In Vivo Biodistribution of Amino-Functionalized Ceria Nanoparticles in Rats Using Positron Emission Tomography

The regulatory mechanisms of cerium oxide nanoparticles in oxidative stress and emerging applications in refractory wound care

Cerium oxide nanoparticles (CeNPs) have emerged as a potent therapeutic agent in the realm of wound healing, attributing their efficacy predominantly to their exceptional antioxidant properties. Mimicking the activity of endogenous antioxidant enzymes, CeNPs alleviate oxidative stress and curtail the generation of inflammatory mediators, thus expediting the wound healing process. Their application spans various disease models, showcasing therapeutic potential in treating inflammatory responses and infections, particularly in oxidative stress-induced chronic wounds such as diabetic ulcers, radiation-induced skin injuries, and psoriasis. Despite the promising advancements in laboratory studies, the clinical translation of CeNPs is challenged by several factors, including biocompatibility, toxicity, effective drug delivery, and the development of multifunctional compounds. Addressing these challenges necessitates advancements in CeNP synthesis and functionalization, novel nano delivery systems, and comprehensive bio effectiveness and safety evaluations. This paper reviews the progress of CeNPs in wound healing, highlighting their mechanisms, applications, challenges, and future perspectives in clinical therapeutics.

[18F]-Radiolabelled Nanoplatforms: A Critical Review of Their Intrinsic Characteristics, Radiolabelling Methods, and Purification Techniques

A wide range of nano-objects is found in many applications of our everyday life. Recognition of their peculiar properties and ease of functionalization has prompted their engineering into multifunctional platforms that are supposed to afford efficient tools for the development of biomedical applications. However, bridging the gap between bench to bedside cannot be expected without a good knowledge of their behaviour in vivo, which can be obtained through non-invasive imaging techniques, such as positron emission tomography (PET). Their radiolabelling with [18F]-fluorine, a technique already well established and widely used routinely for PET imaging, with [18F]-FDG for example, and in preclinical investigation using [18F]-radiolabelled biological macromolecules, has, therefore, been developed. In this context, this review highlights the various nano-objects studied so far, the reasons behind their radiolabelling, and main in vitro and/or in vivo results obtained thereof. Then, the methods developed to introduce the radioelement are presented. Detailed indications on the chemical steps involved are provided, and the stability of the radiolabelling is discussed. Emphasis is then made on the techniques used to purify and analyse the radiolabelled nano-objects, a point that is rarely discussed despite its technical relevance and importance for accurate imaging. The pros and cons of the different methods developed are finally discussed from which future work can develop.

Electrospun polyvinyl alcohol-chitosan dressing stimulates infected diabetic wound healing with combined reactive oxygen species scavenging and antibacterial abilities

Diabetic wounds (DW) are constantly challenged by excessive reactive oxygen species (ROS) accumulation and susceptibility to bacterial contamination. Therefore, the elimination of ROS in the immediate vicinity and the eradication of local bacteria are critical to stimulating the efficient healing of diabetic wounds. In the current study, we encapsulated mupirocin (MP) and cerium oxide nanoparticles (CeNPs) into a polyvinyl alcohol/chitosan (PVA/CS) polymer, and then a PVA/chitosan nanofiber membrane wound dressing was fabricated using electrostatic spinning, which is a simple and efficient method for fabricating membrane materials. The PVA/chitosan nanofiber dressing provided a controlled release of MP, which produced rapid and long-lasting bactericidal activity against both methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) strains. Simultaneously, the CeNPs embedded in the membrane exhibited the desired ROS scavenging capacity to maintain the local ROS at a normal physiological level. Moreover, the biocompatibility of the multifunctional dressing was evaluated both in vitro and in vivo. Taken together, PVA-CS-CeNPs-MP integrated the desirable features of a wound dressing, including rapid and broad-spectrum antimicrobial and ROS scavenging activities, easy application, and good biocompatibility. The results validated the effectiveness of our PVA/chitosan nanofiber dressing, highlighting its promising translational potential in the treatment of diabetic wounds.

Nanoparticle Synthesis and Their Integration into Polymer-Based Fibers for Biomedical Applications

The potential of nanoparticles as effective drug delivery systems combined with the versatility of fibers has led to the development of new and improved strategies to help in the diagnosis and treatment of diseases. Nanoparticles have extraordinary characteristics that are helpful in several applications, including wound dressings, microbial balance approaches, tissue regeneration, and cancer treatment. Owing to their large surface area, tailor-ability, and persistent diameter, fibers are also used for wound dressings, tissue engineering, controlled drug delivery, and protective clothing. The combination of nanoparticles with fibers has the power to generate delivery systems that have enhanced performance over the individual architectures. This review aims at illustrating the main possibilities and trends of fibers functionalized with nanoparticles, focusing on inorganic and organic nanoparticles and polymer-based fibers. Emphasis on the recent progress in the fabrication procedures of several types of nanoparticles and in the description of the most used polymers to produce fibers has been undertaken, along with the bioactivity of such alliances in several biomedical applications. To finish, future perspectives of nanoparticles incorporated within polymer-based fibers for clinical use are presented and discussed, thus showcasing relevant paths to follow for enhanced success in the field.

Radiolabelling and in vivo radionuclide imaging tracking of emerging pollutants in environmental toxicology: A review

Emerging pollutants (EPs) have become a global concern, attracting tremendous attention because of serious threats to human and animal health. EP diversity emanates from their behaviour and ability to enter the body via multiple pathways and exhibit completely different distribution, transport, and excretion. To better understand the in vivo behaviour of EPs, we reviewed radiolabelling and in vivo radionuclide imaging tracking of various EPs, including micro- and nano-plastics, perfluoroalkyl substances, metal oxides, pharmaceutical and personal care products, and so on. Because this accurate and quantitative imaging approach requires the labelling of radionuclides onto EPs, the main strategies for radiolabelling were reviewed, such as synthesis with radioactive precursors, element exchange, proton beam activation, and modification. Spatial and temporal biodistribution of various EPs was summarised in a heat map, revealing that the absorption, transport, and excretion of EPs are markedly related to their type, size, and pathway into the body. These findings implicate the potential toxicity of diverse EPs in organs and tissues. Finally, we discussed the potential and challenges of radionuclide imaging tracking of EPs, which can be considered in future EPs studies.

Cationized silica ceria nanocomposites to target biofilms in chronic wounds

Altered wound healing is a major challenge faced by both developed and developing nations. Biofilm formation has been identified as one of the causative factors for the progression of chronic wounds. The spread of biofilm is controlled by inhibiting the biofilm formation or disrupting the mature biofilm. Functional nanomaterials/enzymes with antimicrobial effects, such as metal oxides, rare earth metals, and carbon nanoparticles have been investigated to treat biofilm and overcome the drawbacks associated with the antibiotic therapy. Cerium oxide nanoparticles (CNPs) have drawn significant attention as a promising antimicrobial agent owing to their antibacterial, enzyme-mimetic, and crystalline properties but they suffer from poor colloidal stability and dispersity in an aqueous environment and size-dependent function. In this work, we have developed a functionalized silica ceria nanocomposite (FSC), as an antibiotic-free system, to treat biofilms. The FSC possesses a high surface area of mesoporous silica nanoparticles (MSNs) combined with the intrinsic antibacterial activity of cerium oxide for biofilm inhibition. The nanocomposite was fabricated using silica and ceria precursors, and it exhibited a high surface area of 436 m²/g and an average particle size of around 450 nm. The physical and chemical properties of nanocomposite were characterized using FTIR, XRD, UV-Vis, BET, EDX, and XPS analysis. It exhibited a potent antioxidant activity (86%), positive haloperoxidase mimetic property, and broad-spectrum antibacterial activities. It showed 99.9% inhibition against S. aureus (Gram-positive) and 81% inhibition against E. coli (Gram-negative) within 12 and 24 h along with the significant inhibition of biofilm formation (80%) as well as the disruptive effect against the established biofilm (77%) of S. aureus. Cell viability assays indicated the proliferative nature of composite in normal basal conditions and increased cell viability (97%) in the presence of oxidative stress. Despite being a cationic nanomaterial, it showed a good hemocompatibility against human blood and caused complete wound closure in mouse fibroblast cell line within 24 h. The functionalized silica ceria nanocomposite developed has a strong potential in chronic wound healing applications.

Mucoadhesive PLGA Nanospheres and Nanocapsules for Lactoferrin Controlled Ocular Delivery

Background: the present work describes the preparation, characterization and optimization of eight types of PLGA-based nanosystems (nanospheres and nanocapsules) as innovative mucoadhesive drug delivery systems of lactoferrin, in order to achieve a preclinical consistent base as an alternative pharmacological treatment to different ocular syndromes and diseases. Methods: All different nanoparticles were prepared via two modified nanoprecipitation techniques, using a three-component mixture of drug/polymer/surfactant (Lf/PLGA/Poloxamer), as a way to overcome the inherent limitations of conventional PLGA NPs. These modified polymeric nanocarriers, intended for topical ophthalmic administration, were subjected to in vitro characterization, surface modification and in vitro and in vivo assessments. Results: An appropriate size range, uniform size distribution and negative ζ potential values were obtained for all types of formulations. Lactoferrin could be effectively included into all types of nanoparticles with appropriate encapsulation efficiency and loading capacity values. A greater, extended, and controlled delivery of Lf from the polymeric matrix was observed through the in vitro release studies. No instability or cytotoxicity was proved for all the formulations by means of organotypic models. Additionally, mucoadhesive in vitro and in vivo experiments show a significant increase in the residence time of the nanoparticles in the eye surface. Conclusions: all types of prepared PLGA nanoparticles might be a potential alternative for the topical ophthalmic administration of lactoferrin.

Antioxidant Activity and Toxicity Study of Cerium Oxide Nanoparticles Stabilized with Innovative Functional Copolymers

Oxidative stress, which is one of the main harmful mechanisms of pathologies including ischemic stroke, contributes to both neurons and endothelial cell damages, leading to vascular lesions. Although many antioxidants are tested in preclinical studies, no treatment is currently available for stroke patients. Since cerium oxide nanoparticles (CNPs) exhibit remarkable antioxidant capacities, the objective is to develop an innovative coating to enhance CNPs biocompatibility without disrupting their antioxidant capacities or enhance their toxicity. This study reports the synthesis and characterization of functional polymers and their impact on the enzyme-like catalytic activity of CNPs. To study the toxicity and the antioxidant properties of CNPs for stroke and particularly endothelial damages, in vitro studies are conducted on a cerebral endothelial cell line (bEnd.3). Despite their internalization in bEnd.3 cells, coated CNPs are devoid of cytotoxicity. Microscopy studies report an intracellular localization of CNPs, more precisely in endosomes. All CNPs reduces glutamate-induced intracellular production of reactive oxygen species (ROS) in endothelial cells but one CNP significantly reduces both the production of mitochondrial superoxide anion and DNA oxidation. In vivo studies report a lack of toxicity in mice. This study therefore describes and identifies biocompatible CNPs with interesting antioxidant properties for ischemic stroke and related pathologies.

Sprayable hydrogel dressing accelerates wound healing with combined reactive oxygen species-scavenging and antibacterial abilities

Wound management poses a considerable economic burden on the global healthcare system, considering the impacts of wound infection, delayed healing and scar formation. To this end, multifunctional dressings based on hydrogels have been developed to stimulate skin healing. Herein, we describe the design, fabrication, and characterization of a sprayable hydrogel-based wound dressing loaded with cerium oxide nanoparticles (CeONs) and an antimicrobial peptide (AMP), for combined reactive oxygen species (ROS)-scavenging and antibacterial properties. We adopted a mussel-inspired strategy to chemically conjugate gelatin with dopamine motifs and prepared a hydrogel dressing with improved binding affinity to wet skin surfaces. Additionally, the release of AMP from the hydrogel demonstrated rapid release ablation and contact ablation against four representative bacterial strains, confirming the desired antimicrobial activities. Moreover, the CeONs-loaded hydrogel dressing exhibited favorable ROS-scavenging abilities. The biocompatibility of the multifunctional hydrogel dressing was further proven in vitro by culturing with HaCaT cells. Overall, the benefits of the developed hydrogel wound dressing, including sprayability, adhesiveness, antimicrobial activity, as well as ROS-scavenging and skin-remodeling ability, highlight its promissing translational potentials in wound management. STATEMENT OF SIGNIFICANCE: Various hydrogel-based wound-dressing materials have been developed to stimulate wound healing. However, from the clinical perspective, few of the current wound dressings meet all the intended multifunctional requirements of preventing infection, promoting rapid wound closure, and minimizing scar formation, while simultaneously offering the convenience of application. In the current study, we adopted a mussel-inspired strategy to functionalize the GelMA hydrogels with DOPA to fabricate GelMA-DOPA hydrogel which exhibited an enhanced binding affinity for wound surfaces, AMP HHC-36 and CeONs are further encapsulated into the GelMA-DOPA hydrogel to confer the hydrogel wound dressing with antimicrobial and ROS-scavenging abilities. The GelMA-DOPA-AMP-CeONs dressing offered the benefits of sprayability, adhesiveness, antimicrobial activity, as well as ROS-scavenging and skin-remodeling ability, which might address the therapeutic and economic burdens associated with chronic wound treatment and management.

Design, Optimization, and Characterization of Lactoferrin-Loaded Chitosan/TPP and Chitosan/Sulfobutylether-β-cyclodextrin Nanoparticles as a Pharmacological Alternative for Keratoconus Treatment

This research study describes the design, optimization, and characterization of two different types of chitosan-based nanoparticles as novel drug delivery systems of a protein drug, lactoferrin. A preclinical consistent base was obtained for both nanosystems, being considered as the first pharmacological treatment for keratoconus as an alternative to current invasive clinical methods. Both types of nanoparticles were obtained via the ionotropic gelation technique. The size and morphology of the nanoparticles were studied as a function of the preparation conditions. A mean size of 180.73 ± 40.67 nm, a size distribution [polydispersity index (PDI)] of 0.170 ± 0.067, and positive ζ-potential values, ranging from 17.13 to 19.89 mV, were achieved. Lactoferrin was successfully incorporated into both types of nanocarriers. In vitro release profiles showed a lactoferrin enhanced, prolonged, and controlled delivery from the polymeric matrix. These formulations also demonstrated no stability or cytotoxicity problems, as well as appropriate mucoadhesive properties, with a high permanence time in the ocular surface. Thus, both types of nanoparticles may be considered as nanocarriers for the controlled release of lactoferrin as novel topical ophthalmic drug delivery systems.

Radiolabeling strategies and pharmacokinetic studies for metal based nanotheranostics

Radiolabeled metal-based nanoparticles (MNPs) have drawn considerable attention in the fields of nuclear medicine and molecular imaging, drug delivery, and radiation therapy, given the fact that they can be potentially used as diagnostic imaging and/or therapeutic agents, or even as theranostic combinations. Here, we present a systematic review on recent advances in the design and synthesis of MNPs with major focuses on their radiolabeling strategies and the determinants of their in vivo pharmacokinetics, and together how their intended applications would be impacted. For clarification, we categorize all reported radiolabeling strategies for MNPs into indirect and direct approaches. While indirect labeling simply refers to the use of bifunctional chelators or prosthetic groups conjugated to MNPs for post-synthesis labeling with radionuclides, we found that many practical direct labeling methodologies have been developed to incorporate radionuclides into the MNP core without using extra reagents, including chemisorption, radiochemical doping, hadronic bombardment, encapsulation, and isotope or cation exchange. From the perspective of practical use, a few relevant examples are presented and discussed in terms of their pros and cons. We further reviewed the determinants of in vivo pharmacokinetic parameters of MNPs, including factors influencing their in vivo absorption, distribution, metabolism, and elimination, and discussed the challenges and opportunities in the development of radiolabeled MNPs for in vivo biomedical applications. Taken together, we believe the cumulative advancement summarized in this review would provide a general guidance in the field for design and synthesis of radiolabeled MNPs towards practical realization of their much desired theranostic capabilities. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > Diagnostic Nanodevices Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Nanoparticulate formulations of radiopharmaceuticals: Strategy to improve targeting and biodistribution properties

Application of nanotechnology principles in drug delivery has created opportunities for treatment of several diseases. Nanotechnology offers the advantage of overcoming the adverse biopharmaceutics or pharmacokinetic properties of drug molecules, to be determined by the transport properties of the particles themselves. Through the manipulation of size, shape, charge, and type of nanoparticle delivery system, variety of distribution profiles may be obtained. However, there still exists greater need to derive and standardize definitive structure property relationships for the distribution profiles of the delivery system. When applied to radiopharmaceuticals, the delivery systems assume greater significance. For the safety and efficacy of both diagnostics and therapeutic radiopharmaceuticals, selective localization in target tissue is even more important. At the same time, the synthesis and fabrication reactions of radiolabelled nanoparticles need to be completed in much shorter time. Moreover, the extensive understanding of the several interesting optical and magnetic properties of materials in nanoscale provides for achieving multiple objectives in nuclear medicine. This review discusses the various nanoparticle systems, which are applied for radionuclides and analyses the important bottlenecks that are required to be overcome for their more widespread clinical adaptation.

Promising antiviral, antimicrobial and therapeutic properties of green nanoceria

Aim: To demonstrate synthesis of cerium oxide nanoparticles (CeO2 NPs) by a green method using Hyphaene thebaica, and investigate their therapeutic applications. Materials & methods: Structural, vibrational and luminescent properties were established using x-ray diffraction, Fourier transformed infrared spectroscopy, Raman spectroscopy, ultraviolet absorption spectroscopy, selected area electron diffraction, electron microscopy and photolumincence spectroscopy. Therapeutic properties were established using different in vitro assays. Results: CeO2 NPs were determined to be crystalline in nature with a grain size of approximately 14 nm. They had characteristic Ce–O vibration at 481 cm-1. Photoluminescence spectra revealed broad bands at 463 and 600 nm. ζ potential was recorded as -17.2 mV. Potent antimicrobial and antiviral properties with hemocompatibility were reported. Conclusion: Biosynthesized CeO2 NPs revealed multifunctional therapeutic properties.

The Aquilegia pubiflora (Himalayan columbine) mediated synthesis of nanoceria for diverse biomedical applications

Herein, we report an eco-friendly, facile, one-pot, green synthesis of nanoceria for multiple biomedical applications. In the study, cerium oxide nanoparticles (CeO₂-NPs) were synthesized using a simple aqueous extract of Aquilegia pubiflora as an effective reducing and capping agent. The biosynthesized nanoparticles were characterized via UV-vis spectroscopy, X-ray powder diffraction (XRD), high-performance liquid chromatography (HPLC), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The NPs were highly stable, exhibited high purity, and had a spherical morphology and mean size of 28 nm. FTIR and HPLC studies confirmed the successful capping of bioactive compounds on the nanoparticles. The well-characterized NPs were evaluated for a number of biomedical applications, and their antimicrobial (antifungal, antibacterial, and antileishmanial), protein kinase inhibition, anticancer, antioxidant, anti-diabetic and biocompatibility properties were studied. Our results showed that the Aquilegia pubiflora mediated CeO₂-NPs were highly active against fungal strains, compared to the tested bacterial strains, with Aspergillus niger resulting in the largest zone of inhibition (15.1 ± 0.27 mm). The particles also exhibited dose dependent leishmanicidal activity with significant LC₅₀ values toward both the amastigote (114 μg mL⁻¹) and promastigote (97 μg mL⁻¹) forms of the parasite Leishmania tropica (KWH23). The NPs were found to be moderately active against the HepG2 cell line, showing 26.78% ± 1.16% inhibition at 200 μg mL⁻¹. Last but not least, their highly biocompatible nature was observed with respect to freshly isolated human red blood cells (hRBCs), making the greenly synthesized CeO₂-NPs a novel candidates for multidimensional medical applications.

Graphical illustration of eco-friendly, facile, one-pot, green synthesis of nanoceria for multiple biomedical applications.

An overview of nanoscale radionuclides and radiolabeled nanomaterials commonly used for nuclear molecular imaging and therapeutic functions

Recent advances in the field of nanotechnology applications in nuclear medicine offer the promise of better diagnostic and therapeutic options. In recent years, increasing efforts have been focused on developing nanoconstructs that can be used as core platforms for attaching medical radionuclides with different strategies for the purposes of molecular imaging and targeted drug delivery. This review article presents an introduction to some commonly used nanomaterials with zero-dimensional, one-dimensional, two-dimensional, and three-dimensional structures, describes the various methods applied to radiolabeling of nanomaterials, and provides illustrative examples of application of the nanoscale radionuclides or radiolabeled nanocarriers in nuclear nanomedicine. Especially, the passive and active nanotargeting delivery of radionuclides with illustrating examples for tumor imaging and therapy was reviewed and summarized. The accurate and early diagnosis of cancer can lead to increased survival rates for different types of this disease. Although, the conventional single-modality diagnostic methods such as positron emission tomography/single photon emission computed tomography or MRI used for such purposes are powerful means; most of these are limited by sensitivity or resolution. By integrating complementary signal reporters into a single nanoparticulate contrast agent, multimodal molecular imaging can be performed as scalable images with high sensitivity, resolution, and specificity. The advent of radiolabeled nanocarriers or radioisotope-loaded nanomaterials with magnetic, plasmonic, or fluorescent properties has stimulated growing interest in the developing multimodality imaging probes. These new developments in nuclear nanomedicine are expected to introduce a paradigm shift in multimodal molecular imaging and thereby opening up an era of new diagnostic medical imaging agents. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 251-285, 2019.

Cerium Oxide Nanoparticles: A Brief Review of Their Synthesis Methods and Biomedical Applications

Cerium oxide nanoparticles (CeNPs) exhibit antioxidant properties both in vitro and in vivo. This is due to the self-regeneration of their surface, which is based on redox-cycling between 3+ and 4+ states for cerium, in response to their immediate environment. Additionally, oxygen vacancies in the lattice structure allow for alternating between CeO₂ and CeO2-x during redox reactions. Research to identify and characterize the biomedical applications of CeNPs has been heavily focused on investigating their use in treating diseases that are characterized by higher levels of reactive oxygen species (ROS). Although the bio-mimetic activities of CeNPs have been extensively studied in vitro, in vivo interactions and associated protein corona formation are not well understood. This review describes: (1) the methods of synthesis for CeNPs, including the recent green synthesis methods that offer enhanced biocompatibility and a need for establishing a reference CeNP material for consistency across studies; (2) their enzyme-mimetic activities, with a focus on their antioxidant activities; and, (3) recent experimental evidence that demonstrates their ROS scavenging abilities and their potential use in personalized medicine.

Dynamic Light Scattering and Zeta Potential Studies of Ceria Nanoparticles

A Cerium (IV) oxide nanoparticle (nanoceria) is widely used in different applications such as biomedicine and catalysis due to its unique structural, morphological and catalytic properties. In this report, the dispersion of nanoceria in both aqueous and non-aqueous (methanol and ethanol) media were studied. Adsorption-desorption processes were observed upon addition of different classes of surfactants such as citric acid (CA), cetrimonium bromide (CTAB) and diethanolamine (DEA). Stable dispersions were obtained in both aqueous, non-aqueous and electrolyte assisted media with the overall mechanism being hydrolysis, dissolution and adsorption. XRD, FE-SEM, FTIR and DLS have been used in the present study to characterize the nanoceria and to quantitatively analyze their average particle size distributions in a unique electrolyte mixture of (0.1 M NaOH/ 65% HNO3:H2O, 1:1 v/v) which has not been reported previously. The surface charge study was carried out across a wide pH range between 1.4 – 9.6 and the isoelectric points (IEP) with respect to 15 ml H2O and 50 ml H2O dispersed phases occurred at a pH of about 6.5 and 6.7 respectively. The present study could be useful in a wide range of applications including nanoparticle synthesis, stabilization, and adsorption of toxic materials, biomedical and pharmaceutical.

Synthesis and biomedical applications of Cerium oxide nanoparticles - A Review

A cerium oxide nanoparticles (nanoceria) has a wide range of applications in different fields, especially biomedical division. As a matter of concern, it has a major impact on the human health and environment. The aim of this review is to address the different ways of synthesis of nanoceria using chemical and green synthesis methods and characterization and the applications of nanoceria for antioxidant, anticancer, antibacterial activities and toxicological studies including the most recent studies carried out in vivo and in vitro to study the problems. We have exclusively discussed on the toxicology of nanoceria exposed to the general public along with recent advances in the studies of antimicrobial, toxicity and anti-oxidant activity.

Advanced Methods for Radiolabeling Multimodality Nanomedicines for SPECT/MRI and PET/MRI

The advent of hybrid cameras that combine MRI with either SPECT or PET has stimulated growing interest in developing multimodality imaging probes. Countless options are available for fusing magnetically active species with positron- or γ-ray-emitting radionuclides. The initial problem is one of choice: which chemical systems are a suitable basis for developing hybrid imaging agents? Any attempt to answer this question must also address how the physical, chemical, and biologic properties of a unified imaging agent can be tailored to ensure that optimum specificity and contrast are achieved simultaneously for both imaging modalities. Nanoparticles have emerged as attractive platforms for building multimodality radiotracers for SPECT/MRI and PET/MRI. A wide variety of nanoparticle constructs have been utilized as radiotracers, but irrespective of the particle class, radiolabeling remains a key step. Classic methods for radiolabeling nanoparticles involve functionalization of the particle surface, core, or coating. These modifications typically rely on using traditional metal ion chelate or prosthetic group chemistries. Though seemingly innocuous, appending nanoparticles with these radiolabeling handles can have dramatic effects on important properties such as particle size, charge, and solubility. In turn, alterations in the chemical and physical properties of the nanoparticle often have a negative impact on their pharmacologic profile. A central challenge in radiolabeling nanoparticles is to identify alternative chemical methods that facilitate the introduction of a radioactive nuclide without detrimental effects on the pharmacokinetic and toxicologic properties of the construct. Efforts to solve this challenge have generated a range of innovative chelate-free radiolabeling methods that exploit intrinsic chemical features of nanoparticles. Here, the chemistry of 9 mechanistically distinct methods for radiolabeling nanoparticles is presented. This discourse illustrates the evolution of nanoparticle radiochemistry from classic approaches to modern chelate-free or intrinsic methods.

Assessment of gold nanoparticles on human peripheral blood cells by metabolic profiling with 1H-NMR spectroscopy, a novel translational approach on a patient-specific basis

Human peripheral blood cells are relevant ex vivo models for characterizing diseases and evaluating the pharmacological effects of therapeutic interventions, as they provide a close reflection of an individual pathophysiological state. In this work, a new approach to evaluate the impact of nanoparticles on the three main fractions of human peripheral blood cells by nuclear magnetic resonance spectroscopy is shown. Thus, a comprehensive protocol has been set-up including the separation of blood cells, their in vitro treatment with nanoparticles and the extraction and characterization of metabolites by nuclear magnetic resonance. This method was applied to assess the effect of gold nanoparticles, either coated with chitosan or supported on ceria, on peripheral blood cells from healthy individuals. A clear antioxidant effect was observed for chitosan-coated gold nanoparticles by a significant increase in reduced glutathione, that was much less pronounced for gold-cerium nanoparticles. In addition, the analysis revealed significant alterations of several other pathways, which were stronger for gold-cerium nanoparticles. These results are in accordance with the toxicological data previously reported for these materials, confirming the value of the current methodology.

A novel synthetic approach of cerium oxide nanoparticles with improved biomedical activity

Cerium oxide nanoparticles (CNPs) are novel synthetic antioxidant agents proposed for treating oxidative stress-related diseases. The synthesis of high-quality CNPs for biomedical applications remains a challenging task. A major concern for a safe use of CNPs as pharmacological agents is their tendency to agglomerate. Herein we present a simple direct precipitation approach, exploiting ethylene glycol as synthesis co-factor, to synthesize at room temperature nanocrystalline sub-10 nm CNPs, followed by a surface silanization approach to improve nanoparticle dispersibility in biological fluids. CNPs were characterized using transmission electron microscopy (TEM) observations, X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), Fourier-transform infrared (FT-IR) spectroscopy, proton nuclear magnetic resonance (1H-NMR) spectroscopy, dynamic light scattering (DLS) and zeta potential measurements. CNP redox activity was studied in abiotic systems using electron spin resonance (ESR) measurements, and in vitro on human cell models. In-situ silanization improved CNP colloidal stability, in comparison with non-functionalized particles, and allowed at the same time improving their original biological activity, yielding thus functionalized CNPs suitable for biomedical applications.

Biokinetics of Nanomaterials: the Role of Biopersistence

Nanotechnology risk management strategies and environmental regulations continue to rely on hazard and exposure assessment protocols developed for bulk materials, including larger size particles, while commercial application of nanomaterials (NMs) increases. In order to support and corroborate risk assessment of NMs for workers, consumers, and the environment it is crucial to establish the impact of biopersistence of NMs at realistic doses. In the future, such data will allow a more refined future categorization of NMs. Despite many experiments on NM characterization and numerous in vitro and in vivo studies, several questions remain unanswered including the influence of biopersistence on the toxicity of NMs. It is unclear which criteria to apply to characterize a NM as biopersistent. Detection and quantification of NMs, especially determination of their state, i.e., dissolution, aggregation, and agglomeration within biological matrices and other environments are still challenging tasks; moreover mechanisms of nanoparticle (NP) translocation and persistence remain critical gaps. This review summarizes the current understanding of NM biokinetics focusing on determinants of biopersistence. Thorough particle characterization in different exposure scenarios and biological matrices requires use of suitable analytical methods and is a prerequisite to understand biopersistence and for the development of appropriate dosimetry. Analytical tools that potentially can facilitate elucidation of key NM characteristics, such as ion beam microscopy (IBM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), are discussed in relation to their potential to advance the understanding of biopersistent NM kinetics. We conclude that a major requirement for future nanosafety research is the development and application of analytical tools to characterize NPs in different exposure scenarios and biological matrices.

Positron emission tomography and nanotechnology: A dynamic duo for cancer theranostics

Development of novel imaging probes for cancer diagnosis is critical for early disease detection and management. The past two decades have witnessed a surge in the development and evolution of radiolabeled nanoparticles as a new frontier in personalized cancer nanomedicine. The dynamic synergism of positron emission tomography (PET) and nanotechnology combines the sensitivity and quantitative nature of PET with the multifunctionality and tunability of nanomaterials, which can help overcome certain key challenges in the field. In this review, we discuss the recent advances in radionanomedicine, exemplifying the ability to tailor the physicochemical properties of nanomaterials to achieve optimal in vivo pharmacokinetics and targeted molecular imaging in living subjects. Innovations in development of facile and robust radiolabeling strategies and biomedical applications of such radionanoprobes in cancer theranostics are highlighted. Imminent issues in clinical translation of radiolabeled nanomaterials are also discussed, with emphasis on multidisciplinary efforts needed to quickly move these promising agents from bench to bedside.

Cerium oxide nanoparticles: a ‘radical’ approach to neurodegenerative disease treatment

Despite advances in understanding the factors that cause many neurodegenerative diseases (NDs), no current therapies have yielded significant results. Cerium oxide nanoparticles (CeONPs) have recently emerged as therapeutics for the treatment of NDs due to their antioxidant properties. This report summarizes the recent findings regarding CeONPs in treatment of various NDs, including Alzheimer's disease, Parkinson's disease, multiple sclerosis, ischemic stroke and amyotrophic lateral sclerosis. Interest in CeONPs as a potential nanomedicine for NDs has increased due to: their ability to alter signaling pathways, small diameter allowing passage through the blood–brain barrier and scavenging of reactive oxygen species. Due to these properties, CeONPs could eventually revolutionize existing treatments for NDs.

Characterization of the Biodistribution and Systemic Absorption of TT-173, a New Hemostatic Agent of Recombinant Human Tissue Factor, Using Radiolabeling with 18F

BACKGROUND AND OBJECTIVES

TT-173 is the first topical hemostatic agent based on tissue factor. To prevent thromboembolic events and intravascular coagulation it is necessary to rule out the systemic absorption of new bioactive hemostats. Here, we radiolabeled TT-173 with [¹⁸F]SBF to characterize its systemic absorption and biodistribution.

METHODS

A group of rats were administered intravenously with [¹⁸F]TT-173 and were subjected to a positron emission tomography study. A second group of animals received the [¹⁸F]TT-173 topically over a skin lesion in the flank. Topical absorption was quantified and the biodistribution patterns observed were compared.

RESULTS

After topical application, low amounts of [¹⁸F]TT-173 were absorbed and distributed without relevant accumulation in any organ. On the other hand, after intravenous injection, [¹⁸F]TT-173 accumulated in lungs, liver and spleen, consistent with intravascular clot formation and the posterior capillary trapping and phagocytosis by the reticuloendothelial system. In both cases, a substantial concentration of radioactive product was found in urine consistent with renal excretion of degradation products of [¹⁸F]TT-173.

CONCLUSIONS

After topical application, [¹⁸F]TT-173 did not show a significant systemic accumulation in animal organs. Minor radioactive concentration found in lungs, liver and spleen likely corresponds with fragments of the product without procoagulant activity. Radiolabeling with [¹⁸F]SFB enables the characterization of systemic absorption and biodistribution of new topical hemostats like TT-173.

Antioxidant Cerium Oxide Nanoparticles in Biology and Medicine

Previously, catalytic cerium oxide nanoparticles (CNPs, nanoceria, CeO2-x NPs) have been widely utilized for chemical mechanical planarization in the semiconductor industry and for reducing harmful emissions and improving fuel combustion efficiency in the automobile industry. Researchers are now harnessing the catalytic repertoire of CNPs to develop potential new treatment modalities for both oxidative- and nitrosative-stress induced disorders and diseases. In order to reach the point where our experimental understanding of the antioxidant activity of CNPs can be translated into useful therapeutics in the clinic, it is necessary to evaluate the most current evidence that supports CNP antioxidant activity in biological systems. Accordingly, the aims of this review are three-fold: (1) To describe the putative reaction mechanisms and physicochemical surface properties that enable CNPs to both scavenge reactive oxygen species (ROS) and to act as antioxidant enzyme-like mimetics in solution; (2) To provide an overview, with commentary, regarding the most robust design and synthesis pathways for preparing CNPs with catalytic antioxidant activity; (3) To provide the reader with the most up-to-date in vitro and in vivo experimental evidence supporting the ROS-scavenging potential of CNPs in biology and medicine.

Synthesis and preliminary in vivo evaluation of well-dispersed biomimetic nanocrystalline apatites labeled with positron emission tomographic imaging agents

In recent years, biomimetic synthetic apatite nanoparticles (AP-NPs), having chemical similarity with the mineral phase of bone, have attracted a great interest in nanomedicine as potential drug carriers. To evaluate the therapeutic perspectives of AP-NPs through the mechanisms of action and organs they interact with, the noninvasive monitoring of their in vivo behavior is of paramount importance. To this aim, here the feasibility to radiolabel AP-NPs ("naked" and surface-modified with citrate to reduce their aggregation) with two positron emission tomographic (PET) imaging agents ([(18)F]NaF and (68)Ga-NO2AP(BP)) was investigated. [(18)F]NaF was used for the direct incorporation of the radioisotope into the crystal lattice, while the labeling by surface functionalization was accomplished by using (68)Ga-NO2AP(BP) (a new radio-metal chelating agent). The labeling results with both tracers were fast, straightforward, and reproducible. AP-NPs demonstrated excellent ability to bind relevant quantities of both radiotracers and good in vitro stability in clinically relevant media after the labeling. In vivo PET studies in healthy Wistar rats established that the radiolabeled AP-NPs gave significant PET signals and they were stable over the investigated time (90 min) since any tracer desorption was detected. These preliminary in vivo studies furthermore showed a clear ability of citrated versus naked AP-NPs to accumulate in different organs. Interestingly, contrary to naked AP-NPs, citrated ones, which unveiled higher colloidal stability in aqueous suspensions, were able to escape the first physiological filter, i.e., the lungs, being then accumulated in the liver and, to a lesser extent, in the spleen. The results of this work, along with the fact that AP-NPs can be also functionalized with targeting ligands, with therapeutic agents, and also with metals for a combination of different imaging modalities, make AP-NPs very encouraging materials for further investigations as theranostic agents in nanomedicine.

Photoactive hybrid material based on pyrene functionalized PbS nanocrystals decorating CVD monolayer graphene

A simple and facile solution-based procedure is implemented for decorating a large area, monolayer graphene film, grown by chemical vapor deposition, with size-tunable light absorbing colloidal PbS nanocrystals (NCs). The hybrid is obtained by exposing a large area graphene film to a solution of 1-pyrene butyric acid surface coated PbS NCs, obtained by a capping exchange procedure onto presynthesized organic-capped NCs. The results demonstrate that at the interface, multiple and cooperative π-π stacking interactions promoted by the pyrene ligand coordinating the NC surface lead to a successful anchoring of the nano-objects on the graphene platform which concomitantly preserves its aromatic structure. Interligand interactions provide organization of the nano-objects in highly interconnected nanostructured multilayer coatings, where the NCs retain geometry and composition. The resulting hybrid exhibits a sheet resistance lower than that of bare graphene, which is explained in terms of electronic communication in the hybrid, due to the interconnection of the NC film and to a hole transfer from photoexcited PbS NCs to graphene, channelled at the interface by pyrene. Such a direct electron coupling makes the manufactured hybrid material an interesting component for optoelectronics, sensors and for optical communication and information technology.

Intracellular antioxidants dissolve man-made antioxidant nanoparticles: using redox vulnerability of nanoceria to develop a responsive drug delivery system

Regeneratable antioxidant property of nanoceria has widely been explored to minimize the deleterious influences of reactive oxygen species. Limited information is, however, available regarding the biological interactions and subsequent fate of nanoceria in body fluids. This study demonstrates a surprising dissolution of stable and ultrasmall (4 nm) cerium oxide nanoparticles (CeO2 NPs) in response to biologically prevalent antioxidant molecules (glutathione, vitamin C). Such a redox sensitive behavior of CeO2 NPs is subsequently exploited to design a redox responsive drug delivery system for transporting anticancer drug (camptothecin). Upon exposing the CeO2 capped and drug loaded nanoconstruct to vitamin c or glutathione, dissolution-accompanied aggregation of CeO2 nanolids unleashes the drug molecules from porous silica to achieve a significant anticancer activity. Besides stimuli responsive drug delivery, immobilization of nanoceria onto the surface of mesoporous silica also facilitates us to gain a basic insight into the biotransformation of CeO2 in physiological mediums.

The Yin: An adverse health perspective of nanoceria: uptake, distribution, accumulation, and mechanisms of its toxicity

This critical review evolved from a SNO Special Workshop on Nanoceria panel presentation addressing the toxicological risks of nanoceria: accumulation, target organs, and issues of clearance; how exposure dose/concentration, exposure route, and experimental preparation/model influence the different reported effects of nanoceria; and how can safer by design concepts be applied to nanoceria? It focuses on the most relevant routes of human nanoceria exposure and uptake, disposition, persistence, and resultant adverse effects. The pulmonary, oral, dermal, and topical ocular exposure routes are addressed as well as the intravenous route, as the latter provides a reference for the pharmacokinetic fate of nanoceria once introduced into blood. Nanoceria reaching the blood is primarily distributed to mononuclear phagocytic system organs. Available data suggest nanoceria's distribution is not greatly affected by dose, shape, or dosing schedule. Significant attention has been paid to the inhalation exposure route. Nanoceria distribution from the lung to the rest of the body is less than 1% of the deposited dose, and from the gastrointestinal tract even less. Intracellular nanoceria and organ burdens persist for at least months, suggesting very slow clearance rates. The acute toxicity of nanoceria is very low. However, large/accumulated doses produce granuloma in the lung and liver, and fibrosis in the lung. Toxicity, including genotoxicity, increases with exposure time; the effects disappear slowly, possibly due to nanoceria's biopersistence. Nanoceria may exert toxicity through oxidative stress. Adverse effects seen at sites distal to exposure may be due to nanoceria translocation or released biomolecules. An example is elevated oxidative stress indicators in the brain, in the absence of appreciable brain nanoceria. Nanoceria may change its nature in biological environments and cause changes in biological molecules. Increased toxicity has been related to greater surface Ce3+, which becomes more relevant as particle size decreases and the ratio of surface area to volume increases. Given its biopersistence and resulting increased toxicity with time, there is a risk that long-term exposure to low nanoceria levels may eventually lead to adverse health effects. This critical review provides recommendations for research to resolve some of the many unknowns of nanoceria's fate and adverse effects.

Radiolabeling of Nanoparticles and Polymers for PET Imaging

Nanomedicine has become an emerging field in imaging and therapy of malignancies. Nanodimensional drug delivery systems have already been used in the clinic, as carriers for sensitive chemotherapeutics or highly toxic substances. In addition, those nanodimensional structures are further able to carry and deliver radionuclides. In the development process, non-invasive imaging by means of positron emission tomography (PET) represents an ideal tool for investigations of pharmacological profiles and to find the optimal nanodimensional architecture of the aimed-at drug delivery system. Furthermore, in a personalized therapy approach, molecular imaging modalities are essential for patient screening/selection and monitoring. Hence, labeling methods for potential drug delivery systems are an indispensable need to provide the radiolabeled analog. In this review, we describe and discuss various approaches and methods for the labeling of potential drug delivery systems using positron emitters.

Cerium oxide nanoparticles: applications and prospects in nanomedicine

Promising results have been obtained using cerium (Ce) oxide nanoparticles (CNPs) as antioxidants in biological systems. CNPs have unique regenerative properties owing to their low reduction potential and the coexistence of both Ce(3+)/Ce(4+) on their surfaces. Defects in the crystal lattice due to the presence of Ce(3+) play an important role in tuning the redox activity of CNPs. The surface Ce(3+):Ce(4+) ratio is influenced by the microenvironment. Therefore, the microenvironment and synthesis method adopted also plays an important role in determining the biological activity and toxicity of CNPs. The presence of a mixed valance state plays an important role in scavenging reactive oxygen and nitrogen species. CNPs are found to be effective against pathologies associated with chronic oxidative stress and inflammation. CNPs are well tolerated in both in vitro and in vivo biological models, which makes CNPs well suited for applications in nanobiology and regenerative medicine.

Carbon-11 radiolabeling of iron-oxide nanoparticles for dual-modality PET/MR imaging

Dual-modality imaging, using Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET) simultaneously, is a powerful tool to gain valuable information correlating structure with function in biomedicine. The advantage of this dual approach is that the strengths of one modality can balance the weaknesses of the other. However, success of this technique requires developing imaging probes suitable for both. Here, we report on the development of a nanoparticle labeling procedure via covalent bonding with carbon-11 PET isotope. Carbon-11 in the form of [(11)C]methyl iodide was used as a methylation agent to react with carboxylic acid (-COOH) and amine (-NH2) functional groups of ligands bound to the nanoparticles (NPs). The surface coating ligands present on superparamagnetic iron-oxide nanoparticles (SPIO NPs) were radiolabeled to achieve dual-modality PET/MR imaging capabilities. The proof-of-concept dual-modality PET/MR imaging using the radiolabeled SPIO NPs was demonstrated in an in vivo experiment.