Facile formation of dendrimer-stabilized gold nanoparticles modified with diatrizoic acid for enhanced computed tomography imaging applications

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.

Significance of Capping Agents of Colloidal Nanoparticles from the Perspective of Drug and Gene Delivery, Bioimaging, and Biosensing: An Insight

The over-growth and coagulation of nanoparticles is prevented using capping agents by the production of stearic effect that plays a pivotal role in stabilizing the interface. This strategy of coating the nanoparticles’ surface with capping agents is an emerging trend in assembling multipurpose nanoparticles that is beneficial for improving their physicochemical and biological behavior. The enhancement of reactivity and negligible toxicity is the outcome. In this review article, an attempt has been made to introduce the significance of different capping agents in the preparation of nanoparticles. Most importantly, we have highlighted the recent progress, existing roadblocks, and upcoming opportunities of using surface modified nanoparticles in nanomedicine from the drug and gene delivery, bioimaging, and biosensing perspectives.

Matrix Metalloproteinase Enzyme Responsive Delivery of 5-Fluorouracil Using Collagen-I Peptide Functionalized Dendrimer-Gold Nanocarrier

ObjectiveThe aim was to develop matrix metalloproteinase 1 (MMP1) responsive nanoparticle system for the delivery of 5-fluorouracil (5Fu) anticancer drug.SignificanceThe MMP1 in the cancer microenvironment induced drug release have advantage of targeted drug release and reduce the distribution of drug to the healthy tissuesMethodG5 polyamidoamine PAMAM dendrimer (G5) coated gold nanoparticles were synthesized and loaded with 5Fu. The drug loaded nanoparticles were further coated with collagen I (Col-I) peptide which is a substrate for MMP1 enzyme (Col-I 5Fu@G5AuNP).ResultThe nanoparticles were highly monodispersed with a particle size of 30 nm and showed high drug encapsulation efficiency. The release of drug from the nanoparticles in HEPES buffer pH 7.4 was faster, higher and better controlled when incubated with MMP1 enzyme. The half-maximum inhibitory concentration for Col-I 5Fu@G5AuNP was eight times lower than the 5Fu against MCF-7, suggesting the improved delivery and anticancer activity of 5Fu after encapsulation in the developed enzyme-responsive nanocarrier system. The computed tomography (CT) x-ray attenuation of Col-I@G5AuNP showed a good contrasting property.ConclusionThe formulation Col-I 5Fu@G5AuNP has improved anticancer activity than free drug and the CT imaging results are promising for its theranostic applications for breast cancer.

Core-Shell Tecto Dendrimers Enable Enhanced Tumor MR Imaging through an Amplified EPR Effect

Development of nanoplatforms that can amplify the passive tumor targeting effect based on enhanced permeability and retention (EPR) effect is crucial for precision cancer nanomedicine applications. Herein, we present the development of core-shell tecto dendrimers (CSTDs) as a platform for enhanced tumor magnetic resonance (MR) imaging through an amplified EPR effect. In this work, poly(amidoamine) (PAMAM) dendrimers of generation 5 (G5) were decorated with β-cyclodextrin (CD) and then assembled with G3 PAMAM dendrimers premodified with adamantane (Ad) via supramolecular recognition of CD and Ad. The formed G5-CD/Ad-G3 CSTDs were conjugated with tetraazacyclododecane tetraacetic acid (DOTA)-Gd(III) chelators and further acetylated to neutralize the remaining CSTD periphery amines. We reveal that the formed CSTD.NHAc-DOTA(Gd) (CSTD-D-Gd) complexes have a narrow size distribution and satisfactory colloidal stability, and are cytocompatible within the concentration range studied. Compared to the single dendrimer counterpart of G5.NHAc-DOTA(Gd) (G5-D-Gd) complexes, the CSTD-D-Gd complexes with a higher molecular weight and volume possess a longer rotation correlation time, hence having a longitudinal relaxivity (r₁) of 7.34 mM^-1 s^-1, which is 1.5 times larger than that of G5-D-Gd complexes (4.92 mM^-1 s^-1). More importantly, the CSTD-D-Gd complexes display better permeability in the three-dimensional (3D) cell spheroids in vitro through fluorescence imaging and a more significant EPR effect for improved tumor MR imaging in vivo than the G5-DOTA-Gd complexes. The generated CSTD-D-Gd complexes may be adopted for enhanced tumor MR imaging through an amplified passive EPR effect and also be further extended for different cancer theranostic applications.

Engineered non-invasive functionalized dendrimer/dendron-entrapped/complexed gold nanoparticles as a novel class of theranostic (radio)pharmaceuticals in cancer therapy

Nanomedicine represents a very significant contribution in current cancer treatment; in addition to surgical intervention, radiation and chemotherapeutic agents that unfortunately also kill healthy cells, inducing highly deleterious and often life-threatening side effects in the patient. Of the numerous nanoparticles used against cancer, gold nanoparticles had been developed for therapeutic applications. Inter alia, a large variety of dendrimers, i.e. soft artificial macromolecules, have turned up as non-viral functional nanocarriers for entrapping drugs, imaging agents, and targeting molecules. This review will provide insights into the design, synthesis, functionalization, and development in biomedicine of engineered functionalized hybrid dendrimer-tangled gold nanoparticles in the domain of cancer theranostic. Several aspects are highlighted and discussed such as 1) dendrimer-entrapped gold(0) hybrid nanoparticles for the targeted imaging and treatment of cancer cells, 2) dendrimer encapsulating gold(0) nanoparticles (Au DENPs) for the delivery of genes, 3) Au DENPs for drug delivery applications, 4) dendrimer encapsulating gold radioactive nanoparticles for radiotherapy, and 5) dendrimer/dendron-complexed gold(III) nanoparticles as technologies to take down cancer cells.

Rapid Sonochemically-Assisted Synthesis of Highly Stable Gold Nanoparticles as Computed Tomography Contrast Agents

One of the most widely used modalities of clinical imaging is computed tomography (CT). Recent reports of new contrast agents toward CT imaging have been numerous. The production of gold nanoparticles (AuNPs) as contrast agents for CT is primarily a topic of intense interest. AuNPs have beneficial features for this application, including excellent X-ray attenuation, flexible sizes and shapes, tailorable surface chemistry, excellent biocompatibility and high levels of contrast generating matter. AuNPs with a size of about 18.5 nm and semi-spherical shape were synthesized using a sonochemical method. The attenuation rate of X-rays as measured in Hounsfield units per unit concentration (HU/mg) was measured. Ultrasound treatment for a duration of five min has been shown to produce highly stable AuNPs in different media (AuNPs in water and phosphate-buffered saline (PBS) was −42.1 mV and −39.5 mV, respectively). The CT value (HU = 395) of the AuNPs increased linearly with an increase in the AuNP dosage. The results confirm the use of ultrasonic treatment for the production of metal nanostructures, particularly highly stable non-toxic AuNPs, with good morphology and high-quality crystal structure using an easy and fast method. Synthesized AuNPs have the potential to be used as a CT contrast agent in medical imaging applications.

New insights into the synthesis, toxicity and applications of gold nanoparticles in CT imaging and treatment of cancer

The past decades have witnessed enormous development of gold nanoparticles (AuNPs) and their applications in the biomedical field, an area in which they show infinite potential. Abundant investigations have been conducted in improving AuNP synthesis, aimed at obtaining water-dispersible ultrasmall AuNPs, which can exhibit biocompatibility, renal clearance and minimal toxicity. Due to their excellent x-ray attenuation ability, special optical properties and surface modification properties, AuNPs are reported to be promising as computed tomography contrast agents and can be applied in radiotherapy, photothermal and photodynamic therapies, and drug delivery. In this review, synthesis methods and toxicity of AuNPs have been summarized, emphasizing the preparation of ultra-small AuNPs. Applications of AuNPs in computed tomography imaging and cancer treatment are also considered, revealing their potential in the clinic.

A Dendrimer-Based Dual Radiodense Element-Containing Nanoplatform for Targeted Enhanced Tumor Computed Tomography Imaging

The exploration of original computed tomography (CT) imaging contrast agents with enhanced sensitivity and specificity is currently one of the major challenging tasks for precision medicine. Herein, we develop an innovative nanoprobe of dendrimer-stabilized gold nanoparticles (Au DSNs) linked with folic acid (FA) as a targeting ligand and diatrizoic acid (DTA) for specific enhanced tumor CT imaging. In current work, poly(amidoamine) (PAMAM) dendrimers of generation 5 (G5) with amine termini were adopted to entrap Au NPs through a stepwise complexation/reduction method to achieve a higher Au loading than the conventional one-step complexation/reduction method. The prepared [(Au⁰)₁₂₀-G5.NH₂] NPs were sequentially functionalized with diatrizoic acid (DTA), a typical CT contrast agent based on iodine(I), FA through a poly(ethylene glycol) (PEG) spacer, and carboxylated PEG monomethyl ether (mPEG-COOH), ended with complete acetylation of the leftover dendrimer amine termini. The generated Au DSNs-DTA-FA (Au core diameter = 5.9 nm) were thoroughly characterized. Our data reveal that the Au DSNs-DTA-FA containing Au and I dual radiodense elements are stable, display enhanced CT imaging performance, much higher than the single-radiodense elemental material solely based on Au or I, and possess a quite good cytocompatibility. With the demonstrated FA-rendered specific targeting, the developed Au DSNs-DTA-FA can be employed as a highly efficient nanoprobe for targeted enhanced CT imaging of cancer cells and a subcutaneous tumor model. Overall, the created Au DSNs-DTA-FA may be a powerful nanoprobe for specific enhanced CT imaging of various kinds of FA receptor-expressing tumors or biosystems.

Nanoparticle- and Nanoporous-Membrane-Mediated Delivery of Therapeutics

Pharmaceutical particulates and membranes possess promising prospects for delivering drugs and bioactive molecules with the potential to improve drug delivery strategies like sustained and controlled release. For example, inorganic-based nanoparticles such as silica-, titanium-, zirconia-, calcium-, and carbon-based nanomaterials with dimensions smaller than 100 nm have been extensively developed for biomedical applications. Furthermore, inorganic nanoparticles possess magnetic, optical, and electrical properties, which make them suitable for various therapeutic applications including targeting, diagnosis, and drug delivery. Their properties may also be tuned by controlling different parameters, e.g., particle size, shape, surface functionalization, and interactions among them. In a similar fashion, membranes have several functions which are useful in sensing, sorting, imaging, separating, and releasing bioactive or drug molecules. Engineered membranes have been developed for their usage in controlled drug delivery devices. The latest advancement in the technology is therefore made possible to regulate the physico-chemical properties of the membrane pores, which enables the control of drug delivery. The current review aims to highlight the role of both pharmaceutical particulates and membranes over the last fifteen years based on their preparation method, size, shape, surface functionalization, and drug delivery potential.

Anti-CD24 bio Modified PEGylated Gold Nanoparticles as Targeted Computed Tomography Contrast Agent

Purpose: Molecular imaging is one of the import methods for recognition of cancer at the early stage in order to enhance the capacity of remedy. This study was aimed to introduce a new contrast agent that was targeted with CD24 so as to improve the CT scan detection of cancer cells with higher CD24 expression. Methods: The surface modifications of gold nanoparticles (Au-NPs) were done with long PEG (HS-PEG-CH3O) and short PEG (HS-PEG-COOH) chains to enhance their stability and capacity for immobilization of different antibodies. MTT assay was carried out to assess the biocompatibility of the NPs. The obtained contrast agent was implemented in the targeted CT imaging based on in vitro and in vivo studies of breast cancer. Results: The results revealed that the attached CD24 to the cell surface of PEGylated Au-NPs could enhance significantly the cells CT number (40.45 HU in 4T1, while it was 16.61 HU in CT26) It was shown that the attenuation coefficient of the molecularly targeted cells was more than 2 times excessive than the control groups. Further, the tumor region in model of xenograft tumor has higher density compare to the omnipaque groups, 60 min after injection (45 Hu vs.81 Hu). These results showed that the nanoparticles stayed in tumor region for longer time. Conclusion: It is predicted that the synthesized nanoparticle can be used as computed tomography contrast agent. Also, it can be used to identify the tumor cells with higher expression of CD24 at the early stages more efficiently compare to the other routine methods.

Dendrimer as a multifunctional capping agent for metal nanoparticles for use in bioimaging, drug delivery and sensor applications

Various strategies (single & multi-pot) to synthesize dendrimer-coated metal nanoparticles and their exploration in various biomedical applications.

Iodinated Echogenic Glycol Chitosan Nanoparticles for X-ray CT/US Dual Imaging of Tumor

Development of biopolymer-based imaging agents which can access rapidly and provide detailed information about the diseases has received much attention as an alternative to conventional imaging agents. However, development of biopolymer-based nanomaterials for tumor imaging still remains challenging due to their low sensitivity and image resolution. To surmount of these limitations, multimodal imaging agents have been developed, and they were widely utilized for theranostic applications. Herein, iodine containing echogenic glycol chitosan nanoparticles are developed for x-ray computed tomography (CT) and ultrasound (US) imaging of tumor diagnosis. X-ray CT/US dual-modal imaging probe was prepared by following below two steps. First, iodine-contained diatrizoic acid (DTA) was chemically conjugated to the glycol chitosan (GC) for the CT imaging. DTA conjugated GC (GC-DTA NPs) formed stable nanoparticles with an average diameter of 315 nm. Second, perfluoropentane (PFP), a US imaging agent, was physically encapsulated into GC-DTA NPs by O/W emulsion method yielding GC-DTA-PFP nanoparticles (GC-DTA-PFP NPs). The GC-DTA-PFP NPs formed nanoparticles in physiological condition, and they presented the strong x-ray CT, and US signals in phantom test in vitro. Importantly, GC-DTA-PFP NPs were effectively accumulated on the tumor site by enhanced permeation and retention (EPR) effects. Moreover, GC-DTA-PFP NPs showed x-ray CT, and US signals in tumor tissues after intratumoral and intravenous injection, respectively. Therefore, GC-DTA-PFP NPs indicated that x-ray CT/US dual-modal imaging using iodinated echogenic nanoparticles could be provided more comprehensive and accurate diagnostic information to diagnosis of tumor.

Folic acid-modified diatrizoic acid-linked dendrimer-entrapped gold nanoparticles enable targeted CT imaging of human cervical cancer

It has been a great challenge to develop multifunctional fluorescent nanoprobes for tumor-targeted imaging. In this study, we developed folic acid (FA) gold nanoparticles (AuNPs) through diatrozic acid (DTA) linking for in vitro and in vivo targeted imaging of HeLa cervical cancer cells by computed tomography (CT). G5 dendrimers were used as templates to synthesize AuNPs within the interiors of dendrimers. The synthesized AuNPs were then sequentially modified by fluorescein isothiocyanate, FA, and DTA and the remaining terminal amines on the dendrimers were acetylated. We further performed hematoxylin and eosin staining, cell viability assay, flow cytometric analysis of cell cycle and apoptosis, and hemolytic assay to examine the cytotoxicity and hemocompatibility of the particles. The specific uptake of the nanoparticles by HeLa cells was determined through inductively coupled plasma atomic emission spectroscopy determination of silver and transmission electron microscopy. Lastly, HeLa cells and a xenografted HeLa tumor model were employed to evaluate the in vitro and in vivo targeted CT imaging performances of the nanoparticles, respectively. We showed that Au DENPs-FA-DTA does not cause cytotoxic effects on both HeLa cancer cells and healthy normal cells in mice, demonstrating the superior biocompatibility and stability of the particles in the given concentration range. Micro-CT images documented that HeLa cells incubated with Au DENPs-FA-DTA in vitro could be identified by X-ray examinations and that HeLa cells xenografts in BALB/c nude mice could be imaged after the mice were administered with the particles intravenously or intratumorally. The FA-modified AuNPs enabled targeted CT imaging of HeLa cells overexpressing FA receptors in vitro and in vivo. Taken together, our results showed that the AuNPs we developed exhibit great potentials as imaging probes for targeted CT imaging of human cervical cancer.

Dendrimer-Modified MoS2 Nanoflakes as a Platform for Combinational Gene Silencing and Photothermal Therapy of Tumors

Exploitation of novel hybrid nanomaterials for combinational tumor therapy is challenging. In this work, we synthesized dendrimer-modified MoS₂ nanoflakes for combinational gene silencing and photothermal therapy (PTT) of cancer cells. Hydrothermally synthesized MoS₂ nanoflakes were modified with generation 5 (G5) poly(amidoamine) dendrimers partially functionalized with lipoic acid via disulfide bond. The formed G5-MoS₂ nanoflakes display good colloidal stability and superior photothermal conversion efficiency and photothermal stability. With the dendrimer surface amines on their surface, the G5-MoS₂ nanoflakes are capable of delivering Bcl-2 (B-cell lymphoma-2) siRNA to cancer cells (4T1 cells, a mouse breast cancer cells) with excellent transfection efficiency, inducing 47.3% of Bcl-2 protein expression inhibition. In vitro cell viability assay data show that cells treated with the G5-MoS₂/Bcl-2 siRNA polyplexes under laser irradiation have a viability of 21.0%, which is much lower than other groups of single mode PTT treatment (45.8%) or single mode of gene therapy (68.7%). Moreover, the super efficacy of combinational therapy was further demonstrated by treating a xenografted 4T1 tumor model in vivo. These results suggest that the synthesized G5-MoS₂ nanoflakes may be employed as a potential nanoplatform for combinational gene silencing and PTT of tumors.

Plasmonic behavior of ionic liquid stabilized gold nanoparticles in molecular solvents

In this paper, we have demonstrated the facile synthesis of stable gold nanoparticles (AuNPs) using imidazolium ionic liquids (ImILs) as a stabilizer as well as a surfactant and their surface plasmon resonance (SPR) in different molecular solvents with varying dielectric properties.

Hyaluronic Acid Stabilized Iodine-Containing Nanoparticles with Au Nanoshell Coating for X-ray CT Imaging and Photothermal Therapy of Tumors

In recent years, considerable efforts have been made for the development of multifunctional nanoparticles with diagnosis and therapy functions. To achieve enhanced CT imaging and photothermal therapy on the tumor, we employed iodinated nanoparticles as template to construct Au nanoshell structure and demonstrated a facile but effective approach to synthesize biocompatible and well-dispersed multifunctional nanoparticles by coating iodinated nanoparticles with Au nanoshell and subsequent surface modification by hyaluronic acid. The resultant poly(2-methacryl(3-amide-2,4,6-triiodobenzoic acid))/polyethylenimine/Au nanoshell/hyaluronic acid (PMATIB/PEI/Au nanoshell/HA) nanoparticles had relatively high X-ray attenuation coefficient and photothermal efficiency. After intravenous injection into MCF-7 tumor-bearing mice, PMATIB/PEI/Au nanoshell/HA nanoparticles were efficiently accumulated in the tumor, remarkably enhanced the tumor CT imaging, and selectively ablated the tumor through the thermal treatment of lesions under the NIR irradiation. Thus, PMATIB/PEI/Au nanoshell/HA nanoparticles displayed a great potential for CT diagnosis and CT-guided, focused photothermal tumor therapy.

(99m)Tc-Labeled Multifunctional Low-Generation Dendrimer-Entrapped Gold Nanoparticles for Targeted SPECT/CT Dual-Mode Imaging of Tumors

Development of cost-effective and highly efficient nanoprobes for targeted tumor single-photon emission computed tomography (SPECT)/computed tomography (CT) dual-mode imaging remains a challenging task. Here, multifunctional dendrimer-entrapped gold nanoparticles (Au DENPs) modified with folic acid (FA) and labeled with (99m)Tc were synthesized for targeted dual-mode SPECT/CT imaging of tumors. Generation 2 (G2) poly(amidoamine) (PAMAM) dendrimers (G2-NH2) conjugated with cyclic diethylenetriamine pentaacetic anhydride (cDTPAA) via an amide linkage and FA via a spacer of polyethylene glycol (PEG) were used for templated synthesis of Au core NPs, followed by labeling of (99m)Tc via chelation. The thus created multifunctional Au DENPs were well-characterized. It is shown that particles with an average Au core diameter of 1.6 nm can be dispersed in water, display stability under different conditions, and are cytocompatible in the studied concentration range. Further results demonstrate that the multifunctional nanoprobe is able to be utilized for targeted SPECT/CT dual-mode imaging of cancer cells having FA receptor (FAR)-overexpression in vitro and the established subcutaneous tumor model in vivo within a time frame up to 4 h. The formed multifunctional Au DENPs synthesized using dendrimers of low-generation may be employed as an effective and economic nanoprobe for SPECT/CT imaging of different types of FAR-expressing tumors.

Multifunctional Fe3O4 @ Au core/shell nanostars: a unique platform for multimode imaging and photothermal therapy of tumors

We herein report the development of multifunctional folic acid (FA)-targeted Fe3O4 @ Au nanostars (NSs) for targeted multi-mode magnetic resonance (MR)/computed tomography (CT)/photoacoustic (PA) imaging and photothermal therapy (PTT) of tumors. In this present work, citric acid-stabilized Fe3O4/Ag composite nanoparticles prepared by a mild reduction route were utilized as seeds and exposed to the Au growth solution to induce the formation of Fe3O4 @ Au core/shell NSs. Followed by successive decoration of thiolated polyethyleneimine (PEI-SH), FA via a polyethylene glycol spacer, and acetylation of the residual PEI amines, multifunctional Fe3O4 @ Au NSs were formed. The designed multifunctional NSs possess excellent colloidal stability, good cytocompatibility in a given concentration range, and specific recognition to cancer cells overexpressing FA receptors. Due to co-existence of Fe3O4 core and star-shaped Au shell, the NSs can be used for MR and CT imaging of tumors, respectively. Likewise, the near infrared plasmonic absorption feature also enables the NSs to be used for PA imaging and PTT of tumors. Our study clearly demonstrates a unique theranostic nanoplatform that can be used for high performance multi-mode imaging-guided PTT of tumors, which may be extendable for theranostics of different diseases in translational medicine.

Dendrimer-functionalized LAPONITE® nanodisks loaded with gadolinium for T1-weighted MR imaging applications

Dendrimer-functionalized LAPONITE® nanodisks loaded with gadolinium can be used as an efficient contrast agent for different MR imaging applications.

Gd-Chelated poly(propylene imine) dendrimers with densely organized maltose shells for enhanced MR imaging applications

Gd-Chelated fourth generation poly(propylene imine) dendrimers with densely organized maltose shells can be designed for enhanced MR imaging applications.

Radionuclide (131)I-labeled multifunctional dendrimers for targeted SPECT imaging and radiotherapy of tumors

We report the synthesis, characterization, and utilization of radioactive (131)I-labeled multifunctional dendrimers for targeted single-photon emission computed tomography (SPECT) imaging and radiotherapy of tumors. In this study, amine-terminated poly(amidoamine) dendrimers of generation 5 (G5·NH2) were sequentially modified with 3-(4'-hydroxyphenyl)propionic acid-OSu (HPAO) and folic acid (FA) linked with polyethylene glycol (PEG), followed by acetylation modification of the dendrimer remaining surface amines and labeling of radioactive iodine-131 ((131)I). The generated multifunctional (131)I-G5·NHAc-HPAO-PEG-FA dendrimers were characterized via different methods. We show that prior to (131)I labeling, the G5·NHAc-HPAO-PEG-FA dendrimers conjugated with approximately 9.4 HPAO moieties per dendrimer are noncytotoxic at a concentration up to 20 μM and are able to target cancer cells overexpressing FA receptors (FAR), thanks to the modified FA ligands. In the presence of a phenol group, radioactive (131)I is able to be efficiently labeled onto the dendrimer platform with good stability and high radiochemical purity, and render the platform with an ability for targeted SPECT imaging and radiotherapy of an FAR-overexpressing xenografted tumor model in vivo. The designed strategy to use the facile dendrimer nanotechnology may be extended to develop various radioactive theranostic nanoplatforms for targeted SPECT imaging and radiotherapy of different types of cancer.

Dendrimer-Assisted Formation of Fe3O4/Au Nanocomposite Particles for Targeted Dual Mode CT/MR Imaging of Tumors

A unique dendrimer-assisted approach is reported to create Fe3O4/Au nanocomposite particles (NCPs) for targeted dual mode computed tomography/magnetic resonance (CT/MR) imaging of tumors. In this approach, preformed Fe3O4 nanoparticles (NPs) are assembled with multilayers of poly(γ-glutamic acid) (PGA)/poly(L-lysine)/PGA/folic acid (FA)-modified dendrimer-entrapped gold nanoparticles via a layer-by-layer self-assembly technique. The interlayers are crosslinked via 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide chemistry, the assembled Au core NPs are then used as seed particles for subsequent seed-mediated growth of Au shells via iterative Au salt reduction process, and subsequent acetylation of the remaining amines of dendrimers leads to the formation of Fe3O4/Au(n.)Ac-FA NCPs with a tunable molar ratio of Au/Fe3O4. It is shown that the Fe3O4/Au(n.)Ac-FA NCPs at an optimized Au/Fe3O4 molar ratio of 2.02 display a relatively high R2 relaxivity (92.67 × 10(-3) M(-1) s(-1)) and good X-ray attenuation property, and are cytocompatible and hemocompatible in the given concentration range. Importantly, with the FA-mediated targeting, the Fe3O4/Au(n.)Ac-FA NCPs are able to be specifically uptaken by cancer cells overexpressing FA receptors, and be used as an efficient nanoprobe for targeted dual mode CT/MR imaging of a xenografted tumor model. With the versatile dendrimer chemistry, the developed Fe3O4/Au NCPs may be differently functionalized, thereby providing a unique platform for diagnosis and therapy of different biological systems.

Arg-Gly-Asp-D-Phe-Lys peptide-modified PEGylated dendrimer-entrapped gold nanoparticles for targeted computed tomography imaging of breast carcinoma

AIM

To investigate cyclo (Arg-Gly-Asp-D-Phe-Lys) peptide (RGD)-modified PEGylated dendrimer-entrapped gold nanoparticles (PEGylated Au DENPs-RGD) for targeted computed tomography (CT) imaging of breast carcinomas.

MATERIALS & METHODS

PEGylated Au DENPs-RGD were synthesized and characterized. Then, the PEGylated Au DENPs-RGD for targeted CT imaging were investigated using the MDA-MB-435 cell line, an integrin-rich breast carcinoma cells, and mice with MDA-MB-435 xenograft tumors. Finally, silver enhancement staining and integrin αvβ3 immunohistochemistry of the tumors were performed.

RESULTS

The synthesized PEGylated Au DENPs-RGD were spherical, water dispersible and biocompatible nanoprobes with a gold nanoparticle core size of 2.8 nm. Due to the presence of the Au nanoparticles, the PEGylated Au DENPs-RGD displayed a higher x-ray attenuation intensity than Omnipaque at the same Au or I concentrations. The conjugated RGD ligand can specifically identify and target overexpressed integrin receptors on MDA-MB-435 cells. After intravenous injection, these nanoprobes accumulated in the targeted area of mice with MDA-MB-435 xenograft tumors, which enabled the tumor to be detected by CT imaging. The histological results confirmed the imaging results.

CONCLUSION

The PEGylated Au DENPs-RGD can be used as targeted nanoprobes with good biocompatibility for targeted CT imaging and diagnosis of integrin-positive tumors.

Facile synthesis of folic acid-functionalized iron oxide nanoparticles with ultrahigh relaxivity for targeted tumor MR imaging

We present the polyethyleneimine (PEI)-assisted synthesis of folic acid (FA)-functionalized iron oxide (Fe₃O₄) nanoparticles (NPs) with ultrahigh relaxivity for in vivo targeted tumor magnetic resonance (MR) imaging. In this work, water-dispersible and stable Fe₃O₄ NPs were synthesized in the presence of PEI via a facile mild reduction approach. The surface PEI coating afforded the formed Fe₃O₄ NPs with the ability to be functionalized with polyethylene glycol (PEG)-linked FA and fluorescein isothiocyanate (FI). A further acetylation step to neutralize the remaining PEI surface amines gave rise to the formation of multifunctional FA-functionalized Fe₃O₄ NPs, which were subsequently characterized via different methods. We show that the developed FA-functionalized Fe₃O₄ NPs have a good water-dispersibility, good colloidal stability, ultrahigh r₂ relaxivity (475.92 mM^-1 s^-1), and good hemocompatibility and cytocompatibility in the studied concentration range. The targeting specificity of the FA-modified Fe₃O₄ NPs to FA receptor (FAR)-overexpressing HeLa cells (a human cervical carcinoma cell line) was subsequently validated by flow cytometry and confocal microscopy. Significantly, the developed FA-modified Fe₃O₄ NPs can be used as a nanoprobe for targeted MR imaging of HeLa cells in vitro and the xenografted tumor model in vivo via an active FA-mediated targeting strategy. The developed multifunctional FA-modified Fe₃O₄ NPs with an ultrahigh r₂ relaxivity may be used as an efficient nanoprobe for the targeted MR imaging of various kinds of FAR-overexpressing tumors.

Dendrimer-entrapped gold nanoparticles modified with RGD peptide and alpha-tocopheryl succinate enable targeted theranostics of cancer cells

We report here the synthesis of multifunctional dendrimer-entrapped gold nanoparticles (Au DENPs) modified with alpha-tocopheryl succinate (α-TOS) and arginine-glycine-aspartic acid (RGD) peptide for targeted chemotherapy and computed tomography (CT) imaging of cancer cells. In this work, generation 5 poly(amidoamine) dendrimers pre-conjugated with fluorescein isothiocyanate (FI), RGD peptide via a polyethylene glycol (PEG) spacer, and PEG-linked α-TOS were used as templates to synthesize AuNPs. Followed by acetylation of the remaining dendrimer terminal amines, multifunctional Au DENPs with an Au core size of 4.0nm were generated. The formed multifunctional Au DENPs were characterized via different techniques. We show that the multifunctional Au DENPs are stable at different pH (5-8) and temperature (4-50°C) conditions and display enhanced efficacy in the generation of reactive oxygen species, which is associated with their increased ability to induce apoptosis. Thanks to the role played by RGD-mediated targeting, the multifunctional Au DENPs are able to target cancer cells overexpressing αvβ3 integrin and specifically inhibit the growth of the cancer cells. Likewise, the existence of AuNPs enabled the multifunctional Au DENPs to have a better X-ray attenuation property than clinically used iodinated CT contrast agents (e.g., Omnipaque) and the use of them as a nanoprobe for targeted CT imaging of cancer cells in vitro. The formed multifunctional Au DENPs may hold great promise to be used as a theranostic platform for cancer theranostics.

Multifunctional dendrimer-entrapped gold nanoparticles modified with RGD peptide for targeted computed tomography/magnetic resonance dual-modal imaging of tumors

We report the use of multifunctional dendrimer-entrapped gold nanoparticles (Au DENPs) loaded with gadolinium (Gd) chelator/Gd(III) complexes and surface-modified with thiolated cyclo(Arg-Gly-Asp-Phe-Lys(mpa)) (RGD) peptide for targeted dual-mode computed tomography (CT)/magnetic resonance (MR) imaging of small tumors. In this study, amine-terminated generation 5 poly(amidoamine) dendrimers were used as a nanoplatform to be covalently modified with Gd chelator, RGD via a polyethylene glycol (PEG) spacer, and PEG monomethyl ether. Then the multifunctional dendrimers were used as templates to entrap gold nanoparticles, followed by chelating Gd(III) ions and acetylation of the remaining dendrimer terminal amines. The thus-formed multifunctional Au DENPs (in short, Gd-Au DENPs-RGD) were characterized via different techniques. We show that the multifunctional Au DENPs with a Au core size of 3.8 nm are water-dispersible, stable under different pH (5-8) and temperature conditions (4-50 °C), and noncytotoxic at a Au concentration up to 100 μM. With the displayed X-ray attenuation property and the r1 relaxivity (2.643 mM(-1) s(-1)), the developed Gd-Au DENPs-RGD are able to be used as a dual-mode nanoprobe for targeted CT/MR imaging of an αvβ3 integrin-overexpressing xenografted small tumor model in vivo via RGD-mediated active targeting pathway. The developed multifunctional Gd-Au DENPs-RGD may be used as a promising dual-mode nanoprobe for targeted CT/MR imaging of different types of αvβ3 integrin-overexpressing cancer.

Dendrimer–nanoparticle conjugates in nanomedicine

Nanomedicine can take advantage of the recent developments in nanobiotechnology research areas for the creation of platforms with superior drug carrier capabilities, selective responsiveness to the environment, unique contrast enhancement profiles and improved accumulation at the disease site. Colloidal inorganic nanoparticles (NPs) have been attracting considerable interest in biomedicine, from drug and gene delivery to imaging, sensing and diagnostics. It is essential to modify the NPs surface to have enhanced biocompatibility and reach multifunctional systems for the in vitro and in vivo applications, especially in delivering drugs locally and recognizing overexpressed biomolecules. This paper describes the rational design for dendrimer–nanoparticle conjugates elaboration and reviews their state-of-the-art uses as efficient nanomedicine tools.

Conjugation of multivalent ligands to gold nanoshells and designing a dual modality imaging probe

Design and synthesis of branched tetraethylene glycol (TEG) based ligands for subsequent conjugation to gold nanoshells are reported. TEG enhances the aqueous solubility of hollow gold nanoshells (HAuNShs), and the branched architecture provides stability. An examination of the supernatant of the surface displacement reaction shows that the structure of the ligand plays an important role in the functionalization of HAuNShs. The binding of multivalent ligands leads to rupturing of the gold nanoshell architecture; most probably due to the large dendron not compensating the replacement of small citrate capping agents. The construction of a probe with dual imaging capabilities is demonstrated by covalent linking of a dendron containing Cy5.5_A dye to gold nanoshells. It leads to fluorescence quenching of Cy5.5_A by the gold nanoshells, as evidenced in solution and in cellular internalization studies with J774 and bEnd.3 cells.

Dendrimer-entrapped metal colloids as imaging agents

This review reports the recent advances in dendrimer-entrapped metal colloids as contrast agents for biomedical imaging applications. The versatile dendrimer scaffolds with 3-dimensional spherical shape, highly branched internal cavity, tunable surface conjugation chemistry, and excellent biocompatibility and nonimmunogenicity afford their uses as templates to create multifunctional dendrimer-entrapped metal colloids for mono- or multi- mode molecular imaging applications. In particular, multifunctional dendrimer-entrapped gold nanoparticles with different surface modifications have been used for fluorescence imaging, targeted tumor computed tomography (CT) imaging, enhanced blood pool CT imaging, dual mode CT/MR imaging, and tumor theranostics (combined CT imaging and chemotherapy) will be introduced and discussed in detail.

Insights into the crystallisation process from anhydrous, hydrated and solvated crystal forms of diatrizoic acid

Diatrizoic acid (DTA), a clinically used X-ray contrast agent, crystallises in two hydrated, three anhydrous and nine solvated solid forms, all of which have been characterised by X-ray crystallography. Single-crystal neutron structures of DTA dihydrate and monosodium DTA tetrahydrate have been determined. All of the solid-state structures have been analysed using partial atomic charges and hardness algorithm (PACHA) calculations. Even though in general all DTA crystal forms reveal similar intermolecular interactions, the overall crystal packing differs considerably from form to form. The water of the dihydrate is encapsulated between a pair of host molecules, which calculations reveal to be an extraordinarily stable motif. DTA presents functionalities that enable hydrogen and halogen bonding, and whilst an extended hydrogen-bonding network is realised in all crystal forms, halogen bonding is not present in the hydrated crystal forms. This is due to the formation of a hydrogen-bonding network based on individual enclosed water squares, which is not amenable to the concomitant formation of halogen bonds. The main interaction in the solvates involves the carboxylic acid, which corroborates the hypothesis that this strong interaction is the last one to be broken during the crystal desolvation and nucleation process.

Encapsulation of doxorubicin within multifunctional gadolinium-loaded dendrimer nanocomplexes for targeted theranostics of cancer cells

Multifunctional gadolinium-loaded dendrimer nanocomplexes can be used to encapsulate doxorubicin for targeted magnetic resonance imaging and chemotherapy of cancer cells.

Targeted CT imaging of human hepatocellular carcinoma using low-generation dendrimer-entrapped gold nanoparticles modified with lactobionic acid

Dendrimer-entrapped gold nanoparticles formed using low-generation dendrimers modified with PEGylated lactobionic acid as templates enable targeted CT imaging of human hepatocellular carcinoma.

Poly(γ-glutamic acid)-stabilized iron oxide nanoparticles: synthesis, characterization and applications for MR imaging of tumors

Poly(γ-glutamic acid)-stabilized iron oxide nanoparticles can be formed via a one-step mild reduction for MR imaging of tumors.

Facile synthesis of RGD peptide-modified iron oxide nanoparticles with ultrahigh relaxivity for targeted MR imaging of tumors

RGD peptide-functionalized iron oxide nanoparticles with ultrahigh relaxivity can be synthesized for targeted MR imaging of α_vβ₃ integrin-overexpressing tumors.

Gold nanostars functionalized with amine-terminated PEG for X-ray/CT imaging and photothermal therapy

We present the great potential of gold nanostars decorated with amine-terminated PEG in the application of X-ray/CT-guided photothermal therapy.

Noninvasive detection of macrophages in atherosclerotic lesions by computed tomography enhanced with PEGylated gold nanoparticles

Macrophages are becoming increasingly significant in the progression of atherosclerosis (AS). Molecular imaging of macrophages may improve the detection and characterization of AS. In this study, dendrimer-entrapped gold nanoparticles (Au DENPs) with polyethylene glycol (PEG) and fluorescein isothiocyanate (FI) coatings were designed, tested, and applied as contrast agents for the enhanced computed tomography (CT) imaging of macrophages in atherosclerotic lesions. Cell counting kit-8 assay, fluorescence microscopy, silver staining, and transmission electron microscopy revealed that the FI-functionalized Au DENPs are noncytotoxic at high concentrations (3.0 μM) and can be efficiently taken up by murine macrophages in vitro. These nanoparticles were administered to apolipoprotein E knockout mice as AS models, which demonstrated that the macrophage burden in atherosclerotic areas can be tracked noninvasively and dynamically three-dimensionally in live animals using micro-CT. Our findings suggest that the designed PEGylated gold nanoparticles are promising biocompatible nanoprobes for the CT imaging of macrophages in atherosclerotic lesions and will provide new insights into the pathophysiology of AS and other concerned inflammatory diseases.