Poly(glycerol) Used for Constructing Mixed Polymeric Micelles as T1 MRI Contrast Agent for Tumor-Targeted Imaging

Antifouling polymers for nanomedicine and surfaces: recent advances

Antifouling polymers are materials that can resist nonspecific interactions with cells, proteins, and other biomolecules. Typically, they are hydrophilic polymers with polar or charged moieties that are capable of strong nonbonding interactions with water molecules. This propensity to bind water generates a surface hydration layer that reduces nonspecific interactions with other molecules and is paramount to the antifouling behavior. This property is especially useful for nanoscale applications such as nanomedicine and surface modifications at the molecular level. In nanomedicine, antifouling polymers such as poly(ethylene glycol) and its alternatives play a key role in shielding drug molecules and therapeutic proteins/genes from the immune system within nanoassemblies, thereby enabling effective delivery to target tissues. For coatings, antifouling polymers help to prevent adhesion of cells and molecules to surfaces and are thus valued in marine and biomedical device applications. In this Review, we survey recent advances in antifouling polymers in the context of nanomedicine and coatings, while shining the spotlight on the major polymer classes such as PEG, polyzwitterions, poly(oxazoline)s, and other nonionic hydrophilic polymers.

Preparation and In Vitro Evaluation of a Gadolinium-Containing Vitamin E TPGS Micelle as a Potential Contrast Agent for MR Imaging

The application of many currently evaluated macromolecular contrast agents for magnetic resonance imaging (MRI) has been limited because of their bio-incompatibility and toxicity. The aim of this study is to synthesize and characterize a new micelle-based TPGS gadolinium chelate as a biocompatible MRI contrast agent for prolonged blood circulation time and good tumor imaging contrast. The TPGS-gadolinium conjugate was prepared through the conjugation between TPGS-SA and bifunctional L-NETA-Gd chelate. The conjugate was characterized with regard to molecular weight, critical micellar concentration and particle sizes, cellular uptake, and in vitro cell MRI. Distributions of the MRI contrast agent in various organs were determined via intravenous injection of the agent into mice bearing xenograft tumors. The successfully prepared TPGS-L-NETA-Gd micelle exhibited improved cellular uptake in HepG2 cells and xenografts and high in vivo safety. Distributions of TPGS-L-NETA-Gd in mice showed enhanced cellular uptake up to 2 h after the contrast agent injection. Its in vitro and in vivo properties make it a favorable macromolecular MRI contrast agent for future in vivo imaging.

Melanin-like nanoparticles: advances in surface modification and tumour photothermal therapy

Currently, tumor treatments are characterized by intelligence, diversity and personalization, but the therapeutic reagents used are often limited in clinical efficacy due to problems with water solubility, targeting, stability and multidrug resistance. To remedy these shortcomings, the application of multifunctional nanotechnology in the biomedical field has been widely studied. Synthetic melanin nanoparticles (MNPs) surfaces which contain highly reactive chemical groups such as carboxyl, hydroxyl and amine groups, can be used as a reaction platform on which to graft different functional components. In addition, MNPs easily adhere to substrate surface, and serve as a secondary reaction platform to modify it. The multifunctionality and intrinsic biocompatibility make melanin-like nanoparticles promising as a multifunctional and powerful nanoplatform for oncological applications. This paper first reviews the preparation methods, polymerization mechanisms and physicochemical properties of melanin including natural melanin and chemically synthesized melanin to guide scholars in MNP-based design. Then, recent advances in MNPs especially synthetic polydopamine (PDA) melanin for various medical oncological applications are systematically and thoroughly described, mainly focusing on bioimaging, photothermal therapy (PTT), and drug delivery for tumor therapy. Finally, based on the investigated literature, the current challenges and future directions for clinical translation are reasonably discussed, focusing on the innovative design of MNPs and further elucidation of pharmacokinetics. This paper is a timely and comprehensive and detailed study of the progress of MNPs in tumor therapy, especially PTT, and provides ideas for the design of personalized and customizable oncology nanomedicines to address the heterogeneity of the tumor microenvironment.

Phosphorylcholine zwitterionic shell-detachable mixed micelles for enhanced cancerous cellular uptakes and increased DOX release

To further enhance the cancerous cellular uptakes and increase the drug release of the drug loaded micelles, herein, we fabricated a series of mixed micelles with different mass ratios using two amphiphilic copolymers P(DMAEMA-co-MaPCL) and PCL-SS-PMPC. The mixed micelles showed a prolonged circulation time due to the zwitterionic shells in a physiological environment (pH 7.4). In addition, because of the protonation of tertiary amine groups in PDMAEMA and the breakage of the disulfide bond in PMPC-SS-PCL in a tumor microenvironment, the mixed micelles aggregated, which led to enhanced cancerous cellular penetration and increased DOX release. Moreover, cytotoxicity assay showed that the mixed micelles had good biocompatibility to L929, HeLa and MCF-7 cells, even at a concentration of up to 1 mg mL^-1. Furthermore, enhanced antitumour activity and cellular uptake of HeLa and MCF-7 cells were detected after loading with DOX, which was determined by confocal laser scanning microscopy (CLSM) and flow cytometry (FC), especially for the DOX@MIX 3 micelles (20% mass ratio of the P(DMAEMA-co-MaPCL)). Therefore, the mixed strategy provides a simple and efficient ways to promote anticancer drug delivery.

PEGylated amphiphilic polymeric manganese(II) complex as magnetic resonance angiographic agent

Currently, the most commonly used clinical magnetic resonance imaging (MRI) contrast agents, Gd(III) chelates, have been found in association with nephrogenic systemic fibrosis (NSF) in renally compromised patients. Toxicity concerns...

Cyclodextrins: promising scaffolds for MRI contrast agents

Magnetic resonance imaging (MRI) is a powerful tool for non-invasive, high-resolution three-dimensional medical imaging of anatomical structures such as organs and tissues. The use of contrast agents based on gadolinium chelates started in 1988 to improve the quality of the image, since researchers and industry focused their attention on the development of more efficient and stable structures. This review is about the state of the art of MRI contrast agents based on cyclodextrin scaffolds. Chemical engineering strategies are herein reported including host-guest inclusion complexation and covalent linkages. It also offers descriptions of the MRI properties and in vitro and in vivo biomedical applications of these emerging macrostructures. It highlights that these supramolecular associations can improve the image contrast, the sensitivity, and the efficiency of MRI diagnosis by targeting cancer tumors and other diseases with success proving the great potential of this natural macrocycle.

Synthesis of Biomimetic Melanin-Like Multifunctional Nanoparticles for pH Responsive Magnetic Resonance Imaging and Photothermal Therapy

The design and development of multifunctional nanoparticles have attracted great interest in biomedical research. This study aims to prepare pH-responsive melanin-like nanoparticles for T₁-weighted magnetic resonance imaging (MRI) and photothermal therapy. The new multifunctional nanoparticles (amino-Fe-PDANPs) are synthesized by copolymerization of dopamine and its derivative amino-N-[2-(diethylamino) ethyl]-3,4-dihydroxy-benzenepropanamide (N-Dopa) at room temperature. The size of nanoparticles can be controlled by NaOH concentration. The incorporation of N-Dopa is characterized by NMR and FT-IR. From transmission electron microscopy (TEM), the nanoparticles exhibit excellent dispersion stability in water and are spherical in shape. The MRI measurement has demonstrated that amino-Fe-PDANPs have a significant signal enhancement in responding to the acidic solution. Confirmed by the photothermal study, the nanoparticles exhibit a high photothermal conversion efficiency. The melanin-like multifunctional nanoparticles integrate both diagnosis and therapeutic functionalities, indicating the potential for theranostic application.

Nanocarrier-based Drug Delivery System for Cancer Therapeutics: A Review of the Last Decade

In recent years, due to the shortcomings of conventional chemotherapy, such as poor bioavailability, low treatment index, and unclear side effects, the focus of cancer research has shifted to new nanocarriers of chemotherapeutic drugs. By using biodegradable materials, nanocarriers generally have the advantages of good biocompatibility, low side effects, targeting, controlled release profile, and improved efficacy. More to the point, nanocarrier based anti-cancer drug delivery systems clearly show the potential to overcome the problems associated with conventional chemotherapy. In order to promote the in-depth research and development in this field, we herein summarized and analyzed various nanocarrier based drug delivery systems for cancer therapy, including the concepts, types, characteristics, and preparation methods. The active and passive targeting mechanisms of cancer therapy were also included, along with a brief introduction of the research progress of nanocarriers used for anti-cancer drug delivery in the past decade.

Simple Host-Guest Assembly for High-Resolution Magnetic Resonance Imaging of Microvasculature

Magnetic resonance angiography (MRA) is an important imaging technique that can be used to identify and characterize various types of vascular diseases. However, currently used molecular contrast agents are unsuitable for MRA due to the short intravascular retention time, the whole-body distribution, and the relatively low contrast effect. In this study, we developed a vascular analysis contrast agent (i.e., VasCA) for MRA, which is a simple and biocompatible 1:1 host-guest assembly of PEGylated β-cyclodextrin and gadolinium chelate with renal clearable size and high relaxivity (r1 = 9.27 mM-1 s-1). Its biocompatibility was confirmed by in vivo animal studies as well as in vitro 3D cell culture. In a tumor-bearing rat model, VasCA circulated in the blood vessels much longer (4.3-fold increase) than gadoterate meglumine (Dotarem) and was mainly excreted by the renal system after intravenous injection. This feature of VasCA allows characterization of tumor microvasculature (e.g., feeding and draining vessels) as well as visualization of small vessels in the brain and body organs. Furthermore, after treatment with an angiogenesis inhibitor (i.e., sorafenib), VasCA revealed the vessel normalization process and allowed the assessment of viable and necrotic tumor regions. Our study provides a useful tool for diverse MRA applications, including tumor characterization, early-stage evaluation of drug efficacy, and treatment planning, as well as diagnosis of cardiovascular diseases.

Multifunctional polymeric micellar nanomedicine in the diagnosis and treatment of cancer

Polymeric micelles are a prevalent topic of research for the past decade, especially concerning their fitting ability to deliver drug and diagnostic agents. This delivery system offers outstanding advantages, such as biocompatibility, high loading efficiency, water-solubility, and good stability in biological fluids, to name a few. The multifunctional polymeric micellar architect offers the added capability to adapt its surface to meet the looked-for clinical needs. This review cross-talks the recent reports, proof-of-concept studies, patents, and clinical trials that utilize polymeric micellar family architectures concerning cancer targeted delivery of anticancer drugs, gene therapeutics, and diagnostic agents. The manuscript also expounds on the underlying opportunities, allied challenges, and ways to resolve their bench-to-bedside translation for allied clinical applications.

Harnessing amphiphilic polymeric micelles for diagnostic and therapeutic applications: Breakthroughs and bottlenecks

Amphiphilic block copolymers are widely utilized in the design of formulations owing to their unique physicochemical properties, flexible structures and functional chemistry. Amphiphilic polymeric micelles (APMs) formed from such copolymers have gained attention of the drug delivery scientists in past few decades for enhancing the bioavailability of lipophilic drugs, molecular targeting, sustained release, stimuli-responsive properties, enhanced therapeutic efficacy and reducing drug associated toxicity. Their properties including ease of surface modification, high surface area, small size, and enhanced permeation as well as retention (EPR) effect are mainly responsible for their utilization in the diagnosis and therapy of various diseases. However, some of the challenges associated with their use are premature drug release, low drug loading capacity, scale-up issues and their poor stability that need to be addressed for their wider clinical utility and commercialization. This review describes comprehensively their physicochemical properties, various methods of preparation, limitations followed by approaches employed for the development of optimized APMs, the impact of each preparation technique on the physicochemical properties of the resulting APMs as well as various biomedical applications of APMs. Based on the current scenario of their use in treatment and diagnosis of diseases, the directions in which future studies need to be carried out to explore their full potential are also discussed.

Polymerizable Gd(iii) building blocks for the synthesis of high relaxivity macromolecular MRI contrast agents

A new synthetic strategy for the preparation of macromolecular MRI contrast agents (CAs) is reported. Four gadolinium(iii) complexes bearing either one or two polymerizable methacrylamide groups were synthesized, serving as monomers or crosslinkers for the preparation of water-soluble, polymeric CAs using Reversible Addition–Fragmentation Chain Transfer (RAFT) polymerization. Using this approach, macromolecular CAs were synthesized with different architectures, including linear, hyperbranched polymers and gels. The relaxivities of the polymeric CAs were determined by NMR relaxometry, revealing an up to 5-fold increase in relaxivity (60 MHz, 310 K) for the linear polymers compared with the clinically used CA, Gd-DOTA. Moreover, hyperbranched polymers obtained from Gd(iii) crosslinkers, displayed even higher relaxivities up to 22.8 mM⁻¹ s⁻¹, approximately 8 times higher than that of Gd-DOTA (60 MHz, 310 K). A detailed NMRD study revealed that the enhanced relaxivities of the hyperbranched polymers were obtained by limiting the local motion of the crosslinked Gd(iii) chelate. The versatility of RAFT polymerization of Gd(iii) monomers and crosslinkers opens the doors to more advanced polymeric CAs capable of multimodal, bioresponsive or targeting properties.

A new synthetic strategy for the preparation of efficient macromolecular MRI contrast agents is reported.

Dual activatable self-assembled nanotheranostics for bioimaging and photodynamic therapy

Multifunctional nanosystems that can transport therapeutic and diagnostic agents into tumor sites and activate their respective functions via tumor-microenvironment recognition are highly desirable for clinical applications. We fabricated pH and redox dual-activatable self-assembled nanotheranostics (named as DA-SNs) via coordination-driven self-assembly of chlorin e6 (Ce6) disulfide-linked pH sensitive polymer ligand, poly (isobutylene-alt-maleic anhydride-graft-methoxy-poly (ethyleneglycol)-graft-imidazole-graft-Cystamine-Ce6) [PIMA-mPEG-API-SS-Ce6], and gadolinium ions (Gd³⁺). DA-SNs exhibited uniform particle size of ~48 nm, excellent stability, and inherent biosafety. Negatively charged DA-SNs could prolong blood circulation time (t_1/2 = 2.91 h) and improve tumor accumulation. Moreover, DA-SNs could undergo surface charge switch from negative charge to positive one in a slightly acidic tumor extracellular environment (pH 6.8), thus enhancing cellular uptake. After entering tumor cells, fluorescence, photodynamic therapeutic activity, and T₁MR contrast from DA-SNs could be activated within this intracellular environment with lowered pH and high level of GSH. Importantly, human tumors implanted in mice could be successfully visualized via distinct pH and redox dual-sensitive T₁MR contrast and fluorescence imaging, indicating that DA-SNs could serve as a dual-modal MR/fluorescence imaging probe for tumor-targeting diagnosis. In addition, DA-SNs exhibited superior photodynamic therapeutic efficiency with negligible side effects. Therefore, this DA-SN shows great promise for synergistic photodynamic therapy and diagnostic imaging.

A Dual-Modality MR/PA Imaging Contrast Agent Based on Ultrasmall Biopolymer Nanoparticles for Orthotopic Hepatocellular Carcinoma Imaging

BACKGROUND

Hepatocellular carcinoma (HCC) is the second leading cause of cancer death and early stage diagnosis can greatly increase the survival rate of patient. However, the accurate detection of HCC remains an urgent challenge in medical diagnosis. The combination of magnetic resonance imaging (MRI) and photoacoustic imaging (PAI) are conducive for accurate locating of cancerous tissue. Therefore, it is necessary to explore a more facile and biosafe dual-modal contrast agent for orthotopic HCC detection.

METHODS

In this study, a promising contrast agent had been identified based on gadolinium chelated melanin nanoparticles and evaluated its usage as a dual-modal T1 MRI and PAI contrast agent for orthotopic HCC detection.

RESULTS

The gadolinium-based melanin nanoparticles presented ultrasmall size, high chelation stability and negligible cytotoxicity estimated by CCK-8 assay. Moreover, the nanoparticle exhibited higher r1 relaxivity (45.762 mM-1 s-1) than clinically approved Gadodiamide (4.975 mM-1 s-1) at 1.5 T MR scanning. A linear regression analysis confirmed that the nanoparticles were ideal candidates for PAI in vitro. After the nanoparticles were injected into vein in mice with orthotopic HCC, a dramatic increase in signal of the liver was observed at 0.5 hr by MRI and PAI, while the tumor exerted remarkable signal enhancement at 7 hrs, showing excellent detection sensitivity. In addition, the nanoparticles exhibited excellent biocompatibility and they can be excreted through both hepatobiliary and renal pathways after diagnosis.

CONCLUSION

These results indicate that the ultrasmall gadolinium chelated melanin nanoparticles is a promising candidate as a dual-modal MRI/PAI contrast agent for the detection of orthotopic HCC.

Macromolecular approach for targeted radioimmunotherapy in non-Hodgkin's lymphoma

Polymers are an attractive anchoring platform for the synthesis of radioimmunoconjugates. They enable independent control over the amount of radioisotope loading and antibody attachment, which is pivotal in developing tailorable formulations for personalised medicine. Herein, we report the synthesis of p(HEMA-ran-GMA) for the conjugation of lutetium ions and rituximab as a functional platform for radioimmunotherapy. We demonstrate the suitability of this platform using non-Hodgkin's lymphoma cells.

Development of a Non-Coding-RNA-based EMT/CSC Inhibitory Nanomedicine for In Vivo Treatment and Monitoring of HCC

The objective of this study is to improve the overall prognosis of patients with hepatocellular carcinoma (HCC); therefore, new therapeutic methods that can be used in vivo are urgently needed. In this study, the relationship between the quantities of microRNA (miR)-125b-5p in clinical specimens and clinicopathological parameters is analyzed. A folate-conjugated nanocarrier is used to transfect miR-125b-5p in vivo and to observe the therapeutic effect on HCC. The inhibitory effect and mechanism of miR-125b-5p on hepatoma cells are also studied. Data from clinical specimens and in vitro experiments confirm that the miR-125b-5p quantity is negatively correlated with progression, and the target protein that regulates the epithelial-mesenchymal transition (EMT)/cancer stem cells (CSC) potential in HCC is STAT3. The miR-125b-5p/STAT3 axis inhibits the invasion, migration, and growth of HCC via inactivation of the wnt/β-Catenin pathway. miR-125b-5p-loaded nanomedicine effectively inhibits the EMT/CSC potential of hepatoma cells in vivo together with their magnetic resonance imaging (MRI) visualization characteristics. An HCC-therapeutic and MRI-visible nanomedicine platform that achieves noninvasive treatment effect monitoring and timely individualized treatment course adjustment is developed.

Melanin-manganese nanoparticles with ultrahigh efficient clearance in vivo for tumor-targeting T1 magnetic resonance imaging contrast agent

Endogenous biomaterials in organisms, with native biocompatibility and biodegradability, appear more advantageous in the development of nanoscale diagnostic and therapeutic systems for future clinical translation. Herein, a novel tumor-targeting Magnetic Resonance Imaging (MRI) contrast agent was developed based on Mn²⁺-chelating ultrasmall water-soluble melanin nanoparticles (MNP-PEG-Mn). The nanoparticles, with a size of about 5.6 nm, presented high chelation stability and showed negligible cytotoxicity as estimated by MTT assay. Moreover, the r₁ longitudinal relaxivity (20.56 mM^-1 s^-1) of MNP-PEG-Mn was much higher than that of Gadodiamide (6.00 mM^-1 s^-1), which is a clinically approved MRI contrast agent. In vivo MRI experiments revealed excellent tumor-targeting specificity after tumor-bearing mice were intravenously injected with MNP-PEG-Mn. Additionally, MNP-PEG-Mn could be excreted via renal and hepatobiliary pathways with negligible toxicity to body tissues. These preliminary results indicated the clinically translatable potential of MNP-PEG-Mn as a T₁ MRI contrast agent for tumor-targeted imaging.

Biodegradable Nanoglobular Magnetic Resonance Imaging Contrast Agent Constructed with Host-Guest Self-Assembly for Tumor-Targeted Imaging

Gadolinium-based macromolecular magnetic resonance imaging (MRI) contrast agents (CAs) have attracted increasing interest in tumor diagnosis. However, their practical application is potentially limited because the long-term retention of gadolinium ion in vivo will induce toxicity. Here, a nanoglobular MRI contrast agent (CA) PAMAM-PG- g-s-s-DOTA(Gd) + FA was designed and synthesized on the basis of the facile host-guest interaction between β-cyclodextrin and adamantane, which initiated the self-assembly of poly(glycerol) (PG) separately conjugated with gadolinium chelates by disulfide bonds and folic acid (FA) molecule onto the surface of poly(amidoamine) (PAMAM) dendrimer, finally realizing the biodegradability and targeting specificity. The nanoglobular CA has a higher longitudinal relaxivity ( r₁) than commercial gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA), showing a value of 8.39 mM^-1 s^-1 at 0.5 T, and presents favorable biocompatibility on the observations of cytotoxicity and tissue toxicity. Furthermore, MRI on cells and tumor-bearing mice both demonstrate the obvious targeting specificity, on the basis of which the effective contrast enhancement at tumor location was obtained. In addition, this CA exhibits the ability of cleavage to form free small-molecule gadolinium chelates and can realize minimal gadolinium retention in main organs and tissues after tumor detection. These results suggest that the biodegradable nanoglobular PAMAM-PG- g-s-s-DOTA(Gd) + FA can be a safe and efficient MRI CA for tumor diagnosis.

Geometrical Confinement of Gadolinium Oxide Nanoparticles in Poly(ethylene glycol)/Arginylglycylaspartic Acid-Modified Mesoporous Carbon Nanospheres as an Enhanced T1 Magnetic Resonance Imaging Contrast Agent

A new strategy for designing contrast agents (CAs) based on geometrical confinement will become a competent way to improve the relaxivity of CAs. Herein, a magnetic resonance imaging (MRI) nanoconstruct is fabricated through loading Gd₂O₃ nanoparticles into mesoporous carbon nanospheres, followed by conjugation of poly(ethylene glycol) (PEG) and the c(RGDyK) peptide (Gd₂O₃@OMCN-PEG-RGD), which could prolong the blood circulation half-life as well as improve the tumor-targeting ability. As a result, the Gd₂O₃@OMCN-PEG-RGD exhibits an outstandingly high relaxivity ( r₁ = 68.02 mM^-1 s^-1), which is ∼5.3 times higher than that of Gd₂O₃ nanoparticles ( r₁ = 12.74 mM^-1 s^-1). Afterward, both the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test and H&E staining show that the Gd₂O₃@OMCN-PEG-RGD has wonderful biocompatibility in vitro and in vivo. Moreover, the in vivo MR images indicate that the Gd₂O₃@OMCN-PEG-RGD could accumulate in the tumor region more rapidly than Gd₂O₃@OMCN-PEG. This study presents a facile method to fabricate an MRI CA with excellent T₁ contrast ability based on geometrical confinement and excellent biocompatibility, which could act as an optimal contender for sensitive in vivo tumor imaging with outstanding targeting ability.

Controlled synthesis of up-conversion luminescent Gd/Tm-MOFs for pH-responsive drug delivery and UCL/MRI dual-modal imaging

Using a facile one-step hydrothermal method, a series of metal–organic frameworks containing Gd/Tm (Gd/Tm-MOFs) were prepared successfully.