Surface Modification and Application of Nanomaterials in Biotechnology

Many studies about nanomaterials have been widely explored in recent decades in different scientific and technological areas. Several authors consider that the discovery of CNTs by Iijima [1] and graphene by Geim and Novoselov [2], stimulated the studies in nanotechnology. Concomitantly, the advances in probe, scanning, and transmission microscopies, it has also contributed to the discovery of new nanostructures and the understanding of others that were not yet well elucidated. It was expected exceptional physico-chemical properties and biocompatibility of nanostructures such as CNTs, graphene, h-BN, BNNTs and metallic nanoparticles, among others [3]. On the one hand, these materials have an enormous potential range of applications in nanotechnology, bioengineering and biomedicine [4,5], such as tumor markers[6], drugs delivers [7], bio-packaging [8], biosensing [9-11], adjuvant in vaccines [5-12,13], among others. However, the compatibility and dispersion of these nanoparticles in the medium of interest are fundamental to their potential applications [3]. The nanoengineering interfaces between host biological system and nanoparticles involves several challenges that need to be overcome. For instance, there-stacking or agglomeration processes of nanoparticles do not allow them to transfer their expected properties to the system, resulting in an inhomogeneous dispersion medium with minimum of biocompatibility. These undesirable processes can be overcome by physical or chemical modification methodologies of their surfaces, such as covalent or non-covalent functionalization. Thus, our choices will depend on the nanoparticles and the biological system in study. The covalent functionalization depends on bonding between the nanoparticles and the functional groups that were chosen, according to the selectivity [3]. Based on this approach, different organic or inorganic functional groups or nanoparticles can be anchored. For instance, it can be introduced on surfaces of oxidized CNTs or graphene oxide (GO), functional groups such as alkoxy (-OR), amino (-NH2), amine (-NHR), alkyl (-R) [14,15], heteroatom doping, metallic nanoparticles, biomolecules and biopolymers, among others. These modifications process alter significantly their interactions with the medium leading them to a large range of solubility in water, co-polymers or organic solvents [3]. On the other hand, non-covalent functionalization processes of nanoparticles are strongly dependent of their physical interaction with host system through intermolecular forces, such as van der Waals, hydrophilic, hydrophobic, hydrogen bonding and π-π interactions, among others [16]. Taking advantages of these physical interactions of molecules (conjugated, surfactants etc), they form homogenously dispersion into different medium with their controlled physicochemical and biological properties [17].