Multifunctional nanocarriers based on the up-conversion luminescent nanoparticles of NaYF₄:Yb³⁺/Er³⁺ core (UCNPs) and thermo/pH-coupling sensitive polymer poly[(N-isopropylacrylamide)-co-(methacrylic acid)] (P(NIPAm-co-MAA)) gated mesoporous silica shell are reported for cancer theranostics, including fluorescence imaging, and for controlled drug release for therapy. The as-synthesized hybrid nanospheres UCNPs@mSiO₂-P(NIPAm-co-MAA) show bright green up-conversion fluorescence under 980 nm laser excitation and the thermo/pH-sensitive polymer is active as a “valve” to moderate the diffusion of the embedded drugs in-and-out of the pore channels of the silica container. The anticancer drug doxorubicin hydrochloride (DOX) can be absorbed into UCNPs@mSiO₂-P(NIPAm-co-MAA) nanospheres and the composite drug delivery system (DDS) shows a low level of leakage at low temperature/high pH values but significantly enhanced release at higher temperature/lower pH values, exhibiting an apparent thermo/pH controlled “on-off” drug release pattern. The as-prepared UCNPs@mSiO₂-P(NIPAm-co-MAA) hybrid nanospheres can be used as bioimaging agents and biomonitors to track the extent of drug release. The reported multifunctional nanocarriers represent a novel and versatile class of platform for simultaneous imaging and stimuli-responsive controlled drug delivery.

A novel approach for the fabrication of multifunctional microspheres integrating several advantages of mesoporous, luminescence, and temperature responses into one single entity is reported. First, the hollow mesoporous silica capsules are fabricated via a sacrificial template route. Then, Gd₂O₃:Eu³⁺ luminescent nanoparticles are incorporated into the internal cavities to form rattle-type mesoporous silica nanocapsules by an incipient-wetness impregnation method. Finally, the rattle-type capsules serve as a nanoreactor for successfully filling temperature-responsive hydrogel via photoinduced polymerization to form the multifunctional composite microspheres. The organic–inorganic hybrid microspheres show a red emission under UV irradiation due to the luminescent Gd₂O₃:Eu³⁺ core. The in vitro cytotoxicity tests show that the samples have good biocompatibility, which indicates that the nanocomposite could be a promising candidate for drug delivery. In addition, flow cytometry and confocal laser scanning microscopy (CLSM) confirm that the sample can be effectively taken up by SKOV3 cells. For in vitro magnetic resonance imaging (MRI), the sample shows the promising spin-lattice relaxation time (T₁) weighted effect and could potentially apply as a T₁-positive contrast agent. This composite drug delivery system (DDS) provides a positive temperature controlled “on-off”drug release pattern and the drug, indomethacin (IMC), is released fast at 45 °C (on phase) and completely shut off at 20 °C (off phase). Meanwhile Gd₂O₃:Eu³⁺ plays an important role as the luminescent tag for tracking the drug loading and release process by the reversible luminescence quenching and recovery phenomenon. These results indicate that the obtained multifunctional composite has the potential to be used as a smart DDS for biomedical applications.

Monodisperse poly(acrylic acid)-modified Fe₃O₄ (PAA@Fe₃O₄) hybrid microspheres with dual responses (magnetic field and pH) were successfully fabricated. The PAA polymer was encapsulated into the inner cavity of Fe₃O₄ hollow spheres by a vacuum-casting route and photo-initiated polymerization. TEM images show that the samples consist of monodisperse porous spheres with a diameter around 200 nm. The Fe₃O₄ spheres, after modification with the PAA polymer, still possess enough space to hold guest molecules. We selected doxorubicin (DOX) as a model drug to investigate the drug loading and release behavior of as-prepared composites. The release of DOX molecules was strongly dependent on the pH value due to the unique property of PAA. The HeLa cell-uptake process of DOX-loaded PAA@Fe₃O₄ was observed by confocal laser scanning microscopy (CLSM). After being incubated with HeLa cells under magnet magnetically guided conditions, the cytotoxtic effects of DOX-loaded PAA@Fe₃O₄ increased. These results indicate that pH-responsive magnetic PAA@Fe₃O₄ spheres have the potential to be used as anticancer drug carriers.

Ordered arrays of luminescent YVO₄:Eu³⁺ films with square (side length 19.17 ± 2.05 μm) and dot (diameter 11.20 ± 1.82 μm) patterns were fabricated by two kinds of soft lithography processes, namely, microtransfer molding (μTM) and microcontact printing (μCP), respectively. Both soft-lithography processes utilize a PDMS elastomeric mold as the stamp combined with a Pechini-type sol-gel process to produce luminescent patterns on quartz plates, in which a YVO₄:Eu³⁺ precursor solution was employed as ink. The ordered luminescent YVO₄:Eu³⁺ patterns are revealed by optical micro­scopy and their microstructure, consisting of nanometer-scale particles, is unveiled by scanning electronic microscopy (SEM) observations. Additionally, photoluminescence (PL) and cathodoluminescence (CL) were carried out to characterize the patterned YVO₄:Eu³⁺ samples. A strong red emission as a result of ⁵D₀–⁷F₂ transition of Eu³⁺ was observed under UV-light or electron-beam excitation, which implies that combining soft lithography with a Pechini-type sol-gel route has potential for fabricating rare-earth luminescent pixels for next-generation field-emission display devices.