Biocompatible crosslinked β-cyclodextrin nanoparticles as multifunctional carriers for cellular delivery

Cross-Linked Cyclodextrin-Based Nanoparticles as Drug Delivery Vehicles: Synthesis Strategy and Degradation Studies

In this work, we report on the synthesis and characterization of cyclodextrin-based nanocarriers, intended as new biogenic and biodegradable drug-delivery agents. Specifically, β-cyclodextrins were covalently cross-linked by carbonyl linkages using carbonyldiimidazole (CDI) and were colloidally stabilized via PEGylation to form β-CD-CO-PEG nanoparticles termed CD-CO NPs. The optimized synthesis results in size-controlled nanoparticles with a narrow particle size distribution and a hydrodynamic diameter around 200-300 nm in water and 100-160 nm as dried powder as observed by scanning electron microscopy. CD-CO nanoparticles are promising drug delivery carriers as they offer an intrinsic pore system originating from the β-cyclodextrin building units and an additional intraparticle pore space created by cross-linking these β-cyclodextrin units. We demonstrate the biodegradability of these materials and show exemplarily their drug delivery potential using two different model cargos. Time-based fluorescence release measurements in cuvette established a stable cargoretention of the fluorescent dye Hoechst at neutral pH, and in contrast, an efficient stimuli-responsive release at pH 5, accompanied by a fast nanoparticle degradation. This cargo-release behavior at low pH is further observed with a small drug molecule, the hydrophobic necrosulfonamide, when followed with infrared spectroscopy. Finally, the drug-delivery potential of these new nanoparticles was established by following the cell uptake of covalently labeled CD-CO nanoparticles into HeLa cells with in vitro fluorescence microscopy, whereby the membrane-permeable Hoechst dye was delivered time-delayed in comparison to free Hoechst dye. In summary, our work aims to contribute to the design and understanding of cyclodextrin-based nanocarriers as a promising drug delivery platform.

Crosslinked hydroxypropyl-β-cyclodextrin nanoparticles for improved efficacy of venetoclax against triple negative breast cancer

Bcl-2 protein plays an integral role in hijacking apoptosis and triggering chemoresistance in triple negative breast cancer (TNBC). The present study explored the therapeutic efficacy of Bcl-2 inhibitor i.e., venetoclax (VTX) loaded HP-β-CD NPs (VTX/HP-β-CD NPs) against TNBC. VTX/HP-β-CD NPs were prepared using nanoprecipitation method. The prepared nanoparticles had optimal size (∼217 ± 4.32 nm), narrow PDI (∼0.23 ± 0.01), higher drug loading (∼15.7 ± 1.94 %) and % entrapment efficiency (∼78.5 ± 1.09 %). Morphology assessment revealed a spherical shape. In-vitro release studies displayed sustained release for up to 72h. Moreover, VTX/HP-β-CD NPs exhibited higher cellular uptake, cytotoxicity, and apoptosis index than free drug. Furthermore, the IC50 values for VTX/HP-β-CD NPs were significantly reduced in 4T1 (∼3.96-fold) and MDA-MB-231 (∼5.23-fold) cells. Additionally, VTX/HP-β-CD NPs showed remarkable potential to induce "mixed cell death" by reducing the glutathione (GSH) levels and increasing ROS in TNBC cells. The pharmacokinetic studies showed a marked increase in the AUC0-∞ (∼2.12-fold), Cmax (∼1.05-fold), and t1/2 (∼1.66-fold). Also, anti-cancer efficacy studies in 4T1-based model revealed improved therapeutic efficacy of VTX when delivered via HP-β-CD NPs. Safety evaluation revealed no signs of toxicity. Overall, the prepared nanocarrier holds significant promise in enhancing the payload and efficacy of VTX.

Microtube self-assembly leads to conformational freezing point depression

HYPOTHESIS

Multi-walled tubular aggregates formed by hierarchical self-assembly of beta-cyclodextrin (β-CD) and sodium dodecylsulfate (SDS) hold a great potential as microcarriers. However, the underlying mechanism for this self-assembly is not well understood. To advance the application of these structures, it is essential to fine-tune the cavity size and comprehensively elucidate the energetic balance driving their formation: the bending modulus versus the microscopic line tension.

EXPERIMENTS

We investigated temperature-induced changes in the hierarchical tubular aggregates using synchrotron small-angle X-ray scattering across a broad concentration range. Detailed analysis of the scattering patterns enabled us to determine the structural parameters of the microtubes and to construct a phase diagram of the system.

FINDINGS

The microtubes grow from the outside in and melt from the inside out. We relate derived structural parameters to enthalpic changes driving the self-assembly process on the molecular level in terms of their bending modulus and microscopic line tension. We find that the conformation of the crystalline bilayer affects the saturation concentration, providing an example of a phenomenon we call conformational freezing point depression. Inspired by the colligative phenomenon of freezing point depression, well known from undergraduate physics, we model this system by including the membrane conformation, which can describe the energetics of this hierarchical system and give access to microscopic properties without free parameters.

Nanoporous air filtering systems made from renewable sources: benefits and challenges

There is a crucial need for air purification systems due to increasing air contamination, while conventional air-filtering materials face challenges in eliminating gaseous and particulate pollutants. This review examines the development and characteristics of nanoporous polymeric materials developed from renewable resources, which have rapidly advanced in recent years. These materials offer more sustainable alternatives for nanoporous structures made out of conventional polymers and significantly impact the properties of porous polymers. The review explores nanoporous materials' production from renewable sources, filtering mechanisms, physicochemical makeup, and sensing capabilities. The recent advancements in this field aim to enhance production techniques, lower pressure drop, and improve adsorption efficiency. Currently, supporting approaches include using adsorbent layers and binders to immobilize nanoporous materials. Furthermore, the prospects and challenges of nanoporous materials obtained from renewable sources used for air purification are discussed.

ESI-IM-MS characterization of cyclodextrin complexes and their chemically cross-linked alpha (α-), beta (β-) and gamma (γ-) cyclodextrin particles as promising drug delivery materials with improved bioavailability

Cyclodextrins (CDs) are natural cyclic oligosaccharides with a relatively hydrophobic cavity and a hydrophilic outer surface. In this study, alpha (α-), beta (β-) and gamma (γ-) CD particles were prepared by directly using α-, β-, and γ-CDs as monomeric units and divinyl sulfone (DVS) as a crosslinker in a single-step via reverse micelle microemulsion crosslinking technique. Particles of p(α-CD), p(β-CD), and p(γ-CD) were perfectly spherical in sub- 10 µm size ranges. The prepared p(CD) particles at 1.0 mg/mL concentrations were found biocompatible with > 95 % cell viability against L929 fibroblasts. Furthermore, p(α-CD) and p(β-CD) particles were found non-hemolytic with < 2 % hemolysis ratios, whereas p(γ-CD) particles were found to be slightly hemolytic with its 2.1 ± 0.4 % hemolysis ratio at 1.0 mg/mL concentration. Furthermore, a toxic compound, Bisphenol A (BPA) and a highly antioxidant polyphenol, curcumin (CUR) complexation with α-, β-, and γ-CD molecules was investigated via Electrospray-Ion Mobility-Mass Spectrometry (ESI-IM-MS) and tandem mass spectrometry (MS/MS) analysis. It was determined that the most stable noncovalent complex was in the case of β-CD, but the complex stoichiometry was changed by the hydrophobic nature of the guest molecules. In addition, BPA and CUR were separately loaded into prepared p(CD) particles as active agents. The drug loading and release studies showed that p(CD) particles possess governable loading and releasing profiles.

Self-assembly of β-cyclodextrin-pillar[5]arene molecules into supramolecular nanoassemblies: morphology control by stimulus responsiveness and host-guest interactions

Macrocyclic molecules have attracted considerable attention as new functional materials owing to their unique pore size structure and excellent host-guest properties. With the development of macrocyclic compounds, the properties of mono-modified macrocyclic materials can be improved by incorporating pillar[n]arene or cyclodextrin derivatives through bridge bonds. Herein, we report the self-assembly of amphiphilic di-macrocyclic host molecules (H1-2) based on β-cyclodextrin and pillar[5]arene units linked by azophenyl or biphenyl groups. In a H₂O/DMSO (19 : 1, v/v) mixed polar solvent, an amphiphile H1 with an azophenyl group self-assembled into unique nanorings and exhibited an obvious photoresponsive colour change. This photochromic behaviour makes H1 suitable for application in carbon paper materials on which arbitrary patterns can be erased and rewritten. The amphiphile H2, with a biphenyl unit, self-assembled into spherical micelles. These differences indicate that various linker units lead to changes in the intermolecular and hydrophilic-hydrophobic interactions. In a CHCl₃/DMSO (19 : 1, v/v) mixed low-polarity solvent, the amphiphile H1 self-assembled into fibrous aggregates, whereas the molecule H2 assembled into unique nanoring aggregates. In this CHCl₃/DMSO mixed solvent system, small nanosheet aggregates were formed by the addition of a guest molecule (G) composed of tetraphenylethene and hexanenitrile groups. With prolonged aggregation time, the small sheet aggregates further aggregated into cross-linked nanoribbons and eventually formed large nanosheet aggregates. The data reveal that the morphology of H1-2 can be controlled by tuning the intermolecular interactions of the molecules via the formation of host-guest complexes. Moreover, the polyhydroxy cyclodextrin unit on H1-2 can be strongly adsorbed on the stationary phase in column chromatography via multiple hydrogen bonds, and the singly modified pillar[5]arenes can be successfully separated by host-guest interactions.

Cyclodextrin-Based Polymeric Materials Bound to Corona Protein for Theranostic Applications

Cyclodextrins (CDs) are cyclic oligosaccharide structures that could be used for theranostic applications in personalized medicine. These compounds have been widely utilized not only for enhancing drug solubility, stability, and bioavailability but also for controlled and targeted delivery of small molecules. These compounds can be complexed with various biomolecules, such as peptides or proteins, via host-guest interactions. CDs are amphiphilic compounds with water-hating holes and water-absorbing surfaces. Architectures of CDs allow the drawing and preparation of CD-based polymers (CDbPs) with optimal pharmacokinetic and pharmacodynamic properties. These polymers can be cloaked with protein corona consisting of adsorbed plasma or extracellular proteins to improve nanoparticle biodistribution and half-life. Besides, CDs have become famous in applications ranging from biomedicine to environmental sciences. In this review, we emphasize ongoing research in biomedical fields using CD-based centered, pendant, and terminated polymers and their interactions with protein corona for theranostic applications. Overall, a perusal of information concerning this novel approach in biomedicine will help to implement this methodology based on host-guest interaction to improve therapeutic and diagnostic strategies.

Nanotechnology-Assisted Cell Tracking

The usefulness of nanoparticles (NPs) in the diagnostic and/or therapeutic sector is derived from their aptitude for navigating intra- and extracellular barriers successfully and to be spatiotemporally targeted. In this context, the optimization of NP delivery platforms is technologically related to the exploitation of the mechanisms involved in the NP-cell interaction. This review provides a detailed overview of the available technologies focusing on cell-NP interaction/detection by describing their applications in the fields of cancer and regenerative medicine. Specifically, a literature survey has been performed to analyze the key nanocarrier-impacting elements, such as NP typology and functionalization, the ability to tune cell interaction mechanisms under in vitro and in vivo conditions by framing, and at the same time, the imaging devices supporting NP delivery assessment, and consideration of their specificity and sensitivity. Although the large amount of literature information on the designs and applications of cell membrane-coated NPs has reached the extent at which it could be considered a mature branch of nanomedicine ready to be translated to the clinic, the technology applied to the biomimetic functionalization strategy of the design of NPs for directing cell labelling and intracellular retention appears less advanced. These approaches, if properly scaled up, will present diverse biomedical applications and make a positive impact on human health.

Nanoparticle Systems for Cancer Phototherapy: An Overview

Photodynamic therapy (PDT) and photothermal therapy (PTT) are photo-mediated treatments with different mechanisms of action that can be addressed for cancer treatment. Both phototherapies are highly successful and barely or non-invasive types of treatment that have gained attention in the past few years. The death of cancer cells because of the application of these therapies is caused by the formation of reactive oxygen species, that leads to oxidative stress for the case of photodynamic therapy and the generation of heat for the case of photothermal therapies. The advancement of nanotechnology allowed significant benefit to these therapies using nanoparticles, allowing both tuning of the process and an increase of effectiveness. The encapsulation of drugs, development of the most different organic and inorganic nanoparticles as well as the possibility of surfaces' functionalization are some strategies used to combine phototherapy and nanotechnology, with the aim of an effective treatment with minimal side effects. This article presents an overview on the use of nanostructures in association with phototherapy, in the view of cancer treatment.

Curcumin Encapsulated in Crosslinked Cyclodextrin Nanoparticles Enables Immediate Inhibition of Cell Growth and Efficient Killing of Cancer Cells

The efficiency of anti-cancer drugs is commonly determined by endpoint assays after extended incubation times, often after days. Here we demonstrate that curcumin encapsulated in crosslinked cyclodextrin nanoparticles (CD-NP) acts extremely rapidly on cell metabolism resulting in an immediate and complete inhibition of cell growth and in efficient cancer-cell killing only few hours after incubation. This early onset of anti-cancer action was discovered by live-cell high-throughput fluorescence microscopy using an environmental stage. To date, only very few examples of covalently crosslinked nanoscale CD-based (CD-NP) drug carriers exist. Crosslinking cyclodextrins enables the adsorption of unusually high payloads of hydrophobic curcumin (762 µg CC/mg CD-NP) reflecting a molar ratio of 2.3:1 curcumin to cyclodextrin. We have investigated the effect of CD-NP encapsulated curcumin (CD-CC-NP) in comparison to free, DMSO-derived curcumin nanoparticles (CC-NP) on 4 different cell lines. Very short incubations times as low as 1 h were applied and cell responses after medium change were subsequently followed over two days. We show that cell proliferation is inhibited nearly immediately in all cell lines and that a cell- and concentration dependent cancer-cell killing occurs. Anti-cancer effects were similar with free and encapsulated curcumin, however, encapsulation in CD-NP drastically extends the long-term photostability and anti-cancer activity of curcumin. Curcumin-sensitivity is highest in HeLa cells reaching up to 90% cell death under these conditions. Sensitivity decreased from HeLa to T24 to MDA MB-231 cells. Strikingly, the immortalized non-cancerous cell line MCF-10A was robust against curcumin concentrations that were highly toxic to the other cell lines. Our results underline the potential of curcumin as gentle and yet effective natural anti-cancer agent when delivered solvent-free in stabilizing and biocompatible drug carriers such as CD-NP that enable efficient cellular delivery.

Multifunctional nanoparticles of paclitaxel and cyclodextrin-polypeptide conjugates with in vitro anticancer activity

In this study, the cyclodextrin polypeptide (R8-CMβCD) was successfully synthesized by the conjugation of a cell-penetrating peptide (R8) with carboxymethyl-β-cyclodextrin (CMβCD) via the carbon diamine reaction. Then, paclitaxel-loaded nanoparticles (PTX@R8-CMβCD NPs) was prepared. Results of transmission electron microscopy (TEM) showed that PTX@R8-CMβCD NPs were spherical with smooth surfaces and an average diameter about 144 nm. The amount of PTX released from NPs was less than 20% at pH7.4, but it increased significantly to 80% in the weakly acidic cytoplasm of tumors (pH5.0). Furthermore, PTX@R8-CMβCD NPs promoted the cellular uptake of PTX. Further studies on the mechanism showed that cellular uptake of PTX@R8-CMβCD NPs could rely on multiple pathways. In addition, the NPs had the ability to inhibit P-gp efflux pumps. Cytotoxicity tests showed that the NPs had no side effects. Taken together, PTX@R8-CMβCD NPs is an effective anticancer drug delivery system, and the material (R8-CMβCD) may be a promising anti-cancer drug carrier.

Citric acid-crosslinked β-cyclodextrin supported zinc peroxide as a biocompatible H2O2 scavenger

The aim of the present study was to evaluate the H₂O₂ scavenging activity of the ZnO₂/β-CD as a biocompatible composite. Zinc peroxide was prepared via sonochemical approach. To synthesize a green composite, β-cyclodextrin was modified by citric acid (CA) and reacted with ZnO₂ under ultrasonic irradiation. The prepared samples were characterized using XRD, SEM, TGA and FTIR analytical techniques. XRD analysis exhibited a typical pattern of ZnO₂ and demonstrated the presence of citric acid and β-cyclodextrin in composite. The results of the catalytic assay showed that the ZnO₂/CA-βCD composite displayed stronger capability to decompose H₂O₂ in comparison to ZnO₂ particles (about seven times). It was attributed to increased adsorption capacity and solubility of composite due to the presence of citric acid and β-cyclodextrin. MTT assay studies confirmed the non-cytotoxic nature of ZnO₂ particles and ZnO₂/CA-βCD composite.

Cyclodextrin Based Nanoparticles for Drug Delivery and Theranostics

Colloidal nanoparticulate technology has been described in the literature as a versatile drug delivery system. But it possesses some inherent lacunae in their formulation. Cyclodextrins (CDs) have been extensively reported for the solubility enhancement of poorly water-soluble drugs. The CDs can cause intervention in aspects related to nanoparticles (NPs) that include improving drug loading in nano-system, improving stability, site-specific/targeted drug delivery, improving solubility profile and absorption of the drug in nanosystem with consequent improvement in bioavailability, with the possibility of controlled release, safety and efficacy. They find application in for simultaneous diagnosis and therapeutics for better treatment procedures. The current communication is focused on the application of CDs to overcome troubles in nanoparticulate formulation and enhancement of their performance. It also envisages the theranostic aspects of CDs.

Thermo- and redox-responsive dumbbell-shaped copolymers: from structure design to the LCST–UCST transition

Redox- and thermo-responsive dumbbell-shaped copolymers and their self-assembly and stimuli-responsive properties were investigated.

A pH-responsive citric-acid/α-cyclodextrin-functionalized Fe3O4 nanoparticles as a nanocarrier for quercetin: An experimental and DFT study

Developing new nanocarriers and understanding the interactions between the drug and host molecules in the nanocarrier at the molecular level is of importance for future of nanomedicine. In this work, we synthesized and characterized a series of iron oxide nanoparticles (IONPs) functionalized with different organic molecules (citric acid, α-cyclodextrin, and citric acid/α-cyclodextrin composite). It was found that incorporation of citric acid into the α-cyclodextrin had negligible effect on the adsorption efficiency (<5%) of citric acid/α-cyclodextrin functionalized IONPs, while the isotherm adsorption data were well described by the Langmuir isotherm model (q_max = 2.92 mg/g at T = 25 °C and pH = 7). In addition, the developed nanocarrier showed pH-responsive behavior for releasing the quercetin molecules as drug model, where the Korsmeyer-Peppas model could describe the release profile with Fickian diffusion (n < 0.45 for at all pH and temperatures). Then, Density functional theory was applied to calculate the absolute binding energies (ΔE_b) of the complexation of quercetin with different host molecules in the developed nanocarriers. The calculated energies are as follow: 1) quercetin and citric acid: ΔE_b = -16.58 kcal/mol, 2) quercetin and α-cyclodextrin: ΔE_b = -46.98 kcal/mol, and 3) quercetin and citric acid/α-cyclodextrin composite: ΔE_b = -40.15 kcal/mol. It was found that quercetin tends to interact with all hosts via formation of hydrogen bonds and van der Waals interactions. Finally, the cytotoxicity of the as-developed nanocarriers was evaluated using MTT assay and both normal NIH-3T3 and cancereous HeLa cells. The cell viability results showed that the quercetin could be delivered effectively to the HeLa cells due to the acidic environment inside the cells with minimum effect on the viability of NIH-3T3 cells. These results might open a new window to design of stimuli-responsive nanocarriers for drug delivery applications.

Manganese dioxide nanosheets: from preparation to biomedical applications

Advancements in nanotechnology and molecular biology have promoted the development of a diverse range of models to intervene in various disorders (from diagnosis to treatment and even theranostics). Manganese dioxide nanosheets (MnO₂ NSs), a typical two-dimensional (2D) transition metal oxide of nanomaterial that possesses unique structure and distinct properties have been employed in multiple disciplines in recent decades, especially in the field of biomedicine, including biocatalysis, fluorescence sensing, magnetic resonance imaging and cargo-loading functionality. A brief overview of the different synthetic methodologies for MnO₂ NSs and their state-of-the-art biomedical applications is presented below, as well as the challenges and future perspectives of MnO₂ NSs.

Efficient Grafting of Cyclodextrin to Alginate and Performance of the Hydrogel for Release of Model Drug

Controlling the rate of release of molecules from a hydrogel is of high interest for various drug delivery systems and medical devices. A strategy to alter the release profiles of soluble and poorly soluble active ingredients from hydrogels can be to combine the hydrogel forming ability of alginate with the inclusion forming ability of cyclodextrins (CyD). Here, β-CyD was grafted to alginate in a three-step synthesis using periodate oxidation, reductive amination and copper(I)-catalyzed azide-alkyne cycloaddition. A grafting degree of 4.7% mol β-CyD/mol sugar residues was obtained. The grafting degree was controlled by varying the reaction parameters where the amount of linker used in reductive amination was especially influential. Ca-alginate gel beads grafted with β-CyD showed increased uptake of the model molecule methyl orange. Release experiments showed that the grafted material had a prolonged release of methyl orange and an increased total amount of released methyl orange. These results show that the β-CyD grafted alginate is still able to form a hydrogel while the grafted cyclodextrins retain their ability to form inclusion complex with methyl orange. Further testing should be done with this system to investigate capability for drug delivery applications.

pH-Responsive Polymer Nanoparticles for Drug Delivery

Stimuli-responsive nanoparticles have the potential to improve the delivery of therapeutics to a specific cell or region within the body. There are many stimuli that have shown potential for specific release of cargo, including variation of pH, redox potential, or the presence of enzymes. pH variation has generated significant interest for the synthesis of stimuli-responsive nanoparticles because nanoparticles are internalized into cells via vesicles that are acidified. Additionally, the tumor microenvironment is known to have a lower pH than the surrounding tissue. In this review, different strategies to design pH-responsive nanoparticles are discussed, focusing on the use of charge-shifting polymers, acid labile linkages, and crosslinking.