Here, the authors report on the manufacturing and in vivo assessment of a bioresorbable nanostructured pH sensor. The sensor consists of a micrometer‐thick porous silica membrane conformably coated layer‐by‐layer with a nanometer‐thick multilayer stack of two polyelectrolytes labeled with a pH‐insensitive fluorophore. The sensor fluorescence changes linearly with the pH value in the range 4 to 7.5 upon swelling/shrinking of the polymer multilayer and enables performing real‐time measurements of the pH level with high stability, reproducibility, and accuracy, over 100 h of continuous operation. In vivo studies carried out implanting the sensor in the subcutis on the back of mice confirm real‐time monitoring of the local pH level through skin. Full degradation of the pH sensor occurs in one week from implant in the animal model, and its biocompatibility after 2 months is confirmed by histological and fluorescence analyses. The proposed approach can be extended to the detection of other (bio)markers in vivo by engineering the functionality of one (at least) of the polyelectrolytes with suitable receptors, thus paving the way to implantable bioresorbable chemical sensors.
Nanoparticle (NP) polymer composites hold the promise to enable material functionalities that are difficult to achieve otherwise, yet hampered to date by the scarce control and tunability of the nanoparticle...
handheld, and in field-portable, enabling a spatiotemporal mapping of the microbiome potentially leading to unprecedented insight into human health and environment conditions. [1] Smartphone-based optical/fluorescence microscopy leverage the scaling down of lens/filter optical components and the computational/networking capabilities of smartphones. [1][2][3][4] These platforms have proved to be very effective for biomedical applications. Nonethless, the cost of manufacturing of miniaturized optical components, i.e., the lenses and filters, for the assembling of add-on optical modules for smartphones with reduced size and weight (yet, hundreds of grams and of cm 3 ) has hampered the diffusion of smartphone-based microscopy to date. [5] To circumvent these limitations researchers have developed strategies to fabricate polymeric (e.g., polydimethylsiloxane, PDMS) magnifying lenses that can be directly attached to the smartphone camera to boost intrinsic magnification and resolution performance. [6][7][8] These strategies include hanging droplet of uncured PDMS deposited by inkjet printing on heated flat surface; [6] moldless thermal curing of PDMS droplet prepared using a moving needle extruder; [7] drop-casting of uncured PDMS droplet onto a smooth circular disk of poly(methyl methacrylate); [8] moldless printing of uncured PDMS droplet using nanostructured porous silicon (PSi) as templating layer. [5] In two cases the polymeric lens also embedded a rejection optical filter that enabled performing smartphone-based fluorescence microscopy leveraging image magnification and light rejection properties of the lens. [5,9] In Ref. [9], the lens-filter element was prepared mixing PDMS prepolymer with dyes featuring high absorbance in specific wavelength regions. The lens was coupled to a smartphone and used in several bioanalytic applications, namely, cell and tissue observation, cell counting, and plasmid transfection evaluation. [9] In Ref.[5], a nanostructured porous silicon oxide (PSiO 2 ) filter, namely, a distributed Bragg reflector (DBR) with stopband tuned to reject light in a selected wavelength region, was integrated into the PDMS lens. The lens-filter element was coupled to a smartphone and used for the fluorescence imaging and counting of CAOV-3 ovarian cancer cells in a conventional live/dead assay. [5] Very recently our research group developed a fluorideassisted chemical route for the in-situ synthesis of metal nanoparticles (NPs) on PDMS. [10] In contrast to conventional in Here the 4D printing of a magnifying polydimethylsiloxane (PDMS) lens encoded with a tunable plasmonic rejection filter is reported. The lens is formed by moldless printing of PDMS pre-polymer on a nanostructured porous silicon (PSi) templating layer. A nanometer-thick plasmonic filter is integrated on the lens surface by in situ synthesis of Ag and Au nanoparticles (NPs) with programmed density. The filter can be designed to reject light at the plasmonic resonance wavelength of the NPs with an optical density tunable from 0 to 3 and re...
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