysis. Pathogenic strains such as M. pneumoniae (M129) and M. genitalium, along with a series of commensal mycoplasma strains, were studied. Scanning electron microscopy, fluorescence imaging, and AFM showed that the Ag nanoparticles were incorporated between the oppositely charged polyelectrolyte layers. SERS spectra showed that LBL encapsulation provides excellent spectral reproducibility. Multivariate statistical analysis of the Raman spectra differentiated the pathogenic strains from the commensal strains with near 90-100% specificity and sensitivity, and low root mean square error. The technique shows promise for adaptation to sample preparation of M. pneumoniae infections in clinical specimens and represents a valuable alternative to current bacterial diagnostic techniques.
Seyed R. Taghavi, University of Arkansas