Corn vs. apple biochars: Efficient detoxication of heavy metals in nerve terminal model

• Biochars were prepared from agricultural waste corn cobs and dry apples by pyrolysis • Biocompatibility and absence of neurotoxic signs of biochars were documented • Biochars were less efficient in detoxication of Hg 2+ , Cd 2+ , Pb 2+ as compared to Cu 2+ • Corn cob biochar abolished harmful Cu 2+ -induced effects in nerve terminal model • Biochars are perspective for cleaning from Cu 2+ in the environment and in medicine Pollution with neurotoxic heavy metals is a global issue and increasingly problematic for environment and health worldwide. Development of efficient sorbents for in vivo detoxication, which are biocompatible, is of urgent necessity. Here, series of biochars for adsorption of heavy metals was prepared using “green” principles from agricultural waste corn cobs (CB) and dry apples (AB) by pyrolysis without additional functionalization. Neurotoxicity risk of CB and AB was assessed using cortex nerve terminals (synaptosomes), which are a sensitive biomodel with a rapid response to changes in key K + /Na + /Ca 2+ -dependent synaptic characteristics and membrane integrity. Sorption capacity of CB and AB was compared in aquatic media and animal model. In synaptosomes, biochars themselves did not affect the extrasynaptosomal levels of excitatory and inhibitory neurotransmitters L-[ 3 H]glutamate and [ 3 H]GABA, respectively, and the mitochondrial membrane potential. Therefore, CB and AB were biocompatible without neurotoxic signs. All studied biochars adsorbed Cu 2+ in synaptosomal suspension. However, CB was more efficient regarding adsorption of Cu 2+ , as compared to AB. CB completely abolished (by 98 %) Cu 2+ -induced increase in the extrasynaptosomal levels of L-[ 3 H]glutamate and [ 3 H]GABA. Both biochars had fewer efficacies in mitigation of toxic effect of Hg 2+ , Cd 2+ and Pb 2+ in nerve terminals as compared to Cu 2+ one. Detoxication radiolabeled data were confirmed by fluorimetry measuring the plasma membrane/mitochondrial membrane potential, and ROS generation using dyes rhodamine 6G, JC-1, DCF, respectively. CB due to its unique ability to completely eliminate harmful Cu 2+ -induced effects in nerve terminal model may be further considered as non-toxic de-coopering agent in Cu 2+ - targeted therapy.