| Tannins are widely found in plants in nature and are widely used in the food industry as well as in nutraceuticals for their antioxidant,anti-aging,food preservation,and tumor prevention functions.Metal ions are commonly used in catalysis,bio-imaging and disease diagnosis and treatment.Tannins molecules and metal ions Fe~Ⅲin aqueous solution can rapidly self-assemble to form Fe~ⅢTA network structures(MPN)through ligand chelation.Due to the super adhesion of tannins molecules to the surface of various entities,the addition of tannins as well as metal ions in solution with various entities as templates can form Fe~ⅢTA surface coatings on the surface of the entities.Given the versatility of tannins molecules as well as metal ions Fe~Ⅲ,MPN has very important research and application value in the field of biomedical engineering.In the treatment of bacterial infections at wound sites,the formation of biofilms can lead to increased bacterial resistance to drugs and disrupt the wound healing process.Conventional countermeasures are to improve drug bioavailability by disrupting biofilm integrity and increasing the effective contact between bacteria and drug.Tannins therapies based on local warming strategies are currently widely used to disrupt biofilms and increase antimicrobial efficacy.However,these methods have disadvantages such as the difficulty of complete biofilm disruption and the lack of targeting and damage to surrounding normal tissues.Therefore,we propose to use metal ions and tannins to self-assemble on the surface of bacteria and their biofilms to achieve tight encapsulation of biofilms and free state bacteria.Meanwhile,the excellent tannins conversion performance of MPN is utilized to achieve low-temperature tannins therapy(m PTT)on bacteria and their biofilms,overcoming the problem of low heat utilization due to the distance barrier in the heat transfer process of conventional PTT drugs.Effective destruction of biofilm and effective killing of bacteria are achieved while generating lower local temperature,which in turn reduces damage to surrounding normal tissues and promotes healing of the wound site.In addition,the acidic conditions at the infected site stimulate the release of tannins(TA),which exert their anti-inflammatory activity and are able to sustain treatment and prevention of infection,further alleviating inflammation caused by PTT and bacterial infection.These benefits make the tight-fitting,low-temperature antimicrobial dressing strategy effective in accelerating and improving wound healing after bacterial infections.Based on the high biocompatibility and biosafety of the Fe~ⅢTA network structure,we propose a bacterial-driven bio-hybrid microrobot prepared by encapsulating the bacterial surface with an MPN coating.It is verified that the MPN coating forms a protective shell on the bacterial surface,which effectively protects the bacteria from the surrounding environment lysozyme,antibiotics and UV light.The thickness of the shell depends on the material concentration and the number of coating wraps,while the thickness affects the movement speed and trajectory of the microrobots.We tuned the preparation parameters to obtain micro-robots with effective propulsion.In addition,the microrobots remain sensitive to external stimuli and exhibit tropism to glucose.Based on this,we loaded the microrobots with the anticancer drug adriamycin and actively transported it to tumor cells 4T1 in vitro to slowly release the drug anti-tumor using the acidic microenvironment at the tumor site.The Fe~ⅢTA coating strategy to modify the bacterial surface is not dependent on genetic manipulation,is efficient,and maintains bacterial viability and chemotaxis,offering great potential for biomedical applications in the design of multifunctional biohybrid micro-robotic platforms. |
