Currently, the technologies accompanying the usage of waste materials for the fabrication of innovative useful materials have been significantly advanced. For the same purpose, a possible sustainable approach was demonstrated for the utilization of jute caddies, known as jute industry waste. From the industrial waste, carbon dots (CDs) were sonochemically prepared, followed by their surface modification with benzalkonium chloride (BZC) to yield waste jute-derived fluorescent surface-quaternized CDs (JB-CDs), which exhibit excellent water solubility, excitation-dependent emission, and good photostability, and were utilized as a fluorescent nanoswitch to detect inorganic pollutants, such as chromium (VI) [Cr­(VI)] ions, in aqueous solutions. JB-CDs can detect Cr­(VI) concentrations as low as 0.03 μM through luminescence quenching (“turn-off”) and further recover their fluorescence (“turn-on”) selectively for sensing ascorbic acid (AA), compared with other metal ions and biomolecules tested. The present technique has the advantages of fast response time and high selectivity and sensitivity in practical applications. JB-CDs were tested against a Gram-negative bacterium, Escherichia coli, and a Gram-positive bacterium, Staphylococcus aureus, to confirm their bactericidal activity. The results indicated that JB-CDs substantially inhibited the growth of the tested bacteria. Besides this, JB-CDs played the role of a nanovehicle to exemplify the release study of a model drug ciprofloxacin. It was observed that the surface-quaternized JB-CDs showed a pH-responsive release behavior, where the release behavior was found to be better controlled at pH 7.4 than at pH 5.2 and 6.8. The synthesis of such a fluorescent nanobutton, stimuli-responsive drug release, and antibacterial nanomaterial using a sustainable material such as jute industrial waste can pave the path for a smart multifunctional material.

In recent years, lignin has drawn increasing attention for different applications due to its intrinsic antibacterial and antioxidant properties, coupled with biodegradability and biocompatibility. However, chemical modification or combination with metals is usually required to increase its antimicrobial functionality and produce biobased added-value materials for applications wherein bacterial growth should be avoided, such as biomedical and food industries. In this work, a sonoenzymatic approach for the simultaneous functionalization and nanotransformation of lignin to prepare metal-free antibacterial phenolated lignin nanoparticles (PheLigNPs) is developed. The grafting of tannic acid, a natural phenolic compound, onto lignin was achieved by an environmentally friendly approach using laccase oxidation upon the application of high-intensity ultrasound to rearrange lignin into NPs. PheLigNPs presented higher antibacterial activity than nonfunctionalized LigNPs and phenolated lignin in the bulk form, indicating the contribution of both the phenolic content and the nanosize to the antibacterial activity. Studies on the antibacterial mode of action showed that bacteria in contact with the functionalized NPs presented decreased metabolic activity and high levels of reactive oxygen species (ROS). Moreover, PheLigNPs demonstrated affinity to the bacterial surface and the ability to cause membrane destabilization. Antimicrobial resistance studies showed that the NPs did not induce resistance in pathogenic bacteria, unlike traditional antibiotics.

A simple one-step process for the polymerization of dopamine has been developed using nitrogen-doped carbon dots (N@C–dots) as the sole initiator. The synthesized amorphous polydopamine (PDA)-doped N@C–dots (PDA–N@C–dots composite) exhibited a negative charge of –39 mV with particle sizes ranging from 200 to 1700 nm. The stable colloidal solution was active against methicillin-resistant Staphylococcus aureus (MRSA), a Gram-negative bacterium. The strong adhesion of the polymer to the bacterial membrane resulted in a limited diffusion of nutrients and wastes in and out of the cell cytosol, which is a generic mechanism to trigger cell death. Another possible route is the autoxidation of the catechol moiety of PDA to form quinone and release reactive oxygen species (ROS) such as superoxide radicle and hydrogen peroxide, two well-known ROS with antimicrobial properties against both Gram-negative and Gram-positive bacteria.

A polydopamine (PDA) composite was synthesized by depositing Zn-doped CuO (Zn@CuO) particles on polydopamine by one-step ultrasonication. XPS, XRD, and FTIR confirmed the formation of spherical Zn@CuO on PDA with resulting diameters ranging from 1 to 5 μm. The PDA-Zn@CuO at 0.125−0.5 mg/mL exhibited a superior activity over Zn@CuO against sensitive and antibiotic-resistant bacteria. The Zn@CuO nanosized hybrid particles could penetrate the cell but interacted less effectively with bacterial biomolecules to provoke rapid cell lysis. PDA above 0.5 mg/mL also had a modest effect against Escherichia coli and Staphylococcus aureus. However, much higher PDA concentrations were required to restrict the flow of essential nutrients and wastes in and out of the cytoplasmic matrix and resulted in eventual cell death. The binding of PDA-Zn@CuO to bacteria played an important role in causing bacterial death, whereas reactive oxygen species (ROS) also effectively contributed to cell killing.

By using ultrasound-assisted coating technology, we modified fabrics with N_Au NPs to fabricate antibiofilm fabrics.