Magnetically Recoverable, Thermostable, Hydrophobic DNA/Silica Encapsulates and Their Application as Invisible Oil Tags

Abstract

A method to encapsulate DNA in heat-resistant and inert magnetic particles was developed. An inexpensive synthesis technique based on co-precipitation was utilized to produce Fe2O3 nanoparticles, which were further functionalized with ammonium groups. DNA was adsorbed on this magnetic support, and the DNA/magnet nanocluster was surface coated with a dense silica layer by sol-gel chemistry. The materials were further surface modified with hexyltrimethoxysilane to achieve particle dispersibility in hydrophobic liquids. The hydrodynamic particle sizes were evaluated by analytical disc centrifugation, and the magnetic properties were investigated by vibrating sample magnetometry. The obtained nanoengineered encapsulates showed good dispersion abilities in various nonaqueous fluids and did not affect the optical properties of the hydrophobic dispersant when present at concentrations lower than 10(3) μg/L. Upon magnetic separation and particle dissolution, the DNA could be recovered unharmed and was analyzed by quantitative real-time PCR and Sanger sequencing. DNA encapsulated within the magnetic particles was stable for 2 years in decalin at room temperature, and the stability was further tested at elevated temperatures. The new magnetic DNA/silica encapsulates were utilized to developed a low-cost platform for the tracing/tagging of oils and oil-derived products, requiring 1 μg/L=1 ppb levels of the taggant and allowing quantification of taggant concentration on a logarithmic scale. The procedure was tested for the barcoding of a fuel (gasoline), a cosmetic oil (bergamot oil), and a food grade oil (extra virgin olive oil), being able to verify the authenticity of the products.

Particles with an identity: Tracking and tracing in commodity products

“…[48] In an more advanced application, DNA comprising particulate tracers have also been used for understanding the animal-to-animal transfer in food chains, [49] the behavior of silica nanoparticles in sewage plants [50] and in in vitro cell cultures.…”

“…In practical applications, tracers with a low detection limit are only suitable when they are homogeneously distributed in the final material. In liquid products encoded particles at a concentration range of ppb can be directly incorporated by dilution series and intensive mixing [47,48]. In the formation of polymer-based products, the need for homogeneous mixtures is not a novel problem, and commonly arises when a polymer is dyed with pigments.…”

Taggant materials in forensic science: A review

“…However, encapsulation of nucleotides within silica microbeads [44] or plant materials [45] may be carried out in order to protect against this potential degradation.…”

A vision for ubiquitous sequencing

“…Recent work has tested the usage of such tags in the food supply chain by delivering exogenous DNA fragments within a coat of silica, a common food additive, at an extremely low cost. It has been shown that these tags could be used to trace the source of milk in dairy products such as yogurt (Bloch et al 2014) and serve as a long-term authentication mark of premium olive oil (Puddu et al 2014). Moving forward, artificial DNA labels can create an edible data structure that includes the type of food, producer, lot number, nutrient information, and presence of known allergens or simply encode a URL to a webpage that contains this information.…”