Upconversion nanoparticles UCNPs

In this chapter, we first divide NIR NMs into five species carbon-based materials, quantum dots (QDs), noble metal-based nanoparticles (NPs), upconversion nanoparticles (UCNPs), and narrow-bandgap semiconductors. Then, we focus primarily on the progress of their toxicity studies in the past several years, discuss in detail how the biophysicochemical properties of NIR NMs influence their in vitro and in vivo toxicity, present a broad overview of the available in vitro and in vivo toxicity assessments of NIR NMs, and finally frame the future outlook for NIR NMs by highlighting areas of exceptional promise and challenges. Our emphasis here is mainly on discussion that could offer future opportunities to design and create NIR NMs with good biocompatibility as well as excellent functionalities, rather than attempting to provide a complete historical survey. 

Xu et al. provide a method to fabricate a nanocomposite system with highly integrated functionalities for multimodal biomedical imaging and cancer therapy [154]. They encapsulated hydrophobic upconversion nanoparticles (UCNPs] together with iron oxide nanoparticles (lONPs] by using an amphiphilic block copolymer, poly (styrene-block-allyl alcohol] (PS g-b-PAA o]- via a microemulsion method, obtaining an UC-IO Polymer multi-... 

ALA, 5-aminolevulinic acid BSA, bovine serum albumin Ce6, chlorin e6 HP, hematoporphyrin M-540, merocyanine 540 02, singlet oxygen PAA, poly(acrylic acid) PDT, photodynamic therapy PEG, polyethylene glycol PS, photosensitiser PTT, photothermal therapy RB, Rose Bengal SPCD, silicon phthalocyanine dihydroxide UCNP, upconversion nanoparticles ZnPc, zinc phthalocyanine. 

The choice of the material is critical in terms of the color and intensity of the emission. For example, upconverting nanoparticles (UCNPs) doped with Er + emit mainly green light (510-570 run) and red light (630-680 nm), but the peak maxima and relative intensities of the bands depend oti the host lattice. The green emission is dominant in fluoride-based lattices, while in oxide-based lattices it is the red emission. Dopants such as Tm + result in mainly blue upconversion fluorescence (450-500 nm) that is accompanied by a weak red fluorescence in certain host crystals. Lattices doped with Ho also show a green and red luminescence that is comparable to that of Er. ... 

LbL = layer-by-layer Ln = lanthanide LSS = liqnid-solid-solntion NIR = near-infrared NPs = nanoparticles OA = oleic acid ODE = octadecene PA = photon avalanche PAA = polyacrylic acid PAH = poly(allyIamine hydrochloride) PEI = polyethylenimine PSS = poly(sodium 4-styre-nesnlfonate) PVP = polyvinylpyrrohdone QDs = qnantum dot SAUCI = smaU-animal upconversion imager SHG = second-harmonic generation STPA = simultaneons two-photon absorption TOPO = trioctylphosphine oxide TPA = two-photon absorption UCNPs = Upconversion nanoparticle UV = nlfraviolet. 

Saleh et al. [66] used a similar approach. Direct binding of avidin to biotin was optically detected by using (1) UCNPs that carry avidin on their surface and (2) biotinylated gold nanoparticles. The spectral overlap between the green upconversion emission and the absorption of the red gold nanoparticles results in a quenching of the UCNP fluorescence upon avidin-biotin interaction (Fig. 13b). 

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