DNA hybridization may be accelerated by nearly homogeneous solution of silica NPs, facilitating the solid-state sensors for single-base mismatch detection ( Wang and Liu, 2007). The formation of a complex with DNA probes and CCP on the surface increases local concentration of donor units and delivers excitations to C ⁎. The silica NP-based DNA hybridization assay with complimentary sequences with cationic-conjugated polymer (CCP) complexes provides 110-fold signal amplification ( Figure 6). The DNA probe was immobilized in a solution and NPs captured the complimentary DNA sequences bringing the chromophore (C ⁎) to the surface and caused intense acceptor emission on polymer excitation. Thus, Wang and Liu (2007) have reported the probe-immobilized silica NP surface as a platform to achieve high sensitivity and selectivity for DNA detection. Labeling of specific DNA targets using silica nanomaterials can be achieved using a detection limit of 1 pM, a dynamic range of approximately four orders of magnitude, and a selectivity ratio of 14:1 against one-base mismatches ( Zhao et al., 2003). The conjugated silica is stable in both aqueous electrolytes and organic solvents and does not aggregate. It has lower susceptibility to photobleaching and produces higher signal intensity in DNA hybridization. The recent application of silica nanomaterials in nucleic acid detection is more beneficial in comparison to other organic fluorophores. The silica surface offers an extensive area for the surface immobilization of DNA molecules, and the shielding of the silica matrix creates better photostability ( Rogers et al., 1999 Santra et al., 2001). DNA fluorophores enclosed by the silica network limit atmospheric oxygen degradation and produce constant fluorescence for ultrasensitive DNA detection ( Zhao et al., 2003). Magnetic silica nanomaterials facilitate bimolecular loading and transportation ( Santra et al., 2001 Trewyn et al., 2007). Thus, the dye-doped fluorescent silica nanomaterials provide increased signal amplification for DNA sensing ( Wang et al., 2006). Nanostructured silica with unique geometric properties can form improved biomaterial conjugates with various hybrid nanomaterials. Recently, they have drawn great attention due to their stability, low toxicity, and ability to be functionalized with a range of molecules and polymers. Nanostructured silica or silicon dioxide nanoparticles or silica nanoparticles are one of the major substrates for widespread utilization in DNA biosensors ( Tan et al., 2004). Bhargava, in Reference Module in Materials Science and Materials Engineering, 2016 2.2 Nanostructured Silica
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