Bacteria cellulose (BC) nanofibers are used as robust biotemplates for the facile fabrication of novel gold nanoparticle (NP)–bacteria cellulose nanofiber (Au–BC) nanocomposites via a one‐step method. The BC nanofibers are uniformly coated with Au NPs in aqueous suspension using poly(ethyleneimine) (PEI) as the reducing and linking agent. With the addition of different halides, Au–BC nanocomposites with different Au shell thicknesses are formed, and a possible formation mechanism is proposed by taking into account the special role played by PEI. A novel H2O2 biosensor is constructed using the obtained Au–BC nanocomposites as excellent support for horseradish peroxidase (HRP) immobilization, which allows the detection of H2O2 with a detection limit lower than 1 µM. The Au–BC nanocomposites could be further used for the immobilization of many other enzymes, and thus, may find potential applications in bioelectroanalysis and bioelectrocatalysis.

Stable protein-clay films were fabricated by casting an aqueous dispersion of protein and clay on pyrolytic graphite electrodes. Myoglobin (Mb), hemoglobin (Hb), and horseradish peroxidase (HRP) in clay films gave a pair of well defined, quasi-reversible cyclic voltammetric peaks at about -0.28 V vs SCE in pH 5.5 buffers, characteristic of the protein heme Fe III /Fe II redox couples. Square wave voltammograms (SWV) of the protein-clay films gave good fits by nonlinear regression analysis to a model that featured thin-layer SWV and formal potential dispersion, providing average apparent heterogeneous electrontransfer rate constants, ks, and average formal potentials, E°′. UV-vis and reflectance absorption infrared spectra showed that the proteins in clay films retained near-native secondary structures. X-ray diffraction revealed that Mb-clay and Hb-clay films feature ordered layered structures with Mb and Hb intercalated between clay layers. Incorporated HRP induced disorder in the clay films. Oxygen, trichloroacetic acid, nitrite, and hydrogen peroxide were catalytically reduced by all three proteins in clay films.

Stable films of clay and hemoglobin (Hb) were assembled layer-by-layer on various solid substrates by alternate adsorption of negatively charged clay platelets from their aqueous dispersions and positively charged Hb from pH 4.5 buffers. Cyclic voltammetry (CV), quartz crystal microbalance, and UV−vis spectroscopy were used to monitor film growth. CV of {clay/Hb} n films on pyrolytic graphite electrodes showed a pair of well-defined, nearly reversible peaks at about −0.27 V versus saturated calomel electrode (−0.02 V vs normal hydrogen electrode) at pH 5.5, characteristic of the HbFeIII/FeII redox couples. Although the amount of Hb adsorbed in each bilayer was essentially the same, the fraction of electroactive Hb decreased with the number of clay/Hb bilayers (n). Electroactivity of Hb extended to six clay/Hb bilayers. The Soret absorption band of Hb in {clay/Hb}6 films showed that Hb retained its secondary structure similar to its native state in the medium pH range. A Bragg peak in X-ray diffraction for {clay/Hb}20 films suggested a partly ordered, layered structure of the films, but without full Hb intercalation. {Clay/Hb}6 film electrodes catalyzed the electrochemical reduction of trichloroacetic acid, oxygen, and hydrogen peroxide.