Upconversion Nanoparticles as Imaging Agents for Dental Caries.

Dental caries (cavities) is the most prevalent disease worldwide; however, current detection methods suffer from issues associated with sensitivity, subjective interpretations, and false positive identification of carious lesions. Therefore, there is a great need for the development of more sensitive, noninvasive imaging methods. The 30 nm core@shell NaYF4; Yb20%, Er2%@NaYF4 upconversion nanoparticles (UCNPs), exhibiting strong upconversion emission from erbium upon excitation at 975 nm, were used in the imaging of locations of demineralized enamel and oral biofilm formation for the detection of dental caries. UCNPs were modified with poly(acrylic acid) (PAA) or poly-d-lysine (PDL), and targeting peptides were conjugated to their surface with affinity for either hydroxyapatite (HA), the material dentin is composed of, or the caries causing bacteria Streptococcus mutans. A statistical difference in the binding of targeted vs nontargeted UCNPs to HA was observed after 15 min, using both upconversion fluorescence of UCNP (p < 0.001) and elemental analysis (p = 0.0091). Additionally, using the HA targeted UCNPs, holes drilled in the enamel of bovine teeth with diameters of 1.0 and 0.5 mm were visible by the green emission after a 20 min incubation with no observable nonspecific binding. A statistical difference was also observed in the binding of targeted versus nontargeted UCNPs to S. mutans biofilms. This difference was observed after 15 min, using the fluorescence measurements (p = 0.0125), and only 10 min (p < 0.001) using elemental analysis via ICP-OES measurements of Y3+ concentration present in the biofilms. These results highlight the potential of these UCNPs for use in noninvasive imaging diagnosis of oral disease.

Laser-ablative aqueous synthesis and characterization of elemental boron nanoparticles for biomedical applications.

Boron-based nano-formulations look very promising for biomedical applications, including photo- and boron neutron capture therapies, but the fabrication of non-toxic water-dispersible boron nanoparticles (NPs), which contain the highest boron atom concentration, is difficult using currently available chemical and plasma synthesis methods. Here, we demonstrate purely aqueous synthesis of clean boron NPs by methods of femtosecond laser ablation from a solid boron target in water, thus free of any toxic organic solvents, and characterize their properties. We show that despite highly oxidizing water ambience, the laser-ablative synthesis process follows an unusual scenario leading to the formation of boron NPs together with boric acid (H3BO3) as an oxidation by-product coating the nanoparticles, which acts to stabilize the elemental boron NPs dispersion. We then demonstrate the purification of boron NPs from residual boric acid in deionized water, followed by their coating with polyethylene glycol to improve colloidal stability and biocompatibility. It was found that the formed NPs have a spherical shape with averaged size of about 37 nm, and are composed of elemental boron in mostly amorphous phase with the presence of certain crystalline fraction. The synthesized NPs demonstrate low toxicity and exhibit strong absorption in the NIR window of relative tissue transparency, promising their use in photoacoustic imaging and phototherapy, in addition to their promise for neutron capture therapy. This combined potential ability of generating imaging and therapy functionalities makes laser-synthesized B NPs a very promising multifunctional agent for biomedical applications.

Photoacoustic and Magnetic Resonance Imaging of Hybrid Manganese Dioxide-Coated Ultra-small NaGdF4 Nanoparticles for Spatiotemporal Modulation of Hypoxia in Head and Neck Cancer.

There is widespread interest in developing agents to modify tumor hypoxia in head and neck squamous cell carcinomas (HNSCC). Here, we report on the synthesis, characterization, and potential utility of ultra-small NaYF4:Nd3+/NaGdF4 nanocrystals coated with manganese dioxide (usNP-MnO2) for spatiotemporal modulation of hypoxia in HNSCC. Using a dual modality imaging approach, we first visualized the release of Mn2+ using T1-weighted magnetic resonance imaging (MRI) and modulation of oxygen saturation (%sO2) using photoacoustic imaging (PAI) in vascular channel phantoms. Combined MRI and PAI performed in patient-derived HNSCC xenografts following local and systemic delivery of the hybrid nanoparticles enabled mapping of intratumoral nanoparticle accumulation (based on T1 contrast enhancement) and improvement in tumor oxygenation (increased %sO2) within the tumor microenvironment. Our results demonstrate the potential of hybrid nanoparticles for the modulation of tumor hypoxia in head and neck cancer. Our findings also highlight the potential of combined MRI-PAI for simultaneous mapping nanoparticle delivery and oxygenation changes in tumors. Such imaging methods could be valuable in the precise selection of patients that are likely to benefit from hypoxia-modifying nanotherapies.

Laser-Ablative Synthesis of Stable Aqueous Solutions of Elemental Bismuth Nanoparticles for Multimodal Theranostic Applications.

Elemental bismuth (Bi) nanoparticles (NPs), with the high atomic density of the Bi nuclei, could serve as efficient targeted agents for cancer treatment, with applications such as contrast agents for computed tomography (CT) imaging, sensitizers for image-guided X-ray radiotherapy, and photothermal therapy. However, the synthesis of elemental Bi NPs suitable for biological applications is difficult using conventional chemical routes. Here, we explore the fabrication of ultrapure Bi-based nanomaterials by femtosecond laser ablation from a solid Bi target in ambient liquids and characterize them by a variety of techniques, including TEM, SEM, XRD, FTIR, Raman, and optical spectroscopy. We found that laser-ablative synthesis using an elemental Bi solid target leads to the formation of spherical Bi NPs having the mean size of 20-50 nm and a low size-dispersion. The NPs prepared in water experience a fast (within a few minutes) conversion into 400-500 nm flake-like nanosheets, composed of bismuth subcarbonates, (BiO)2CO3 and (BiO)4CO3(OH)2, while the NPs prepared in acetone demonstrate high elemental stability. We introduce a procedure to obtain a stable aqueous solution of elemental Bi NPs suitable for biological applications, based on the coating of Bi NPs prepared in acetone with Pluronic® F68 and their subsequent transfer to water. We also show that the laser-synthesized elemental Bi NPs, due to their vanishing band gap, exhibit remarkable absorption in the infrared range, which can be used for the activation of photothermal therapy in the near IR-to-IR window with maximum optical transparency in biological media. Exempt of any toxic synthetic by-products, laser-ablated elemental Bi NPs present a novel appealing nanoplatform for combination image-guided photoradiotherapies.

A Multimodal Theranostic Nanoformulation That Dramatically Enhances Docetaxel Efficacy Against Castration Resistant Prostate Cancer.

In this work, a multifunctional hierarchical nanoformulation composed of biodegradable chitosan (CS) coated poly (lactic-co-glycolic acid) (PLGA) nanocarriers loaded with docetaxel (Doc) and interleukin-8 (IL-8) small interfering RNA (siRNA) electrostatically bound to upconversion nanoparticles (UCNPs), is developed to treat castration-resistant prostate cancer (CRPC). This theranostic nanoformulation facilitates simultaneous delivery of chemotherapy and gene therapy, as well as a bimodal optical and magnetic resonance imaging agent that could enable image-guided combination therapy. Poly-d-lysine coated NaYF4; Yb20%, Er2%@NaYF4; Gd50% core@shell UCNPs are effective siRNA transfection agents, and Er3+ doping provides upconversion imaging capabilities, while Gd3+ doping enables magnetic resonance contrast enhancement. These properties are maintained upon encapsulation in PLGA-CS. PLGA-CS nanocarriers containing Doc and UCNP-siRNA are 235 ± 5 nm with a zeta potential of +17 ± 4 meV, and have a high Doc encapsulation efficiency of 57 ± 6%. Compared to free Doc, this PLGA-CS nanoformulation containing Doc and UCNP-siRNA exhibits a dramatic decrease in IC50 of ~14,000 fold (p < 0.001) through combination therapy in human PC-3 prostate cancer cells. This biocompatible, multimodal, theranostic nanoformulation demonstrates paradigm-shifting enhancement in anticancer activity over free Doc, with unique potential for use in image-guided combination therapy to treat CRPC.

Laser ablation for pharmaceutical nanoformulations: Multi-drug nanoencapsulation and theranostics for HIV.

We introduce the use of laser ablation to develop a multi-drug encapsulating theranostic nanoformulation for HIV-1 antiretroviral therapy. Laser ablated nanoformulations of ritonavir, atazanavir, and curcumin, a natural product that has both optical imaging and pharmacologic properties, were produced in an aqueous media containing Pluronic® F127. Cellular uptake was confirmed with the curcumin fluorescence signal localized in the cytoplasm. Formulations produced with F127 had improved water dispersibility, are ultrasmall in size (20-25 nm), exhibit enhanced cellular uptake in microglia, improve blood-brain barrier (BBB) crossing in an in vitro BBB model, and reduce viral p24 by 36 fold compared to formulations made without F127. This work demonstrates that these ultrasmall femtosecond laser-ablated nanoparticles are effective in delivering drugs across the BBB for brain therapy and show promise as an effective method to formulate nanoparticles for brain theranostics, reducing the need for organic solvents during preparation.