The Theranostic Path to Personalized Nanomedicine

Recent advances and strategies for nanocarrier-mediated topical therapy and theranostic for posterior eye disease

Posterior eye disorders, such as age-related macular degeneration, diabetic retinopathy, and glaucoma, have a significant impact on human quality of life and are the primary cause of age-related retinal diseases among adults. There is a pressing need for innovative topical approaches to treat posterior eye disorders, as current methods often rely on invasive procedures with inherent risks. Limited success was attained in the realm of topical ophthalmic delivery through non-invasive means. Additionally, there exists a dearth of literature that delves into the potential of this approach for drug delivery and theranostic purposes, or that offers comprehensive design strategies for nanocarrier developers to surmount the significant physiological ocular barriers. This review offers a thorough and up-to-date state-of-the-art overview of 40 studies on therapeutic loaded nanocarriers and theranostic devices that, to the best of our knowledge, represent all successful works that reached posterior eye segments through a topical non-invasive administration. Most importantly, based on the successful literature studies, this review provides a comprehensive summary of the potential design strategies that can be implemented during nanocarrier development to overcome each ocular barrier.

Application of nanotechnology in the treatment of glomerulonephritis: current status and future perspectives

Glomerulonephritis (GN) is the most common cause of end-stage renal failure worldwide; in most cases, it cannot be cured and can only delay the progression of the disease. At present, the main treatment methods include symptomatic therapy, immunosuppressive therapy, and renal replacement therapy. However, effective treatment of GN is hindered by issues such as steroid resistance, serious side effects, low bioavailability, and lack of precise targeting. With the widespread application of nanoparticles in medical treatment, novel methods have emerged for the treatment of kidney diseases. Targeted transportation of drugs, nucleic acids, and other substances to kidney tissues and even kidney cells through nanodrug delivery systems can reduce the systemic effects and adverse reactions of drugs and improve treatment effectiveness. The high specificity of nanoparticles enables them to bind to ion channels and block or enhance channel gating, thus improving inflammation. This review briefly introduces the characteristics of GN, describes the treatment status of GN, systematically summarizes the research achievements of nanoparticles in the treatment of primary GN, diabetic nephropathy and lupus nephritis, analyzes recent therapeutic developments, and outlines promising research directions, such as gas signaling molecule nanodrug delivery systems and ultrasmall nanoparticles. The current application of nanoparticles in GN is summarized to provide a reference for better treatment of GN in the future.

Imaging biomarkers for clinical applications in neuro-oncology: current status and future perspectives

Biomarker discovery and development are popular for detecting the subtle diseases. However, biomarkers are needed to be validated and approved, and even fewer are ever used clinically. Imaging biomarkers have a crucial role in the treatment of cancer patients because they provide objective information on tumor biology, the tumor's habitat, and the tumor's signature in the environment. Tumor changes in response to an intervention complement molecular and genomic translational diagnosis as well as quantitative information. Neuro-oncology has become more prominent in diagnostics and targeted therapies. The classification of tumors has been actively updated, and drug discovery, and delivery in nanoimmunotherapies are advancing in the field of target therapy research. It is important that biomarkers and diagnostic implements be developed and used to assess the prognosis or late effects of long-term survivors. An improved realization of cancer biology has transformed its management with an increasing emphasis on a personalized approach in precision medicine. In the first part, we discuss the biomarker categories in relation to the courses of a disease and specific clinical contexts, including that patients and specimens should both directly reflect the target population and intended use. In the second part, we present the CT perfusion approach that provides quantitative and qualitative data that has been successfully applied to the clinical diagnosis, treatment and application. Furthermore, the novel and promising multiparametric MR imageing approach will provide deeper insights regarding the tumor microenvironment in the immune response. Additionally, we briefly remark new tactics based on MRI and PET for converging on imaging biomarkers combined with applications of bioinformatics in artificial intelligence. In the third part, we briefly address new approaches based on theranostics in precision medicine. These sophisticated techniques merge achievable standardizations into an applicatory apparatus for primarily a diagnostic implementation and tracking radioactive drugs to identify and to deliver therapies in an individualized medicine paradigm. In this article, we describe the critical principles for imaging biomarker characterization and discuss the current status of CT, MRI and PET in finiding imaging biomarkers of early disease.

Novel Tumor-Targeted Self-Nanostructured and Compartmentalized Water-in-Oil-in-Water Polyurethane-Polyurea Nanocapsules for Cancer Theragnosis

Encapsulation of water-soluble bioactive compounds for enabling specific accumulation in tumor locations, while avoiding premature clearance and/or degradation in the bloodstream, is one of the main hallmarks in nanomedicine, especially that of NIR fluorescent probes for cancer theragnosis. The herein reported technology furnishes water-dispersible double-walled polyurethane-polyurea hybrid nanocapsules (NCs) loaded with indocyanine green (ICG-NCs), using a versatile and highly efficient one-pot and industrially scalable synthetic process based on the use of two different prepolymers to set up the NCs walls. Flow cytometry and confocal microscopy confirmed that both ICG-loaded NCs internalized in monocyte-derived dendritic cells (moDCs). The in vivo analysis of xenograft A375 mouse melanoma model revealed that amphoteric functionalization of NCs' surface promotes the selective accumulation of ICG-NCs in tumor tissues, making them promising agents for a less-invasive theragnosis of cancer.

Gastrin-releasing peptide receptor agonists and antagonists for molecular imaging of breast and prostate cancer: from pre-clinical studies to translational perspectives

INTRODUCTION

Prostate and breast cancer represent a leading cause of cancer-related death worldwide with a dramatic social and demographic impact. Gastrin-releasing peptide receptors (GRPRs), part of the bombesin (BBN) family, have been found overexpressed in both the aforementioned malignancies, and have emerged as a potentially useful target to combine imaging and therapy in a unique, synergistic approach, namely 'theranostics.'

AREAS COVERED

The biological characteristics of GRPRs, as well as their aberrant expression in breast and prostate cancer, are covered. Furthermore, the role of the different available GRPR agonists and antagonists, labeled with radionuclides suitable for molecular imaging through single photon computed tomography (SPECT) or positron emission computed (PET/CT), is reviewed, with a particular focus on the potential theranostic implications.

EXPERT OPINION

GRPR-targeted molecular imaging of breast and prostate cancer gave promising results in pre-clinical studies. Notably, GRPRs' expression was found to be inversely correlated with disease progression in both prostate and breast cancer. Among the different GRPR agonists and antagonists applied as imaging probes, RM26 presented particularly interesting applications, with meaningful theranostic potential, but its diagnostic performance resulted highly influenced by the choice of the chelator-radionuclide complex, being long-life radionuclides more suitable for obtaining high-contrast imaging.

Pretargeted Imaging beyond the Blood–Brain Barrier—Utopia or Feasible?

Pretargeting is a promising nuclear imaging technique that allows for the usage of antibodies (Abs) with enhanced imaging contrast and reduced patient radiation burden. It is based on bioorthogonal chemistry with the tetrazine ligation—a reaction between trans-cyclooctenes (TCOs) and tetrazines (Tzs)—currently being the most popular reaction due to its high selectivity and reactivity. As Abs can be designed to bind specifically to currently ‘undruggable’ targets such as protein isoforms or oligomers, which play a crucial role in neurodegenerative diseases, pretargeted imaging beyond the BBB is highly sought after, but has not been achieved yet. A challenge in this respect is that large molecules such as Abs show poor brain uptake. Uptake can be increased by receptor mediated transcytosis; however, it is largely unknown if the achieved brain concentrations are sufficient for pretargeted imaging. In this study, we investigated whether the required concentrations are feasible to reach. As a model Ab, we used the bispecific anti-amyloid beta (Aβ) anti-transferrin receptor (TfR) Ab 3D6scFv8D3 and conjugated it to a different amount of TCOs per Ab and tested different concentrations in vitro. With this model in hand, we estimated the minimum required TCO concentration to achieve a suitable contrast between the high and low binding regions. The estimation was carried out using pretargeted autoradiography on brain sections of an Alzheimer’s disease mouse model. Biodistribution studies in wild-type (WT) mice were used to correlate how different TCO/Ab ratios alter the brain uptake. Pretargeted autoradiography showed that increasing the number of TCOs as well as increasing the TCO-Ab concentration increased the imaging contrast. A minimum brain concentration of TCOs for pretargeting purposes was determined to be 10.7 pmol/g in vitro. Biodistribution studies in WT mice showed a brain uptake of 1.1% ID/g using TCO-3D6scFv8D3 with 6.8 TCO/Ab. According to our estimations using the optimal parameters, pretargeted imaging beyond the BBB is not a utopia. Necessary brain TCO concentrations can be reached and are in the same order of magnitude as required to achieve sufficient contrast. This work gives a first estimate that pretargeted imaging is indeed possible with antibodies. This could allow the imaging of currently ‘undruggable’ targets and therefore be crucial to monitor (e.g., therapies for intractable neurodegenerative diseases).

Recent Advances in the Development of Tetrazine Ligation Tools for Pretargeted Nuclear Imaging

Tetrazine ligation has gained interest as a bio-orthogonal chemistry tool within the last decade. In nuclear medicine, tetrazine ligation is currently being explored for pretargeted approaches, which have the potential to revolutionize state-of-the-art theranostic strategies. Pretargeting has been shown to increase target-to-background ratios for radiopharmaceuticals based on nanomedicines, especially within early timeframes. This allows the use of radionuclides with short half-lives which are more suited for clinical applications. Pretargeting bears the potential to increase the therapeutic dose delivered to the target as well as reduce the respective dose to healthy tissue. Combined with the possibility to be applied for diagnostic imaging, pretargeting could be optimal for theranostic approaches. In this review, we highlight efforts that have been made to radiolabel tetrazines with an emphasis on imaging.

Micro/Nanosystems for Magnetic Targeted Delivery of Bioagents

Targeted delivery of pharmaceuticals is promising for efficient disease treatment and reduction in adverse effects. Nano or microstructured magnetic materials with strong magnetic momentum can be noninvasively controlled via magnetic forces within living beings. These magnetic carriers open perspectives in controlling the delivery of different types of bioagents in humans, including small molecules, nucleic acids, and cells. In the present review, we describe different types of magnetic carriers that can serve as drug delivery platforms, and we show different ways to apply them to magnetic targeted delivery of bioagents. We discuss the magnetic guidance of nano/microsystems or labeled cells upon injection into the systemic circulation or in the tissue; we then highlight emergent applications in tissue engineering, and finally, we show how magnetic targeting can integrate with imaging technologies that serve to assist drug delivery.

Microfluidic Roadmap for Translational Nanotheranostics

Nanotheranostic materials (NTMs) shed light on the mechanisms responsible for complex diseases such as cancer because they enable making a diagnosis, monitoring the disease progression, and applying a targeted therapy simultaneously. However, several issues such as the reproducibility and mass production of NTMs hamper their application for clinical practice. To address these issues and facilitate the clinical application of NTMs, microfluidic systems have been increasingly used. This perspective provides a glimpse into the current state-of-art of NTM research, emphasizing the methods currently employed at each development stage of NTMs and the related open problems. This work reviews microfluidic technologies used to develop NTMs, ranging from the fabrication and testing of a single NTM up to their manufacturing on a large scale. Ultimately, a step-by-step vision on the future development of NTMs for clinical practice enabled by microfluidics techniques is provided.

Advanced Optical Imaging-Guided Nanotheranostics towards Personalized Cancer Drug Delivery

Nanomedicine involves the use of nanotechnology for clinical applications and holds promise to improve treatments. Recent developments offer new hope for cancer detection, prevention and treatment; however, being a heterogenous disorder, cancer calls for a more targeted treatment approach. Personalized Medicine (PM) aims to revolutionize cancer therapy by matching the most effective treatment to individual patients. Nanotheranostics comprise a combination of therapy and diagnostic imaging incorporated in a nanosystem and are developed to fulfill the promise of PM by helping in the selection of treatments, the objective monitoring of response and the planning of follow-up therapy. Although well-established imaging techniques, such as Magnetic Resonance Imaging (MRI), Computed Tomography (CT), Positron Emission Tomography (PET) and Single-Photon Emission Computed Tomography (SPECT), are primarily used in the development of theranostics, Optical Imaging (OI) offers some advantages, such as high sensitivity, spatial and temporal resolution and less invasiveness. Additionally, it allows for multiplexing, using multi-color imaging and DNA barcoding, which further aids in the development of personalized treatments. Recent advances have also given rise to techniques permitting better penetration, opening new doors for OI-guided nanotheranostics. In this review, we describe in detail these recent advances that may be used to design and develop efficient and specific nanotheranostics for personalized cancer drug delivery.

The Hitchhiker's Guide to Human Therapeutic Nanoparticle Development

Nanomedicine plays an essential role in developing new therapies through novel drug delivery systems, diagnostic and imaging systems, vaccine development, antibacterial tools, and high-throughput screening. One of the most promising drug delivery systems are nanoparticles, which can be designed with various compositions, sizes, shapes, and surface modifications. These nanosystems have improved therapeutic profiles, increased bioavailability, and reduced the toxicity of the product they carry. However, the clinical translation of nanomedicines requires a thorough understanding of their properties to avoid problems with the most questioned aspect of nanosystems: safety. The particular physicochemical properties of nano-drugs lead to the need for additional safety, quality, and efficacy testing. Consequently, challenges arise during the physicochemical characterization, the production process, in vitro characterization, in vivo characterization, and the clinical stages of development of these biopharmaceuticals. The lack of a specific regulatory framework for nanoformulations has caused significant gaps in the requirements needed to be successful during their approval, especially with tests that demonstrate their safety and efficacy. Researchers face many difficulties in establishing evidence to extrapolate results from one level of development to another, for example, from an in vitro demonstration phase to an in vivo demonstration phase. Additional guidance is required to cover the particularities of this type of product, as some challenges in the regulatory framework do not allow for an accurate assessment of NPs with sufficient evidence of clinical success. This work aims to identify current regulatory issues during the implementation of nanoparticle assays and describe the major challenges that researchers have faced when exposing a new formulation. We further reflect on the current regulatory standards required for the approval of these biopharmaceuticals and the requirements demanded by the regulatory agencies. Our work will provide helpful information to improve the success of nanomedicines by compiling the challenges described in the literature that support the development of this novel encapsulation system. We propose a step-by-step approach through the different stages of the development of nanoformulations, from their design to the clinical stage, exemplifying the different challenges and the measures taken by the regulatory agencies to respond to these challenges.

The Application of Nanoparticles in Diagnosis and Treatment of Kidney Diseases

Nanomedicine is currently showing great promise for new methods of diagnosing and treating many diseases, particularly in kidney disease and transplantation. The unique properties of nanoparticles arise from the diversity of size effects, used to design targeted nanoparticles for specific cells or tissues, taking renal clearance and tubular secretion mechanisms into account. The design of surface particles on nanoparticles offers a wide range of possibilities, among which antibodies play an important role. Nanoparticles find applications in encapsulated drug delivery systems containing immunosuppressants and other drugs, in imaging, gene therapies and many other branches of medicine. They have the potential to revolutionize kidney transplantation by reducing and preventing ischemia-reperfusion injury, more efficiently delivering drugs to the graft site while avoiding systemic effects, accurately localizing and visualising the diseased site and enabling continuous monitoring of graft function. So far, there are known nanoparticles with no toxic effects on human tissue, although further studies are still needed to confirm their safety.

A Review on Drug Delivery System for Tumor Therapy

In recent years, with the development of nanomaterials, the research of drug delivery systems has become a new field of cancer therapy. Compared with conventional antitumor drugs, drug delivery systems such as drug nanoparticles (NPs) are expected to have more advantages in antineoplastic effects, including easy preparation, high efficiency, low toxicity, especially active tumor-targeting ability. Drug delivery systems are usually composed of delivery carriers, antitumor drugs, and even target molecules. At present, there are few comprehensive reports on a summary of drug delivery systems applied for tumor therapy. This review introduces the preparation, characteristics, and applications of several common delivery carriers and expounds the antitumor mechanism of different antitumor drugs in delivery carriers in detail which provides a more theoretical basis for clinical application of personalized cancer nanomedicine in the future.

Direct Cu-mediated aromatic 18F-labeling of highly reactive tetrazines for pretargeted bioorthogonal PET imaging

Pretargeted imaging can be used to visualize and quantify slow-accumulating targeting vectors with short-lived radionuclides such as fluorine-18 - the most popular clinically applied Positron Emission Tomography (PET) radionuclide. Pretargeting results in higher target-to-background ratios compared to conventional imaging approaches using long-lived radionuclides. Currently, the tetrazine ligation is the most popular bioorthogonal reaction for pretargeted imaging, but a direct 18F-labeling strategy for highly reactive tetrazines, which would be highly beneficial if not essential for clinical translation, has thus far not been reported. In this work, a simple, scalable and reliable direct 18F-labeling procedure has been developed. We initially studied the applicability of different leaving groups and labeling methods to develop this procedure. The copper-mediated 18F-labeling exploiting stannane precursors showed the most promising results. This approach was then successfully applied to a set of tetrazines, including highly reactive H-tetrazines, suitable for pretargeted PET imaging. The labeling succeeded in radiochemical yields (RCYs) of up to approx. 25%. The new procedure was then applied to develop a pretargeting tetrazine-based imaging agent. The tracer was synthesized in a satisfactory RCY of ca. 10%, with a molar activity of 134 ± 22 GBq μmol-1 and a radiochemical purity of >99%. Further evaluation showed that the tracer displayed favorable characteristics (target-to-background ratios and clearance) that may qualify it for future clinical translation.

Using Stock-Flow Diagrams to Visualize Theranostic Approaches to Solid Tumors in Personalized Nanomedicine

Personalized nanomedicine has rapidly evolved over the past decade to tailor the diagnosis and treatment of several diseases to the individual characteristics of each patient. In oncology, iron oxide nano-biomaterials (NBMs) have become a promising biomedical product in targeted drug delivery as well as in magnetic resonance imaging (MRI) as a contrast agent and magnetic hyperthermia. The combination of diagnosis and therapy in a single nano-enabled product (so-called theranostic agent) in the personalized nanomedicine has been investigated so far mostly in terms of local events, causes-effects, and mutual relationships. However, this approach could fail in capturing the overall complexity of a system, whereas systemic approaches can be used to study the organization of phenomena in terms of dynamic configurations, independent of the nature, type, or spatial and temporal scale of the elements of the system. In medicine, complex descriptions of diseases and their evolution are daily assessed in clinical settings, which can be thus considered as complex systems exhibiting self-organizing and non-linear features, to be investigated through the identification of dynamic feedback-driven behaviors. In this study, a Systems Thinking (ST) approach is proposed to represent the complexity of the theranostic modalities in the context of the personalized nanomedicine through the setting up of a stock-flow diagram. Specifically, the interconnections between the administration of magnetite NBMs for diagnosis and therapy of tumors are fully identified, emphasizing the role of the feedback loops. The presented approach has revealed its suitability for further application in the medical field. In particular, the obtained stock-flow diagram can be adapted for improving the future knowledge of complex systems in personalized nanomedicine as well as in other nanosafety areas.

Fluorescent nanocarriers targeting VCAM-1 for early detection of senescent endothelial cells

Endothelial senescence has been identified as an early event in the development of endothelial dysfunction, a hallmark of cardiovascular disease. This study developed theranostic nanocarriers (NC) decorated with VCAM-1 antibodies (NC-VCAM-1) in order to target cell surface VCAM-1, which is overexpressed in senescent endothelial cells (ECs) for diagnostic and therapeutic purposes. Incubation of Ang II-induced premature senescent ECs or replicative senescent ECs with NC-VCAM-1 loaded with lipophilic fluorescent dyes showed higher fluorescence signals than healthy EC, which was dependent on the NC size and VCAM-1 antibodies concentration, and not observed following masking of VCAM-1. NC loaded with omega 3 polyunsaturated fatty acid (NC-EPA:DHA6:1) were more effective than native EPA:DHA 6:1 to prevent Ang II-induced VCAM-1 and p53 upregulation, and SA-β-galactosidase activity in coronary artery segments. These theranostic NC might be of interest to evaluate the extent and localization of endothelial senescence and to prevent pro-senescent endothelial responses.

Preparation of parenteral nanocrystal suspensions of etoposide from the excipient free dry state of the drug to enhance in vivo antitumoral properties

Nanoparticle technology in cancer chemotherapy is a promising approach to enhance active ingredient pharmacology and pharmacodynamics. Indeed, drug nanoparticles display various assets such as extended blood lifespan, high drug loading and reduced cytotoxicity leading to better drug compliance. In this context, organic nanocrystal suspensions for pharmaceutical use have been developed in the past ten years. Nanocrystals offer new possibilities by combining the nanoformulation features with the properties of solid dispersed therapeutic ingredients including (i) high loading of the active ingredient, (ii) its bioavailability improvement, and (iii) reduced drug systemic cytotoxicity. However, surprisingly, no antitumoral drug has been marketed as a nanocrystal suspension until now. Etoposide, which is largely used as an anti-cancerous agent against testicular, ovarian, small cell lung, colon and breast cancer in its liquid dosage form, has been selected to develop injectable nanocrystal suspensions designed to be transferred to the clinic. The aim of the present work is to provide optimized formulations for nanostructured etoposide solutions and validate by means of in vitro and in vivo evaluations the efficiency of this multiphase system. Indeed, the etoposide formulated as a nanosuspension by a bottom-up approach showed higher blood life span, reduced tumor growth and higher tolerance in a murine carcinoma cancer model. The results obtained are promising for future clinical evaluation of these etoposide nanosuspensions.

Integrating Artificial Intelligence and Nanotechnology for Precision Cancer Medicine

Artificial intelligence (AI) and nanotechnology are two fields that are instrumental in realizing the goal of precision medicine-tailoring the best treatment for each cancer patient. Recent conversion between these two fields is enabling better patient data acquisition and improved design of nanomaterials for precision cancer medicine. Diagnostic nanomaterials are used to assemble a patient-specific disease profile, which is then leveraged, through a set of therapeutic nanotechnologies, to improve the treatment outcome. However, high intratumor and interpatient heterogeneities make the rational design of diagnostic and therapeutic platforms, and analysis of their output, extremely difficult. Integration of AI approaches can bridge this gap, using pattern analysis and classification algorithms for improved diagnostic and therapeutic accuracy. Nanomedicine design also benefits from the application of AI, by optimizing material properties according to predicted interactions with the target drug, biological fluids, immune system, vasculature, and cell membranes, all affecting therapeutic efficacy. Here, fundamental concepts in AI are described and the contributions and promise of nanotechnology coupled with AI to the future of precision cancer medicine are reviewed.

Translational considerations in nanomedicine: The oncology perspective

Nanoparticles can provide effective control of the release rate and tissue distribution of their drug payload, leading to major pharmacokinetic and pharmacodynamic changes vis-à-vis the conventional administration of free drugs. In the last two decades, we have witnessed major progress in the synthesis and characterization of engineered nanoparticles for imaging and treatment of cancers, resulting in the approval for clinical use of several products and in new and promising approaches. Despite these advances, clinical applications of nanoparticle-based therapeutic and imaging agents remain limited due to biological, immunological, and translational barriers. There is a need to make high impact advances toward translation. In this review, we address biological, toxicological, immunological, and translational aspects of nanomedicine and discuss approaches to move the field forward productively. Overcoming these barriers may dramatically improve the development potential and role of nanomedicines in the oncology field and help meet the high expectations.

Alzheimer's disease: pathogenesis, diagnostics, and therapeutics

Currently, 47 million people live with dementia globally, and it is estimated to increase more than threefold (~131 million) by 2050. Alzheimer's disease (AD) is one of the major causative factors to induce progressive dementia. AD is a neurodegenerative disease, and its pathogenesis has been attributed to extracellular aggregates of amyloid β (Aβ) plaques and intracellular neurofibrillary tangles made of hyperphosphorylated τ-protein in cortical and limbic areas of the human brain. It is characterized by memory loss and progressive neurocognitive dysfunction. The anomalous processing of APP by β-secretases and γ-secretases leads to production of Aβ40 and Aβ42 monomers, which further oligomerize and aggregate into senile plaques. The disease also intensifies through infectious agents like HIV. Additionally, during disease pathogenesis, the presence of high concentrations of Aβ peptides in central nervous system initiates microglial infiltration. Upon coming into vicinity of Aβ, microglia get activated, endocytose Aβ, and contribute toward their clearance via TREM2 surface receptors, simultaneously triggering innate immunoresponse against the aggregation. In addition to a detailed report on causative factors leading to AD, the present review also discusses the current state of the art in AD therapeutics and diagnostics, including labeling and imaging techniques employed as contrast agents for better visualization and sensing of the plaques. The review also points to an urgent need for nanotechnology as an efficient therapeutic strategy to increase the bioavailability of drugs in the central nervous system.

Convenient Entry to 18F-Labeled Amines through the Staudinger Reduction

Fluorine-18 possesses outstanding decay characteristics for positron emission tomography (PET) imaging. Therefore, it is ideally suited for clinical applications. As such, improved strategies to incorporate fluorine-18 into bioactive molecules are of utmost importance. Indirect 18F-labeling with amino-functionalized synthons is a convenient and versatile approach to synthesize a broad variety of PET tracers. Herein, we report a method to convert 18F-labeled azides to primary amines by means of the Staudinger reduction. Aliphatic and aromatic 18F-labeled azides were converted into the corresponding amines with high conversion yields. The method was easily automated. From a broader perspective, the applied strategy results in two useful synthons from a single precursor and thus increases the flexibility to label diverse chemical scaffolds with minimal synthetic effort.

Improved radiosynthesis and preliminary in vivo evaluation of the 11C-labeled tetrazine [11C]AE-1 for pretargeted PET imaging

Pretargeted nuclear imaging based on the ligation between tetrazines and nano-sized targeting agents functionalized with trans-cyclooctene (TCO) has recently been shown to improve both imaging contrast and dosimetry in nuclear imaging of nanomedicines. Herein, we describe the improved radiosynthesis of a ¹¹C-labeled tetrazine ([¹¹C]AE-1) and its preliminary evaluation in both mice and pigs. Pretargeted imaging in mice was carried out using both a new TCO-functionalized polyglutamic acid and a previously reported TCO-functionalized bisphosphonate system as targeting agents. Unfortunately, pretargeted imaging was not successful using these targeting agents in pair with [¹¹C]AE-1. However, brain imaging in pig indicated that the tracer crossed the blood-brain-barrier. Hence, we suggest that this tetrazine scaffold could be used as a starting point for the development of pretargeted brain imaging, which has so far been a challenging task.

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.

Histidine-rich glycoprotein-induced vascular normalization improves EPR-mediated drug targeting to and into tumors

Tumors are characterized by leaky blood vessels, and by an abnormal and heterogeneous vascular network. These pathophysiological characteristics contribute to the enhanced permeability and retention (EPR) effect, which is one of the key rationales for developing tumor-targeted drug delivery systems. Vessel abnormality and heterogeneity, however, which typically result from excessive pro-angiogenic signaling, can also hinder efficient drug delivery to and into tumors. Using histidine-rich glycoprotein (HRG) knockout and wild type mice, and HRG-overexpressing and normal t241 fibrosarcoma cells, we evaluated the effect of genetically induced and macrophage-mediated vascular normalization on the tumor accumulation and penetration of 10-20 nm-sized polymeric drug carriers based on poly(N-(2-hydroxypropyl)methacrylamide). Multimodal and multiscale optical imaging was employed to show that normalizing the tumor vasculature improves the accumulation of fluorophore-labeled polymers in tumors, and promotes their penetration out of tumor blood vessels deep into the interstitium.

Pretargeting in nuclear imaging and radionuclide therapy: Improving efficacy of theranostics and nanomedicines

Pretargeted nuclear imaging and radiotherapy have recently attracted increasing attention for diagnosis and treatment of cancer with nanomedicines. This is because it conceptually offers better imaging contrast and therapeutic efficiency while reducing the dose to radiosensitive tissues compared to conventional strategies. In conventional imaging and radiotherapy, a directly radiolabeled nano-sized vector is administered and allowed to accumulate in the tumor, typically on a timescale of several days. In contrast, pretargeting is based on a two-step approach. First, a tumor-accumulating vector carrying a tag is administered followed by injection of a fast clearing radiolabeled agent that rapidly recognizes the tag of the tumor-bound vector in vivo. Therefore, pretargeting circumvents the use of long-lived radionuclides that is a necessity for sufficient tumor accumulation and target-to-background ratios using conventional approaches. In this review, we give an overview of recent advances in pretargeted imaging strategies. We will critically reflect on the advantages and disadvantages of current state-of-the-art conventional imaging approaches and compare them to pretargeted strategies. We will discuss the pretargeted imaging concept and the involved chemistry. Finally, we will discuss the steps forward in respect to clinical translation, and how pretargeted strategies could be applied to improve state-of-the-art radiotherapeutic approaches.

Functional Diagnostic and Therapeutic Nanoconstructs for Efficient Probing of Circulating Tumor Cells

The circulation of tumor cells in peripheral blood is mostly recognized as a prerequisite for cancer progression or systemic invasion, and it correlates with the pivotal hallmark of malignancies known as metastasis. Multiple detection schemes for circulating tumor cells (CTCs) have emerged as the most discerning criteria for monitoring the outcome of anticancer therapy. Therefore, there has been a tremendous increase in the use of robust nanostructured platforms for observation of these mobile tumor cells through various simultaneous diagnosis and treatment regimens developed from conventional techniques. This review seeks to give detailed information about the nature of CTCs as well as techniques for exploiting specific biomarkers to help monitor cancer via detection, capturing, and analysis of unstable tumor cells. We will further discuss nanobased diagnostic interventions and novel platforms which have recently been developed from versatile nanomaterials such as polymer nanocomposites, metal organic frameworks, bioderived nanomaterials and other physically responsive particles with desirable intrinsic and external properties. Herein, we will also include in vivo nanotheranostic platforms which have received a lot of attention because of their enormous clinical potential. In all, this review sums up the general potential of key promising nanoinspired systems as well as other advanced strategies under research and those in clinical use.

Personalized nanomedicine for CNS diseases

Central nervous system (CNS) diseases are rapidly increasing globally. Currently used therapeutic agents to treat CNS diseases exhibit significant efficacy. However, the inability of these drugs to cross the blood-brain barrier (BBB) and invasiveness of the technologies to achieve localized drug delivery in disease-specific parts of the brain have thwarted pain-free and complete treatment of CNS diseases. Therefore, the safe, non-invasive, and targeted delivery of drugs to the brain using nanoparticles (NPs) is currently receiving considerable research attention. Here, we highlight advances in state-of-the-art personalized nanomedicine for the treatment of CNS diseases (with a focus on dementia), the related challenges, possible solutions, and prospects for nano-enabled personalized medicine.

Augmented reality for personalized nanomedicines

As our understanding of onset and progress of diseases at the genetic and molecular level rapidly progresses, the potential of advanced technologies, such as 3D-printing, Socially-Assistive Robots (SARs) or augmented reality (AR), that are applied to personalized nanomedicines (PNMs) to alleviate pathological conditions, has become more prominent. Among advanced technologies, AR in particular has the greatest potential to address those challenges and facilitate the translation of PNMs into formidable clinical application of personalized therapy. As AR is about to adapt additional new methods, such as speech, voice recognition, eye tracing and motion tracking, to enable interaction with host response or biological systems in 3-D space, a combination of multiple approaches to accommodate varying environmental conditions, such as public noise and atmosphere brightness, will be explored to improve its therapeutic outcomes in clinical applications. For instance, AR glasses still being developed by Facebook or Microsoft will serve as new platform that can provide people with the health information they are interested in or various measures through which they can interact with medical services. This review has addressed the current progress and impact of AR on PNMs and its application to the biomedical field. Special emphasis is placed on the application of AR based PNMs to the treatment strategies against senior care, drug addiction and medication adherence.

Peptide-functionalized nanoparticles for the selective induction of apoptosis in target cells

AIM

The study developed a prohibitin (PHB) targeted nanotherapy for selective induction of apoptosis in target cells.

METHODS

Gold nanoparticles (AuNPs) were bifunctionalized with adipose homing and proapoptotic peptides. The efficacy and mode of cell death induced by the AuNPs were investigated in vitro on three cancer cell lines.

RESULTS

The antiproliferative activity of PHB-targeted bifunctionalized AuNPs was more pronounced on cells that express the PHB receptor, and demonstrated receptor-mediated targeting and selectivity. The bifunctionalized AuNPs induced cell death by apoptosis.

CONCLUSION

The PHB-targeted nanotherapy under study could potentially be used for treatment of diseases that are characterized by overexpression of PHB. As such, further investigations will be conducted in vivo.

Theranostic barcoded nanoparticles for personalized cancer medicine

Personalized medicine promises to revolutionize cancer therapy by matching the most effective treatment to the individual patient. Using a nanoparticle-based system, we predict the therapeutic potency of anticancer medicines in a personalized manner. We carry out the diagnostic stage through a multidrug screen performed inside the tumour, extracting drug activity information with single cell sensitivity. By using 100 nm liposomes, loaded with various cancer drugs and corresponding synthetic DNA barcodes, we find a correlation between the cell viability and the drug it was exposed to, according to the matching barcodes. Based on this screen, we devise a treatment protocol for mice bearing triple-negative breast-cancer tumours, and its results confirm the diagnostic prediction. We show that the use of nanotechnology in cancer care is effective for generating personalized treatment protocols.

Determining the most effective treatment for each cancer patient is a key challenge in cancer therapy. In this article, the authors show, in a mouse model of breast cancer, that DNA barcoded nanoparticles can be used for pre-screening the efficacy of anticancer drugs.

Variable asialoglycoprotein receptor 1 expression in liver disease: Implications for therapeutic intervention

AIM

One of the most promising strategies for the treatment of liver diseases is targeted drug delivery via the asialoglycoprotein receptor (ASGPR). The success of this approach heavily depends on the ASGPR expression level on parenchymal liver cells. In this study, we assessed the mRNA and protein expression levels of the major receptor subunit, ASGR1, in hepatocytes both in vitro and in vivo.

METHODS

In vitro, various liver cancer-derived cell lines were evaluated. In vivo, we screened the ASGR1 mRNA on 59 hepatocellular carcinoma and matched non-neoplastic tissue using RNA microarray. In addition, 350 human liver specimens of patients with hepatocellular carcinoma or non-neoplastic liver diseases were screened for ASGR1 protein level using tissue microarray analysis.

RESULTS

Our data reveal that the ASGR1 mRNA expression directly correlates with the protein level. We demonstrate that the ASGR1 expression is upregulated in cirrhotic specimens and is significantly decreased with increasing hepatocellular carcinoma grade.

CONCLUSION

Because the ASGR1 expression levels are variable between patients, our findings suggest that ASGPR-based targeting strategies should be combined with ASGPR-companion diagnostics to maximize clinical benefit.

Nanotechnology: Future of Oncotherapy

Recent advances in nanotechnology have established its importance in several areas including medicine. The myriad of applications in oncology range from detection and diagnosis to drug delivery and treatment. Although nanotechnology has attracted a lot of attention, the practical application of nanotechnology to clinical cancer care is still in its infancy. This review summarizes the role that nanotechnology has played in improving cancer therapy, its potential for affecting all aspects of cancer care, and the challenges that must be overcome to realize its full promise.

Versatile Nanosystem-Based Cancer Theranostics: Design Inspiration and Predetermined Routing

The relevance of personalized medicine, aimed at a more individualized drug therapy, has inspired research into nano-based concerted diagnosis and therapeutics (theranostics). As the intention is to "kill two birds with one stone", scientists have already described the emerging concept as a treasured tailor for the future of cancer therapy, wherein the main idea is to design "smart" nanosystems to concurrently discharge both therapeutic and diagnostic roles. These nanosystems are expected to offer a relatively clearer view of the ingenious cellular trafficking pathway, in-situ diagnosis, and therapeutic efficacy. We herein present a detailed review of versatile nanosystems, with prominent examples of recently developed intelligent delivery strategies which have gained attention in the field of theranostics. These nanotheranostics include various mechanisms programmed in novel platforms to enable predetermined delivery of cargo to specific sites, as well as techniques to overcome the notable challenges involved in the efficacy of theranostics.

Sonoporation enhances liposome accumulation and penetration in tumors with low EPR

The Enhanced Permeability and Retention (EPR) effect is a highly variable phenomenon. To enhance EPR-mediated passive drug targeting to tumors, several different pharmacological and physical strategies have been evaluated over the years, including e.g. TNFα-treatment, vascular normalization, hyperthermia and radiotherapy. Here, we systematically investigated the impact of sonoporation, i.e. the combination of ultrasound (US) and microbubbles (MB), on the tumor accumulation and penetration of liposomes. Two different MB formulations were employed, and their ability to enhance liposome accumulation and penetration was evaluated in two different tumor models, which are both characterized by relatively low levels of EPR (i.e. highly cellular A431 epidermoid xenografts and highly stromal BxPC-3 pancreatic carcinoma xenografts). The liposomes were labeled with two different fluorophores, enabling in vivo computed tomography/fluorescence molecular tomography (CT-FMT) and ex vivo two-photon laser scanning microscopy (TPLSM). In both models, in spite of relatively high inter- and intra-individual variability, a trend towards improved liposome accumulation and penetration was observed. In treated tumors, liposome concentrations were up to twice as high as in untreated tumors, and sonoporation enhanced the ability of liposomes to extravasate out of the blood vessels into the tumor interstitium. These findings indicate that sonoporation may be a useful strategy for improving drug targeting to tumors with low EPR.

Translational nanomedicine – through the therapeutic window

Translational nanomedicine occurs only through the successful integration of multiple inputs and iterative modifications. The therapeutic window plays a pivotal role in the trajectory of translational nanomedicine. Often defined in terms of the range of dosage for safe and effective therapeutic effect, a second definition of the therapeutic window refers to the often narrow temporal window in which a therapeutic effect can be obtained. Expanding the second definition to explicitly include the spatial dimension, this article explores aspects of the therapeutic spaces created by nanomedicine that shift the traditional dimensions of symptom, sign and pathology. This article analyzes three aspects of the therapeutic window in nanomedicine – temporal, spatial and manner of construction and their impact on the dimensions of modern medicine.

Development of nanotheranostics against metastatic breast cancer--A focus on the biology & mechanistic approaches

Treatment for metastatic breast cancer still remains to be a challenge since the currently available diagnostic and treatment strategies fail to detect the micro-metastasis resulting in higher mortality rate. Moreover, the lack of specificity to target circulating tumor cells is also a factor. In addition, currently available imaging modalities to identify the secondaries vary with respect to various metastatic anatomic areas and size of the tumor. The drawbacks associated with the existing clinical management of the metastatic breast cancer demands the requirement of multifunctional nanotheranostics, which could diagnose at macro- and microscopic level, target the solid as well as circulating tumor cells and control further progression with the simultaneous evaluation of treatment response in a single platform. However, without the understanding of the biology as well as preferential homing ability of circulating tumor cells at distant organs, it is quite impossible to address the existing challenges in the present diagnostics and therapeutics against the breast cancer metastasis. Hence this review outlines the severity of the problem, basic biology and organ specificity with the sequential steps for the secondary progression of disease followed by the various mechanistic approaches in diagnosis and therapy at different stages.

[Ultrasmall nanoparticles for radiotherapy: AGuIX]

Since twenty years, many nanoparticles based on high atomic number elements have been developed as radiosensitizers. The design of these nanoparticles is limited by the classical rules associated with the development of nanoparticles for oncology and by the specific ones associated to radiosensitizers, which aim to increase the effect of the dose in the tumor area and to spare the health tissues. For this application, systemic administration of nanodrugs is possible. This paper will discuss the development of AGuIX nanoparticles and will emphasize on this example the critical points for the development of a nanodrug for this application. AGuIX nanoparticles display hydrodynamic diameters of a few nanometers and are composed of polysiloxane and gadolinium chelates. This particle has been used in many preclinical studies and is evaluated for a further phase I clinical trial. Finally, in addition to its high radiosensitizing potential, AGuIX display MRI functionality and can be used as theranostic nanodrug for personalized medicine.

Applications of nanoparticles for diagnosis and therapy of cancer

During the last decades, a plethora of nanoparticles have been developed and evaluated and a real hype has been created around their potential application as diagnostic and therapeutic agents. Despite their suggestion as potential diagnostic agents, only a single diagnostic nanoparticle formulation, namely iron oxide nanoparticles, has found its way into clinical routine so far. This fact is primarily due to difficulties in achieving appropriate pharmacokinetic properties and a reproducible synthesis of monodispersed nanoparticles. Furthermore, concerns exist about their biodegradation, elimination and toxicity. The majority of nanoparticle formulations that are currently routinely used in the clinic are used for therapeutic purposes. These therapeutic nanoparticles aim to more efficiently deliver a (chemo-) therapeutic drug to the pathological site, while avoiding its accumulation in healthy organs and tissues, and are predominantly based on the "enhanced permeability and retention" (EPR) effect. Furthermore, based on their ability to integrate diagnostic and therapeutic entities within a single nanoparticle formulation, nanoparticles hold great promise for theranostic purposes and are considered to be highly useful for personalizing nanomedicine-based treatments. In this review article, we present applications of diagnostic and therapeutic nanoparticles, summarize frequently used non-invasive imaging techniques and describe the role of EPR in the accumulation of nanotheranostic formulations. In this context, the clinical potential of nanotheranostics and image-guided drug delivery for individualized and improved (chemo-) therapeutic interventions is addressed.