Cell and Tissue Imaging with Molecularly Imprinted Polymers as Plastic Antibody Mimics.

Molecularly imprinted polymers can be used as "plastic antibodies" for cell and tissue imaging, as demonstrated using hyaluronan on cell surfaces as a model target. Fluorescent nanoparticles binding a hyaluronan substructure, glucuronic acid, are used to image fixated and living cells and tissues. Plastic antibodies can be tailored to specific targets and easily labeled, and are physically and chemically stable.

Versatile synthetic strategy for coating upconverting nanoparticles with polymer shells through localized photopolymerization by using the particles as internal light sources.

We present a straightforward and generic strategy for coating upconverting nanoparticles (UCPs) with polymer shells for their protection, functionalization, conjugation, and for biocompatibility. UCPs are attracting much attention for their potential use as fluorescent labels in biological applications. However, they are hydrophobic and non-compatible with aqueous media; thus prior surface modification is essential. Our method uses the internal UV or visible light emitted from UCPs upon photoexcitation with near-infrared radiation, to locally photopolymerize a thin polymer shell around the UCPs. In this way, a large variety of monomers with different chemical functionalities can be incorporated. If required, a second layer can be added on top of the first. Our method can provide a large spectrum of surface functional groups rapidly and in one pot, hence offering a platform for the preparation of libraries of functional polymer-encapsulated UCPs for applications in bioassays, biosensing, optical imaging, and theranostics.

One-pot synthesis of iniferter-bound polystyrene core nanoparticles for the controlled grafting of multilayer shells.

A novel approach using one-pot synthesis for the production of uniform, iniferter-bound polystyrene core nanoparticles of size 30-40 nm is described. Conventional oil-in-water emulsion polymerisation of styrene and divinylbenzene, combining a hybrid initiation system (thermal and UV), triggered sequentially, was employed to form the surface-bound thiocarbamate iniferters in situ. The iniferter cores were then used as seeds for re-initiating further polymerisation by UV irradiation to produce water-compatible core-shell nanoparticles. Grafting of various shell-types is demonstrated: linear polymers of poly(N-isopropylacrylamide) brushes, crosslinked polymers bearing different surface charges and molecularly imprinted polymers. The shell thickness was readily tuned by varying the monomers' concentration and polymerisation time. Our method is straightforward and in addition, gives access to the preparation of fluorescent seeds and the possibility of grafting nanosized multiple shells. The core-shell nanoparticles were fully characterised by dynamic light scattering, transmission electron microscopy, Fourier transform infrared spectroscopy and microelemental analysis.

Multi-objective optimization and design of experiments as tools to tailor molecularly imprinted polymers specific for glucuronic acid.

We present a multi-objective optimization of the binding properties of a molecularly imprinted polymer (MIP) which specifically binds glucuronic acid (GA). A design of experiments approach is used to improve four different parameters that describe the binding properties of the polymer. Eleven different methacrylamide-co-ethyleneglycol dimethacrylate polymers imprinted with GA were synthesized according to a full factorial experimental design plan with 3 influencing factors (degree of cross-linking, molar equivalent of monomer to template and initiator concentration). These polymers were characterized by adsorption of the radiolabeled target analyte in methanol:water 9:1. The binding parameters were computed to optimize the polymer composition, taking into account four objective variables: the maximum binding capacity at high (Bmax) and low (B2) analyte concentrations, the equilibrium constant K50, and the imprinting factor (IF, binding to MIP/binding to NIP). With the multi-objective optimization method based on a desirability approach the composition of a twelfth "ideal" polymer could be predicted. This predicted polymer with highest "desirability" was synthesized with a composition of 0.65 mol% of initiator and a 1:4:20 ratio of template:functional monomers:cross-linker (T:M:X) (80% of cross-linking), and found to be the overall best MIP. Improvements over the original starting polymer were a 6 times lower K50, which corresponds to higher affinity, 20% higher capacity at low analyte concentration (B2), 40% higher capacity (Bmax) and 1.3 times increased imprinting factor (IF). Binding assays were also performed in aqueous solvents. Good binding properties were obtained in pure water with an imprinting factor of 3.2. Thus, this polymer is potentially applicable to biological samples like urine where glucuronides occur.