Bio-Conjugated CNT-Bridged 3D Porous Graphene Oxide Membrane for Highly Efficient Disinfection of Pathogenic Bacteria and Removal of Toxic Metals from Water

Abstract

More than a billion people lack access to safe drinking water that is free from pathogenic bacteria and toxic metals. The World Health Organization estimates several million people, mostly children, die every year due to the lack of good quality water. Driven by this need, we report the development of PGLa antimicrobial peptide and glutathione conjugated carbon nanotube (CNT) bridged three-dimensional (3D) porous graphene oxide membrane, which can be used for highly efficient disinfection of Escherichia coli O157:H7 bacteria and removal of As(III), As(V), and Pb(II) from water. Reported results demonstrate that versatile membrane has the capability to capture and completely disinfect pathogenic pathogenic E. coli O157:H7 bacteria from water. Experimentally observed disinfection data indicate that the PGLa attached membrane can dramatically enhance the possibility of destroying pathogenic E. coli bacteria via synergistic mechanism. Reported results show that glutathione attached CNT-bridged 3D graphene oxide membrane can be used to remove As(III), As(V), and Pb(II) from water sample at 10 ppm level. Our data demonstrated that PGLa and glutathione attached membrane has the capability for high efficient removal of E. coli O157:H7 bacteria, As(III), As(V), and Pb(II) simultaneously from Mississippi River water.

Keywords: 3D porous graphene oxide membrane; As(V) and Pb(II) from water; CNT-bridged graphene oxide; E. coli O157:H7 bacteria removal; bacteria disinfection; separation of As(III).

Figure 1

(A) EDX mapping shows the presence of C and O in water-soluble graphene oxide. (B) TEM image of freshly prepared PEG amine functionalized SWCNT. (C) SEM image of PGLa and glutathione-conjugated CNT-bridged graphene oxide membrane shows the 3D structure with pore sizes of 300–500 nm. (D) EDX mapping shows the presence of C, N, S, and O in PGLa and glutathione-conjugated CNT-bridged graphene oxide 3D network membranes. (E) FTIR spectrum shows the existence of amide A, I, and II bands, which indicates the presence of peptides on the 3D membrane. Similarly, the presence of −SH and −CS bands clearly indicate the presence of glutathione on the 3D membrane. The stretches of −CO, −OH, −CN, and –C–OH groups from graphene oxide and CNT can also be seen on the FTIR spectra. (F) Raman spectrum from freshly prepared hybrid membrane clearly indicates the presence of D and G bands in PGLa and glutathione-conjugated CNT-bridged graphene oxide 3D network membranes. (G) Photograph shows freshly prepared PGLa and glutathione-conjugated CNT-bridged porous hybrid graphene oxide membrane.

Figure 2

(A) Plot shows E. coli O157:H7 removal efficiency using PGLa conjugated CNT-bridged 3D graphene oxide membrane. Reverse transcription polymerase chain reaction (RTPCR) was used to quantify the amount of E. coli O157:H7 present. (B) TEM image shows the capture of E. coli O157:H7 by CNT-bridged hybrid graphene oxide membrane. (C) SEM image demonstrating the capture of E. coli O157:H7 by PGLa-conjugated CNT-bridged 3D graphene oxide based membrane. Colonies of E. coli O157:H7 showing the amount of live E. coli O157:H7 bacteria (D) after filtration by our membrane and (E) before filtration. (F) Fluorescence image shows the presence of E. coli O157:H7 bacteria on membrane after E. coli O157:H7 infected water was filtered by membrane. (G) Fluorescence image shows the absence of E. coli O157:H7 bacteria in water after separation by membrane.

Figure 3

(A) RTPCR data show E. coli O157:H7 killing efficiency using CNT-bridged 3D GO without PGLa, with only PGLa, and with PGLa conjugated CNT-bridged 3D graphene oxide membrane. Colonies of E. coli O157:H7 bacteria demonstrating the amount of live bacteria after filtration by membrane in the presence of (B) PGLa-conjugated CNT-bridged 3D graphene oxide membrane and (C) CNT-bridged 3D graphene oxide based membrane without PGLa.

Figure 4

(A) As(III) removal efficiency using glutathione-conjugated CNT-bridged 3D graphene oxide membrane. ICP-MS was used to quantify the amount of As(III) present. (B) As(V) removal efficiency using glutathione-conjugated CNT-bridged 3D graphene oxide membrane. ICP-MS was used to quantify the amount of As(V) present. (C) Pb(II) removal efficiency using glutathione-conjugated CNT-bridged 3D graphene oxide membrane. ICP-MS was used to quantify the amount of Pb(II) present. (D) Percentage of removal efficiency for different toxic metals using CNT-bridged 3D graphene oxide membrane without glutathione. Reported data clearly show that the presence of gluthione is very important for high efficiency As(III), As(V), and Pb(II) removal.

Figure 5

Plot showing percentage of removal efficiency of different toxic metals and E. coli bacteria by PGLa and glutathione attached CNT-bridged 3D graphene oxide membrane from Mississippi River water.

Scheme 1. Schematic Representation of the Disinfection of E. coli O157:H7 Pathogens and Separation of Toxic Metals Using PGLa and Glutathione-Conjugated CNT-Bridged Porous Graphene Oxide Membrane^a

^a(Inset, left) TEM picture of E. coli pathogens being captured by 3D membrane. (Inset, top right) Bacteria colony counting results show that no E. coli O157:H7 is present in the water once it has been passed through the membrane. (Inset, bottom right) Removal efficiency data shows the membrane cab be used to separate biological and chemical toxin simultaneously.

Scheme 2

Schematic Representation Showing (A) the Synthesis Procedure for Graphene Oxide from Graphite, (B) Our Synthesis Procedure to Develop PEG-Amine-Functionalized CNT, and (C) the Synthesis Procedure for the CNT-Bridged 3D Graphene Oxide Membrane