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Pathogenic bacterial contamination is a major threat to human health and safety. In this review, we summarize recent strategies for the integration of recognition elements with nanomaterials for the detection and sensing of pathogenic bacteria. Nanoprobes can provide sensitive and specific detection of bacterial cells, which can be applied across multiple applications and industries.

Optical techniques have proven to be well suited for in situ biomolecular sensing because they enable high fidelity measurements in aqueous environments, are minimally affected by background solution pH or ionic strength, and facilitate label-free detection. Recently, there has been significant interest in developing new classes of optically resonant biosensors possessing very high quality-factors. This high quality-factor enables them to resolve the presence of very small amounts of bound mass and leads to very low limits of detection. A drawback of these devices is that the majority of the resonant electromagnetic energy is confined within the solid light-guiding structure thus limiting the degree to which it overlaps with the bound matter. This in turn lowers the ultimate device sensitivity, or the change in output signal in response to changes in bound mass. Here we present a novel optofluidic biosensor platform that incorporates a unique one-dimensional photonic crystal resonator array which enables significantly stronger light-matter interaction. We show here how this, coupled with the ability of planar photonic crystals to spatially localize the optical field to mode volumes on the order of a wavelength cubed, enables a limit of detection on the order of 63 ag total bound mass (estimated using a polyelectrolyte growth model) and a device sensitivity an order of magnitude better than similar devices. The multiplexing capabilities of our sensor are demonstrated by the individual and concurrent detection of interleukins 4, 6 and 8 using a sandwich assay.

Surface-functionalization chemistries were optimized to tailor the surface chemistry of polyethylene, and this made covalent attachment of bioactive molecules possible. This concept has relevance in biomaterials, biosensors, textiles, and active food-packaging applications. Clean polyethylene films were subjected to chromic acid oxidation to introduce carboxylic acids. A range of functional groups, including amine, aldehyde, thiol, and hydroxyl, were then introduced to the surface of the oxidized films with functionalized crosslinking agents and covalent bioconjugation chemistries. The quantity of functional groups was further increased by subsequent grafting of polyfunctional agents such as polyethylenimine and poly(acrylic acid). The number and type of functional groups were quantified by contact-angle, dye-assay, attenuated total reflectance/Fourier transform infrared, and X-ray photoelectron spectroscopy analyses. We optimized chemistries to introduce a variety of functional groups to the surface of low-density polyethylene in numbers ranging from several picomoles per centimeter squared to tens of nanomoles per centimeter squared. A range of bioactive compounds, including antimicrobials, antibodies, oligonucleotides, cell precursors, drugs, peptides, enzymes, and synthetic biomimetic agents, can be covalently bound to these functional groups in the development of nonmigratory biofunctionalized polymers.

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Active packaging is an innovative strategy in preventing lipid oxidation. Different active substances with different mechanisms of action have been investigated for imparting antioxidant activity to active packaging systems, including free radical scavengers, metal chelators, ultraviolet (UV) absorbers, oxygen scavengers, and singlet oxygen quenchers. Antioxidant agents have been incorporated into active packaging systems in different forms, mainly including independent sachet packages, adhesive-bonded labels, physical adsorption/coating on packaging material surface, being incorporated into packaging polymer matrix, multilayer films, and covalent immobilization onto the food contact packaging surface. In this paper, we review recent advances in antioxidant active packaging with the highlight of the development and application of non-migratory active packaging systems. The potential use of emerging technologies in antioxidant active packaging is also emphasized. We further describe challenges and opportunities towards the commercial application of such antioxidant active packaging systems, with a focus on maintaining safety, quality and nutrition of packaged foods.

Active food packaging involves the packaging of foods with materials that provide an enhanced functionality, such as antimicrobial, antioxidant or biocatalytic functions. This can be achieved through the incorporation of active compounds into the matrix of the commonly used packaging materials, or by the application of coatings with the corresponding functionality through surface modification. The latter option offers the advantage of preserving the packaging materials' bulk properties nearly intact. Herein, different coating technologies like embedding for controlled release, immobilization, layer-by-layer deposition, and photografting are explained and their potential application for active food packaging is explored and discussed.