Figure 4 Generalized synthetic scheme of a multifunctional nanoparticle system (MFNPS). Metal alkoxides (i.e. Si(OR)4, Ti(OR)4where R = H, hydrocarbon) undergo rapid to slow hydrolysis and condensation reaction steps under acidic or basic conditions to form a metal oxide network (matrix). Depending on the presence and nature of additives, MFNPS characteristics will be precisely determined. Matrix density and the degree of polymerization are highly dependent upon reaction conditions that can be the type of additive, time of aging, reaction temperature, and purity of additive contents. Four key components are (1) an optical probe (e.g. fluorophore), (2) a secondary imaging probe (e.g. magnetically susceptible or radio-active), (3) porous structure and/or chemical functionality, and (4) biologically active load or cargo (i.e. antibodies for targeted delivery; drugs, nucleic acids and other proteins for therapeutic applications or control over biological processes).