A novel application of a highly sensitive biosensor based on long-period fiber gratings (LPFG) coated with microporous polyelectrolyte coating for Gram-negative bacteria detection was investigated. The uniform microporous coating with large surface area was fabricated with weak polyelectrolytes poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) via layer-by-layer (LbL) assembly, followed by a brief exposure to acidic aqueous solutions at pH=4. The diameter of the micropores could be adjusted in a wide range by thermal treatment and ionic etching. The effect of pore size and surface topography on bacteria adhesion was examinged. Optofluidic LPFG platform for real-time monitoring of the bacteria binding/ adhesion in a flowing condition was investigated by measuring the spectral shift in the resonance wavelength. The coated LPFG platform was further functionalized with covalently immobilized bacteria antibody for specific bacterial detection with a concentration as low as 104 CFU/ml. Comparing with the widely used biosensors based on surface plasmon resonance (SPR), no moving part or metal deposition is required in our biosensor, making it highly sensitive, accurate, compact and cost effective.
Hospital acquired infections in indwelling device have become a life-threatening issue accompanied by the wide use of medical devices and implants. The infection process typically involves the attachment, growth and eventual assemblage of microbial cells into biofilms, with the latter exhibiting extremely higher antibiotic tolerance than planktonic bacteria. Surface constructed antimicrobial coatings offer a viable solution for bacteria responsive antibiotic strategy in medical devices such as catheter and stents. Therapeutic peptide has pioneered the field for their attractive pharmacological profile with broad antibacterial spectrum, great efficacy and long life-span. It has been a common practice to separately assess bacteria responses through commercially available activity assay kits after their exposure to antibiotic coatings, limiting the assessment of their activity in vitro with a discontinuous fashion. We developed and demonstrated an innovative all-optical lab-on-fiber optofluidic platform (LOFOP) to fill in this technical gap by allowing in situ measurement of the bacteria attachment in a continuous manner. This LOFOP allows for evaluation of drug release and resultant bacterial response by integrating glass capillary with lytic peptide-containing LbL-coated long period graing (LPG) as its core. S. aureus suspension is introduced through the assembled optofluidic platform with the capillary and the peptide-coated LPG. The efficacy of the peptide-containing coating is evaluated in situ by monitoring the attachment of bacteria and the ensuing development of biofilms using the LPG. LPG without antimicrobial coatings will be explored and compared as control.
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