Aptamer-free upconversion nanoparticle/silk biosensor system for low-cost and highly sensitive detection of antibiotic residues

The detection of antibiotics is crucial for safeguarding the environment, ensuring food safety, and promoting human health. However, developing a rapid, convenient, low-cost, and sensitive method for antibiotic detection presents significant challenges. Herein, an aptamer-free biosensor was successfully constructed using upconversion nanoparticles (UCNPs) coated with silk fibroin (SF), based on Förster resonance energy transfer (FRET) and the charge-transfer effect, for detecting roxithromycin (RXM). A synergistic FRET efficiency was achieved by utilizing alizarin red and RXM complexes as energy acceptors, with UCNP as the energy donor, and immobilizing an ultrathin SF protein corona within 10 nm. The biosensor detects RXM in deionized water with high sensitivity primarily through monolayer adsorption, with a detection range of 1.0 nM-141.6 nM and a detection limit as low as 0.68 nM. The performance of this biosensor was compared with the ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS) method for detecting antibiotics in river water separately and a strong correlation between the two methods was observed. The biosensor exhibited long-term stability in aqueous solutions (up to 60 d) with no attenuation of fluorescence intensity. Furthermore, the biosensor's applicability extended to the highly sensitive detection of other antibiotics, such as azithromycin. This study introduces a low-cost, eco-friendly, and highly sensitive method for antibiotic detection, with broad potential for future applications in environmental, healthcare, and food-related fields.

Upconverting Nanoparticles Coated with Light-Breakable Mesoporous Silica for NIR-Triggered Release of Hydrophobic Molecules

Upconverting nanoparticles (UCNPs) doped with Yb3+ and Tm3+ are near-infrared (NIR) to ultraviolet (UV) transducers that can be used for NIR-controlled drug delivery. However, due to the low quantum yield of upconversion, high laser powers and long irradiation times are required to trigger this drug release. In this work, we report the one-step synthesis of a nanocomposite consisting of a LiYbF4:Tm3+@LiYF4 UCNP coated with mesoporous UV-breakable organosilica shells of various thicknesses. We demonstrate that a thin shell accelerates the breakage of the shell at 1 W/cm2 NIR light exposure, a laser power up to 9 times lower than that of conventional systems. When the mesopores are loaded with hydrophobic vitamin D3 precursor 7-dehydrocholesterol (7-DH), shell breakage results in subsequent cargo release. Its minimal toxicity in HeLa cells and successful internalization into the cell cytoplasm demonstrate its biocompatibility and potential application in biological systems. The tunability of this system due to its simple, one-step synthesis process and its ability to operate at low laser powers opens up avenues in UCNP-powered NIR-triggered drug delivery toward a more scalable, flexible, and ultimately translational option.

Degradable bifunctional phototherapy composites based on upconversion nanoparticle-metal phenolic network for multimodal tumor therapy in the near-infrared biowindow

Phototherapy has garnered increasing attention as it allows for precise treatment of tumor sites with its accurate spatiotemporal control. In this study, we have successfully synthesized degradable bifunctional phototherapy agents (UCNPs@mSiO2@MPN-MC540/DOX) based on upconversion nanoparticle (UCNPs) and metal phenolic network (MPN), serving as a novel nanoplatform for multimodal tumor treatment in the near-infrared (NIR) biological window. To address the issue of low light penetration depth, the UCNPs we synthesized exhibited efficient light conversion ability under 808 nm laser irradiation to activate the photosensitizer Merocyanine 540 (MC540) for photodynamic therapy. Simultaneously, the 808 nm NIR light can also excite the MPN layer to achieve photothermal therapy for tumors. Additionally, the MPN layer possesses the capability of self-degradation under weakly acidic conditions. Within the tumor microenvironment, the MPN layer gradually degrades, facilitating the controlled release of the chemotherapy drug doxorubicin (DOX), thus achieving pH-responsive drug release and reducing the side effects of chemotherapy. This study provides an example of NIR-excited multimodal tumor treatment and pH-responsive drug release, offering a therapy model for precise tumor therapy.

"Three Musketeers" Enhances Photodynamic Effects by Reducing Tumor Reactive Oxygen Species Resistance

Photodynamic therapy (PDT) based on upconversion nanoparticles (UCNPs) has been widely used in the treatment of a variety of tumors. Compared with other therapeutic methods, this treatment has the advantages of high efficiency, strong penetration, and controllable treatment range. PDT kills tumors by generating a large amount of reactive oxygen species (ROS), which causes oxidative stress in the tumor. However, this killing effect is significantly inhibited by the tumor's own resistance to ROS. This is because tumors can either deplete ROS by high concentration of glutathione (GSH) or stimulate autophagy to eliminate ROS-generated damage. Furthermore, the tumor can also consume ROS through the lactic acid metabolic pathway, ultimately hindering therapeutic progress. To address this conundrum, we developed a UCNP-based nanocomposite for enhanced PDT by reducing tumor ROS resistance. First, Ce6-doped SiO2 encapsulated UCNPs to ensure the efficient energy transfer between UCNPs and Ce6. Then, the biodegradable tetrasulfide bond-bridged mesoporous organosilicon (MON) was coated on the outer layer to load chloroquine (CQ) and α-cyano4-hydroxycinnamic acid (CHCA). Finally, hyaluronic acid was utilized to modify the nanomaterials to realize an active-targeting ability. The obtained final product was abbreviated as UCNPs@MON@CQ/CHCA@HA. Under 980 nm laser irradiation, upconverted red light from UCNPs excited Ce6 to produce a large amount of singlet oxygen (1O2), thus achieving efficient PDT. The loaded CQ and CHCA in MON achieved multichannel enhancement of PDT. Specifically, CQ blocked the autophagy process of tumor cells, and CHCA inhibited the uptake of lactic acid by tumor cells. In addition, the coated MON consumed a high level of intracellular GSH. In this way, these three functions complemented each other, just as the "three musketeers" punctured ROS resistance in tumors from multiple angles, and both in vitro and in vivo experiments had demonstrated the elevated PDT efficacy of nanomaterials.

Biomimetic Biomembrane Encapsulation and Targeted Delivery of a Nitric Oxide Release Platform for Therapy of Parkinson's Disease

The existence of the blood-brain barrier (BBB) and the complex inflammatory environment in the brain are two major obstacles in the treatment of Parkinson's disease (PD). As a target group, we modified the red blood cell membrane (RBCM) on the surface of upconversion nanoparticles (UCNPs) in this study to effectively target the brain. Mesoporous silicon, coated with UCNPs (UCM), was loaded with S-nitrosoglutathione (GSNO) as the nitric oxide (NO) donor. Then, UCNPs were excited to emit green light (540 nm) by 980 nm near-infrared (NIR). In addition, it produced a light-responsive anti-inflammatory effect by promoting the release of NO from GSNO and lowering the brain's level of proinflammatory factors. A series of experiments demonstrated that this strategy could effectively mitigate the inflammatory response damage of neurons in the brain.

The Coming of Age of Neodymium: Redefining Its Role in Rare Earth Doped Nanoparticles

Among luminescent nanostructures actively investigated in the last couple of decades, rare earth (RE³⁺) doped nanoparticles (RENPs) are some of the most reported family of materials. The development of RENPs in the biomedical framework is quickly making its transition to the ∼800 nm excitation pathway, beneficial for both in vitro and in vivo applications to eliminate heating and facilitate higher penetration in tissues. Therefore, reports and investigations on RENPs containing the neodymium ion (Nd³⁺) greatly increased in number as the focus on ∼800 nm radiation absorbing Nd³⁺ ion gained traction. In this review, we cover the basics behind the RE³⁺ luminescence, the most successful Nd³⁺-RENP architectures, and highlight application areas. Nd³⁺-RENPs, particularly Nd³⁺-sensitized RENPs, have been scrutinized by considering the division between their upconversion and downshifting emissions. Aside from their distinctive optical properties, significant attention is paid to the diverse applications of Nd³⁺-RENPs, notwithstanding the pitfalls that are still to be addressed. Overall, we aim to provide a comprehensive overview on Nd³⁺-RENPs, discussing their developmental and applicative successes as well as challenges. We also assess future research pathways and foreseeable obstacles ahead, in a field, which we believe will continue witnessing an effervescent progress in the years to come.

Near-Infrared Light-Controlled and Real-Time Detection of Osteogenic Differentiation in Mesenchymal Stem Cells by Upconversion Nanoparticles for Osteoporosis Therapy

Osteoporosis (OP) is one of the most common diseases in the elderly, and it is not effectively solved by current treatments. Mesenchymal stem cells (MSCs) have multiple differentiation potentials, which can induce osteogenic differentiation to treat OP; however, it is important to understand how to remotely control and detect osteogenic differentiation in vivo in real time. Here, we developed an upconversion nanoparticle (UCNP)-based photoresponsive nanoplatform for near-infrared (NIR) light-mediated control of intracellular icariin (ICA) release to regulate the osteogenic differentiation of MSCs for OP therapy. We simultaneously detected osteogenic differentiation in vivo in real time to evaluate the treatment effects. The Tm/Er-doped UCNPs were synthesized and coated with mesoporous silica (UCNP@mSiO₂) first. Then, the photocaged linker 4-(hydroxymethyl)-3-nitrobenzoic acid (ONA) and the PEG linker (OH-PEG4-MAL) were linked to the surface of UCNP@mSiO₂ to conjugate to the cap β-cyclodextrin (β-CD) and the Arg-Gly-Asp (RGD)-targeted peptide/matrix metalloproteinase 13 (MMP13)-sensitive peptide-BHQ (CGPLGVRGK-BHQ₃) to form the UCNP nanoplatform (UCNP@mSiO₂-peptide-BHQ-ONA-CD) for drug loading. Under 980 nm NIR light, the upconverted UV from the UCNPs triggered the cleavage of cap β-CD and the intracellular release of ICA to induce the osteogenic differentiation of MSCs for OP therapy. Meanwhile, MMP13, which was produced by osteogenic differentiation of MSCs, cleaved the MMP13-sensitive peptide to remove BHQ and recover the fluorescence of UCNPs, allowing real-time detection of osteogenic differentiation and the evaluation of the OP treatment effect. This photoresponsive UCNP nanoplatform has the potential to be used for the remote control and real-time detection of osteogenic differentiation of MSCs for OP therapy by NIR.

Upconversion nanoparticles regulated drug & gas dual-effective nanoplatform for the targeting cooperated therapy of thrombus and anticoagulation

Thromboembolism is the leading cause of cardiovascular mortality. Currently, for the lack of targeting, short half-life, low bioavailability and high bleeding risk of the classical thrombolytic drugs, pharmacological thrombolysis is usually a slow process based on micro-pumping. In addition, frequently monitoring and regulating coagulation functions are also required during (and after) the process of thrombolysis. To address these issues, a targeted thrombolytic and anticoagulation nanoplatform (UCATS-UK) is developed based on upconversion nanoparticles (UCNPs) that can convert 808 or 980 nm near-infrared (NIR) light into UV/blue light. This nanoplatform can target and enrich in the thrombus site. Synergistic thrombolysis and anticoagulation therapy thus could be realized through the controlled release of urokinase (UK) and nitric oxide (NO). Both in vitro and in vivo experiments have confirmed the excellent thrombolytic and anticoagulative capabilities of this multifunctional nanoplatform. Combined with the unique fluorescent imaging capability of UCNPs, this work is expected to contribute to the development of clinical thrombolysis therapy towards an integrated system of imaging, diagnosis and treatment.

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This work is not only the first application of UCNPs in the thrombolysis therapy, but also the first attempt to develop a dual effective drug & gas nanoplatform for thrombolytic & anticoagulation therapy.

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Besides conventional in vitro and animal experiments, a 3D printed vascular model is also constructed to further verify the feasibility of UCATS-UK.

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Through surface chemical modification, the nanoplatform possesses the capabilities of targeting thrombus, as well as light-controlled NO release for drug-free anticoagulation therapy.

Near-Infrared Light and Upconversion Nanoparticle Defined Nitric Oxide-Based Osteoporosis Targeting Therapy

Osteoporosis is one of the most common diseases affecting bone metabolism. Nitric oxide (NO), an endogenous gas molecule involved in osteogenesis, can effectively promote the proliferation and differentiation of osteoblasts. Although exogenous NO can reverse osteoporosis to a certain extent, the transitory half-life and short diffusion radius of NO severely limit its application. In this work, a gas generation nanoplatform of NO with bone targeting property (UCPA) is developed based on the upconversion nanoparticles (UCNPs) that can convert 808 nm near-infrared (NIR) light into UV/blue light, and further stimulate the NO donor (BNN) to release NO. With an adjustment of the output power of the 808 nm NIR, the amount of released NO can be precisely controlled. Both in vitro and in vivo experiments demonstrate the favorable affinity of UCPA to bone due to the modification of alendronate; thus, it can directly release NO in bone and reverse osteoporosis. In addition, the cellular uptake of nanocomposites and intracellular NO release can be observed in preosteoblasts, thereby promoting their differentiation efficiently.

Protein-Gated Upconversion Nanoparticle-Embedded Mesoporous Silica Nanovehicles via Diselenide Linkages for Drug Release Tracking in Real Time and Tumor Chemotherapy

Two novel stimuli-responsive drug delivery systems (DDSs) were successfully created from bovine serum albumin- or myoglobin-gated upconversion nanoparticle-embedded mesoporous silica nanovehicles (UCNP@mSiO2) via diselenide (Se-Se)-containing linkages. More importantly, multiple roles of each scaffold of the nanovehicles were achieved. The controlled release of the encapsulated drug doxorubicin (DOX) within the mesopores was activated by triple stimuli (acidic pH, glutathione, or H2O2) of tumor microenvironments, owing to the conformation/surface charge changes in proteins or the reductive/oxidative cleavages of the Se-Se bonds. Upon release of DOX, the Förster resonance energy transfer between the UCNP cores and encapsulated DOX was eliminated, resulting in an increase in ratiometric upconversion luminescence for DOX release tracking in real time. The two protein-gated DDSs showed some differences in the drug release performances, relevant to structures and properties of the protein nanogates. The introduction of the Se-Se linkages not only increased the versatility of reductive/oxidative cleavages but also showed less cytotoxicity to all cell lines. The DOX-loaded protein-gated nanovehicles showed the inhibitory effect on tumor growth in tumor-bearing mice and negligible damage/toxicity to the normal tissues. The constructed nanovehicles in a spatiotemporally controlled manner have fascinating prospects in targeted drug delivery for cancer chemotherapy.

PEI functionalized NaCeF4:Tb3+/Eu3+ for photoluminescence sensing of heavy metal ions and explosive aromatic nitro compounds

This work reports an eco-friendly hydrothermal approach for the synthesis of hexagonal NaCeF4:Tb3+/Eu3+ nanophosphors. The phase, morphology and optical properties were characterized by Powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy and photoluminescence (PL) spectroscopy respectively. Herein, the as-synthesized nanophosphor was functionalized with amine rich polyethylenimine (PEI) resulting in development of a luminescent nanoprobe bearing dual sensing functions for hazardous nitroaromatics and heavy metal ions. The strong photoluminescence emission of Eu3+ ions was selectively quenched upon addition of toxic analytes at concentrations from 10 to 100 ppm due to complex formation between the analytes and PEI functionalized nanostructure. The synthesized nanomaterial shows sharp emission peaks at 493, 594, 624, 657 and 700 nm. Significantly, the peak at 594 nm shows a noticeable quenching effect on addition of toxic analytes to the aqueous solution of the nanocrystals. The nanophosphors are sensitive and efficient for the PA and Fe3+ ion detection with an LOD of 1.32 ppm and 1.39 ppm. The Stern-Volmer (SV) quenching constant (K SV) is found to be 2.25 × 105 M-1 for PA and 3.8 × 104 M-1 for Fe3+ ions. The high K SV value and low LOD suggest high selectivity and sensitivity of the nanosensor towards PA and Fe3+ ions over other analytes. Additionally, a reduced graphene oxide and nanophosphor based nanocomposite was also synthesized to investigate the role of energy transfer involving delocalized energy levels of reduced graphene oxide in regulating the luminescence properties of the nanophosphor. It was observed that PEI plays central role in inhibiting the quenching effect of reduced graphene oxide on the nanophosphor.

Measurement of Temperature Distribution at the Nanoscale with Luminescent Probes Based on Lanthanide Nanoparticles and Quantum Dots

It is very challenging to probe the temperature in a nanoscale because of the lack of detection technique. Temperature-sensitive luminescent probes at a nanoscale provide the possibility to solve this problem. Herein, we fabricated a model, which combined two kinds of temperature sensitive nanoprobes and gold nanoparticle heater within mesoporous silica nanoparticles. Upconverting nanoparticles and quantum dots located at different positions inside 110 nm nanoparticles reported different temperatures when the gold nanoparticles generated heat by 532 nm laser irradiation. The temperature difference between two probes with an average distance of 55 nm can reach about 30 °C. Our results prove that the temperature distribution at a nanoscale can be measured, and it will be noteworthy if a nano-heater is applied.

Core-shell nanostructures: perspectives towards drug delivery applications

Nanosystems have shown encouraging outcomes and substantial progress in the areas of drug delivery and biomedical applications. However, the controlled and targeted delivery of drugs or genes can be limited due to their physicochemical and functional properties. In this regard, core-shell type nanoparticles are promising nanocarrier systems for controlled and targeted drug delivery applications. These functional nanoparticles are emerging as a particular class of nanosystems because of their unique advantages, including high surface area, and easy surface modification and functionalization. Such unique advantages can facilitate the use of core-shell nanoparticles for the selective mingling of two or more different functional properties in a single nanosystem to achieve the desired physicochemical properties that are essential for effective targeted drug delivery. Several types of core-shell nanoparticles, such as metallic, magnetic, silica-based, upconversion, and carbon-based core-shell nanoparticles, have been designed and developed for drug delivery applications. Keeping the scope, demand, and challenges in view, the present review explores state-of-the-art developments and advances in core-shell nanoparticle systems, the desired structure-property relationships, newly generated properties, the effects of parameter control, surface modification, and functionalization, and, last but not least, their promising applications in the fields of drug delivery, biomedical applications, and tissue engineering. This review also supports significant future research for developing multi-core and shell-based functional nanosystems to investigate nano-therapies that are needed for advanced, precise, and personalized healthcare systems.

Mesoporous silica nanoparticles: synthesis methods and their therapeutic use-recent advances

Mesoporous silica nanoparticles (MSNPs) are a particular example of innovative nanomaterials for the development of drug delivery systems. MSNPs have recently received more attention for biological and pharmaceutical applications due to their capability to deliver therapeutic agents. Due to their unique structure, they can function as an effective carrier for the delivery of therapeutic agents to mitigate diseases progress, reduce inflammatory responses and consequently improve cancer treatment. The potency of MSNPs for the diagnosis and management of various diseases has been studied. This literature review will take an in-depth look into the properties of various types of MSNPs (e.g. shape, particle and pore size, surface area, pore volume and surface functionalisation), and discuss their characteristics, in terms of cellular uptake, drug delivery and release. MSNPs will then be discussed in terms of their therapeutic applications (passive and active tumour targeting, theranostics, biosensing and immunostimulative), biocompatibility and safety issues. Also, emerging trends and expected future advancements of this carrier will be provided.

Engineering of monodisperse core-shell up-conversion dendritic mesoporous silica nanocomposites with a tunable pore size

Fabricating lanthanide doped up-conversion luminescence based nanocomposites has drawn increasing attention in nanoscience and nanotechnology. Although challenging in precise synthesis, structure manipulation and interfacial engineering, fabricating dendritic mesoporous silica coated up-conversion nanoparticles (UCNP@dMSNs) with a tunable pore size is of great importance for the functionalization and application of UCNPs. Herein, we report a strategy to prepare uniform monodisperse UCNP@dMSNs with a core-shell structure. The silica shell has tunable center-radial and dendritic mesoporous channels. The synthesis was carried out in the heterogeneous oil-water microemulsion phase of the Winsor III system reaction system, which allows silica to be deposited directly on hydrophobic UCNPs through the self-anchoring of micelle complexes on the oleic acid ligand. The average pore size of UCNP@dMSNs could be tailored from ∼10 to ∼35 nm according to the varied amounts of co-solvent in the mixture. The microemulsion approach could also be used to prepare hierarchical UCNP@dMSNs with a multi-generational mesostructure. The resultant UCNP@dMSNs exhibit the unique advantage of loading "guest" nanoparticles in a self-absorption manner. We proved that Cu1.8S NPs (∼10 nm), Au NPs (∼10 nm) and Fe3O4 NPs (∼25 nm) could be incorporated in UCNP@dMSNs, which in turn validates the high adsorption capacity of UCNP@dMSNs.

Recent advances of lanthanide-doped upconversion nanoparticles for biological applications

Near infrared (NIR) excited lanthanide-doped upconversion nanoparticles (UCNPs) are emerging as a new type of fluorescent tag for biological applications, which can emit multi-photon ultraviolet, visible or NIR luminescence for imaging or activation of photosensitive molecules. Here, we present a comprehensive review on recent advances of UCNPs for a manifold of biological applications, including upconversion mechanisms, building bright multicolor upconversion nanocrystals, single nanoparticle and super resolution imaging, in vivo optical and multimodal imaging, photodynamic therapy, light-controlled drug release, biosensing, and toxicities. Our perspectives on the future development of UCNPs are also described.

Upconversion Nanoparticle Powered Microneedle Patches for Transdermal Delivery of siRNA

Microneedles (MNs) permit the delivery of nucleic acids like small interfering RNA (siRNA) through the stratum corneum and subsequently into the skin tissue. However, skin penetration is only the first step in successful implementation of siRNA therapy. These delivered siRNAs need to be resistant to enzymatic degradation, enter target cells, and escape the endosome-lysosome degradation axis. To address this challenge, this article introduces a nanoparticle-embedding MN system that contains a dissolvable hyaluronic acid (HA) matrix and mesoporous silica-coated upconversion nanoparticles (UCNPs@mSiO₂ ). The mesoporous silica (mSiO₂ ) shell is used to load and protect siRNA while the upconversion nanoparticle (UCNP) core allows the tracking of MN skin penetration and NP diffusion through upconversion luminescence imaging or optical coherence tomography (OCT) imaging. Once inserted into the skin, the HA matrix dissolves and UCNPs@mSiO₂ diffuse in the skin tissue before entering the cells for delivering the loaded genes. As a proof of concept, this system is used to deliver molecular beacons (MBs) and siRNA targeting transforming growth factor-beta type I receptor (TGF-βRI) that is potentially used for abnormal scar treatment.

Histone H2A-peptide-hybrided upconversion mesoporous silica nanoparticles for bortezomib/p53 delivery and apoptosis induction

The design and development of advanced gene/drug codelivery nanocarrier with good biocompatibility for cancer gene therapy is desirable. Herein, we reported a gene delivery nanoplatform to synergized bortezomib (BTZ) for cancer treatment with histone H2A-hybrided, upconversion luminescence (UCL)-guided mesoporous silica nanoparticles [UCNPs(BTZ)@mSiO₂-H2A]. The functionalization of H2A on the surface of UCNPs(BTZ)@mSiO₂ nanoparticles realized the improvement of biocompatibility and enhancement of gene encapsulation and transfection efficiency. More importantly, then UCNPs(BTZ)@mSiO₂-H2A/p53 induced specific and efficient apoptotic cell death in p53-null cancer cells and restored the functional activity of tumor suppressor p53 by the success of co-delivery of BTZ/p53. Moreover, the transfection with UCNPs(BTZ)@mSiO₂-H2A/p53 in p53-deficient non-small cell lung cancer cells changed the status of p53 and substantially enhanced the p53-mediated sensitivity of encapsulated BTZ inside the UCNPs(BTZ)@mSiO₂/p53. Meanwhile, core-shell structured mesoporous silica nanoparticles UCNPs@mSiO₂ as an UCL agent can detect the real-time interaction of nanoparticles with cells and uptake/penetration processes. The results here suggested that the as-developed UCNPs(BTZ)@mSiO₂-H2A/p53 nanoplatform with coordinating biocompatibility, UCL image, and sustained release manner might be desirable gene/drug codelivery nanocarrier for clinical cancer therapy.

Toxicity response of highly colloidal, bioactive, monodisperse SiO2@ Pr(OH)3 hollow microspheres

In a facile synthesis, highly colloidal, bioactive Pr(OH)₃-encapsulated silica microspheres (PSMSs) with an average diameter of 500-700 nm were successfully prepared via a sol-gel process followed by heat treatment. The phase formation, morphology, surface and optical properties of the as-synthesized PSMSs were characterized by various techniques including X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), transmission electron microscope (TEM), N₂-adsorption-desorption, energy dispersive X-ray (EDX) analysis, Fourier transform infrared (FTIR) and UV/vis spectroscopy. The PSMSs were semi-amorphous or ultra-small in size, highly dispersible in water, mesoporous, irregular in size and spherical in shape. The SEM images show a well-ordered broad nanoporous structure which is preserved after coating with Pr(OH)₃ molecules, demonstrating interaction between the optically active Pr³⁺ ion and silanol (Si-OH) groups via hydrogen bonding. Optical spectra show well-resolved weak intensity 4f-4f absorption transitions in the visible region of the Pr³⁺ ion, indicating successful grafting of the Pr(OH)₃ layer. Toxicity was measured by MTT and NRU assays to determine potential toxicity. Cell viability was suppressed with increasing dosage of PSMSs, but showed greater than 55% cell viability at a concentration of 200 μg/mL, resulting in low toxicity. Due to its high aqueous dispersibility, optical activity, excellent biocompatibility and low toxic nature, it could be a favorable material for biomedical and drug delivery applications.

Aqueous dispersible green luminescent yttrium oxide:terbium microspheres with nanosilica shell coating

Tb-doped Y₂O₃ microspheres (MSs) were prepared via a homogeneous thermal degradation process at a low temperature and then coated with a nanosilica shell (Y₂O₃:Tb@SiO₂) using a sol-gel process. The core MSs were highly crystalline and spherical with a porous surface, single cubic phase, and particle size of 100-250 nm. Transmission electron microscopy (TEM) images clearly showed the spherical shape of the as-prepared core MSs, which were fully covered with a thick and mesoporous nanosilica shell. Fourier transform infrared (FTIR) spectra displayed the well-resolved infrared absorption peaks of silica (SiO, SiOSi, etc.), confirming the presence of the silica surface coating. The core MSs retained their spherical shape even after heat treatment and subsequent silica surface coating. It was observed that the core/shell MSs are easily dispersible in aqueous media and form a semi-transparent colloidal solution. Ultraviolet/visible and zeta potential studies were tested to prove the changes in the surface chemistry of the as-designed core/shell MSs and compare with their core counterpart. The growth of the amorphous silica shell not only increased the particle size but also enhanced remarkably the solubility and colloidal stability of the MSs in aqueous media. The strongest emission lines originating from the characteristic intra-shell 4f-4f electronic transitions of Tb ions were quenched after silica layer deposition, but the MSs still showed strong green (⁵D₄ → ⁷F₅ at 530-560 nm as most dominant) emission efficiency, which indicates great potential in fluorescent bio-probes. The emission intensity is discussed in relation to the quenching mechanism induced by surface silanol (Si-OH) groups, particle size, and surface charge.

Upconversion luminescence in sub-10 nm β-NaGdF4:Yb3+,Er3+ nanoparticles: an improved synthesis in anhydrous ionic liquids

The microwave-assisted synthesis of β-NaGdF₄:Er³⁺,Yb³⁺ in anhydrous ionic liquids yields efficient upconversion luminescence nanoparticles. A core–shell structure raises the nanoparticle emission intensity to 0.12% of the bulk material.

Modification of Bi6Fe1.9Co0.1Ti3O18/SiO2/NaGdF4:Yb3+,Er3+ nanocomposites with different SiO2 thicknesses for tunable upconversion luminescent and ferromagnetic properties

Modification of Bi₆Fe_1.9Co_0.1Ti₃O₁₈/SiO₂/NaGdF₄:Yb³⁺,Er³⁺ nanocomposites with different SiO₂ thickness for tunable upconversion emission and ferromagnetic properties.

Triple function nanocomposites of porous silica-CoFe2O4-MWCNTs as a carrier for pH-sensitive anti-cancer drug controlled delivery

Cobalt ferrite nanoparticles loaded on multiwalled carbon nanotube (MWCNT) magnetic hybrids have been demonstrated to be promising magnetic resonance imaging contrast agents and drug carriers. However, the hydrophobic, less biocompatible characteristics and low loading capacity for the drug hamper their wide biological applications. To solve the above problem, an alternative strategy is to coat the MWCNTs@CoFe₂O₄ nanoparticles with a mesoporous silica (mSiO₂) shell. Herein, the reasonable fabrication process results in successful coating mSiO₂ on the as-obtained MWCNTs@CoFe₂O₄ nanoparticles, forming well-defined core-shell-structured MWCNTs@CoFe₂O₄@mSiO₂ nanocomposites. The as-synthesized mesoporous nanocarrier possesses a high surface area and large pore volume for the loading of the drug, and has a superparamagnetic feature for drug targeting. Moreover, the anticancer drug doxorubicin (DOX)-loaded MWCNTs@CoFe₂O₄@mSiO₂ nanoplatforms show an excellent pH-responsive drug release character within 48 h. Therefore, a novel nanocarrier based on MWCNTs@CoFe₂O₄@mSiO₂ was proposed, and its potential application for targeted cancer therapy was highlighted.

Advances in Multicompartment Mesoporous Silica Micro/Nanoparticles for Theranostic Applications

Mesoporous silica nanoparticles (MSNs) are promising functional nanomaterials for a variety of biomedical applications, such as bioimaging, drug/gene delivery, and cancer therapy. This is due to their low density, low toxicity, high biocompatibility, large specific surface areas, and excellent thermal and mechanical stability. The past decade has seen rapid advances in the development of MSNs with multiple compartments. These include hierarchical porous structures and core-shell, yolk-shell, and Janus structured particles for efficient diagnosis and therapeutic applications. We review advances in this area, covering the categories of multicompartment MSNs and their synthesis methods, with an emphasis on hierarchical structures and the incorporation of multiple functions. We classify multicompartment mesoporous silica micro/nanostructures, ranging from core-shell and yolk-shell structures to Janus and raspberry-like nanoparticles, and discuss their synthesis methods. We review applications of these multicompartment MSNs, including bioimaging, targeted drug/gene delivery, chemotherapy, phototherapy, and in vitro diagnostics. We also highlight the latest trends and new opportunities.

Construction of a targeted photodynamic nanotheranostic agent using upconversion nanoparticles coated with an ultrathin silica layer

A photodynamic nanotheranostic agent prepared using UCNPs coated with an ultrathin silica layer was applied in living cells and tumor-bearing mice.

Redox-responsive UCNPs-DPA conjugated NGO-PEG-BPEI-DOX for imaging-guided PTT and chemotherapy for cancer treatment

The disulfide bond (–S–S–) is an enormously valuable functional group in a variety of chemical and biological agents that display effective reactivity or biological activities (e.g., antitumor activities).

Household Fluorescent Lateral Flow Strip Platform for Sensitive and Quantitative Prognosis of Heart Failure Using Dual-Color Upconversion Nanoparticles

Heart failure (HF) is the end-stage of cardiovascular diseases, which is associated with a high mortality rate and high readmission rate. Household early diagnosis and real-time prognosis of HF at bedside are of significant importance. Here, we developed a highly sensitive and quantitative household prognosis platform (termed as UC-LFS platform), integrating a smartphone-based reader with multiplexed upconversion fluorescent lateral flow strip (LFS). Dual-color core-shell upconversion nanoparticles (UCNPs) were synthesized as probes for simultaneously quantifying two target antigens associated with HF, i.e., brain natriuretic peptide (BNP) and suppression of tumorigenicity 2 (ST2). With the fluorescent LFS, we achieved the specific detection of BNP and ST2 antigens in spiked samples with detection limits of 5 pg/mL and 1 ng/mL, respectively, both of which are of one order lower than their clinical cutoff. Subsequently, a smartphone-based portable reader and an analysis app were developed, which could rapidly quantify the result and share prognosis results with doctors. To confirm the usage of UC-LFS platform for clinical samples, we detected 38 clinical serum samples using the platform and successfully detected the minimal concentration of 29.92 ng/mL for ST2 and 17.46 pg/mL for BNP in these clinical samples. Comparing the detection results from FDA approved clinical methods, we obtained a good linear correlation, indicating the practical reliability and stability of our developed UC-LFS platform. Therefore, the developed UC-LFS platform is demonstrated to be highly sensitive and specific for sample-to-answer prognosis of HF, which holds great potential for risk assessment and health monitoring of post-treatment patients at home.

UV and Temperature-Sensing Based on NaGdF4:Yb3+:Er3+@SiO2-Eu(tta)3

A multifunctional nanosystem was synthesized to be used as a dual sensor of UV light and temperature. NaGdF4:Yb3+:Er3+ upconverting nanoparticles (UCNPs) were synthesized and coated with a silica shell to which a europium(III) complex was incorporated. The synthesis of NaGdF4 UCNPs was performed via thermal decomposition of lanthanide ion fluoride precursors in the presence of oleic acid. To achieve sufficient water dispersibility, the surface of the hydrophobic oleate-capped UCNPs in the hexagonal phase was modified by a silica coating through a modified Stöber process through a reverse microemulsion method. An Eu(tta)3 (tta: thenoyltrifluoroacetonate) complex was prepared in situ at the silica shell. A dual-mode nanothermometer was obtained from a near infrared to visible upconversion fluorescence signal of Er3+ ions together with UV-excited downshifting emission from the Eu3+ complex. Measurements were recorded near the physiological temperature range (293-323 K), revealing excellent linearity (R 2 > 0.99) and relatively high thermal sensitivities (≥1.5%·K-1). The Eu(tta)3 complex present in the silica shell was tested as the UV sensor because of the Eu3+ luminescence dependence on UV-light exposure time.

Fluorescent proteins as efficient tools for evaluating the surface PEGylation of silica nanoparticles

Surface PEGylation is essential for preventing non-specific binding of biomolecules when silica nanoparticles are utilized for in vivo applications. Methods for installing poly(ethylene glycol) on a silica surface have been widely explored but varies from study to study. Because there is a lack of a satisfactory method for evaluating the properties of silica surface after PEGylation, the prepared nanoparticles are not fully characterized before use. In some cases, even non-PEGylated silica nanoparticles were produced, which is unfortunately not recognized by the end-user. In this work, a fluorescent protein was employed, which acts as a sensitive material for evaluating the surface protein adsorption properties of silica nanoparticles. Eleven different methods were systematically investigated for their reaction efficiency towards surface PEGylation. Results showed that both reaction conditions (including pH, catalyst) and surface functional groups of parent silica nanoparticles play critical roles in producing fully PEGylated silica nanoparticles. Great care needs to be taken in choosing the proper coupling chemistry for surface PEGylation. The data and method shown here will guarantee high-quality PEGylated silica nanoparticles to be produced and guide their applications in biology, chemistry, industry and medicine.

A targeted drug delivery system based on folic acid-functionalized upconversion luminescent nanoparticles

In this paper, multifunctional upconversion luminescent NaYF₄:Yb,Er nanoparticles with excellent hollow mesoporous structure were first fabricated. The effects of various reaction conditions on the morphology and size of the as-prepared samples were investigated in detail and Ostwald ripening effect was adapted to explain the formation mechanism of the HMUCNPs. Then, folic acid, a well-known ligand for the selective targeting of drugs into tumor cells, was conjugated to the surface of the hollow mesoporous structured upconversion luminescent nanoparticles (HMUCNPs) via amide reaction for targeted delivery of anticancer drugs so as to enhance the therapeutic efficacy. The properties were extensively studied, which indicated the obtained samples showed a typical hollow mesoporous structure and excellent upconversion luminescence that were useful for cell imaging and drug delivery. Drug storage/release properties were demonstrated to be pH responsive, in which the drug release might be beneficial at the reduced pH in certain cancerous tissues for targeted release and controlled therapy at the pathological sites. Meanwhile, DOX-NaYF₄:Yb,Er-FA HMUCNPs exhibited greater cytotoxicity than free doxorubicin hydrochloride because folic acid-conjugated HMUCNPs can be specifically taken up by FR-positive KB cells via a receptor-mediated endocytosis. Therefore, the folic acid-functionalized nanoparticles combining upconversion luminescent property and hollow mesoporous structure have potential for simultaneous targeted anticancer drug delivery and cell imaging.

Fluorescent carbon dots: rational synthesis, tunable optical properties and analytical applications

This review summarizes current advances on the design and the employment of fluorescent carbon dots in sensing applications, especially from the point of analytical view.

Multifunctional chitosan modified Gd2O3:Yb3+,Er3+@nSiO2@mSiO2 core/shell nanoparticles for pH responsive drug delivery and bioimaging

Chitosan modified Gd₂O₃:Yb³⁺,Er³⁺@nSiO₂@mSiO₂ core/shell nanoparticles were synthesized for pH responsive drug delivery and bioimaging.

808 nm near-infrared light controlled dual-drug release and cancer therapy in vivo by upconversion mesoporous silica nanostructures

A dual-drug co-delivery and 808 nm NIR photo-controlled release system can control drug release behaviour and enhance anticancer efficacy.

Upconversion nanoparticle-decorated gold nanoshells for near-infrared induced heating and thermometry

The present work involves the design of a multifunctional system based on gold nanoshells (AuNSs) decorated with lanthanide-based upconversion nanoparticles (UCNPs) intended as an optical heater and temperature probe at the nanoscale.

Polydopamine-Functionalized Graphene Oxide Loaded with Gold Nanostars and Doxorubicin for Combined Photothermal and Chemotherapy of Metastatic Breast Cancer

Breast cancer is the leading cancer type diagnosed in the female population, and cancer metastasis is the main reason for cancer-caused mortality. A novel nanoplatform is herein presented integrating polydopamine-functionalized nanosized reduced graphene oxide (NRGO), gold nanostars (GNS), and doxorubicin (DOX) (denoted as NRGO-GNS@DOX) for combinational treatment of metastatic breast cancer. Upon localized near infrared (NIR) laser irradiation, the NRGO-GNS@DOX nanocomposites induce significant cytotoxicity in 4T1 breast cancer cells due to a cumulative therapy effect of NRGO-GNS-elicited hyperthermia and DOX-induced cytotoxicity. Antitumor studies in orthotopic 4T1 breast tumor-bearing nude mice demonstrate that NRGO-GNS@DOX in combination with NIR laser irradiation inhibit the tumor growth and suppress the lung metastasis. Contribution of DOX-caused apoptosis of the cancer cells and hyperthermia-induced deconstruction of the tumor-associated blood vessels may account for the superior antitumor performance of the NRGO-GNS@DOX nanocomposites. These results imply a good potential of NRGO-GNS@DOX for combined photothermal and chemotherapy of the metastatic cancer.

Lanthanide-Doped Upconversion Nanoparticles: Emerging Intelligent Light-Activated Drug Delivery Systems

The development of drug delivery systems (DDSs) using near infrared (NIR) light and upconversion nanoparticles (UCNPs) has generated intensive interest over the past five years. These NIR-initiated DDSs not only offer a high degree of spatial and temporal determination of therapeutic release but also provide precise control over the released dosage. Furthermore, these nanoplatforms confer several advantages over conventional light-based DDSs-NIR offers better tissue penetration depth and a reduced risk of cellular photo-damage caused by exposure to light at high-energy wavelengths (e.g., ultraviolet light, <400 nm). The development of DDSs that can be activated by low intensity NIR illumination is highly desirable to avoid exposing living tissues to excessive heat that can limit the in vivo application of these DDSs. This encompasses research in three directions: (i) enhancing the quantum yield of the UCNPs; (ii) incorporation of photo-responsive materials with red-shifted absorptions into the UCNPs; and (iii) tuning the UCNPs excitation wavelength. This review focuses on recent advances in the development of NIR-initiated DDS, with emphasis on the use of photo-responsive compounds and polymeric materials conjugated onto UCNPs. The challenges that limit UCNPs clinical applications, alongside with the aforementioned techniques that have emerged to overcome these limitations, are highlighted.

Self-assembled gold nanostar–NaYF4:Yb/Er clusters for multimodal imaging, photothermal and photodynamic therapy

A grand challenge for medicine is to develop tools to selectively image and treat diseased cells.

Upconversion nanocomposites for photo-based cancer theranostics

Upconversion nanoparticles (UCNPs) are able to convert long wavelength excitation light into high energy ultraviolet (UV) or visible emissions, and they have attracted significant attention because of their distinct photochemical properties including sharp emission bands, low autofluorescence, high tissue penetration depth and minimal photodamage to tissues.