Labeling and Selective Inactivation of Gram‐Positive Bacteria Employing Bimodal Photoprobes with Dual Readouts

Abstract

Carbohydrate-conjugated silicon(IV) phthalocyanines with bimodal photoactivity were developed as probes with both fluorescent labeling and photosensitizing capabilities, and the concomitant fluorescent labeling and photoinduced inactivation of Gram-positive and Gram-negative models was explored. The maltohexaose-conjugated photoprobe provides a dual readout to distinguish between both groups of pathogens, as only the Gram-positive species was inactivated, even though both appeared labeled with near-infrared luminescence. Antibiotic resistance did not hinder the phototoxic effect, as even the methicillin-resistant pathogen Staphylococcus aureus (MRSA) was completely photoinactivated. Time-resolved confocal fluorescence microscopy analysis suggests that the photoprobe sticks onto the outer rim of the microorganisms, explaining the resistance of Gram-negative species on the basis of their membrane constitution. The mannose-conjugated photoprobe yields a different readout because it is able to label and to inactivate only the Gram-positive strain.

Harnessing the Maltodextrin Transport Mechanism for Targeted Bacterial Imaging: Structural Requirements for Improved in vivo Stability in Tracer Design

“…The maltohexaose derivative MB1143 was prepared in a convergent manner starting from commercially available peracetylated maltohexaose (Scheme A). Following selective deprotection of the anomeric position, the resulting alcohol was converted, via a trichloroacetimidate, into the propargylic glycoside as a platform for a copper(I)‐mediated click reaction …”

Axially Decorated SiIV‐phthalocyanines Bearing Mannose‐ or Ammonium‐conjugated Siloxanes: Comparative Bacterial Labeling and Photodynamic Inactivation,

“…and implemented in our group by Galstyan et al . as a synthetic precursor (for further details, see ). The axial decoration with silanes has many advantages if compared with the direct linkage of alcohols: The C 3 ‐Si‐O‐Si‐C 3 backbone is hydrophobic and chemically inert, bearing a high stability toward heat, hydrolysis and radiation .…”

“…1 was synthesized as previously reported with only one minor modification concerning the activation of the azidoacetic acid with the use of oxalylchloride . For details, please refer to the and Scheme 1.…”

“…Optimized synthetic route toward 1 employing the azide‐substituted “ click ” building‐block Si IV P c[ OS i( CH 3 ) 2 ( CH 2 ) 3 ( NH ) COCH 2 N 3 ] 2 and the acetylated mannose‐functionalized intermediate Si IV P c(AcetylMan) 2 as previously reported by Galstyan et al . The synthesis of 1 was improved and optimized by activation of the azidoacetic acid with oxalylchloride and reaction of the resulting acyl chloride with Si IV P c[ OS i( CH 3 ) 2 ( CH 2 ) 3 ( NH 2 )] 2 .…”

“…Herein, we compare the targeting and PDI efficiency of two axially substituted Si IV Pcs: a neutral Si IV Pc with two mannose units axially attached ( 1 , previously published by our group, see Galstyan et al …”