Dendrimer-based molecular imaging contrast agents

CT and X-ray contrast agents: Current clinical challenges and the future of contrast

Computed tomography (CT) is a powerful and widely used imaging technique in modern medicine. However, it often requires the use of contrast agents to visualize structures with similar radiographic density. Unfortunately, current clinical contrast agents (CAs) for CT have remained largely unchanged for decades and come with several significant drawbacks, including serious nephrotoxicity and short circulation half-lives. The next generation of CT radiocontrast agents should strive to be long-circulating, non-toxic, and non-immunogenic. Nanoparticle contrast agents have shown promise in recent years and are likely to comprise the majority of next-generation CT contrast agents. This review highlights the fundamental mechanism and background of X-ray and contrast agents. It also focuses on the challenges associated with current clinical contrast agents and provides a brief overview of potential future agents that are based on various materials such as lipids, polymers, dendrimers, metallic, and non-metallic inorganic nanoparticles (NPs). STATEMENT OF SIGNIFICANCE: We realized a need for clarification on a number of concerns related to the use of iodinated contrast material as debates regarding the safety of these agents with patients with kidney disease, shellfish allergies, and thyroid dysfunction remain ongoing in medical practice. This review was partially inspired by debates witnessed in medical practice regarding outdated misconceptions of contrast material that warrant clarification in translational and clinical arenas. Given that conversation around currently available agents is at somewhat of a high water mark, and nanoparticle research has now reached an unprecedented number of readers, we find that this review is timely and unique in the context of recent discussions in the field.

Sodium alginate encapsulated iron oxide decorated with thymoquinone nanocomposite induces apoptosis in human breast cancer cells via PI3K-Akt-mTOR pathway

The present study investigated the cytotoxicity and proapoptotic properties of iron oxide-sodium-alginate-thymoquinone nanocomposites against breast cancer MDA-MB-231 cells in vitro and in silico. This study used chemical synthesis to formulate the nanocomposite. Electron microscopies such as scanning (SEM) and transmission (TEM), Fourier transform infrared (FT-IR), Ultraviolet-Visible, Photoluminescence spectroscopy, selected area (electron) diffraction (SAED), energy dispersive X-ray analysis (EDX), and X-ray diffraction studies (XRD) were used to characterize the synthesized ISAT-NCs and the average size of them was found to be 55 nm. To evaluate the cytotoxic, antiproliferative, and apoptotic potentials of ISAT-NCs on MDA-MB-231 cells, MTT assays, FACS-based cell cycle studies, annexin-V-PI staining, ELISA, and qRT-PCR were used. PI3K-Akt-mTOR receptors and thymoquinone were predicted using in-silico docking studies. Cell proliferation is reduced in MDA-MB-231 cells due to ISAT-NC cytotoxicity. As a result of FACS analysis, ISAT-NCs had nuclear damage, ROS production, and elevated annexin-V levels, which resulted in cell cycle arrest in the S phase. The ISAT-NCs in MDA-MB-231 cells were found to downregulate PI3K-Akt-mTOR regulatory pathways in the presence of inhibitors of PI3K-Akt-mTOR, showing that these regulatory pathways are involved in apoptotic cell death. We also predicted the molecular interaction between thymoquinone and PI3K-Akt-mTOR receptor proteins using in-silico docking studies which also support PI3K-Akt-mTOR signaling inhibition by ISAT-NCs in MDA-MB-231 cells. As a result of this study, we can conclude that ISAT-NCs inhibit the PI3K-Akt-mTOR pathway in breast cancer cell lines, causing apoptotic cell death.

Multifunctional Low-Generation Dendrimer Nanogels as an Emerging Probe for Tumor-Specific CT/MR Dual-Modal Imaging

The development of nanoprobes that have amplified enhanced permeability and retention (EPR) effect is crucial for their precise cancer diagnosis performance. Here, we present the development of functional dendrimer-based nanogels (DNGs) with the generation three primary amine-terminated poly(amidoamine) (PAMAM) dendrimers (G3·NH₂) cross-linked by N,N'-bis(acryloyl) cystamine (BAC). The DNGs were prepared through a Michael addition reaction between G3·NH₂ dendrimers and BAC via an inverse microemulsion method and entrapped with gold nanoparticles (Au NPs) to form Au-DNGs. The Au-DNGs were sequentially modified with diethylenetriamine penta-acetic acid (DTPA)-gadolinium (Gd) complex, poly(ethylene glycol) (PEG)-linked arginine-glycine-aspartic (RGD) peptide, and 1,3-propanesultone (1,3-PS). The formed multifunctional RGD-Gd@Au-DNGs-PS (R-G@ADP) possessing an average diameter of 122 nm are colloidally stable and display a high X-ray attenuation coefficient, excellent r₁ relaxivity (9.13 mM^-1 s^-1), desired protein resistance rendered by the zwitterionic modification, and cytocompatibility. With the targeting specificity mediated by RGD and the much better tumor penetration capability than the counterpart material of single dendrimer-entrapped Au NPs, the developed multifunctional R-G@ADP enable targeted and enhanced computed tomography (CT)/magnetic resonance (MR) dual-modal imaging of a pancreatic tumor model in vivo. The current work demonstrates a unique design of targeted and zwitterionic DNGs with prolonged blood circulation time as an emerging nanoprobe for specific tumor CT/MR imaging through amplified passive EPR effect.

Properties and Bioapplications of Amphiphilic Janus Dendrimers: A Review

Amphiphilic Janus dendrimers are arrangements containing both hydrophilic and hydrophobic units, capable of forming ordered aggregates by intermolecular noncovalent interactions between the dendrimer units. Compared to conventional dendrimers, these molecular self-assemblies possess particular and effective attributes i.e., the presence of different terminal groups, essential to design new elaborated materials. The present review will focus on the pharmaceutical and biomedical application of amphiphilic Janus dendrimers. Important information for the development of novel optimized pharmaceutical formulations, such as structural classification, synthetic pathways, properties and applications, will offer the complete characterization of this type of Janus dendrimers. This work will constitute an up-to-date background for dendrimer specialists involved in designing amphiphilic Janus dendrimer-based nanomaterials for future innovations in this promising field.

Polyethyleneimine-Based Drug Delivery Systems for Cancer Theranostics

With the development of nanotechnology, various types of polymer-based drug delivery systems have been designed for biomedical applications. Polymer-based drug delivery systems with desirable biocompatibility can be efficiently delivered to tumor sites with passive or targeted effects and combined with other therapeutic and imaging agents for cancer theranostics. As an effective vehicle for drug and gene delivery, polyethyleneimine (PEI) has been extensively studied due to its rich surface amines and excellent water solubility. In this work, we summarize the surface modifications of PEI to enhance biocompatibility and functionalization. Additionally, the synthesis of PEI-based nanoparticles is discussed. We further review the applications of PEI-based drug delivery systems in cancer treatment, cancer imaging, and cancer theranostics. Finally, we thoroughly consider the outlook and challenges relating to PEI-based drug delivery systems.

Advances in Polymeric Colloids for Cancer Treatment

Polymer colloids have remarkable features and are gaining importance in many areas of research including medicinal science. Presently, the innovation of cancer drugs is at the top in the world. Polymer colloids have been used as drug delivery and diagnosis agents in cancer treatment. The polymer colloids may be of different types such as micelles, liposomes, emulsions, cationic carriers, and hydrogels. The current article describes the state-of-the-art polymer colloids for the treatment of cancer. The contents of this article are about the role of polymeric nanomaterials with special emphasis on the different types of colloidal materials and their applications in targeted cancer therapy including cancer diagnoses. In addition, attempts are made to discuss future perspectives. This article will be useful for academics, researchers, and regulatory authorities.

Recent advances in near-infrared-II hollow nanoplatforms for photothermal-based cancer treatment

Near-infrared-II (NIR-II, 1000–1700 nm) light-triggered photothermal therapy (PTT) has been regarded as a promising candidate for cancer treatment, but PTT alone often fails to achieve satisfactory curative outcomes. Hollow nanoplatforms prove to be attractive in the biomedical field owing to the merits including good biocompatibility, intrinsic physical-chemical nature and unique hollow structures, etc. On one hand, hollow nanoplatforms themselves can be NIR-II photothermal agents (PTAs), the cavities of which are able to carry diverse therapeutic units to realize multi-modal therapies. On the other hand, NIR-II PTAs are capable of decorating on the surface to combine with the functions of components encapsulated inside the hollow nanoplatforms for synergistic cancer treatment. Notably, PTAs generally can serve as good photoacoustic imaging (PAI) contrast agents (CAs), which means such kind of hollow nanoplatforms are also expected to be multifunctional all-in-one nanotheranostics. In this review, the recent advances of NIR-II hollow nanoplatforms for single-modal PTT, dual-modal PTT/photodynamic therapy (PDT), PTT/chemotherapy, PTT/catalytic therapy and PTT/gas therapy as well as multi-modal PTT/chemodynamic therapy (CDT)/chemotherapy, PTT/chemo/gene therapy and PTT/PDT/CDT/starvation therapy (ST)/immunotherapy are summarized for the first time. Before these, the typical synthetic strategies for hollow structures are presented, and lastly, potential challenges and perspectives related to these novel paradigms for future research and clinical translation are discussed.

Role of Iron Oxide (Fe2O3) Nanocomposites in Advanced Biomedical Applications: A State-of-the-Art Review

Nanomaterials have demonstrated a wide range of applications and recently, novel biomedical studies are devoted to improving the functionality and effectivity of traditional and unmodified systems, either drug carriers and common scaffolds for tissue engineering or advanced hydrogels for wound healing purposes. In this regard, metal oxide nanoparticles show great potential as versatile tools in biomedical science. In particular, iron oxide nanoparticles with different shape and sizes hold outstanding physiochemical characteristics, such as high specific area and porous structure that make them idoneous nanomaterials to be used in diverse aspects of medicine and biological systems. Moreover, due to the high thermal stability and mechanical strength of Fe₂O₃, they have been combined with several polymers and employed for various nano-treatments for specific human diseases. This review is focused on summarizing the applications of Fe₂O₃-based nanocomposites in the biomedical field, including nanocarriers for drug delivery, tissue engineering, and wound healing. Additionally, their structure, magnetic properties, biocompatibility, and toxicity will be discussed.

Synthesis of a Dual-Color Fluorescent Dendrimer for Diagnosis of Cancer Metastasis in Lymph Nodes

Detection of cancer metastasis spread in lymph nodes is important in cancer diagnosis. In this study, a fluorescence imaging probe was designed for the detection of both lymph node and tumor cells using always-ON and activatable fluorescence probes with different colors. Rhodamine B (Rho), a matrix metalloproteinase-2 (MMP-2)-responsive green fluorescence probe, and a tumor-homing peptide were conjugated to a carboxy-terminal dendrimer that readily accumulates in lymph nodes. The activatable green fluorescence signal increased in the presence of MMP-2, which is secreted by tumor cells. Both the always-ON Rho signal and the activatable green fluorescence signal were observed from tumor cells, but only the weak always-ON Rho signal was from immune cells. Thus, this type of dendrimer may be useful for non-invasive imaging to diagnose cancer metastasis in lymph nodes.

Advances of nano drug delivery system for the theranostics of ischemic stroke

From the global perspective, stroke refers to a highly common cause of disability and death. Ischemic stroke (IS), attributed to blood vessel blockage, preventing the flow of blood to brain, acts as the most common form of stroke. Thus far, thrombolytic therapy is the only clinical treatment for IS with the approval from the FDA. Moreover, the physiology barrier complicates therapeutically and diagnostically related intervention development of IS. Accordingly, developing efficient and powerful curative approaches for IS diagnosis and treatment is urgently required. The advent of nanotechnology has brought dawn and hope to better curative and imaging forms for the management of IS. This work reviews the recent advances and challenges correlated with the nano drug delivery system for IS therapy and diagnosis. The overview of the current knowledge of the important molecular pathological mechanisms in cerebral ischemia and how the drugs cross the blood brain barrier will also be briefly summarized.

An Orthogonal Protection Strategy for Synthesizing Scaffold-Modifiable Dendrons and Their Application in Drug Delivery

Dendrons have well-defined dendritic structures. However, it is a great challenge to preserve their high structural definition after multiple functionalization because the site-selective conjugation of different functional molecules is quite difficult. Scaffold-modifiable dendrons that have orthogonal reactive groups at the scaffold and periphery are ideal for achieving the site-specific bifunctionalization. In this paper, we present a new strategy for synthesizing scaffold-modifiable dendrons via orthogonal amino protection and a solid-phase synthesis method. This strategy renders the reactive sites at the scaffold and periphery of the dendrons a super selectivity, high reactivity, and wide applicability to various reaction types. The fourth-generation dendrons can be facilely synthesized within 2 days without structural defects as demonstrated by mass spectrometry. We conjugated doxorubicin (DOX) and phenylboronic acid (PBA) groups to the scaffold and periphery, respectively. Thanks to the PBA-enhanced lysosome escape, tumor targeting ability, and tumor permeability as well as the high drug loading content larger than 30%, the dendron-based prodrug exhibited extraordinary antitumor efficacy and could eradicate the tumors established in mice by multiple intravenous administration. This work provides a practical strategy for synthesizing scaffold-modifiable dendrons that can be a promising nanoplatform to achieve function integration in a precisely controlled manner.

Theranostic applications of stimulus-responsive systems based on Fe2O3

According to the interaction of nanoparticles with biological systems, enthusiasm for nanotechnology in biomedical applications has been developed in the past decades. Fe2O3 nanoparticles, as the most stable iron oxide, have special merits that make them useful widely for detecting diseases, therapy, drug delivery, and monitoring the therapeutic process. This review presents the fabrication methods of Fe2O3-based materials and their photocatalytic and magnetic properties. Then, we highlight the application of Fe2O3-based nanoparticles in diagnosis and imaging, different therapy methods, and finally, stimulus-responsive systems, such as pH-responsive, magnetic-responsive, redox-responsive, and enzyme-responsive, with an emphasis on cancer treatment. In addition, the potential of Fe2O3 to combine diagnosis and therapy within a single particle called theranostic agent will be discussed.

Investigating the properties of L-lysine dendrimers through physico-chemical characterisation techniques and atomistic molecular dynamics simulations

Poly(L-lysine) (PLL) dendrimers up to generation 6, both as their ammonium trifluoroacetate salts and their boc-protected intermediates were characterised using multi-detector size exclusion chromatography (MD-SEC) and Taylor dispersion analysis (TDA)...

The advanced synthetic modifications and applications of multifunctional PAMAM dendritic composites

The profound advances in dendrimer chemistry have led to new horizons in polymer science.

Polymers for Improved Delivery of Iodinated Contrast Agents

X-ray computed tomography (CT), as one of the most widely used noninvasive imaging modalities, can provide three-dimensional anatomic details with high resolution, which plays a key role in disease diagnosis and treatment assessment. However, although they are the most prevalent and FDA-approved contrast agents, iodinated water-soluble molecules still face some challenges in clinical applications, such as fast clearance, serious adverse effects, nonspecific distribution, and low sensitivity. Because of their high biocompatibility, tunable designability, controllable biodegradation, facile synthesis, and modification capability, the polymers have demonstrated great potential for efficient delivery of iodinated contrast agents (ICAs). Herein, we comprehensively summarized the applications of multifunctional polymeric materials for ICA delivery in terms of increasing circulation time, decreasing nephrotoxicity, and improving the specificity and sensitivity of ICAs for CT imaging. We mainly focused on various iodinated polymers from the aspects of preparation, functionalization, and application in medical diagnosis. Future perspectives for achieving better imaging and clinical translation are also discussed to motivate new technologies and solutions.

Organic Nanoplatforms for Iodinated Contrast Media in CT Imaging

X-ray computed tomography (CT) imaging can produce three-dimensional and high-resolution anatomical images without invasion, which is extremely useful for disease diagnosis in the clinic. However, its applications are still severely limited by the intrinsic drawbacks of contrast media (mainly iodinated water-soluble molecules), such as rapid clearance, serious toxicity, inefficient targetability and poor sensitivity. Due to their high biocompatibility, flexibility in preparation and modification and simplicity for drug loading, organic nanoparticles (NPs), including liposomes, nanoemulsions, micelles, polymersomes, dendrimers, polymer conjugates and polymeric particles, have demonstrated tremendous potential for use in the efficient delivery of iodinated contrast media (ICMs). Herein, we comprehensively summarized the strategies and applications of organic NPs, especially polymer-based NPs, for the delivery of ICMs in CT imaging. We mainly focused on the use of polymeric nanoplatforms to prolong circulation time, reduce toxicity and enhance the targetability of ICMs. The emergence of some new technologies, such as theragnostic NPs and multimodal imaging and their clinical translations, are also discussed.

Advanced Delivery Systems Based on Lysine or Lysine Polymers

Polylysine and materials that integrate lysine form promising drug delivery platforms. As a cationic macromolecule, a polylysine polymer electrostatically interacts with cells and is efficiently internalized, thereby enabling intracellular delivery. Although polylysine is intrinsically pH-responsive, the conjugation with different functional groups imparts smart, stimuli-responsive traits by adding pH-, temperature-, hypoxia-, redox-, and enzyme-responsive features for enhanced delivery of therapeutic agents. Because of such characteristics, polylysine has been used to deliver various cargos such as small-molecule drugs, genes, proteins, and imaging agents. Furthermore, modifying contrast agents with polylysine has been shown to improve performance, including increasing cellular uptake and stability. In this review, the use of lysine residues, peptides, and polymers in various drug delivery systems has been discussed comprehensively to provide insight into the design and robust manufacturing of lysine-based delivery platforms.

Chitosan, Polyethylene Glycol and Polyvinyl Alcohol Modified MgFe2O4 Ferrite Magnetic Nanoparticles in Doxorubicin Delivery: A Comparative Study In Vitro

Cancer-based magnetic theranostics has gained significant interest in recent years and can contribute as an influential archetype in the effective treatment of cancer. Owing to their excellent biocompatibility, minute sizes and reactive functional surface groups, magnetic nanoparticles (MNPs) are being explored as potential drug delivery systems. In this study, MgFe₂O₄ ferrite MNPs were evaluated for their potential to augment the delivery of the anticancer drug doxorubicin (DOX). These MNPs were successfully synthesized by the glycol-thermal method and functionalized with the polymers; chitosan (CHI), polyvinyl alcohol (PVA) and polyethylene glycol (PEG), respectively, as confirmed by Fourier transform infrared (FTIR) spectroscopy. X-ray diffraction (XRD) confirmed the formation of the single-phase cubic spinel structures while vibrating sample magnetometer (VSM) analysis confirmed the superparamagnetic properties of all MNPs. Transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA) revealed small, compact structures with good colloidal stability. CHI-MNPs had the highest DOX encapsulation (84.28%), with the PVA-MNPs recording the lowest encapsulation efficiency (59.49%). The 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide (MTT) cytotoxicity assays conducted in the human embryonic kidney (HEK293), colorectal adenocarcinoma (Caco-2), and breast adenocarcinoma (SKBR-3) cell lines showed that all the drug-free polymerized MNPs promoted cell survival, while the DOX loaded MNPs significantly reduced cell viability in a dose-dependent manner. The DOX-CHI-MNPs possessed superior anticancer activity (<40% cell viability), with approximately 85.86% of the drug released after 72 h in a pH-responsive manner. These MNPs have shown good potential in enhancing drug delivery, thus warranting further optimizations and investigations.

Vancomycin-dendrimer based multivalent magnetic separation nanoplatforms combined with multiplex quantitative PCR assay for detecting pathogenic bacteria in human blood

Sepsis caused by bacteria has high morbidity and mortality, and it is neccerssay to establish a fast, convenient, and facility assays for detection of bacteria. In this study, we have developed established a simple, rapid, and ultrasensitive vancomycin (Van) and dendrimer nanoparticles-based method to isolate and detect bacteria in human blood using a multivalent binding strategy. The proposed Bio-den-Van multivalent capture nanoplatform combined with m-qPCR for simultaneous detection of two kinds of bacteria was demonstrated with rapid 2 min bacteria isolation with a linear range at 3.2 × 10¹-3.2 × 10⁶ CFU·mL^-1 for L. monocytogenes and 4.1 × 10¹-4.1 × 10⁶ CFU·mL^-1 for S. aureus, respectively. The limit of detection (LOD) for simultaneous detection of L. monocytogenes and S. aureus were 32 and 41 CFU·mL^-1 in spiked human blood samples, respectively. Other bacteria had an insignificant interference with the test results. This Bio-den-Van multivalent capture nanoplatform combined with m-qPCR detection exhibited rapid, high sensitivity and specificity in simultaneous detection of various bacteria. To our knowledge, this is the first time that Bio-den-Van multivalent capture nanoplatform was used with Van as a recognition molecule for the simultaneous capture and subsequent detection of two bacteria from spiked human blood sample. This method holds great potential for future clinical applications.

Dendrimers based cancer nanotheranostics: An overview

Cancer is a known deadliest disease that requires a judicious diagnostic, targeting, and treatment strategy for an early prognosis and selective therapy. The major pitfalls of the conventional approach are non-specificity in targeting, failure to precisely monitor therapy outcome, and cancer progression leading to malignancies. The unique physicochemical properties offered by nanotechnology derived nanocarriers have the potential to radically change the landscape of cancer diagnosis and therapeutic management. An integrative approach of utilizing both diagnostic and therapeutic functionality using a nanocarrier is termed as nanotheranostic. The nanotheranostics platform is designed in such a way that overcomes various biological barriers, efficiently targets the payload to the desired locus, and simultaneously supports planning, monitoring, and verification of treatment delivery to demonstrate an enhanced therapeutic efficacy. Thus, a nanotheranostic platform could potentially assist in drug targeting, image-guided focal therapy, drug release and distribution monitoring, predictionof treatment response, and patient stratification. A class of highly branched nanocarriers known as dendrimers is recognized as an advanced nanotheranostic platform that has the potential to revolutionize the oncology arena by its unique and exciting features. A dendrimer is a well-defined three-dimensional globular chemical architecture with a high level of monodispersity, amenability of precise size control, and surface functionalization. All the dendrimer properties exhibit a reproducible pharmacokinetic behavior that could ensure the desired biodistribution and efficacy. Dendrimers are thus being exploited as a nanotheranostic platform embodying a diverse class of therapeutic, imaging, and targeting moieties for cancer diagnosis and treatment.

Dendrimer-based nanohybrids in cancer photomedicine

Cancer phototherapy with non-invasiveness and high therapeutical efficiency has emerged as a hot spot research in cancer management. Various nanomaterials have been involved in the development of novel photoactive agents to overcome the current limitations in cancer phototherapy. Dendrimers, as an excellent nanocarrier with unique physicochemical properties, have received extensive attention and much effort has been made in the development of dendrimer-based hybrid platforms for photomedicine applications. Dendrimers can be entrapped with photosensitive agents within their internal cavities and be surface modified with reactive molecules, constructing multifunctional nanoplatforms for cancer treatment. In this review, we concisely survey the design of several different kinds of dendrimer-based nanohybrids for cancer photomedicine applications, and provide an overview of their recent applications in molecular imaging, single-modality photothermal therapy or photodynamic therapy, combination therapy, and theranostics of cancer. In addition, we also briefly discuss the future perspectives in the area of dendrimer-based nanohybrids for cancer photomedicine.

Construction of Poly(amidoamine) Dendrimer/Carbon Dot Nanohybrids for Biomedical Applications

Design of intelligent hybrid nanoparticles that can integrate diagnosis and therapy components plays an important role in the field of nanomedicine. Poly(amidoamine) (PAMAM) dendrimers possessing a unique architecture and tunable functional groups have been widely developed for various biomedical applications. Carbon dots (CDs) are considered as a promising fluorescence probe or drug delivery system due to their stable fluorescence property and excellent biocompatibility. The distinctive merits of PAMAM dendrimers and CDs are amenable for them to be constructed as perfect nanohybrids for different biomedical applications, in particular for cancer nanomedicine. Here, the recent advances in the construction of PAMAM dendrimer/CD nanohybrids for diverse biomedical applications, in particular for sensing and cancer theranostics are summarized. Finally, the future perspectives of the PAMAM dendrimer/CD nanohybrids are also briefly discussed.

Antifouling Dendrimer-Entrapped Copper Sulfide Nanoparticles Enable Photoacoustic Imaging-Guided Targeted Combination Therapy of Tumors and Tumor Metastasis

The development of functional intelligent theranostic nanoplatform for imaging-directed synchronous inhibition of primary tumor and tumor metastasis is still a challenging task. We present here the creation of functional dendrimer-entrapped CuS nanoparticles (CuS DENPs) complexed with plasmid DNA-encoding hypermethylation in cancer 1 (pDNA-HIC1) for photoacoustic (PA) imaging-directed simultaneous inhibition of tumors and tumor metastasis. Poly(amidoamine) dendrimers of generation 5 were covalently attached with 1,3-propane sultone and arginine-glycine-aspartic acid (RGD) peptide through a spacer of poly(ethylene glycol) and adopted for the templated synthesis of CuS NPs. The prepared functional RGD-CuS DENPs possess a mean CuS core diameter of 4.2 nm, good colloidal stability, and an excellent absorption feature in the second near-infrared window, thus having a photothermal conversion efficiency of 49.8% and an outstanding PA imaging capability. The functional DENPs can effectively deliver pDNA-HIC1 to prevent cancer cell invasion and metastasis in a serum-enhancing manner by virtue of zwitterionic modification-rendered antifouling property. The developed RGD-CuS DENPs/pDNA polyplexes display α_vβ₃ integrin-targeted enhanced anticancer activity through the combined CuS NP-mediated photothermal therapy (PTT) and pDNA delivery-rendered cancer cell metastasis inhibition. This can also be proven by the therapeutic efficacy of a triple-negative breast cancer model in vivo, where inhibition of both the primary subcutaneous tumor and lung metastasis can be realized. The created dendrimer-CuS hybrid nanoplatform represents one of the updated designs of nanomedicine for PA imaging-directed combination PTT/gene therapy of tumors and tumor metastasis.

Supramolecular dendrimer-containing layer-by-layer nanoassemblies for bioapplications: current status and future prospects

This review provides a comprehensive and critical overview of the supramolecular dendrimer-containing multifunctional layer-by-layer nanoassemblies driven by a multitude of intermolecular interactions for biological and biomedical applications.

Peptide-based supramolecular hydrogels for bioimaging applications

Peptide-based supramolecular hydrogels have unique merits in bioimaging applications.

Chronic intermittent hypobaric hypoxia improves markers of iron metabolism in a model of dietary-induced obesity

BACKGROUND

Obesity, a risk factor for many chronic diseases, is a potential independent risk factor for iron deficiency. Evidence has shown that chronic intermittent hypobaric hypoxia (CIHH) has protective or improved effects on cardiovascular, nervous, metabolic and immune systems. We hypothesized that CIHH may ameliorate the abnormal iron metabolism in obesity. This study was aimed to investigate the effect and the underlying mechanisms of CIHH on iron metabolism in high-fat-high-fructose-induced obese rats.

METHODS

Six to seven weeks old male Sprague-Dawley rats were fed with different diet for 16 weeks, and according to body weight divided into four groups: control (CON), CIHH (28-day, 6-h daily hypobaric hypoxia treatment simulating an altitude of 5000 m), dietary-induced obesity (DIO; induced by high fat diet and 10% fructose water feeding), and DIO + CIHH groups. The body weight, systolic arterial pressure (SAP), Lee index, fat coefficient, blood lipids, blood routine, iron metabolism parameters, interleukin6 (IL-6) and erythropoietin (Epo) were measured. The morphological changes of the liver, kidney and spleen were examined. Additionally, hepcidin mRNA expression in liver was analyzed.

RESULTS

The DIO rats displayed obesity, increased SAP, lipids metabolism disorders, damaged morphology of liver, kidney and spleen, disturbed iron metabolism, increased IL-6 level and hepcidin mRNA expression, and decreased Epo compared to CON rats. But all the aforementioned abnormalities in DIO rats were improved in DIO + CIHH rats.

CONCLUSIONS

CIHH improves iron metabolism disorder in obese rats possibly through the down-regulation of hepcidin by decreasing IL-6 and increasing Epo.

Surface Charge of Supramolecular Nanosystems for In Vivo Biodistribution: A MicroSPECT/CT Imaging Study

Bioimaging has revolutionized medicine by providing accurate information for disease diagnosis and treatment. Nanotechnology-based bioimaging is expected to further improve imaging sensitivity and specificity. In this context, supramolecular nanosystems based on self-assembly of amphiphilic dendrimers for single photon emission computed tomography (SPECT) bioimaging are developed. These dendrimers bear multiple In³⁺ radionuclides at their terminals as SPECT reporters. By replacing the macrocyclic 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid cage with the smaller 1,4,7-triazacyclononane-1,4,7-triacetic acid scaffold as the In³⁺ chelator, the corresponding dendrimer exhibits neutral In³⁺ -complex terminals in place of negatively charged In³⁺ -complex terminals. This negative-to-neutral surface charge alteration completely reverses the zeta-potential of the nanosystems from negative to positive. As a consequence, the resulting SPECT nanoprobe generates a highly sought-after biodistribution profile accompanied by a drastically reduced uptake in liver, leading to significantly improved tumor imaging. This finding contrasts with current literature reporting that positively charged nanoparticles have preferential accumulation in the liver. As such, this study provides new perspectives for improving the biodistribution of positively charged nanosystems for biomedical applications.

Fluorescent Phosphorus Dendrimers: Towards Material and Biological Applications

Fluorescent derivatives of phosphorhydrazone dendrimers are reviewed. Diverse types of fluorophores have been used, such as pyrene, naphthol, anthracene, dansyl, diketone, phthalocyanine, maleimide, julolidine, rhodamine, fluorescein, or fluorene derivatives. The fluorescent groups can be located either as terminal groups on the surface, at the core, linked to the core (off-center), or to the branches of the dendritic structure. After fundamental research on their synthesis, these compounds have been used in the fields of catalysis, nanomaterials, OLEDs, sensors and biology/nanomedicine, in particular for monitoring transfection, or for their anti-inflammatory or anti-cancer properties.

Integrated POSS-dendrimer nanohybrid materials: current status and future perspective

Polyhedral oligomeric silsesquioxane (POSS)-dendrimer hybrid materials have attracted great interest in the past ten years. The integration of inorganic POSS and organic dendrimer blocks in a single-phase material offers numerous possibilities to access desirable mechanical, optical, and biomedical properties for various applications. In this review article, we describe several kinds of POSS-dendrimer hybrid materials (POSS as the core, surface functionality, repeating unit of dendrimers and the POSS-dendron conjugates) with an emphasis on their synthetic strategies, tunable macroscopic properties, and potential applications. Moreover, the current trends, challenges and future directions of POSS-dendrimer hybrid materials are elaborated.

Tuning the Brightness and Photostability of Organic Dots for Multivalent Targeted Cancer Imaging and Surgery

Specific labeling of biomarkers with bright and high photostable fluorophores is vital in fluorescent imaging applications. Here, we report a general strategy to develop single-molecule dendritic nanodots with finely tunable optical properties for in vivo fluorescent imaging. The well-defined nanodots are based on the divergent growth of biodegradable polylysine dendrimers with a fluorophore as the core. By tuning the size and surface chemistry, we obtained fluorescent nanodots with excellent brightness and photostability, favorable pharmacokinetics, and multivalent tumor-targeting capability. The nanodots provided robust, stable, long-lasting, and specific fluorescence enhancement in tumor tissue with an in situ tumor-to-normal ratio (TNR) of ∼3 and lasting over 5 days and an ex vivo TNR up to ∼17, holding considerable promise for cancer imaging and image-guided surgery. This strategy significantly improves the in vivo performance of fluorophores and can be applied to other modality imaging probes.

Multifunctional Dendrimer-Entrapped Gold Nanoparticles for Labeling and Tracking T Cells Via Dual-Modal Computed Tomography and Fluorescence Imaging

Nanosystems for monitoring and tracking T cells provide an important basis for evaluating the functionality and efficacy of T cell-based immunotherapy. To this end, we designed herein an efficient nanoprobe for T cell monitoring and tracking using poly(amidoamine) (PAMAM) dendrimer-entrapped gold nanoparticles (Au DENPs) conjugated with Fluo-4 for dual-mode computed tomography (CT) and fluorescence imaging. In this study, PAMAM dendrimers of generation 5 (G5) were modified with hydroxyl-terminated polyethylene glycol (PEG) and then used to entrap 2.0 nm Au NPs followed by acetylation of the excess amine groups on the dendrimer surface. Subsequently, the calcium ion probe was covalently attached to the dendrimer nanohybrids through the PEG hydroxyl end groups to gain the functional {(Au⁰)₂₅-G5.NHAc-(PEG)₁₄-(Fluo-4)₂} nanoprobe. This nanoprobe had excellent water solubility, high X-ray attenuation coefficient, and good cytocompatibility in the given concentration range, as well as a high T cell labeling efficiency. Confocal microscopy and flow cytometry results demonstrated that the nanoprobe was able to fluorescently sense activated T cells. Moreover, the nanoprobe was able to realize both CT and fluorescence imaging of subcutaneously injected T cells in vivo. Thus, the developed novel dendrimer-based nanosystem may hold great promise for advancing and improving the clinical application of T cell-based immunotherapy.

Progress in Polymeric Nano-Medicines for Theranostic Cancer Treatment

Cancer is a life-threatening disease killing millions of people globally. Among various medical treatments, nano-medicines are gaining importance continuously. Many nanocarriers have been developed for treatment, but polymerically-based ones are acquiring importance due to their targeting capabilities, biodegradability, biocompatibility, capacity for drug loading and long blood circulation time. The present article describes progress in polymeric nano-medicines for theranostic cancer treatment, which includes cancer diagnosis and treatment in a single dosage form. The article covers the applications of natural and synthetic polymers in cancer diagnosis and treatment. Efforts were also made to discuss the merits and demerits of such polymers; the status of approved nano-medicines; and future perspectives.

Superparamagnetic iron oxide nanoparticulate system: synthesis, targeting, drug delivery and therapy in cancer

Cancer is a global epidemic and is considered a leading cause of death. Various cancer treatments such as chemotherapy, surgery, and radiotherapy are available for the cure but those are generally associated with poor long-term survival rates. Consequently, more advanced and selective methods that have better outcomes, fewer side effects, and high efficacies are highly in demand. Among these is the use of superparamagnetic iron oxide nanoparticles (SPIONs) which act as an innovative kit for battling cancer. Low cost, magnetic properties and toxicity properties enable SPIONs to be widely utilized in biomedical applications. For example, magnetite and maghemite (Fe3O4 and γ-Fe2O3) exhibit superparamagnetic properties and are widely used in drug delivery, diagnosis, and therapy. These materials are termed SPIONs when their size is smaller than 20 nm. This review article aims to provide a brief introduction on SPIONs, focusing on their fundamental magnetism and biological applications. The quality and surface chemistry of SPIONs are crucial in biomedical applications; therefore an in-depth survey of synthetic approaches and surface modifications of SPIONs is provided along with their biological applications such as targeting, site-specific drug delivery and therapy.

Therapeutic efficacy of nanoparticles and routes of administration

In modern-day medicine, nanotechnology and nanoparticles are some of the indispensable tools in disease monitoring and therapy. The term “nanomaterials” describes materials with nanoscale dimensions (< 100 nm) and are broadly classified into natural and synthetic nanomaterials. However, “engineered” nanomaterials have received significant attention due to their versatility. Although enormous strides have been made in research and development in the field of nanotechnology, it is often confusing for beginners to make an informed choice regarding the nanocarrier system and its potential applications. Hence, in this review, we have endeavored to briefly explain the most commonly used nanomaterials, their core properties and how surface functionalization would facilitate competent delivery of drugs or therapeutic molecules. Similarly, the suitability of carbon-based nanomaterials like CNT and QD has been discussed for targeted drug delivery and siRNA therapy. One of the biggest challenges in the formulation of drug delivery systems is fulfilling targeted/specific drug delivery, controlling drug release and preventing opsonization. Thus, a different mechanism of drug targeting, the role of suitable drug-laden nanocarrier fabrication and methods to augment drug solubility and bioavailability are discussed. Additionally, different routes of nanocarrier administration are discussed to provide greater understanding of the biological and other barriers and their impact on drug transport. The overall aim of this article is to facilitate straightforward perception of nanocarrier design, routes of various nanoparticle administration and the challenges associated with each drug delivery method.

Morpholino-functionalized phosphorus dendrimers for precision regenerative medicine: osteogenic differentiation of mesenchymal stem cells

A novel bioactive macromolecule based on morpholino-functionalized phosphorus dendrimers (generation 2, G2-Mor⁺) was developed for osteogenic differentiation of mesenchymal stem cells (MSCs). Interestingly, through in vitro tests, it was shown that G2-Mor⁺ dendrimer can strongly promote the transformation of MSCs into osteoblasts, which implies the potential application of phosphorus dendrimers in bone regeneration for precision regenerative medicine.

Multimodal Composite Iron Oxide Nanoparticles for Biomedical Applications

Background

Iron oxide nanoparticles (IONPs) are excellent candidates for biomedical imaging because of unique characteristics like enhanced colloidal stability and excellent in vivo biocompatibility. Over the last decade, material scientists have developed IONPs with better imaging and enhanced optical absorbance properties by tuning their sizes, shape, phases, and surface characterizations. Since IONPs could be detected with magnetic resonance imaging, various attempts have been made to combine other imaging modalities, thereby creating a high-resolution imaging platform. Composite IONPs (CIONPs) comprising IONP cores with polymeric or inorganic coatings have recently been documented as a promising modality for therapeutic applications.

Methods

In this review, we provide an overview of the recent advances in CIONPs for multimodal imaging and focus on the therapeutic applications of CIONPs.

Result

CIONPs with phototherapeutics, IONP-based nanoparticles are used for theranostic application via imaging guided photothermal therapy.

Conclusion

CIONP-based nanoparticles are known for theranostic application, longstanding effects of composite NPs in in vivo systems should also be studied. Once such issues are fixed, multifunctional CIONP-based applications can be extended for theranostics of diverse medical diseases in the future.

Polyethylenimine-Based Nanogels for Biomedical Applications

Nanogels (NGs) are 3-dimensional (3D) networks composed of hydrophilic or amphiphilic polymer chains, allowing for effective and homogeneous encapsulation of drugs, genes, or imaging agents for biomedical applications. Polyethylenimine (PEI), possessing abundant positively charged amine groups, is an ideal platform for the development of NGs. A variety of effective PEI-based NGs have been designed and much effort has been devoted to study the relationship between the structure and function of the NGs. In particular, PEI-based NGs can be prepared either using PEI as the major NG component or using PEI as a crosslinker. This review reports the recent progresses in the design of PEI-based NGs for gene and drug delivery and for bioimaging applications with a target focus to tackle the diagnosis and therapy of cancer.

Zwitterionic Gadolinium(III)-Complexed Dendrimer-Entrapped Gold Nanoparticles for Enhanced Computed Tomography/Magnetic Resonance Imaging of Lung Cancer Metastasis

Design of dual mode or multimode contrast agents or nanoplatforms with antifouling properties is crucial for improved cancer diagnosis since the antifouling materials are able to escape the clearance of the reticuloendothelial system with improved pharmacokinetics. Herein, we present the creation of zwitterionic gadolinium(III) (Gd(III))-complexed dendrimer-entrapped gold nanoparticles (Au DEN) for enhanced dual mode computed tomography (CT)/magnetic resonance (MR) imaging of lung cancer metastasis. In the present work, poly(amidoamine) (PAMAM) dendrimers of generation 5 were partially decorated with carboxybetanie acrylamide (CBAA), 2-methacryloyloxyethyl phosphorylcholine (MPC), and 1,3-propane sultone (1,3-PS), respectively at different degrees, then used to entrap Au NPs within their interiors, and finally acetylated to cover their remaining amine termini. Through protein resistance, macrophage cellular uptake, and pharmacokinetics assays, we show that zwitterionic Au DEN modified with 1,3-PS exhibit the best antifouling property with the longest half-decay time (37.07 h) when compared to the CBAA- and MPC-modified Au DEN. Furthermore, with the optimized zwitterion type, we then prepared zwitterionic Gd(III)-loaded Au DEN modified with arginine-glycine-aspartic acid peptide for targeted dual mode CT/MR imaging of a lung cancer metastasis model. We disclose that the designed multifunctional Au DEN having an Au core size of 2.7 nm and a surface potential of 7.6 ± 0.9 mV display a good X-ray attenuation property, relatively high r₁ relaxivity (13.17 mM s^-1), acceptable cytocompatibility, and targeting specificity to α_vβ₃ integrin-expressing cancer cells and enable effective dual mode CT/MR imaging of a lung cancer metastasis model in vivo. The developed multifunctional zwitterion-functionalized Au DEN may be potentially adopted as an effective nanoprobe for enhanced dual-modal CT/MR imaging of other cancer types.

Poly(amidoamine) Dendrimer-Coordinated Copper(II) Complexes as a Theranostic Nanoplatform for the Radiotherapy-Enhanced Magnetic Resonance Imaging and Chemotherapy of Tumors and Tumor Metastasis

The development of a powerful nanoplatform to realize the simultaneous therapy and diagnosis of cancer using a similar element for theranostics remains a critical challenge. Herein, we report such a theranostic nanoplatform based on pyridine (Pyr)-functionalized generation 5 (G5) poly(amidoamine) dendrimers complexed with copper(II) (Cu(II)) for radiotherapy-enhanced T₁-weighted magnetic resonance (MR) imaging and the synergistic radio-chemotherapy of both tumors and tumor metastasis. In this study, amine-terminated G5 dendrimers were covalently linked with 2-pyridinecarboxylic acid, acetylated to neutralize their remaining terminal amines, and complexed with Cu(II) through both the internal tertiary amines and the surface Pyr groups to form the G5.NHAc-Pyr/Cu(II) complexes. We show that the complexes are able to inhibit the proliferation of different cancer cell lines with half-maximal inhibitory concentrations ranging from 4 to 10 μM and induce significant cancer cell apoptosis. Due to the presence of Cu(II), the G5.NHAc-Pyr/Cu(II) complexes display an r₁ relaxivity of 0.7024 mM^-1 s^-1, enabling effective in vivo MR imaging of tumor xenografts and lung metastatic nodules. Further, under radiotherapy (RT) conditions, the tumor MR imaging sensitivity can be significantly enhanced, and the G5.NHAc-Pyr/Cu(II) complexes enable the enhanced chemotherapy of both a xenografted tumor model and a blood-vessel metastasis model. With the demonstrated theranostic potential of the dendrimer-Cu(II) nanocomplexes without additional agents or elements for RT-enhanced MR imaging and chemotherapy of tumor and tumor metastasis, this novel Cu(II)-based nanohybrids may hold great promise for the theranostics of different cancer types and metastases.

Design of dual drug-loaded dendrimer/carbon dot nanohybrids for fluorescence imaging and enhanced chemotherapy of cancer cells

Dual drug-loaded dendrimer/CD nanohybrids can be developed for fluorescence imaging and enhanced chemotherapy of cancer cells.