Biogenic Melanin-Modified Graphene as a Cathode Catalyst Yields Greater Bioelectrochemical Performances by Stimulating Oxygen–Reduction and Microbial Electron Transfer

Bioelectrochemical systems (BES) can recover energy from organic-bearing waste streams, but their use has been stymied by poor electron transfer from the cathode. Redox-active electron shuttles could stimulate electron transfer provided that they are compatible with the exoelectrogenic bacteria. This work evaluated melanin-modified carboxylated graphene (M/CG) as a novel cathode catalyst in a microbial fuel cell. Biogenic melanin catalysts (i.e., bio-M/CG) significantly increased bioelectricity production due to its abundant pyrrole N, which lowered charge-transfer resistance and, thus, promoted the cathodic oxygen–reduction reaction (ORR). The high content of pyrrole N in the bio-M/CG catalyst also enriched exoelectrogens, such as Azospirillum, Chryseobacterium, and Azoarcus, which accounted for over 50% of the total abundance of bacteria in biofilms on the anode. Moreover, the functional genes of key enzymes involved in microbial electron transfer (MET) were increased by the bio-M/CG catalyst. These data confirm that the bio-M/CG catalyst improved the bioelectrochemical performance via synergetic promotion of cathodic ORR and microbial electron transfer, thus providing a new alternative for advancing BES technology. This work highlights the potential application of melanin in enhancing cathodic oxygen–reduction reaction kinetics and improving microbial electron transfer in BES. This study emphasizes the promising application of melanin in enhancing the ORR kinetics and improving MET in BES, offering exciting prospects for future sustainable and environmentally friendly applications

Development of Anti-CD74 Antibody–Drug Conjugates to Target Glucocorticoids to Immune Cells

Glucocorticoids (GCs) are excellent anti-inflammatory drugs but are dose-limited by on-target toxicity. We sought to solve this problem by delivering GCs to immune cells with antibody–drug conjugates (ADCs) using antibodies containing site-specific incorporation of a non-natural amino acid, novel linker chemistry for in vitro and in vivo stability, and existing and novel glucocorticoid receptor (GR) agonists as payloads. We directed fluticasone propionate to human antigen-presenting immune cells to afford GR activation that was dependent on the targeted antigen. However, mechanism of action studies pointed to accumulation of free payload in the tissue culture supernatant as the dominant driver of activity and indeed administration of the ADC to human CD74 transgenic mice failed to activate GR target genes in splenic B cells. Suspecting dissipation of released payload, we designed an ADC bearing a novel GR agonist payload with reduced permeability which afforded cell-intrinsic activity in human B cells. Our work shows that antibody-targeting offers significant potential for rescuing existing and new dose-limited drugs outside the field of oncology