Folic acid modified cationic γ-cyclodextrin-oligoethylenimine star polymer with bioreducible disulfide linker for efficient targeted gene delivery

Cyclodextrin in drug delivery: Exploring scaffolds, properties, and cutting-edge applications

Cyclodextrins (CDs) are unique cyclic compounds that can form inclusion complexes via host-guest complexation with a wide range of molecules, thereby altering their physicochemical properties. These molecules offer the formation of inclusion complexes without the formation of covalent bonds, making them suitable for a variety of applications in pharmaceutical and biomedical fields. Due to their supramolecular host-guest properties, CDs are being utilized in the fabrication of biomaterials, metal-organic frameworks, and nano-drug carriers. Additionally, CDs in combination with biomolecules are biocompatible and can deliver nano to macromolecules at the site of drug actions. However, the availability of free hydroxyl groups and a simple crosslinking process for supramolecular fabrication show immense opportunities for researchers in the field of tissue engineering and biomedical applications. In this review article, we have covered the historical development, various types of chemical frameworks, unique chemical and physical properties, and important applications of CDs in drug delivery and biomedical sciences.

Folic Acid-Functionalized β-Cyclodextrin for Delivery of Organelle-Targeted Peptide Chemotherapeutics in Cancer

Recent emphasis on the design of drug delivery systems typically involves the effective transport of a pharmaceutical substance to the disease site with the desired therapeutic efficacy and minimal cytotoxicity. Organelle-targeted peptides have become an integral part of designing an important class of prodrug/prodrug assemblies for new supramolecular therapeutics owing to their favorable biocompatibility, synthetic ease, tunability of their aggregation behavior, and desired functionalization for site-specificity. However, it is still limited due to the low selectivity. We designed a folic acid-functionalized β-cyclodextrin (FA-CD) as a delivery platform for specific and selective delivery of organelle-targeted (such as microtubule, lysosome, and mitochondria) peptide chemotherapeutics to the folate receptor (FR) overexpressing cancer cell lines. Low toxicity was found for the FA-CD and organelle-targeted peptide inclusion complex in FR-negative normal cells, but superior inhibition of tumor growth with no in vivo toxicity was found for the inclusion complex in the xenograft tumor model.

Codelivery of Doxorubicin and p53 Gene by β-Cyclodextrin-Based Supramolecular Nanoparticles Formed via Host-Guest Complexation and Electrostatic Interaction

We developed a supramolecular system for codelivery of doxorubicin (Dox) and p53 gene based on a β-CD-containing star-shaped cationic polymer. First, a star-shaped cationic polymer consisting of a β-CD core and 3 arms of oligoethylenimine (OEI), named CD-OEI, was used to form a supramolecular inclusion complex with hydrophobic Dox. The CD-OEI/Dox complex was subsequently used to condense plasmid DNA via electrostatic interactions to form CD-OEI/Dox/DNA polyplex nanoparticles with positive surface charges that enhanced the cellular uptake of both Dox and DNA. This supramolecular drug and gene codelivery system showed high gene transfection efficiency and effective protein expression in cancer cells. The codelivery of Dox and DNA encoding the p53 gene resulted in reduced cell viability and enhanced antitumor effects at low Dox concentrations. With its enhanced cellular uptake and anticancer efficacy, the system holds promise as a delivery carrier for potential combination cancer therapies.

Cyclodextrin-Based Polymeric Drug Delivery Systems for Cancer Therapy

Cyclodextrins (CDs) are one of the most extensively studied cyclic-oligosaccharides due to their low toxicity, good biodegradability and biocompatibility, facile chemical modification, and unique inclusion capacity. However, problems such as poor pharmacokinetics, plasma membrane disruption, hemolytic effects and a lack of target specificity still exist for their applications as drug carriers. Recently, polymers have been introduced into CDs to combine the advantages of both biomaterials for the superior delivery of anticancer agents in cancer treatment. In this review, we summarize four types of CD-based polymeric carriers for the delivery of chemotherapeutics or gene agents for cancer therapy. These CD-based polymers were classified based on their structural properties. Most of the CD-based polymers were amphiphilic with the introduction of hydrophobic/hydrophilic segments and were able to form nanoassemblies. Anticancer drugs could be included in the cavity of CDs, encapsulated in the nanoparticles or conjugated on the CD-based polymers. In addition, the unique structures of CDs enable the functionalization of targeting agents and stimuli-responsive materials to realize the targeting and precise release of anticancer agents. In summary, CD-based polymers are attractive carriers for anticancer agents.

Implementation of Water-Soluble Cyclodextrin-Based Polymers in Biomedical Applications: How Far are we?

Cyclodextrin-based polymers can be prepared starting from the naturally occurring monomers following green and low-cost procedures. They can be selectively derivatized pre- or post-polymerization allowing to fine-tune functionalities of ad hoc customized polymers. Preparation nowadays has reached the 100 g scale thanks also to the interest of industries in these extremely versatile compounds. During the last 15 years these macromolecules have been the object of intense investigations in view of possible biomedical applications as the ultimate goal and large amounts of scientific data are now available. Compared to their monomeric models, already used in the formulation of various therapeutic agents, they display superior behavior in terms of their solubility in water and solubilizing power towards drugs incompatible with biological fluids. Moreover, they allow the combination of more than one type of therapeutic agent in the polymeric system. In this review we provide a complete state-of-the-art on the knowledge and potentialities of water-soluble cyclodextrin-based polymers as therapeutic agents as well as carrier systems for different types of therapeutics to implement combination therapy. Finally, we give a perspective on their assets for innovation in disease treatment as well as their limits that still need to be addressed. This article is protected by copyright. All rights reserved.

Stimulus-responsive drug/gene delivery system based on polyethylenimine cyclodextrin nanoparticles for potential cancer therapy

Combination therapy through simultaneous delivery of anti-cancer drugs and genes with nano-assembled structure has been proved to be a simple and effective approach for treating breast cancer. In this study, redox-sensitive folate-appended-polyethylenimine-β-cyclodextrin (roFPC) host-guest supramolecular nanoparticles (HGSNPs) were developed as a targeted co-delivery system of doxorubicin (Dox) and Human telomerase reverse transcriptase-small interfering RNA) hTERT siRNA) for potential cancer therapy. The nanotherapeutic system was prepared by loading adamantane-conjugated doxorubicin (Ad-Dox) into roFPC through the supramolecular assembly, followed by electrostatically-driven self-assembly between hTERT siRNA and roFPC/Ad-Dox. The roFPC' host-guest structures allow pH-dependent intracellular drug release in a sustained manner, as well as simultaneous and effective gene transfection. This co-delivery vector displayed combined anti-tumor properties of the Dox-enhanced gene transfection, good water-solubility, and biocompatibility, possesses considerably enhanced hemocompatibility, and especially targets folate receptor-positive cells only at low N/P levels to prompt effective cell apoptosis for cancer treatment.

Lignin-Based Nonviral Gene Carriers Functionalized by Poly[2-(Dimethylamino)ethyl Methacrylate]: Effect of Grafting Degree and Cationic Chain Length on Transfection Efficiency

Lignin is a natural renewable biomass resource with great potential for applications, while its development into high value-added molecules or materials is rare. The development of biomass lignin as potential nonviral gene delivery carriers was initiated by our group through the "grafting-from" approach. Firstly, the lignin was modified into macroinitiator using 2-bromoisobutyryl bromide. Then cationic polymer chains of poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) were grown from the lignin backbone using atom transfer radical polymerization (ATRP) to yield lignin-PDMAEMA graft copolymers (LPs) with branched structure. To gain a deep understanding of the relationship between the nonviral gene transfection efficiency of such copolymers and their structural and compositional factors, herein eight lignin-based macroinitiators with different modification degrees (MDs, from 3.0 to 100%) were synthesized. Initiated by them, a series of 20 LPs were synthesized with varied structural factors such as grafting degree (GD, which is equal to MD, determining the cationic chain number per lignin macromolecule), cationic chain length (represented by number of repeating DMAEMA units per grafted arm or degree of polymerization, DP) as well as the content of N element (N%) which is due to the grafted PDMAEMA chains and proportional to molecular weight of the LPs. The in vitro gene transfection capability of these graft copolymers was evaluated by luciferase assay in HeLa, COS7 and MDA-MB-231cell lines. Generally, the copolymers LP-12 (N% = 7.28, MD = 36.7%, DP = 13.6) and LP-14 (N% = 6.05, MD = 44.4%, DP = 5.5) showed good gene transfection capabilities in the cell lines tested. Overall, the performance of LP-12 was the best among all the LPs in the three cell lines at the N/P ratios from 10 to 30, which was usually several times higher than PEI standard. However, in MDA-MB-231 at N/P ratio of 30, LP-14 showed the best gene transfection performance among all the LPs. Its gene transfection efficiency was ca. 11 times higher than PEI standard at this N/P ratio. This work demonstrated that, although the content of N element (N%) which is due to the grafted PDMAEMA chains primarily determines the gene transfection efficiency of the LPs, it is not the only factor in explaining the performance of such copolymers with the branched structure. Structural factors of these copolymers such as grafting degree and cationic chain length could have a profound effect on the copolymer performance on gene transfection efficiency. Through carefully adjusting these factors, the gene transfection efficiency of the LPs could be modulated and optimized for different cell lines, which could make this new type of biomass-based biomaterial an attractive choice for various gene delivery applications.

Folic Acid-Decorated β-Cyclodextrin-Based Poly(ε-caprolactone)-dextran Star Polymer with Disulfide Bond-Linker as Theranostic Nanoparticle for Tumor-Targeted MRI and Chemotherapy

β-cyclodextrin(βCD)-based star polymers have attracted much interest because of their unique structures and potential biomedical and biological applications. Herein, a well-defined folic acid (FA)-conjugated and disulfide bond-linked star polymer ((FA-Dex-SS)-βCD-(PCL)₁₄) was synthesized via a couple reaction between βCD-based 14 arms poly(ε-caprolactone) (βCD-(PCL)₁₄) and disulfide-containing α-alkyne dextran (alkyne-SS-Dex), and acted as theranostic nanoparticles for tumor-targeted MRI and chemotherapy. Theranostic nanoparticles were obtained by loading doxorubicin (DOX), and superparamagnetic iron oxide (SPIO) particles were loaded into the star polymer nanoparticles to obtain ((FA-Dex-SS)-βCD-(PCL)₁₄@DOX-SPIO) theranostic nanoparticles. In vitro drug release studies showed that approximately 100% of the DOX was released from disulfide bond-linked theranostic nanoparticles within 24 h under a reducing environment in the presence of 10.0 mM GSH. DOX and SPIO could be delivered into HepG2 cells efficiently, owing to the folate receptor-mediated endocytosis process of the nanoparticles and glutathione (GSH), which triggered disulfide-bonds cleaving. Moreover, (FA-Dex-SS)-βCD-(PCL)₁₄@DOX-SPIO showed strong MRI contrast enhancement properties. In conclusion, folic acid-decorated reduction-sensitive star polymeric nanoparticles are a potential theranostic nanoparticle candidate for tumor-targeted MRI and chemotherapy.

Smart MSN-Drug-Delivery System for Tumor Cell Targeting and Tumor Microenvironment Release

Tumor-targeted delivery and controlled release of antitumor drugs are promising strategies for increasing chemotherapeutic efficacy and reducing adverse effects. Although mesoporous silica nanoparticles (MSNs) have been known as a potential delivery system for doxorubicin (DOX), they have restricted applications due to their uncontrolled leakage and burst release from their large open pores. Herein, we engineered a smart drug-delivery system (smart MSN-drug) based on MSN-drug loading, cell membrane mimetic coating, on-demand pore blocking/opening, and tumor cell targeting strategies. The pore size of DOX-loaded MSNs was narrowed by polydopamine coating, and the pores/channels were blocked with tumor-targeting ligands anchored by tumor environment-rupturable -SS- chains. Furthermore, a cell membrane mimetic surface was constructed to enhance biocompatibility of the smart MSN-drug. Confocal microscopy results demonstrate highly selective uptake (12-fold in comparison with L929 cell) of the smart MSN-drug by HeLa cells and delivery into the HeLa cellular nuclei. Further in vitro IC₅₀ studies showed that the toxicity of the smart MSN-drug to HeLa cells was 4000-fold higher than to the normal fibroblast cells. These exciting results demonstrate the utility of the smart MSN-drug capable of selectively killing tumor cells and saving the normal cells.

Nanotechnology-based delivery of CRISPR/Cas9 for cancer treatment

CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats-associated protein 9) is a potent technology for gene-editing. Owing to its high specificity and efficiency, CRISPR/Cas9 is extensity used for human diseases treatment, especially for cancer, which involves multiple genetic alterations. Different concepts of cancer treatment by CRISPR/Cas9 are established. However, significant challenges remain for its clinical applications. The greatest challenge for CRISPR/Cas9 therapy is how to safely and efficiently deliver it to target sites in vivo. Nanotechnology has greatly contributed to cancer drug delivery. Here, we present the action mechanisms of CRISPR/Cas9, its application in cancer therapy and especially focus on the nanotechnology-based delivery of CRISPR/Cas9 for cancer gene editing and immunotherapy to pave the way for its clinical translation. We detail the difficult barriers for CRISIR/Cas9 delivery in vivo and discuss the relative solutions for encapsulation, target delivery, controlled release, cellular internalization, and endosomal escape.

Structurally nanoengineered antimicrobial peptide polymers: design, synthesis and biomedical applications

Antimicrobial resistance not only increases the contagiousness of infectious diseases but also a threat for the future as it is one of the health care concern around the globe. Conventional antibiotics are unsuccessful in combating chronic infections caused by multidrug-resistant (MDR) bacteria, therefore it is important to design and develop novel strategies to tackle this problems. Among various novel strategies, Structurally Nanoengineered Antimicrobial Peptide Polymers (SNAPPs) have been introduced in recent years to overcome this global health care issue and they are found to be more efficient in their performance. Many facile methods are adapted to synthesize complex SNAPPs with required dimensions and unique functionalities. Their unique characteristics and remarkable properties have been exploited for their immense applications in various fields including biomedicine, targeting therapies, gene delivery, bioimaging, and many more. This review article deals with its background, design, synthesis, mechanism of action, and wider applications in various fields of SNAPPs.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

Versatile Types of Cyclodextrin-Based Nucleic Acid Delivery Systems

Nowadays, nucleic acid therapy has become a promising way for the treatment of various malignant diseases. Cyclodextrin (CD)-based nucleic acid delivery systems have attracted widespread attention due to the favorable chemical structures and excellent biological properties of CD. Recently, a variety of CD-based nucleic acid delivery systems has been designed according to the different functions of CD for flexible gene therapies. In this review, the construction strategies and biomedical applications of CD-based nucleic acid delivery systems are mainly focused on. The review begins with an introduction to the synthesis and properties of simple CD-grafted polycations. Thereafter, CD-related supramolecular assemblies based on different guest components are discussed in detail. Finally, different CD-based organic/inorganic nanohybrids and their relevant functions are demonstrated. It is hoped that this brief review will motivate the delicate design of CD-based nucleic acid delivery systems for potential clinical applications.

Dual Redox/pH-Sensitive Micelles Self-Assembled From Star-Like Amphiphilic Copolymers Based On Sucrose For Controlled Doxorubicin Delivery

Novel dual redox/pH-sensitive star-like amphiphilic sucrose-oligo(butyl fumarate) (thioglycolic acid conjugate)-SS-poly(ethylene glycol) (Suc-OBF(TGA)-SS-PEG) copolymers and their self-assembled micelles were prepared and utilized for intracellular doxorubicin delivery. Importance of changing the hydrophobic chain length on micelles properties was investigated. Results showed that the micelles with longer hydrophobic chain exhibited smaller size and were more stable in aqueous solution. The redox and pH sensitivity of the micelles was confirmed by the change of micelle diameter/diameter distribution measured by dynamic light scattering and the change of micellar morphology observed by scanning electron microscope. The micelles display a decent doxorubicin loading capacity. In vitro release studies showed that only 14.3% doxorubicin was released from doxorubicin-loaded micelles under physiological conditions in 30 h. The release of doxorubicin was accelerated at pH 5.5 or in the presence of 10 mM glutathione at pH 7.4 (46.9% and 76.9% of doxorubicin was released, respectively, in 30 h). The doxorubicin release was further expedited under pH 5.5 and 10 mM GSH conditions (91.4%). Suc-OBF(TGA)-SS-PEG micelles displayed no cytotoxicity toward HDF cells. MTT assays indicated that doxorubicin-loaded micelles had good cytotoxicity against MCF-7 cells. This work suggested that star-like amphiphilic Suc-OBF(TGA)-SS-PEG copolymer micelles may provide a promising platform for delivering doxorubicin and other hydrophobic anticancer drugs.

Cancer-Targeting Nanoparticles for Combinatorial Nucleic Acid Delivery

Nucleic acids are a promising type of therapeutic for the treatment of a wide range of conditions, including cancer, but they also pose many delivery challenges. For efficient and safe delivery to cancer cells, nucleic acids must generally be packaged into a vehicle, such as a nanoparticle, that will allow them to be taken up by the target cells and then released in the appropriate cellular compartment to function. As with other types of therapeutics, delivery vehicles for nucleic acids must also be designed to avoid unwanted side effects; thus, the ability of such carriers to target their cargo to cancer cells is crucial. Classes of nucleic acids, hurdles that must be overcome for effective intracellular delivery, types of nonviral nanomaterials used as delivery vehicles, and the different strategies that can be employed to target nucleic acid delivery specifically to tumor cells are discussed. Additonally, nanoparticle designs that facilitate multiplexed delivery of combinations of nucleic acids are reviewed.

Folate-Targeted Anticancer Drug Delivery via a Combination Strategy of a Micelle Complex and Reducible Conjugation

Conjugation of various active targeting ligands to the surface of nanocarriers to realize specific recognition by the corresponding receptors localized on the membrane of the cancer cells has provided a powerful means toward enhanced cancer therapy. Folic acid (FA) is one of the most used targeting ligands due to the overexpressed FA receptors in many cancer cell lines. However, conjugation of hydrophobic FA to the surface of nanocarriers usually alters the hydrophilic/hydrophobic balance of the stabilized nanoparticles, leading to their thermodynamic instability and subsequent formation of aggregates, which apparently compromises the in vivo long circulation and minimized side effects of nanocarriers. The currently leading strategy to overcome this issue is to incorporate a protecting hydrophilic stealth that can be deshielded to expose the targeting ligand at the desired tumor site, which generally involves multistep chemical modifications, conjugations, and purifications. To develop a simple alternative toward FA-mediated enhanced anticancer drug delivery, a combination strategy of micelle complex and reducible conjugation was reported in this study. FA was first conjugated to the terminus of the hydrophilic block of a reduction-sensitive miktoarm star-shaped amphiphilic copolymer, PCL₃-SS-POEGMA₁, with the previously optimized star structure by click coupling via a reducible disulfide link. The resulting PCL₃-SS-POEGMA₁-SS-FA was further mixed with the parent PCL₃-SS-POEGMA₁ to afford a micelle complex with both reducibly conjugated and relatively low amount of FA-targeting ligands toward excellent FA-mediated targeted drug delivery without compromised salt stability in vitro and in vivo. Therefore, the combined strategy developed herein provides a simple and powerful means to promote FA-mediated anticancer drug delivery.

The classification and application of cyclodextrin polymers: a review

After introducing the concept of cyclodextrin polymers, their classification and applications have been summarized.

Ligand targeting and peptide functionalized polymers as non-viral carriers for gene therapy

Ligand targeting and peptide functionalized polymers serve as gene carriers for efficient gene delivery.

Synthesis of polymeric micelles with dual-functional sheddable PEG stealth for enhanced tumor-targeted drug delivery

We reported the synthesis of polymeric micelles with a dual-functional sheddable mPEG stealth to realize simultaneously tumor-triggered targeting and intracellular micelle destabilization for enhanced anticancer drug delivery.

Diblock brush-arm star copolymers via a core-first/graft-from approach using γ-cyclodextrin and ROMP: a modular platform for drug delivery

Water-soluble diblock brush-arm star copolymers using γ-CD-based core-first ring-opening metathesis polymerization, allowing for anticancer drug delivery via host–guest interaction.

In vitro and in vivo characteristics of doxorubicin-loaded cyclodextrine-based polyester modified gadolinium oxide nanoparticles: a versatile targeted theranostic system for tumour chemotherapy and molecular resonance imaging

β-Cyclodextrine-based polyester was coated on the surface of gadolinium oxide nanoparticles (NPs) and then functionalised with folic acid to produce an efficient pH-sensitive targeted theranostic system (Gd₂O₃@PCD-FA) for doxorubicin delivery and magnetic resonance imaging (MRI). Gd₂O₃@PCD-FA was fully characterised by FTIR, vibrating sample magnetometer, TGA, XRD, SEM and TEM analyses. The dissolution profile of DOX showed a pH sensitive release. No significant toxicity was observed for the targeted NPs (Gd₂O₃@PCD-FA) and DOX-loaded NPs inhibiting M109 cells viability more efficiently than free DOX. Moreover, the negligible hemolytic activity of the targeted NPs showed their appropriate hemocompatibility. The preferential uptake was observed for the developed Gd₂O₃@PCD-FA-DOX NPs in comparison with Dotarem using T₁- and T₂-weighted MRI in the presence of folate receptor-positive and folate receptor-negative cancer cells (M109 and 4T1, respectively). Furthermore, in vivo studies revealed that Gd₂O₃@PCD-FA-DOX not only exhibited considerably relaxivity performance as a contrast agent for MRI, but also improved in vivo anti-tumour efficacy of the system. The results suggest that Gd₂O₃@PCD-FA-DOX improves its therapeutic efficacy in the treatment of solid tumours and also reduces the adverse effects, so it could be proposed as a promising drug delivery system for chemotherapy and molecular imaging diagnosis in MRI.

Macrocyclic Compounds for Drug and Gene Delivery in Immune-Modulating Therapy

For decades, macrocyclic compounds have been widely applied in various fields owing to essential physicochemical properties such as their rigid cyclic structures, geometric dimensions (diameter and height), hydrophobic cavity, and hydrophilic interface. This review is an attempt to summarize various research accomplishments involving macrocyclic compounds for drug and gene delivery in immune-modulating therapies: the structures and benefits of main host molecules, their mechanisms regulating the immune system from cell uptake to activation of dendritic cells and T helper lymphocytes, as well as their potential immunotherapy for different diseases. Macrocyclic compounds including cucurbiturils (CBs), calixarenes, pillararenes, cyclodextrins (CyDs), macrocyclic peptides and metallo-supramolecular compounds, have their own unique physicochemical properties and functional derivatizations that enable to improve the biocompatibility, responsiveness to stimuli, and effectiveness of immune-modulating therapy. Based on abundant clarifications of the biological immunity mechanisms, representative constructions of macrocyclic compounds for immune therapies have been conducted for the investigation of treatment of different diseases including cancer, atherosclerosis, Niemann-Pick type C1 disease (NPC1), diabetes, and inflammations. Although there are critical challenges that remain to be conquered, we believe the future of macrocyclic compounds in the immune-modulating therapy must be bright.

In Vitro and In Vivo Co-delivery of siRNA and Doxorubicin by Folate-PEG-Appended Dendrimer/Glucuronylglucosyl-β-Cyclodextrin Conjugate

We have previously reported the utility of folate-polyethylene glycol-appended dendrimer conjugate with glucuronylglucosyl-β-cyclodextrin (Fol-PEG-GUG-β-CDE) (generation 3) as a tumor-selective carrier for siRNA against polo-like kinase 1 (siPLK1) in vitro. In the present study, we evaluated the potential of Fol-PEG-GUG-β-CDE as a carrier for the low-molecular antitumor drug doxorubicin (DOX). Further, to fabricate advanced antitumor agents, we have prepared a ternary complex of Fol-PEG-GUG-β-CDE/DOX/siPLK1 and evaluated its antitumor activity both in vitro and in vivo. Fol-PEG-GUG-β-CDE released DOX in an acidic pH and enhanced the cellular accumulation and cytotoxic activity of DOX in folate receptor-α (FR-α)-overexpressing KB cells. Importantly, the Fol-PEG-GUG-β-CDE/DOX/siPLK1 ternary complex exhibited higher cytotoxic activity than a binary complex of Fol-PEG-GUG-β-CDE with DOX or siPLK1 in KB cells. In addition, the cytotoxic activity of the ternary complex was reduced by the addition of folic acid, a competitor against FR-α. Furthermore, the ternary complex showed a significant antitumor activity after intravenous administration to the tumor-bearing mice. These results suggest that Fol-PEG-GUG-β-CDE has the potential of a tumor-selective co-delivery carrier for DOX and siPLK1.

Gadolinium (III) oxide nanoparticles coated with folic acid-functionalized poly(β-cyclodextrin-co-pentetic acid) as a biocompatible targeted nano-contrast agent for cancer diagnostic: in vitro and in vivo studies

OBJECTIVES

In this study, a novel targeted MRI contrast agent was developed by coating gadolinium oxide nanoparticles (Gd₂O₃ NPs) with β-cyclodextrin (CD)-based polyester and targeted by folic acid (FA).

MATERIALS AND METHODS

The developed Gd₂O₃@PCD-FA MRI contrast agent was characterized and evaluated in relaxivity, in vitro cell targeting, cell toxicity, blood compatibility and in vivo tumor MR contrast enhancement.

RESULTS

In vitro cytotoxicity and hemolysis assays revealed that Gd₂O₃@PCD-FA NPs have no significant cytotoxicity after 24 and 48 h against normal human breast cell line (MCF-10A) at concentration of up to 50 µg Gd⁺³/mL and have high blood compatibility at concentration of up to 500 µg Gd⁺³/mL. In vitro MR imaging experiments showed that Gd₂O₃@PCD-FA NPs enable targeted contrast T₁- and T₂-weighted MR imaging of M109 as overexpressing folate receptor cells. Besides, the in vivo analysis indicated that the maximum contrast-to-noise ratio (CNR) of tumor in mice increased after injection of Gd₂O₃@PCD-FA up to 5.89 ± 1.3 within 1 h under T₁-weighted imaging mode and reduced to 1.45 ± 0.44 after 12 h. While CNR increased up to maximum value of 1.98 ± 0.28 after injection of Gd₂O₃@PCD within 6 h and reduced to 1.12 ± 0.13 within 12 h.

CONCLUSION

The results indicate the potential of Gd₂O₃@PCD-FA to serve as a novel targeted nano-contrast agent in MRI.

A Polycationic Brush Mediated Co-Delivery of Doxorubicin and Gene for Combination Therapy

The combination of drug and gene strategies for cancer therapy, has exhibited greater effectiveness than drug or gene therapy alone. In this paper, a coil-comb shaped polycationic brush was used as a multifunctional carrier for co-delivery of drug and gene. The side chains of the comb block of the brush were composed of cyclodextrin (CD)-containing cationic star polymers, with a super-high density of positive charge. Doxorubicin (DOX) could be loaded into the cavity of CD polymers to form DOX-loaded nanoparticles (DOX-NPs) and the p53 gene could be subsequently condensed by DOX-NPs. The obtained DOX-NPs/pDNA complexes were less than 150 nm in size, and so could transport DOX and the gene into the same cell. The complexes performed well with regards to their transfection efficiency on MCF-7 cancer cells. As a result, enhanced cell growth inhibition, with decreased DOX dosage was achieved due to the synergistic effect of co-delivery of DOX and the p53 gene. This finding provides an efficient approach for the development of a co-delivery system in combination therapy.

Inhibition of proliferation and migration of tumor cells through lipoic acid-modified oligoethylenimine-mediated p53 gene delivery

Inhibition of proliferation and migration of tumor cells through lipoic acid-modified oligoethylenimine-mediated p53 gene delivery.

Cyclodextrin-based delivery systems for cancer treatment

Cyclodextrins, one of safe excipients, are able to form host-guest complexes with fitted molecules given the unique nature imparted by their structure in result of a number of pharmaceutical applications. On the other hand, targeted or responsive materials are appealing therapeutic platforms for the development of next-generation precision medications. Meanwhile, cyclodextrin-based polymers or assemblies can condense DNA and RNA in result to be used as genetic therapeutic agents. Armed with a better understanding of various pharmaceutical mechanisms, especially for cancer treatment, researchers have made lots of works about cyclodextrin-based drug delivery systems in materials chemistry and pharmaceutical science. This Review highlights recent advances in cyclodextrin-based delivery systems for cancer treatment capable of targeting or responding to the physiological environment. Key design principles, challenges and future directions, including clinical translation, of cyclodextrin-based delivery systems are also discussed.

Biotin-Tagged Polysaccharide Vesicular Nanocarriers for Receptor-Mediated Anticancer Drug Delivery in Cancer Cells

Biotin-conjugated multistimuli-responsive polysaccharide vesicular nanocarriers are designed and developed, for the first time, to accomplish receptor-mediated endocytosis in cancer cells and to deliver anticancer drugs to intracellular compartments. For this purpose, a new renewable hydrophobic unit was custom designed with redox-degradable disulfide and enzyme-biodegradable aliphatic ester chemical linkages, and it was conjugated along with biotin on the dextran backbone. The dextran derivative self-assembled into nanovesicles of <200 nm in size, which were characterized by dynamic and static light scattering, electron, and atomic force microscopes. Avidin-HABA assay established the high affinity of biotin-tagged dextran vesicles toward membrane-receptors up to 25 nM concentration. Doxorubicin-hydrochloride (DOX.HCl)-loaded dextran vesicles exhibited stable formulation in phosphate-buffered saline (PBS) and fetal bovine serum (FBS). Redox-degradation by glutathione (GSH) showed 60% drug release, whereas lysosomal esterase enzyme enabled >98% drug release in 12 h. Confocal microscope and flow cytometry-assisted time-dependent cellular uptake studies revealed that the biotin-receptors overexpressed in cervical cancer cells (HeLa) exhibited larger drug accumulation through the receptor-assisted endocytosis process. This process enabled the delivery of higher amount of DOX and significantly enhanced the killing in cancer cells (HeLa) compared to wild-type mouse embryonic fibroblast cells (WT-MEF, normal cells). Control experiments such as biotin pretreatment in cancer cells and energy-suppressed cellular uptake at 4 °C further supported the occurrence of receptor-mediated endocytosis by the biotin-tagged polymer vesicles. This report provides first insights into the targeted polysaccharide vesicle platform, and the proof-of-concept is successfully demonstrated in biotin receptor-overexpressed cervical cancer cells.

Supramolecular Host-Guest Chemistry-Based Folate/Riboflavin Functionalization and Cancer Cell Labeling of Nanoparticles

Nanoparticle-based cellular probes are commonly designed via covalent conjugation with affinity biomolecules. Those nanobioconjugates selectively interact with cell surface receptors and induce endocytosis followed by intracellular trafficking. However, this approach requires functional modification of biomolecules that may alter their biochemical activity. Here, we show that supramolecular host-guest chemistry can be utilized as an alternative approach in nanoparticle functionalization and selective cell labeling. We have used cyclodextrin-conjugated quantum dots (QDs) for supramolecular host-guest interaction-based functionalization with folate (QD-folate) and riboflavin (QD-riboflavin), where cyclodextrin acts as a host for the folate/riboflavin guest. We demonstrate that QD-folate and QD-riboflavin selectively label cells that have over-expressed folate/riboflavin receptors and induce the endocytosis pathway similar to covalently conjugated folate-/riboflavin-based nanoprobes. However, labeling is highly sensitive to the molar ratio of folate/riboflavin to cyclodextrin and incubation time. The presented functionalization/labeling approach is unique as it does not require covalent conjugation and may be extended for in vivo targeting application via simultaneous delivery of host and guest molecules.

Reductive nanocomplex encapsulation of cRGD-siRNA conjugates for enhanced targeting to cancer cells

In this study, through covalent conjugation and lipid material entrapment, a combined modification strategy was established for effective delivery of small interfering RNA (siRNA). Single strands of siRNA targeting to BRAF^V600E gene (siMB3) conjugated with cRGD peptide at 3'-terminus or 5'-terminus via cleavable disulfide bond was synthesized and then annealed with corresponding strands to obtain single and bis-cRGD-siRNA conjugates. A cationic lipid material (CLD) developed by our laboratory was mixed with the conjugates to generate nanocomplexes; their uniformity and electrical property were revealed by particle size and zeta potential measurement. Compared with CLD/siBraf, CLD/cRGD-siBraf achieved higher cell uptake and more excellent tumor-targeting ability, especially 21 (sense-5'/antisense-3″-cRGD-congjugate) nanocomplex. Moreover, they can regulate multiple pathways to varying degree and reduce acidification of endosome. Compared with the gene silencing of different conjugates, single or bis-cRGD-conjugated siRNA showed little differences except 22 (5/5) which cRGD was conjugated at 5'-terminus of antisense strand and sense strand. However bis-cRGD conjugate 21 nanocomplex exhibited better specific target gene silencing at multiple time points. Furthermore, the serum stabilities of the bis-cRGD conjugates were higher than those of the single-cRGD conjugates. In conclusion, all these data suggested that CLD/bis-conjugates, especially CLD/21, can be an effective system for delivery of siRNA to target BRAF^V600E gene for therapy of melanoma.

Low Molecular Weight Branched PEI Binding to Linear DNA

Polyethylenimine (PEI) is one of the most versatile non-viral vectors used in gene therapy, especially for delivering plasmid DNA to human cells. However, a good understanding of PEI binding to DNA, the fundamental basis for the functioning of PEI as a vector, has been missing in the literature. In this study, PEI (branched, 600 Da) binding to DNA was examined by isothermal titration calorimetry (ITC), quartz crystal microbalance (QCM) and a complementary set of analysis tools. We demonstrated that a separation between the binding heat and the condensation heat is needed and that the excluded site model should be used for PEI binding stage in the ITC analysis. The equilibrium constant for PEI binding to DNA was determined to be 2.5×10⁵ M^-1 from the ITC analysis, and as 2.3×10⁵ M^-1 from the QCM analysis. Additionally, we suggested that the 600 Da branched PEI binds to the major groove of DNA and the rearrangement of PEI on DNA may be difficult to occur because of the small dissociation rate. The binding analysis presented here can be employed to improve our understanding of the functioning of PEI and PEI-like non-viral vectors.

Cyclodextrin-based supramolecular nanoparticles for biomedical applications

Supramolecular host-guest interactions are ideal for engineering supramolecular nanoparticles (SNPs), because their modular character offers the possibility of using the same basic SNPs made of very similar building blocks in a variety of applications. The most widely used host is cyclodextrin (CD), therefore, this review will focus on SNPs involving CD as the host entity. In the first part, particle formation and size control are described, and the forces that induce the assembly between the different components and, therefore, result in the formation of stable and controllable nanoparticles. In the second part, the use of CD-based SNPs for diagnostics and therapeutics is described. Here, the emphasis is on how the therapeutic agent/imaging component is included in the system and how it is released at the target site. CD-based SNPs provide great possibilities for the formulation of nanoparticles for biomedical applications because of their high flexibility, stability, modular character, and biocompatibility.

Recent advances in siRNA delivery

In the 1990s an unexpected gene-silencing phenomena in plants, the later called RNA interference (RNAi), perplexed scientists. Following the proof of activity in mammalian cells, small interfering RNAs (siRNAs) have quickly crept into biomedical research as a new powerful tool for the potential treatment of different human diseases based on altered gene expression. In the past decades, several promising data from ongoing clinical trials have been reported. However, despite surprising successes in many pre-clinical studies, concrete obstacles still need to be overcome to translate therapeutic siRNAs into clinical reality. Here, we provide an update on the recent advances of RNAi-based therapeutics and highlight novel synthetic platforms for the intracellular delivery of siRNAs.

PGMA-Based Star-Like Polycations with Plentiful Hydroxyl Groups Act as Highly Efficient miRNA Delivery Nanovectors for Effective Applications in Heart Diseases

Poly(glycidyl methacrylate)-based star-like polycations with rich hydrophilic hydroxyl groups can efficiently transfer miRNA into primary cardiac fibroblasts for effective applications in cardiac diseases, such as inhibition of cardiac fibrosis and hypertrophy.

Synthesis of intracellular reduction-sensitive amphiphilic polyethyleneimine and poly(ε-caprolactone) graft copolymer for on-demand release of doxorubicin and p53 plasmid DNA

This study aims to present a new intelligent polymeric nano-system used for combining chemotherapy with non-viral gene therapy against human cancers. An amphiphilic copolymer synthesized through the conjugation of low molecular weight polyethyleneimine (LMw-PEI) and poly(ε-caprolactone) (PCL) via a bio-cleavable disulfide linkage was successfully employed for the simultaneous delivery of drug and gene molecules into target cells. Compared to the conventional PCL copolymerization pathway, this paper represents a straightforward and efficient reaction pathway including the activation of PCL-diol hydroxyl end groups, cystamine attachment and LMw-PEI conjugation which are successfully performed at mild conditions as confirmed by FTIR and (1)H NMR. Thermal, morphological characteristics as well as biocompatibility of the copolymer were investigated. The copolymer showed great tendency to form positively charged nanoparticles (∼163.1nm, +35.3mV) with hydrophobic core and hydrophilic shell compartments implicating its potential for encapsulation of anti-cancer drug and plasmid DNA, respectively. The gel retardation assay confirmed that the nanoparticles could successfully inhibit the migration of pDNA at ∼5 nanoparticle/pDNAw/w. The in vitro cytotoxicity tests and LDH assay revealed that the cationic amphiphilic copolymer was essentially non-toxic in different carcinoma cell lines in contrast to branched PEI 25K. Moreover, the presence of redox sensitive disulfide linkages provided smart nanoparticles with on-demand release behavior in response to reducing agents such as cytoplasmic glutathione (GSH). Importantly, confocal microscopy images revealed that in contrast to free Dox, the nanoparticles were capable of faster internalizing into the cells and accumulating in the perinuclear region or even in the nucleus. Finally, the co-delivery of Dox and p53-pDNA using the copolymer displayed greater cytotoxic effect compared with the Dox-loaded nanoparticle counterpart as revealed by cell viability and Caspase 3 expression assay. These results suggest the copolymer as a promising candidate for the development of smart delivery systems.

STATEMENT OF SIGNIFICANCE

We employed cystamine dihydrochloride as a disulfide linkage for the conjugation of PCL diol and low molecular weight PEI segments through a straightforward and efficient reaction pathway at mild conditions. The new copolymer was essentially non-toxic in different carcinoma cell lines and showed great tendency to form positively charged nanoparticles. Therefore, it can be utilized as a promising platform for simultaneous drug and gene delivery to aggressive cancers. The results of drug and gene co-delivery experiments confirmed the pivotal role of disulfide linkage on the controlled release of both drug and gene molecules in response to glutathione concentration gradient between extracellular and intracellular microenvironments. In addition, the co-delivery of doxorubicin and p53 plasmid DNA using the new copolymer displayed greater cytotoxic effect compared with single agent (i.e. Dox) loaded counterpart, which indicated the significance of rapid dissociation of therapeutic agents from the carrier for synergistic cytotoxic effects on cancer cells.

Post-Transcriptional Regulation of the GASC1 Oncogene with Active Tumor-Targeted siRNA-Nanoparticles

Basal-like breast cancer (BLBC) accounts for the most aggressive types of breast cancer, marked by high rates of relapse and poor prognoses and with no effective clinical therapy yet. Therefore, investigation of new targets and treatment strategies is more than necessary. Here, we identified a receptor that can be targeted in BLBC for efficient and specific siRNA mediated gene knockdown of therapeutically relevant genes such as the histone demethylase GASC1, which is involved in multiple signaling pathways leading to tumorigenesis. Breast cancer and healthy breast cell lines were compared regarding transferrin receptor (TfR) expression via flow cytometry and transferrin binding assays. Nanobioconjugates made of low molecular weight polyethylenimine (LMW-PEI) and transferrin (Tf) were synthesized to contain a bioreducible disulfide bond. siRNA complexation was characterized by condensation assays and dynamic light scattering. Cytotoxicity, transfection efficiency, and the targeting specificity of the conjugates were investigated in TfR positive and negative healthy breast and breast cancer cell lines by flow cytometry, confocal microscopy, RT-PCR, and Western blot. Breast cancer cell lines revealed a significantly higher TfR expression than healthy breast cells. The conjugates efficiently condensed siRNA into particles with 45 nm size at low polymer concentrations, showed no apparent toxicity on different breast cancer cell lines, and had significantly greater transfection and gene knockdown activity on mRNA and protein levels than PEI/siRNA leading to targeted and therapeutic growth inhibition post GASC1 knockdown. The synthesized nanobioconjugates improved the efficiency of gene transfer and targeting specificity in transferrin receptor positive cells but not in cells with basal receptor expression. Therefore, these materials in combination with our newly identified siRNA sequences are promising candidates for therapeutic targeting of hard-to-treat BLBC and are currently further investigated regarding in vivo targeting efficacy and biocompatibility.

Star Polymers

Recent advances in controlled/living polymerization techniques and highly efficient coupling chemistries have enabled the facile synthesis of complex polymer architectures with controlled dimensions and functionality. As an example, star polymers consist of many linear polymers fused at a central point with a large number of chain end functionalities. Owing to this exclusive structure, star polymers exhibit some remarkable characteristics and properties unattainable by simple linear polymers. Hence, they constitute a unique class of technologically important nanomaterials that have been utilized or are currently under audition for many applications in life sciences and nanotechnologies. This article first provides a comprehensive summary of synthetic strategies towards star polymers, then reviews the latest developments in the synthesis and characterization methods of star macromolecules, and lastly outlines emerging applications and current commercial use of star-shaped polymers. The aim of this work is to promote star polymer research, generate new avenues of scientific investigation, and provide contemporary perspectives on chemical innovation that may expedite the commercialization of new star nanomaterials. We envision in the not-too-distant future star polymers will play an increasingly important role in materials science and nanotechnology in both academic and industrial settings.

Oligonucleotide-based theranostic nanoparticles in cancer therapy

Theranostic approaches, combining the functionality of both therapy and imaging, have shown potential in cancer nanomedicine. Oligonucleotides such as small interfering RNA and microRNA, which are powerful therapeutic agents, have been effectively employed in theranostic systems against various cancers. Nanoparticles are used to deliver oligonucleotides into tumors by passive or active targeting while protecting the oligonucleotides from nucleases in the extracellular environment. The use of quantum dots, iron oxide nanoparticles and gold nanoparticles and tagging with contrast agents, like fluorescent dyes, optical or magnetic agents and various radioisotopes, has facilitated early detection of tumors and evaluation of therapeutic efficacy. In this article, we review the advantages of theranostic applications in cancer therapy and imaging, with special attention to oligonucleotide-based therapeutics.

Disulfide-bridged cleavable PEGylation in polymeric nanomedicine for controlled therapeutic delivery

PEGylation in polymeric nanomedicine has gained substantial predominance in biomedical applications due to its resistance to protein absorption, which is critically important for a therapeutic delivery system in blood circulation. The shielding layer of PEGylation, however, creates significant steric hindrance that negatively impacts cellular uptake and intracellular distribution at the target site. This unexpected effect compromises the biological efficacy of the encapsulated payload. To address this issue, one of the key strategies is to tether the disulfide bond to PEG for constructing a disulfide-bridged cleavable PEGylation. The reversible disulfide bond can be cleaved to enable selective PEG detachment. This article provides an overview on the strategy, method and progress of PEGylation nanosystem with the cleavable disulfide bond.