Constructions And Properties Of Pillar[n]arene-based Antibacterial Nanomaterials

Bacterial infections aroused by pathogens have been the major threats to human health,which led to high morbidity and mortality in the third world countries.The discovery and application of antibiotics have relieved the situation.However,the long-term abuse of conventional antibiotics has promoted the generation of drug-resistant bacteria,which would further do serious harm to public security in many aspects,such as water,food and livestock,etc.Thus,developing novel,effective and safe antibacterial strategies remain imperative.Recently,with the advances of nanotechnology,researchers have fabricated a series of functional nanomaterials with supramolecular macrocyclic molecules and covalent self-assembly by rational design.Covalent self-assembly is a strategy which is easily synthesized without templates and able to construct high stable assemblies by utilizing building blocks with multiple functional groups.Supramolecular macrocyclic molecules have excellent host-guest properties and can be functionalized by chemical modifications.Based on this design concept,we utilized functionalized pillar[5]arene as the building block and built three kinds of polymer assemblies by covalent self-assembly,which was further developed to construct photodynamic antibacterial nanosheets,chemodynamic antibacterial capsules and selective photothermal antibacterial nanosheets in order to overcome bacterial infections.1.Pillar[5]arene-based photodynamic antibacterial nanomaterialsPDT is a therapy with photosensitizers and light irradiation to generate ROS,which attracts the interest of scientists in antibacterial fields.Nevertheless,many photosensitizers face the drawbacks of poor water-solubility and aggregation in water,which would decrease the generation efficiency of ROS and influence the antibacterial performance.In this work,single-layered nanosheets were prepared by covalent self-assembly with TPy P-Zn as the photosensitizer and BMCP5 as the crosslinker.Nanosheets were well dispersed both in water as well as physiological conditions and exhibited strong binding ability with SA.Besides,due to the bulk size of BMCP5 and electrostatic repulsions among nanosheets,nanosheets could avoid the aggregation of TPy P-Zn.Nanosheets could generate single oxygen under white-light illumination,which showed excellent photodynamic antibacterial effect towards SA.More importantly,ethylene glycol derivative modified with quaternary ammonium salt was introduced through host-guest interactions with BMCP5,thus further enhancing the water-solubility and biocompatibility of nanosheets.2.Pillar[5]arene-based chemodynamic antibacterial nanomaterialsCDT can covert H₂O₂ into·OH by Fenton or Fenton-like reaction.During the CDT process,the effect was affected by H₂O₂ concentration and p H values.With GOx efficiently catalyzing glucose to generate H₂O₂ and gluconic acid,the problem could be addressed.In this work,polymer capsules were constructed by covalent self-assembly with BDMP5 as the building block and diamine as the crosslinker,which could encapsulate Fe₃O₄ nanoparticles.The polymer capsules could be further methylated to be positively surface-charged.Positively charged capsules could absorb GOx and coordinate with Fe₃O₄ nanoparticles to form cascade catalytic reactor.With the presence of glucose,GOx could catalyze glucose to produce H₂O₂ and gluconic acid,which would degrade Fe₃O₄ nanoparticles to generate Fe²⁺.With the catalyzing of Fe²⁺,H₂O₂ could be converted into·OH by Fenton reaction,realizing effective chemodynamic antibacterial effect towards E.coli.Furthermore,quaternary ammonium salt modified with mannose was introduced through host-guest interactions with BDMP5.In this way,the water-solubility and biocompatibility of capsules were greatly improved.Mannose could also interact with E.coli,promoting much better chemodynamic antibacterial performance.3.Pillar[5]arene-based selective photothermal antibacterial nanomaterialsPTT can covert the energy of light to generate high temperature,which would lead to the protein denaturation of bacteria.PDI can be selectively reduced to generate radical anions by E.coli,which can absorb the energy of NIR light to achieve photothermal conversion.However,due to the chemical structure of PDI,it is poorly water soluble and results in the quenching of radical anions by?-?stacking.In this work,single-layered nanosheets were fabricated by covalent self-assembly with BDMP5 being the building block and tertiary aminated PDI being the crosslinker.The nanosheets could bind with E.coli and be reduced to produce radical anions.Owing to the bulk size of BDMP5 and electrostatic repulsions among nanosheets,nanosheets could avoid the?-?stacking of PDI and the quenching of radical anions.Radical anions had good absorption at NIR region and caused hyperthermia under 808 nm irradiation,which could realize selective photothermal antibacterial therapy.