The Control Of Bacterial Biofilm Based On Aptamer-Functioned Carbon Nanotubes

Biofilms are stable bacterial extracellular communities consisted of polysaccharides,proteins,nucleic acids and lipids.It is always difficult to treat when bacteria form communities known as biofilm in host,which is considered a major stimulative factor to bring about chronic infection and the rising of multiresistant bacteria.Therefore,seeking efficient approaches to control and eradicate biofilm is significant.Aptamers are single-stranded DNA or RNA generated in an in vitro process called SELEX(Systematic Evolution of Ligands by Exponential Enrichment),which can bind to their targets stably with high affinity and specificity.They could bind to a range of targets like small molecules,proteins and even whole cells.Based on the excellent properties above,aptamers have been widely applied in diagnostics and therapeutics.Single-walled carbon nanotubes(SWNTs)are a kind of carbon nanomaterial that possess good physicochemical properties like fluorescence quenching activity,penetrability and electrical conductivity,which have been used broadly in chemistry,materialogy and biomedicine.Furthermore,SWNTs also have been confirmed that could exhibit both antimicrobial and antibiofilm activity.This study aims to use aptamer that targets Pseudomonas aeruginosa(P.aeruginosa)cell to investigate whether it can play a role of targeting agent to enhance the efficiency of antibiofilm compounds.And two complexes were constructed and their inhibition effects or eradication activities against P.aeruginosa biofilm were assessed.(1)SWNTs have excellent surface properties,nucleic acid molecules could absorb onto their surface tightly.So after incubation of aptamer targets P.aeruginosa cell(PAap1)with SWNTs,PA-ap1 could absorb onto the surface of SWNTs to form a stable complex AP-SWNTs.The complex then could inhibit about 68% biofilm formation according to the results of crystal assay and microscopic observations,which inhibited about 36% more biofilm formation than SWNTs alone.Furthermore,a combination of AP-SWNTs and sodium nitroprusside(SNP)that can disperse formed biofilm was also used to treat formed biofilm,and the results showed that 72% formed biofilm decrease was observed,which outperformed simple mixture of SWNTs and SNP.The results of this section underscore the availability of aptamer acts as targeting agent to enhance the efficiency of antibiofilm agents preliminarily,and also provide a new method to treat formed biofilm.(2)Here,a complex by means of high selectivity between aptamer and its target was designed to control bacterial biofilm.Specifically,5,-amino-modified PA-ap1 was interacted with ciprofloxacin(CPX)containing a carboxyl group to form a conjugation AP-CPX.Ultraviolet spectrum scanning and agarose gel electrophoresis were used to confirm the formation and specificity of AP-CPX respectively.Then the conjugation wrapped onto SWNTs to construct a tertiary complex AP-CPX-SWNTs.The tertiary complex was then tested to inhibit biofilm formation or eradicate formed biofilm by use of crystal assay and microscopic observations.The results demonstrated that APCPX-SWNTs could inhibit about 90% biofilm formation and eradicate about 75% formed one,which performed better than either component significantly.The design of AP-CPX-SWNTs has several merits,which may be a potential tool to treat biofilm in the future.