Preparation Of Self-Assembled LDHs/DNA Layer-by-layer Films And Their Interactions

DNA-containing multilayer films have attracted increasing attentions in the research areas in biochemistry and biotechnology, due to their potential application as biomaterials for fabrication of biomolecular sensor, devices, and drug-releasing mats. Layered double hydroxides (LDHs) are a large family as hydrotalcite-like layered clays. The layered materials with two-dimensional nanostructures consist of positively charged layer with charge balancing anions and water moleculars between the layers. LDHs have been demonstrated one type of promising materials in applications such as catalysts, sorbents, lithium-ion battery electrodes, and carriers for cellular drug and gene delivery. So far, LDHs involved in the this fields are usually in powder form, which inevitablly give rise to problems such as easily lost, low utilization, poor contact efficiency and difficulties in separation.Layer-by-layer self-assembly (LBL) technique offers an easy process and allows to control the multilayer formation in a molecular scale. In this present study, we report on fabrication of LDHs/DNA hybrid film via LBL self-assembly technique. By variation of LDHs size, different substrates as well as different self-assembly routines, we were able to construct LDHs/DNA composite films with different film structures. The film morphologies and structures as well as the structure of DNA were also invetigated. The obtained results are presented as follows:(1) Two kinds of LDH nanosheets with different sizes were synthesized as building block. The LDHNS/DNA films were fabricated via LBL self-assembly technique on modified quartz and mica substrates. Both films show linear and three-dimensional network structures containing DNA and small LDH nanosheets. Circular Dichroism (CD) results show that the structure of DNA preserve the supercoiled conformation.(2) Two kinds of films (two layers) were prepared, containing large and small size modified LDH, respectively, and DNA. AFM results indicate that DNA molecules exhibited agglomeration in the films which containing large modified LDH and DNA, but show the network-like structure in the film which assembled by small modified LDH and DNA. The CD results also demonstrate that the structure of DNA shows the supercoiled conformation in large LDH/DNA films, but not in the small LDH/DNA films.