Recent advances of metal-based nanoparticles in nucleic acid delivery for therapeutic applications

Recent efforts in designing nanomaterials to deliver potential therapeutics to the targeted site are overwhelming and palpable. Engineering nanomaterials to deliver biological molecules to exert desirable physiological changes, with minimized side effects and optimal dose, has revolutionized the next-generation therapy for several diseases. The rapid progress of nucleic acids as biopharmaceutics is going to alter the traditional pharmaceutics practices in modern medicine. However, enzymatic instability, large size, dense negative charge (hydrophilic for cell uptake), and unintentional adverse biological responses-such as prolongation of the blood coagulation and immune system activation-hamper the potential use of nucleic acids for therapeutic purposes. Moreover, the safe delivery of nucleic acids into the clinical setting is an uphill task, and several efforts are being put forward to deliver them to targeted cells. Advances in Metal-based NanoParticles (MNPs) are drawing attention due to the unique properties offered by them for drug delivery, such as large surface-area-to-volume ratio for surface modification, increased therapeutic index of drugs through site-specific delivery, increased stability, enhanced half-life of the drug in circulation, and efficient biodistribution to the desired targeted site. Here, the potential of nanoparticles delivery systems for the delivery of nucleic acids, specially MNPs, and their ability and advantages over other nano delivery systems are reviewed.

Rare-Earth Doping in Nanostructured Inorganic Materials

Impurity doping is a promising method to impart new properties to various materials. Due to their unique optical, magnetic, and electrical properties, rare-earth ions have been extensively explored as active dopants in inorganic crystal lattices since the 18th century. Rare-earth doping can alter the crystallographic phase, morphology, and size, leading to tunable optical responses of doped nanomaterials. Moreover, rare-earth doping can control the ultimate electronic and catalytic performance of doped nanomaterials in a tunable and scalable manner, enabling significant improvements in energy harvesting and conversion. A better understanding of the critical role of rare-earth doping is a prerequisite for the development of an extensive repertoire of functional nanomaterials for practical applications. In this review, we highlight recent advances in rare-earth doping in inorganic nanomaterials and the associated applications in many fields. This review covers the key criteria for rare-earth doping, including basic electronic structures, lattice environments, and doping strategies, as well as fundamental design principles that enhance the electrical, optical, catalytic, and magnetic properties of the material. We also discuss future research directions and challenges in controlling rare-earth doping for new applications.

Effect of the Concentration of SrAl2O4: Eu2+and Dy3+ (SAO) on Characteristics and Properties of Environment-Friendly Long-Persistent Luminescence Composites from Polylactic Acid and SAO

We report luminous polylactic acid (PLA) composite prepared via a solvent casting method using different amounts of phosphor strontium aluminate (SrAl2O4: Eu2+ and Dy3+) (SAO). The reason for doing this is that the changes of fluorescence and mechanical properties in the composites with different SAO contents can be directly evaluated. The SAO particles should have a variety of excellent characteristics in the PLA matrix, among which dispersibility and compatibility are particularly important; so, they can be modified by 3-aminopropyltriethoxysilane (APS) to achieve the target characteristics. The results showed that the fluorescence and mechanical properties were affected by SAO addition. The mechanical properties significantly improved with 5 wt% SAO; further, addition had no impact. And the emission band of fluorescence and phosphorescence is just at the peak of 524 nm. The composites with 15 wt% SAO have the best fluorescence properties. The fluorescence decreased with further doping. Fluorescence decay curves with various amounts of SAO particles show a similar tendency as pure SAO particles; the speed of decrease in afterglow intensity was higher for the first 30 min. In addition, the detailed morphological scanning and study by scanning electron microscope (SEM) showed that the particles had good adhesion to the matrix. In conclusion, the concentration of SAO into the PLA matrix impacts the fluorescence and mechanical properties of a SAO/PLA composite material.

Luminescent Nanomaterials (II)

In this review, we focus on sensing techniques and biological applications of various luminescent nanoparticles including quantum dot (QD), up-conversion nanoparticles (UCNPs) following the previous chapter. Fluorescent phenomena can be regulated or shifted by interaction between biological targets and luminescence probes depending on their distance, which is so-called Fӧrster resonance energy transfer (FRET). QD-based FRET technique, which has been widely applied as a bioanalytical tool, is described. We discuss time-resolved fluorescence (TRF) imaging and flow cytometry technique, using photoluminescent nanoparticles with unique properties for effectively improving selectivity and sensitivity. Based on these techniques, bioanalytical and biomedical application, bioimaging with QD, UCNPs, and Euripium-activated luminescent nanoprobes are covered. Combination of optical property of these luminescent nanoparticles with special functions such as drug delivery, photothermal therapy (PTT), and photodynamic therapy (PDT) is also described.

Biomaterials for Interfacing Cell Imaging and Drug Delivery: An Overview

This feature article provides an overview of different kinds of futuristic biomaterials which have the potential to be used for fluorescent imaging and drug delivery, often simultaneously. The synthesis route or preparation process, fluorescence property, release profile, biocompatibility, bioimaging, and mechanistic approaches are vividly discussed. These include bioimaging with fluorescently doped quantum dots, mesoporous silica, noble metals, metal clusters, hydrophilic/hydrophobic polymers, semiconducting polymer dots, carbon/graphene dots, dendrimers, fluorescent proteins, and other nanobiomaterials. Another section discusses the controlled and targeted drug, gene, or biologically active material delivery using various vehicles such as micelles, 2D nanomaterials, organic nanoparticles, polymeric nanohybrids, and chemically modified polymers. In the last section, we discuss biomaterials, which can deliver biologically active molecules, and imaging the cell/tissue.

Large-scale synthesis and luminescence of GdPO4 hollow microspheres

GdPO₄ hollow microspheres were synthesized by using a novel multi-step route for the first time with polystyrene (PS) spheres as the template, followed by the combination of a facile homogeneous precipitation method, an ion-exchange process, and a calcination process.

A bifunctional nanomodulator for boosting CpG-mediated cancer immunotherapy

Unmethylated cytosine-phosphate-guanine (CpG) oligonucleotides (ODNs) possess high immunostimulatory activity and represent attractive tools for cancer treatment. However, their success in eliminating large solid tumors was hampered by the immunosuppressive tumor microenvironment. Herein, we report that the design of a novel MnO₂-CpG-silver nanoclusters (AgNCs)-doxorubicin (DOX) conjugate for enhanced cancer immunotherapy, in which MnO₂ nanosheets function as unique supports to integrate the chemotherapy drug DOX and the immunotherapeutic agent CpG-AgNCs. Importantly, DOX could be conjugated with MnO₂ nanosheets through π-π interactions to serve as a bifunctional modulator of the tumor microenvironment to activate a tumor-specific immune response by inducing immunogenic cell death, and reverse the immunosuppressive tumor microenvironment via abrogating the immune-suppressive activity of regulatory T cells, both of which would greatly improve the immune response of CpG-AgNCs. In this way, the T-cell immune responses of CpG-AgNCs which are linked to MnO₂ nanosheets were significantly enhanced and could exhibit remarkable antitumor activity against large solid tumors. Our study may guide the rational design of immunotherapeutic boosters for improving cancer treatment.

Multiple imaging and excellent anticancer efficiency of an upconverting nanocarrier mediated by single near infrared light

It is difficult to meet the requirements of clinical diagnosis through a single imaging technique. Similarly, satisfactory therapy efficacy is also hard to achieve by a single therapeutic modality. It is therefore highly desirable and interesting to simultaneously achieve multimodal imaging and therapies in one single structure. In this study, we developed a core-shell-satellite NaGdF₄:Yb,Er,Mn,Co@mSiO₂-CuS structure using up-conversion luminescent (UCL) NaGdF₄:Yb,Er,Mn,Co as the core, mesoporous silica as the layer, and the photoactive CuS nanoparticles as the satellites. The further linked photosensitizer (ZnPc) and doxorubicin hydrochloride (DOX) allow the system to have photodynamic therapy (PDT) and chemotherapy functions. The doping of Co²⁺ ions in the core endows the carrier with T₂-weighted magnetic resonance imaging (MRI) properties, and the co-doping of Mn²⁺ ions can efficiently enhance the red emission which further improves the PDT efficiency by reacting with the attached ZnPc upon near-infrared (NIR) light irradiation. The nanoplatform exhibits excellent anti-tumor efficiency due to a synergistic effect arising from combined PDT, photo-thermal therapy (PTT) and chemotherapy, which has been evidenced by in vitro and in vivo results. Due to the multimodal imaging (MRI, CT, and UCL) properties, the drug delivery process and therapeutic efficacy can be monitored in real time and assessed, thus achieving the target of imaging-guided therapy.

An overview of nanoparticles commonly used in fluorescent bioimaging

This article gives an overview of the various kinds of nanoparticles (NPs) that are widely used for purposes of fluorescent imaging, mainly of cells and tissues. Following an introduction and a discussion of merits of fluorescent NPs compared to molecular fluorophores, labels and probes, the article assesses the kinds and specific features of nanomaterials often used in bioimaging. These include fluorescently doped silicas and sol-gels, hydrophilic polymers (hydrogels), hydrophobic organic polymers, semiconducting polymer dots, quantum dots, carbon dots, other carbonaceous nanomaterials, upconversion NPs, noble metal NPs (mainly gold and silver), various other nanomaterials, and dendrimers. Another section covers coatings and methods for surface modification of NPs. Specific examples on the use of nanoparticles in (a) plain fluorescence imaging of cells, (b) targeted imaging, (c) imaging of chemical species, and (d) imaging of temperature are given next. A final section covers aspects of multimodal imaging (such as fluorescence/nmr), imaging combined with drug and gene delivery, or imaging combined with therapy or diagnosis. The electronic supplementary information (ESI) gives specific examples for materials and methods used in imaging, sensing, multimodal imaging and theranostics such as imaging combined with drug delivery or photodynamic therapy. The article contains 273 references in the main part, and 157 references in the ESI.

Syntheses and biomedical applications of hollow micro-/nano-spheres with large-through-holes

This review mainly discussed the syntheses and biomedical applications of hollow micro-/nano-spheres with large-through-holes in shells.

Biomimetic nanoassembly for targeted antigen delivery and enhanced Th1-type immune response

A new type of biomimetic nanoassembly for targeted antigen delivery and enhanced Th1-type response is reported for the first time, to combat the major challenges in the treatment of infected cells.

Diol glycidyl ether-bridged low molecular weight PEI as potential gene delivery vehicles

PEI 600-based polymers were synthesized via ring-opening polymerization and exhibited much better transfection efficiency and biocompatibility than PEI 25 kDa.

Gene therapy and imaging in preclinical and clinical oncology: recent developments in therapy and theranostics

In the case of disseminated cancer, current treatment options reach their limit. Gene theranostics emerge as an innovative route in the treatment and diagnosis of cancer and might pave the way towards development of an efficacious treatment of currently incurable cancer. Various gene vectors have been developed to realize tumor-specific nucleic acid delivery and are considered crucial for the successful application of cancer gene therapy. By adding reporter genes and imaging agents, these systems gain an additional diagnostic function, thereby advancing the theranostic paradigm into cancer gene therapy. Numerous preclinical studies have demonstrated the feasibility of combined tumor gene therapy and diagnostic imaging, and clinical trials in human and veterinary oncology have been executed with partly encouraging results.

Multifunctional superparamagnetic nanoshells: combining two-photon luminescence imaging, surface-enhanced Raman scattering and magnetic separation

With the increasing need for multi-purpose analysis in the biomedical field, traditional single diagnosis methods cannot meet the requirements. Therefore new multifunctional technologies and materials for the integration of sample collection, sensing and imaging are in great demand. Core-shell nanoparticles offer a unique platform to combine multifunctions in a single particle. In this work, we have constructed a novel type of core-shell superparamagnetic nanoshell (Fe₃O₄@SiO₂@Au), composed of a Fe₃O₄ cluster core, a thin Au shell and a SiO₂ layer in between. The obtained multifunctional nanoparticles combine the magnetic properties and plasmonic optical properties effectively, which were well investigated by a number of experimental characterization methods and theoretical simulations. We have demonstrated that Fe₃O₄@SiO₂@Au nanoparticles can be utilized for two-photon luminescence (TPL) imaging, near-infrared surface-enhanced Raman scattering (NIR SERS) and cell collection by magnetic separation. The TPL intensity could be further greatly enhanced through the plasmon coupling effect in the self-assembled nanoparticle chains, which were triggered by an external magnetic field. In addition, Fe₃O₄@SiO₂@Au nanoparticles may have great potential applications such as enhanced magnetic resonance imaging (MRI) and photo-thermotherapy. Successful combination of multifunctions including magnetic response, biosensing and bioimaging in single nanoparticles allows further manipulation, real-time tracking, and intracellular molecule analysis of live cells at a single-cell level.

A semipermeable enzymatic nanoreactor as an efficient modulator for reversible pH regulation

Here we propose a new concept for the fabrication of a semipermeable enzymatic nanoreactor as an efficient modulator to reversibly switch the pH of an aqueous environment. We used amino-functionalized, expanded mesoporous silica nanoparticles (EMSN) as a model nanocarrier to load enzymes. In order to protect enzymes from the interference of a complicated environment, polyelectrolyte multilayers (PEMs) were coated on the surface of the EMSN through layer by layer (LbL) assembly. These PEMs can serve as semipermeable membranes, allowing small molecules to diffuse in and out freely while trapping the enzymes in the nanoreactors. Compared with traditional electrochemical stimulation or optical control methods, our enzymatic regulation platform is easy to operate without complicated instruments. In addition, this system can cover a wide range of pH values and conveniently regulate pH values by simply controlling the concentrations of catalysts or reactants. Meanwhile, this strategy could be generalized to other enzymes or nanocarriers to achieve reversible pH regulation for different purposes. The switched pH values can be implemented for the modulation of the conformational changes of nucleic acids and activation of the charge conversion in drug delivery applications.

Lanthanide-doped hollow nanomaterials as theranostic agents

The field of theranostics has sprung up to achieve personalized medicine. The theranostics fuses diagnostic and therapeutic functions, empowering early diagnosis, targeted drug delivery, and real-time monitoring of treatment effect into one step. One particularly attractive class of nanomaterials for theranostic application is lanthanide-doped hollow nanomaterials (LDHNs). Because of the existence of lanthanide ions, LDHNs show outstanding fluorescent and paramagnetic properties, enabling them to be used as multimodal bioimaging agents. Synchronously, the huge interior cavities of LDHNs are able to be applied as efficacious tools for storage and delivery of therapeutic agents. The LDHNs can be divided into two types based on difference of component: single-phase lanthanide-doped hollow nanomaterials and lanthanide-doped hollow nanocomposites. We describe the synthesis of first kind of nanomaterials by use of hard template, soft template, template-free, and self-sacrificing template method. For lanthanide-doped hollow nanocomposites, we divide the preparation strategies into three kinds (one-step, two-step, and multistep method) according to the synthetic procedures. Furthermore, we also illustrate the potential bioapplications of these LDHNs, including biodetection, imaging (fluorescent imaging and magnetic resonance imaging), drug/gene delivery, and other therapeutic applications.