Advancing Spinal Cord Injury Bioimaging and Repair with Multifunctional Gold Nanodots Tracking

High levels of reactive oxygen species (ROS) are known to play a critical role in the secondary cascade of spinal cord injury (SCI). The scavenging of ROS has emerged as a promising approach for alleviating acute SCI. Moreover, identifying the precise location of the SCI site remains challenging. Enhancing the visualization of the spinal cord and improving the ability to distinguish the lesion site are crucial for accurate and safe treatment. Therefore, there is an urgent clinical need to develop a biomaterial that integrates diagnosis and treatment for SCI. Herein, ultra-small-sized gold nanodots (AuNDs) were designed for dual-mode imaging-guided precision treatment of SCI. The designed AuNDs demonstrate two important functions. First, they effectively scavenge ROS, inhibit oxidative stress, reduce the infiltration of inflammatory cells, and prevent apoptosis. This leads to a significant improvement in SCI repair and promotes a functional recovery after injury. Second, leveraging their excellent dual-mode imaging capabilities, the AuNDs enable rapid and accurate identification of SCI sites. The high contrast observed between the injured and adjacent uninjured areas highlights the tremendous potential of AuNDs for SCI detection. Overall, by integrating ROS scavenging and dual-mode imaging in a single biomaterial, our work on functionalized AuNDs provides a promising strategy for the clinical diagnosis and treatment of SCI.

Natural alkaloids from Dicranostigma leptopodum (Maxim.) Fedde and their G5. NHAc-PBA dendrimer-alkaloid complexes for targeting chemotherapy in breast cancer MCF-7 cells

Herein, we isolated five natural alkaloids, iso-corydine (iso-CORY), corydine (CORY), sanguinarine (SAN), chelerythrine (CHE) and magnoflorine (MAG), from traditional medicinal herb Dicranostigma leptopodum (Maxim.) Fedde (whole herb) and elucidated their structures. Then we synthesised G5. NHAc-PBA as targeting dendrimer platform to encapsulate the alkaloids into G5. NHAc-PBA-alkaloid complexes, which demonstrated alkaloid-dependent positive zeta potential and hydrodynamic particle size. G5. NHAc-PBA-alkaloid complexes demonstrated obvious breast cancer MCF-7 cell targeting effect. Among the G5. NHAc-PBA-alkaloid complexes, G5.NHAc-PBA-CHE (IC50=13.66 μM) demonstrated the highest MCF-7 cell inhibition capability and G5.NHAc-PBA-MAG (IC50=24.63 μM) had equivalent inhibitory effects on cell proliferation that comparable to the level of free MAG (IC50=23.74 μM), which made them the potential breast cancer targeting formulation for chemotherapeutic application. This work successfully demonstrated a pharmaceutical research model of 'natural bioactive product isolation-drug formulation preparation-breast cancer cell targeting inhibition'.

Recent Advances in Engineering Carriers for siRNA Delivery

RNA interference (RNAi) technology has been a promising treatment strategy for combating intractable diseases. However, the applications of RNAi in clinical are hampered by extracellular and intracellular barriers. To overcome these barriers, various siRNA delivery systems have been developed in the past two decades. The first approved RNAi therapeutic, Patisiran (ONPATTRO) using lipids as the carrier, for the treatment of amyloidosis is one of the most important milestones. This has greatly encouraged researchers to work on creating new functional siRNA carriers. In this review, the recent advances in siRNA carriers consisting of lipids, polymers, and polymer-modified inorganic particles for cancer therapy are summarized. Representative examples are presented to show the structural design of the carriers in order to overcome the delivery hurdles associated with RNAi therapies. Finally, the existing challenges and future perspective for developing RNAi as a clinical modality will be discussed and proposed. It is believed that the addressed contributions in this review will promote the development of siRNA delivery systems for future clinical applications.

An application of carbohydrate polymers-based surface-modified gold nanoparticles for improved target delivery to liver cancer therapy - A systemic review

Gold nanoparticles have been broadly investigated as cancer diagnostic and therapeutic agents. Gold nanoparticles are a favorable drug delivery vehicle with their unique subcellular size and good biocompatibility. Chitosan, agarose, fucoidan, porphyran, carrageenan, ulvan and alginate are all examples of biologically active macromolecules. Since they are biocompatible, biodegradable, and irritant-free, they find extensive application in biomedical and macromolecules. The versatility of these compounds is enhanced because they are amenable to modification by functional groups like sulfation, acetylation, and carboxylation. In an eco-friendly preparation process, the biocompatibility and targeting of GNPs can be improved by functionalizing them with polysaccharides. This article provides an update on using carbohydrate-based GNPs in liver cancer treatment, imaging, and drug administration. Selective surface modification of several carbohydrate types and further biological uses of GNPs are focused on.

Hetero-Trifunctional Malonate-Based Nanotheranostic System for Targeted Breast Cancer Therapy

Designing multifunctional linkers is crucial for tricomponent theranostic targeted nanomedicine development as they are essential to enrich polymeric systems with different functional moieties. Herein, we have obtained a hetero-trifunctional linker from malonic acid and demonstrated its implication as an amphiphilic targeted nanotheranostic system (CB DX UN PG FL). We synthesized it with varying hydrophilic segment to fine-tune the hydrophobic/hydrophilic ratio to optimize its self-assembly. pH-responsive hydrazone-linked doxorubicin was conjugated to the backbone (UN PG FL) containing folate as a targeting ligand. Cobalt carbonyl complex was used for T₂-weighted magnetic resonance imaging (MRI). Electron micrographs of optimized molecule CB DX UN PG_(4 kDa) FL in an aqueous system have demonstrated about 50-60 nm-sized uniform micelles. The relaxivity study and the one-dimensional (1D) imaging experiments clearly revealed the effect of the nanotheranostics system on transverse relaxation (T₂) of water molecules, which validated the system as a T₂-weighted MRI contrast agent. The detailed in vitro biological studies validated the targeted delivery and anticancer potential of CB DX UN PG_(4 kDa) FL. Combining the data on transverse relaxation, folate mediated uptake, and anticancer activity, the designed molecule will have a significant impact on the development of targeted theranostic.

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.

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.

Targeted Combination of Antioxidative and Anti-Inflammatory Therapy of Rheumatoid Arthritis using Multifunctional Dendrimer-Entrapped Gold Nanoparticles as a Platform

Abundant reactive oxygen species and tumor necrosis factor-α (TNF-α) cytokine supply of M1-type macrophages boost rheumatoid arthritis (RA) pathological process. For efficient RA therapy, here a multifunctional nanoplatform is presented based on generation 5 (G5) poly(amidoamine) dendrimer-entrapped gold nanoparticles (Au DENPs) to achieve co-delivery of antioxidant alpha-tocopheryl succinate (α-TOS) and anti-inflammatory anti-TNF-α siRNA to macrophage cells. G5 dendrimers with amine termini are sequentially functionalized with 1,3-propane sultone (1,3-PS), α-TOS through a polyethylene glycol (PEG) spacer, and PEGylated folic acid (FA), and subsequently entrapped with Au NPs. The generated functional Au DENPs exhibit desired cytocompatibility, zwitterion-rendered antifouling property, and FA-mediated targeting specificity, enabling serum-enhanced siRNA delivery to M1-type macrophage cells. Meanwhile, the attached α-TOS affords enhanced oxidation resistance of macrophage cells. In vivo investigation shows that the treatment of a collagen-induced arthritis mouse model using α-TOS-modified Au DENPs/TNF-α siRNA polyplexes can achieve excellent combination therapy effect in inflammatory cytokines downregulation of RA lesion and bone erosions. The therapeutic efficacy is also supported by 3D micro-computed tomography analysis and TNF-α cytokine reduction of RA lesion joints in the mRNA, protein, and histology levels. The created multifunctional nanoplatform may be employed in antioxidative and anti-inflammatory combination therapy of RA.

Functional LAPONITE Nanodisks Enable Targeted Anticancer Chemotherapy in Vivo

Development of nanoplatforms for targeted anticancer drug delivery for effective tumor therapy still remains challenging in the development of nanomedicine. Here, we present a facile method to formulate a LAPONITE (LAP) nanodisk-based nanosystem for anticancer drug doxorubicin (DOX) delivery to folic acid (FA) receptor-overexpressing tumors. In the current work, aminated LAP nanodisks were first prepared through silanization, then functionalized with polyethylene glycol-linked FA (PEG-FA) via 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) chemistry, and finally employed to physically encapsulate DOX. The formed functional LAP nanodisks (for short, LM-PEG-FA) possess a high DOX loading efficiency (88.6 ± 1.2%) and present a pH-dependent release feature with a quicker DOX release under acidic pH conditions (pH 5.0) than under physiological pH conditions (pH 7.4). In vitro flow cytometry, confocal microscopic observation, and cell viability assay show that the LM-PEG-FA/DOX complexes can be specifically taken up by FAR-overexpressing human ovarian cancer cells (SK-OV-3 cells) and present a specific cancer cell therapeutic effect. Further tumor treatment results reveal that the LM-PEG-FA/DOX complexes can exert a specific therapeutic efficacy to a xenografted SK-OV-3 tumor model in vivo when compared with nontargeted LM-mPEG/DOX complexes. Therefore, the developed LM-PEG-FA nanodisks could be employed as a potential platform for targeted cancer chemotherapy.

Review on marine carbohydrate-based gold nanoparticles represented by alginate and chitosan for biomedical application

Gold nanoparticles (AuNPs) have been attracted considerable attention in cancer therapy, drug delivery and other applications due to their unique physical, chemical, and optical properties. Marine carbohydrates are important biological macromolecules that widely exist in marine algae and animals, such as alginate, carrageenan, porphyran, fucoidan, ulvan, agarose, and chitosan. Their excellent properties, such as biocompatibility, biodegradability and no irritation, make them widely used in biomedicine and nanomaterials fields. More importantly, they can be easily modified by functional groups, such as sulfation, acetylation, and carboxylation, to further extend their applications. The marine carbohydrates functionalized AuNPs can increase their biocompatibility and targeting in a green preparation method. Here, we review recent advances on marine carbohydrate-based AuNPs for cancer therapy, imaging, drug delivery and other biomedical fields. The topics of selective surface modification in different carbohydrates and further biomedical applications of AuNPs are also discussed.

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.

Imaging-based Biomarkers for Predicting and Evaluating Cancer Immunotherapy Response

Proper patient selection for immunotherapy is critical, as certain tumor microenvironments are more permissible to therapy than others. Currently, the use of programmed cell death ligand-1 (PD-L1) and microsatellite instability high and/or mismatch repair deficiency are used as biomarkers for immunotherapy response. To improve tumor characterization, methodologies are being developed to combine imaging with tumor immune environment characterization. Imaging of tumors from immunotherapy responders and nonresponders with various imaging modalities has led to the development of criteria that could predict patient response to immunotherapy. Additionally, radiomics-based artificial intelligence methods are being used to characterize tumor microenvironments to predict and evaluate immunotherapy responses, as well as to predict risk of immune-related adverse events. Molecular imaging techniques are also being developed for various modalities to observe tumor expression of immunotherapy targets, such as PD-L1 and, to confirm the target is being expressed on resident tumors. In all, the advancements of imaging techniques to define tumor immunologic characteristics will help to stratify patients who are more likely to respond to immunotherapies. Keywords: Computer Aided Diagnosis (CAD), Computer Applications-Virtual Imaging, Efficacy Studies, MR-Imaging, Molecular Imaging-Cancer, Molecular Imaging-Immunotherapy, Molecular Imaging-Nanoparticles, Molecular Imaging-Probe Development, Molecular Imaging-Target Development, SPECT/CT © RSNA, 2019.

Targeted gold nanoparticles enable molecular CT imaging of head and neck cancer: An in vivo study

The development of various cost-effective multifunctional contrast agent for specific targeting molecular imaging of tumors presents a great challenge. We report here the in vivo targeting imaging of folic acid (FA) gold nanoparticles (AuNPs) through cysteamine (Cys) linking for targeted of human nasopharyngeal head and neck cancer by computed tomography (CT). The toxicity of nanoparticles in kidney, heart, spleen, brain and liver was evaluated by H&E (hematoxylin and eosin) assay. We showed that the formed FA-Cys-AuNPs with an Au core size of ˜13 nm are non-cytotoxic in the particle concentration of 3 × 10³ μg/ ml. The nude mice were scanned using a 64-slice CT scan with parameters (80 kVp, slice thickness: 0.625 mm, mAs: 200, pitch: 1). CT scan was performed before and after (Three and six hours) I.V (Intra Venous) injection of AuNPs and FA-Cys-AuNPs. The distribution of nanoparticles in the nude mice was evaluated by imaging and coupled plasma optical emission spectrometry (ICP-OES) analysis. The findings clearly illustrated that a small tumor, which is undetectable via computed tomography, is enhanced by X-ray attenuation and becomes visible (4.30-times) by the molecularly targeted AuNPs. It was further demonstrated that active tumor cells targeting (FA-Cys-AuNPs) is more specific and efficient (2.03-times) than passive targeting AuNPs. According to the results, FA-Cys-AuNPs can be employed as a promising contrast agent in CT scan imaging and maybe in radiotherapy that require enhanced radiation dose.

Biomedical Imaging: Principles, Technologies, Clinical Aspects, Contrast Agents, Limitations and Future Trends in Nanomedicines

This review article presents the state-of-the-art in the major imaging modalities supplying relevant information on patient health by real-time monitoring to establish an accurate diagnosis and potential treatment plan. We draw a comprehensive comparison between all imagers and ultimately end with our focus on two main types of scanners: X-ray CT and MRI scanners. Numerous types of imaging probes for both imaging techniques are described, as well as reviewing their strengths and limitations, thereby showing the current need for the development of new diagnostic contrast agents (CAs). The role of nanoparticles in the design of CAs is then extensively detailed, reviewed and discussed. We show how nanoparticulate agents should be promising alternatives to molecular ones and how they are already paving new routes in the field of nanomedicine.

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.

Effects of bisphosphonate ligands and PEGylation on targeted delivery of gold nanoparticles for contrast-enhanced radiographic detection of breast microcalcifications

A preclinical murine model of hydroxyapatite (HA) breast microcalcifications (µcals), which are an important clinical biomarker for breast cancer detection, was used to investigate the independent effects of high affinity bisphosphonate (BP) ligands and a polyethylene glycol (PEG) spacer on targeted delivery of gold nanoparticles (Au NPs) for contrast-enhanced radiographic detection. The addition of BP ligands to PEGylated Au NPs (BP-PEG-Au NPs) resulted in five-fold greater binding affinity for targeting HA µcals, as expected, due to the strong binding affinity of BP ligands for calcium. Therefore, BP-PEG-Au NPs were able to target HA µcals in vivo after intramammary delivery, which enabled contrast-enhanced radiographic detection of µcals in both normal and radiographically dense mammary tissues similar to previous results for BP-Au NPs, while PEG-Au NPs did not. The addition of a PEG spacer between the BP targeting ligand and Au NP surface enabled improved in vivo clearance. PEG-Au NPs and BP-PEG-Au NPs were cleared from all mammary glands (MGs) and control MGs, respectively, within 24-48 h after intramammary delivery, while BP-Au NPs were not. PEGylated Au NPs were slowly cleared from MGs by lymphatic drainage and accumulated in the spleen. Histopathology revealed uptake of PEG-Au NPs and BP-PEG-Au NPs by macrophages in the spleen, liver, and MGs; there was no evidence of toxicity due to the accumulation of NPs in organs and tissues compared with untreated controls for up to 28 days after delivery. STATEMENT OF SIGNIFICANCE: Au NP imaging probes and therapeutics are commonly surface functionalized with PEG and/or high affinity targeting ligands for delivery. However, direct comparisons of PEGylated Au NPs with and without a targeting ligand, or ligand-targeted Au NPs with and without a PEG spacer, on in vivo targeting efficiency, biodistribution, and clearance are limited. Therefore, the results of this study are important for the rationale design of targeted NP imaging probes and therapeutics, including the translation of BP-PEG-Au NPs which enable improved sensitivity and specificity for the radiographic detection of abnormalities (e.g., µcals) in women with dense breast tissue.

Targeted tumor dual mode CT/MR imaging using multifunctional polyethylenimine-entrapped gold nanoparticles loaded with gadolinium

We report the construction and characterization of polyethylenimine (PEI)-entrapped gold nanoparticles (AuNPs) chelated with gadolinium (Gd) ions for targeted dual mode tumor CT/MR imaging in vivo. In this work, polyethylene glycol (PEG) monomethyl ether-modified PEI was sequentially modified with Gd chelator and folic acid (FA)-linked PEG (FA-PEG) was used as a template to synthesize AuNPs, followed by Gd(III) chelation and acetylation of the remaining PEI surface amines. The formed FA-targeted PEI-entrapped AuNPs loaded with Gd (FA-Gd-Au PENPs) were well characterized in terms of structure, composition, morphology, and size distribution. We show that the FA-Gd-Au PENPs with an Au core size of 3.0 nm are water dispersible, colloidally stable, and noncytotoxic in a given concentration range. Thanks to the coexistence of Au and Gd elements within one nanoparticulate system, the FA-Gd-Au PENPs display a better X-ray attenuation property than clinical iodinated contrast agent (e.g. Omnipaque) and reasonable r1 relaxivity (1.1 mM-1s-1). These properties allow the FA-targeted particles to be used as an efficient nanoprobe for dual mode CT/MR imaging of tumors with excellent FA-mediated targeting specificity. With the demonstrated organ biocompatibility, the designed FA-Gd-Au PENPs may hold a great promise to be used as a nanoprobe for CT/MR dual mode imaging of different FA receptor-overexpressing tumors.

Folic acid-cysteamine modified gold nanoparticle as a nanoprobe for targeted computed tomography imaging of cancer cells

Development of various cost-effective multifunctional nanoprobes for efficient targeted molecular imaging of tumors remains a great challenge in medicine. Herein, we report a simple method of forming folic acid-targeted multifunctional gold nanoparticles via cost-effective cysteamine as a template for tumor molecular computed tomography (CT) imaging technique. The formed multifunctional cysteamine-folic acid conjugated gold nanoparticles (FA-Cys-AuNPs) were characterized via different techniques. Colony assay, hematoxylin and eosin (H&E), MTT, and flow cytometry analysis were used to evaluate the cytocompatibility of the particles. We showed that the formed FA-Cys-AuNPs with an Au core size of ~15 nm are non-cytotoxic in a given concentration range and revealed greater X-ray attenuation intensity than iodine-based contrast agent under the same concentration of the active element. At 80 kVp, FA-Cys-AuNPs enable 1.77-times greater contrast per unit mass compared with iodine at a concentration of 2000 μg/ml, and importantly, the developed FA-Cys-AuNPs can be used as a contrast media for targeted CT imaging of folic acid receptor-expressing cancer cells in vitro. CT values of the targeted cells were 2-times higher than that of non-targeted cells at 80 kVp. These findings propose that the designed FA-Cys-AuNPs can be used as a promising contrast agent for molecular CT imaging. This data can be also considered for the application of gold nanostructures in radiation dose enhancement where nanoparticles with high X-ray attenuation are applied.

99mTc-Labeled RGD-Polyethylenimine Conjugates with Entrapped Gold Nanoparticles in the Cavities for Dual-Mode SPECT/CT Imaging of Hepatic Carcinoma

We report the construction and characterization of ^99mTc-labeled arginine-glycine-aspartic acid (RGD)-polyethylenimine (PEI) conjugates with entrapped gold nanoparticles in the cavities (RGD-^99mTc-Au PENPs) for dual-mode single-photon emission computed tomography (SPECT)/computed tomography (CT) imaging of an orthotopic hepatic carcinoma model. In this study, PEI was successively decorated with diethylenetriaminepentaacetic acid, poly(ethylene glycol) (PEG), and PEGylated RGD segments, and was utilized as an effective nanoplatform to entrap Au NPs and to be labeled with ^99mTc. We showed that the designed RGD-^99mTc-Au PENPs displayed desirable colloidal stability and radiostability, and cytocompatibility in the investigated concentration range, and could be specifically uptaken by α_vβ₃ integrin-overexpressing liver cancer cells in vitro. In vivo CT and SPECT imaging results indicated that the particles were able to be accumulated within an orthotopic hepatic carcinoma and displayed both CT and SPECT contrast enhancement in the tumor tissue. With the proven biocompatibility in vivo via histological examinations, the designed RGD-^99mTc-Au PENPs may be potentially employed as an effective nanoprobe for a highly efficient dual-mode SPECT/CT imaging of various α_vβ₃ integrin-overexpressing tumors.

A unique nanogel-based platform for enhanced dual mode tumor MR/CT imaging

Alginate nanogels loaded with gold nanoparticles and gadolinium can be synthesized via a nanoparticle-crosslinking approach for enhanced tumor MR/CT imaging.

Green synthesis of bioactive polysaccharide-capped gold nanoparticles for lymph node CT imaging

The development of biologically targeted contrast agents for X-ray computed tomography (CT) imaging remains a major challenge. Here, we investigated a green chemistry-based synthesis of lymph node-targeted mannan-capped gold nanoparticles (M-GNPs) as a CT contrast agent. In this study, mannan was used as a reducing and stabilizing agent for gold nanoparticles (AuNPs). M-GNPs were readily internalized by antigen-presenting cells (APCs) through mannose receptors-mediated endocytosis. The M-GNPs, which had a spherical morphology, had an average diameter of 9.18±0.71nm and surface plasmon resonance (SPR) absorption spectra with maximal absorption at 522nm. The M-GNPs displayed a concentration-based X-ray attenuation property with a maximum Hounsfield unit (HU) value of 303.2±10.83. The local administration of M-GNPs led to significantly enhanced X-ray contrast for the imaging of popliteal lymph nodes. These findings demonstrated that M-GNPs can be used as biologically targeted contrast agents for CT imaging.

Optimization of the composition and dosage of PEGylated polyethylenimine-entrapped gold nanoparticles for blood pool, tumor, and lymph node CT imaging

Gold nanoparticles (Au NPs) with a high X-ray attenuation coefficient have a good potential in CT imaging applications. Here, we report the design and synthesis of Au NPs entrapped within polyethylene glycol (PEG)-modified branched polyethyleneimine (PEI) with varying the initial Au salt/PEI molar ratios and with the remaining PEI surface amines being acetylated for blood pool, lung tumor and lymph node CT imaging. The formed unacetylated and acetylated PEGylated PEI-entrapped Au NPs (Au PENPs) were characterized via different methods. We show that the PEGylated PEI is an effective template to entrap Au NPs having a uniform size ranging from 1.7nm to 4.4nm depending on the Au salt/PEI molar ratio. After optimization of the composition-dependent X-ray attenuation effect, we then selected {(Au⁰)₁₀₀-PEI·NHAc-mPEG} NPs for biological testing and show that the particles have good cytocompatibility in the given concentration range and can be used as a contrast agent for effective CT imaging of the blood pool of rats, lung cancer model of nude mice and lymph node of rabbits after intravenous injection. For each application, the injected dosage of the particles was optimized. In addition, the {(Au⁰)₁₀₀-PEI·NHAc-mPEG} NPs could be excreted out of the body with time. Our results indicate that the formed Au PENPs with an appropriate composition and dosage hold a great promise to be used for CT imaging of various biosystems.

An update on nanoparticle-based contrast agents in medical imaging

Despite the great value of current exogenous contrast agents for providing main diagnostic information, they still have certain drawbacks such as short blood half life, nonspecific biodistribution, fast clearance, slight renal toxicity and poor contrast in fat patients. Nanoparticles (NPs) are used as novel contrast agents that represent a promising strategy for the non invasive diagnosis. As a platform, nanoparticulates are compatible for developing targeted contrast agents. Advances in nanotechnology will provide enhanced sensitivity and specificity for tumor imaging enabling earlier detection of metastases. This article focuses on fundamental issue such as biological interactions, clearance routes, coating of NPs and presents a wide discussion about most recent category of NPs that are used as contrast agents and thebenefits/concerns issues associated with their use in clinical procedures.

Dendrimers meet zwitterions: development of a unique antifouling nanoplatform for enhanced blood pool, lymph node and tumor CT imaging

We report the synthesis and characterization of antifouling zwitterion carboxybetaine acrylamide (CBAA)-modified dendrimer-entrapped gold nanoparticles (Au DENPs) for enhanced CT imaging applications. The CBAA-modified nanodevice displays a better protein resistance property, less macrophage cellular uptake and liver accumulation, and longer blood half-delay time than the PEGylated counterpart material, thereby enabling enhanced blood pool, lymph node, and tumor CT imaging.

Polyaniline-loaded γ-polyglutamic acid nanogels as a platform for photoacoustic imaging-guided tumor photothermal therapy

We report the facile synthesis of polyaniline (PANI)-loaded γ-polyglutamic acid (γ-PGA) nanogels (NGs) for photoacoustic (PA) imaging-guided photothermal therapy (PTT) of tumors. In this work, γ-PGA NGs were first formed via a double emulsion approach, followed by crosslinking with cystamine dihydrochloride (Cys) via 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride coupling chemistry. The formed γ-PGA/Cys NGs were employed as a nanoreactor to load aniline monomers via an electrostatic interaction for subsequent in situ polymerization in the presence of ammonium persulfate. The resulting γ-PGA/Cys@PANI NGs were thoroughly characterized. It is shown that the γ-PGA/Cys@PANI NGs with an average size of 71.9 nm are dispersible in water, colloidally stable, and cytocompatible and hemocompatible in the concentration range studied. The strong near-infrared (NIR) absorbance renders the NGs with good PA imaging contrast enhancement and photothermal conversion properties. With these excellent properties and biocompatibility, the developed γ-PGA/Cys@PANI NGs are able to be used for PA imaging-guided PTT of cancer cells in vitro and a xenografted tumor model in vivo. This unique theranostic nanoplatform may be further loaded with other imaging or therapeutic elements, or modified with targeting ligands, thereby providing a ubiquitous platform for multimode imaging and combinational therapy of different biosystems.

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.

LAPONITE®-stabilized iron oxide nanoparticles for in vivo MR imaging of tumors

We report the synthesis, characterization and utilization of LAPONITE®-stabilized magnetic iron oxide nanoparticles (LAP-Fe3O4 NPs) as a high performance contrast agent for in vivo magnetic resonance (MR) detection of tumors. In this study, Fe3O4 NPs were synthesized by a facile controlled coprecipitation route in LAP solution, and the formed LAP-Fe3O4 NPs have great colloidal stability and about 2-fold increase of T2 relaxivity than Fe3O4 NPs (from 247.6 mM(-1) s(-1) to 475.9 mM(-1) s(-1)). Moreover, cytotoxicity assay and cell morphology observation demonstrate that LAP-Fe3O4 NPs display good biocompatibility in the given Fe concentration range, and in vivo biodistribution results prove that NPs can be metabolized and cleared out of the body. Most importantly, LAP-Fe3O4 NPs can not only be used as a contrast agent for MR imaging of cancer cells in vitro due to the effective uptake by tumor cells, but also significantly enhance the contrast of a xenografted tumor model. Therefore, the developed LAP-based Fe3O4 NPs with good colloidal stability and exceptionally high transverse relaxivity may have tremendous potential in MR imaging applications.

A multifunctional polyethylenimine-based nanoplatform for targeted anticancer drug delivery to tumors in vivo

The development of cost-effective targeted drug delivery systems for cancer chemotherapy still remains a great challenging task. Here, we describe the synthesis and characterization of multifunctional polyethylenimine (PEI) as an effective vehicle to load an anticancer drug doxorubicin (DOX) for in vivo targeted cancer therapy. In this study, PEI was sequentially conjugated with polyethylene glycol (PEG) monomethyl ether, PEGylated folic acid (FA), and fluorescein isothiocyanate (FI). This was followed by the acetylation of the remaining PEI surface amines. The formed FA-targeted multifunctional PEI (FA-mPEI) was used as a vehicle to encapsulate DOX. We show that the formed FA-mPEI/DOX complexes with each PEI encapsulating 6.9 DOX molecules are water dispersible and can sustainably release DOX in a pH-dependent manner, showing a higher release rate under acidic pH conditions than under physiological pH conditions. Furthermore, the complexes display specific therapeutic efficacy to cancer cells in vitro and a subcutaneous tumor model in vivo, and have good organ compatibility. The designed multifunctional PEI may be used as an effective vehicle for targeted cancer chemotherapy.

Multifunctional Dendrimers for Drug Nanocarriers

Dendrimers are nanosized, monodisperse, highly branched polymers with well-defined topological structure which have attracted much attention for drug delivery recently. To further improve the performance of dendrimers in drug delivery, various functional dendrimers are developed by decorating the dendrimers with targeting agents, imaging agents, or stimuli-sensitive moieties. They show good biocompatibility, visibility, tumor targeting and stimuli-sensitive properties for drug or gene delivery. This chapter will focus on the design of multifunctional nanocarriers based on the dendrimers. Therefore, the chapter will provide the ideas for designing the dendrimers based nanocarriers for controllable drug delivery and let more people know the development of dendrimers for drug delivery in recent years.

Efficient delivery of therapeutic siRNA into glioblastoma cells using multifunctional dendrimer-entrapped gold nanoparticles

AIM

To synthesize the arginine-glycine-aspartic (RGD) functionalized dendrimer-entrapped gold nanoparticles (Au DENPs) for siRNA delivery to induce gene silencing of cancer cells in vitro and in vivo.

MATERIALS & METHODS

Au DENPs modified with RGD peptide via a polyethylene glycol spacer were used as a vector of two distinct small interfering RNAs (siRNAs) (VEGFvascular endothelial growth factor siRNA and B-cell lymphoma/leukemia-2 siRNA), and the physicochemical properties, cytocompatibility and transfection efficiency of Au DENP/siRNA polyplexes were characterized.

RESULTS

The Au DENP/siRNA polyplexes with good cytocompatibility and highly efficient transfection capacity can be used for the transfection of siRNAs.

CONCLUSION

The developed functional RGD-modified Au DENPs may be used for efficient gene therapy of different types of cancer.

(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.

PEGylated polyethylenimine-entrapped gold nanoparticles loaded with gadolinium for dual-mode CT/MR imaging applications

Aim: To synthesize and characterize cost-efficient polyethylenimine-entrapped gold nanoparticles loaded with gadolinium (Gd@Au PENPs) for dual-mode computed tomography (CT)/magnetic resonance (MR) imaging applications. Materials & methods: PEGylated PEI modified with gadolinium (Gd) chelator (DOTA) was used as a template to synthesize the Gd@Au PENPs and the particles were well characterized in terms of their physicochemical properties, cytotoxicity and performances in CT and MR imaging in vitro and in vivo. Results: The formed Gd@Au PENPs with low cytotoxicity can be used as a highly efficient contrast agent for dual-mode CT/MR imaging of blood pool and major organs of animals. Conclusion: The designed Gd@Au PENPs may be used as a versatile nanoplatform for dual-mode CT/MR imaging of different biological systems.