An enzyme-free fluorometric nanoprobe for chloramphenicol based on signal amplification using graphene oxide sheets.

A sensitive and selective method for the determination of the antibiotic chloramphenicol (CAP) is described, which is based on double signal amplification and GO as an efficient fluorescence quencher. The nucleic acid probe is composed of three well-defined regions, viz. the signal probe I, the signal probe II, and the capture probe. The capture probe will bind to CAP specifically and the signal probes produce a significant fluorescence signal. One end of the signal probes is labeled with the fluorophore 6-carboxyfluorescein (FAM). The labeled probes can be adsorbed on graphene oxide (GO) via π-stacking interactions, upon which the green fluorescence of FAM (measured at excitation/emission wavelengths of 490/514 nm) is quenched. On addition of CAP, the aptamer/CAP complexes are formed, and this leads to the restoration of fluorescence due to the removal of the probes from GO. The double signal probes, together with GO as quencher, improve the fluorescence signal significantly and lower the detection limit. Under optimized conditions, the assay works in the 20- to 200-ppb CAP concentration range and has a 0.3-ppb detection limit. It is also successfully applied to the determination of CAP in spiked swine urine samples. The recoveries from spiked swine urine samples are between 97.73 and 108.56%, and the repeatability (expressed as the RSD) is between 4.66 and 8.90%. Graphical abstract The constructed DNA probes form a stable structure and bind to chloramphenicol specifically. One end of signal probes was labeled with the fluorophore 6-carboxyfluorescein (FAM). The detection sensitivity of chloramphenicol was significantly enhanced by using double signal amplification, which was superior to the traditional methods. The quantities of CAP can be achieved by fluorescence increment.

Pd-Cu nanoalloy for dual stimuli-responsive chemo-photothermal therapy against pathogenic biofilm bacteria.

Photothermal therapy (PTT) is a promising strategy for antimicrobial therapy. However, the application of PTT to treat bacterial infections remains a challenge as the high temperature required for bacterial elimination can partly damage healthy tissues. Selecting the appropriate treatment temperature is therefore a key factor for PTT. In this work, we designed a near-infrared/pH dual stimuli-responsive activated procedural antibacterial system based on zeolitic imidazolate framework-8 (ZIF-8), which was bottom-up synthesized and utilized to encapsulate both Pd-Cu nanoalloy (PC) and the antibiotic amoxicillin (AMO). This procedural antibacterial therapy comprises chemotherapy (CT) and PTT. The former disrupts the bacterial cell wall by releasing AMO in an acidic environment, which depends on the sensitive response of ZIF-8 to pH value change. With the progression in time, the AMO release rate decreased gradually. The latter can then significantly stimulate drug release and further complete the antibacterial effect. This impactful attack consisted of two waves that constitute the procedural therapy for bacterial infection. Accordingly, the treatment temperature required for antibacterial therapy can be significantly lowered under this mode of treatment. This antibacterial system has a significant therapeutic effect on planktonic bacteria (G+/G-) and their biofilms and also has good biocompatibility; thus, it provides a promising strategy to develop an effective and safe treatment against bacterial infections. STATEMENT OF SIGNIFICANCE: We have developed a near infrared/pH dual stimuli-responsive activated procedural antibacterial system that combines enhanced antibiotic delivery with photothermal therapy and has highly efficient antimicrobial activity. The antibacterial effect of this therapy was based on two mechanisms of action: chemotherapy, in which the bacterial cell wall was first destroyed, followed by photothermal therapy. After exposure to irradiation with an 808 nm laser, the inhibition rates were 99.8% and 99.1% for Staphylococcus aureus and Pseudomonas aeruginosa, respectively, and the clearance rates for their established biofilms were 75.3% and 74.8%, respectively. Thus, this procedural antibacterial therapy has shown great potentiality for use in the photothermal therapy of bacterial infectious diseases, including biofilm elimination.

Efficient Eradication of Bacterial Biofilms with Highly Specific Graphene-Based Nanocomposite Sheets.

Bacterial biofilms are usually resistant to antibiotics, thus powerful methods are required for removal. Nanomaterial involving a combination of treatment modalities recently has been recognized as an effective alternative to combat biofilm. However, its targeted and controlled release in bacterial infection is still a major challenge. Here, we present an intelligent phototherapeutic nanoplatform consisting of an aptamer (Apt), indocyanine green (ICG), and carboxyl-functionalized graphene oxide (GO-COOH), namely, ICG@GO-Apt, for targeted treatment of the biofilm formed by Salmonella Typhimurium. Since Apt-conjugated nanosheets (NSs) can specifically accumulate near abscess caused by the pathogens, they enhance greatly the local drug molecule concentration and promote their precise delivery. They can simultaneously generate heat and reactive oxygen species under near-infrared irradiation for photothermal/photodynamic therapy, thereby significantly enhancing biofilm elimination. The phototherapeutic ICG@GO-Apt also displays a good biocompatibility. More importantly, the multifunction phototherapeutic platform shows an efficient biofilm elimination with an efficiency of greater than 99.99% in an abscess formation model. Therefore, ICG@GO-Apt NSs with bacteria-targeting capability provide a reliable tool for clinical bacterial infection that circumvents antibiotic resistance.