β-Cyclodextrin polymer nanoparticles as carriers for doxorubicin and artemisinin: a spectroscopic and photophysical study

Exploring the Potential of Nanogels: From Drug Carriers to Radiopharmaceutical Agents

Nanogels open up access to a wide range of applications and offer among others hopeful approaches for use in the field of biomedicine. This review provides a brief overview of current developments of nanogels in general, particularly in the fields of drug delivery, therapeutic applications, tissue engineering, and sensor systems. Specifically, cyclodextrin (CD)-based nanogels are important because they have exceptional complexation properties and are highly biocompatible. Nanogels as a whole and CD-based nanogels in particular can be customized in a wide range of sizes and equipped with a desired surface charge as well as containing additional molecules inside and outside, such as dyes, solubility-mediating groups or even biological vector molecules for pharmaceutical targeting. Currently, biological investigations are mainly carried out in vitro, but more and more in vivo applications are gaining importance. Modern molecular imaging methods are increasingly being used for the latter. Due to an extremely high sensitivity and the possibility of obtaining quantitative data on pharmacokinetic and pharmacodynamic properties, nuclear methods such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) using radiolabeled compounds are particularly suitable here. The use of radiolabeled nanogels for imaging, but also for therapy, is being discussed.

Nanocrystals Slow-Releasing Ropivacaine and Doxorubicin to Synergistically Suppress Tumor Recurrence and Relieve Postoperative Pain

Although surgical resection provides a straightforward and effective treatment for most malignant solid tumors, tumor recurrence and acute postoperative pain continue to be two big problems associated with this treatment. To resolve these problems, a nanocrystal composite slow-releasing ropivacaine and doxorubicin was fabricated in this study. Briefly, a self-assembling peptide was used to form nanoparticle complexes with the two drugs, based on which homogeneous nanocrystals were obtained by adjusting the pH. In cultured human melanoma cells, the nanocrystals exhibited improved antitumor activity due to a synergistic effect and enhanced cellular uptake of the two drugs. On the other hand, the nanocrystals could slowly release ropivacaine in vitro and in vivo, generating long-acting analgesia on the rat sciatic nerve block model and incisional pain model. On a nude mouse tumor resection model, the nanocrystals simultaneously suppressed the recurrence of solid tumor and relieved postoperative pain, indicating a potential postoperative treatment for tumor resection patients. This nanocrystal system also suggested a promising and facile strategy for developing multifunctional formulations combining different drugs, which could achieve better therapeutic outcomes in a synergistic and sustained manner.

Robust Inclusion Complex of Topotecan Comprised within a Rhodamine-Labeled β-Cyclodextrin: Competing Proton and Energy Transfer Processes

Monitoring the biological fate of medicaments within the environments of cancer cells is an important challenge which is nowadays the object of intensive studies. In this regard, rhodamine-based supramolecular systems are one of the most suitable probes used in drug delivery thanks to their high emission quantum yield and sensitivity to the environment which helps to track the medicament in real time. In this work, we used steady-state and time-resolved spectroscopy techniques to investigate the dynamics of the anticancer drug, topotecan (TPT), in water (pH ~6.2) in the presence of a rhodamine-labeled methylated β-cyclodextrin (RB-RM-βCD). A stable complex of 1:1 stoichiometry is formed with a K_eq value of ~4 × 10⁴ M^-1 at room temperature. The fluorescence signal of the caged TPT is reduced due to: (1) the CD confinement effect; and (2) a Förster resonance energy transfer (FRET) process from the trapped drug to the RB-RM-βCD occurring in ~43 ps with 40% efficiency. These findings provide additional knowledge about the spectroscopic and photodynamic interactions between drugs and fluorescent functionalized CDs, and may lead to the design of new fluorescent CD-based host-guest nanosystems with efficient FRET to be used in bioimaging for drug delivery monitoring.

Three-in-one: exploration of co-encapsulation of cabazitaxel, bicalutamide and chlorin e6 in new mixed cyclodextrin-crosslinked polymers

Three-in-one: a single bCyD polymer easily prepared in water is used to co-encapsulate cabazitaxel and bicalutamide with chlorin e6 affording a nanoplatform to implement multimodal cancer therapy.

Synthesis of Magneto-Controllable Polymer Nanocarrier Based on Poly(N-isopropylacrylamide-co-acrylic Acid) for Doxorubicin Immobilization

In this work, the preparation procedure and properties of anionic magnetic microgels loaded with antitumor drug doxorubicin are described. The functional microgels were produced via the in situ formation of iron nanoparticles in an aqueous dispersion of polymer microgels based on poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM-PAA). The composition and morphology of the resulting composite microgels were studied by means of X-ray diffraction, Mössbauer spectroscopy, IR spectroscopy, scanning electron microscopy, atomic-force microscopy, laser microelectrophoresis, and static and dynamic light scattering. The forming nanoparticles were found to be β-FeO(OH). In physiological pH and ionic strength, the obtained composite microgels were shown to possess high colloid stability. The average size of the composites was 200 nm, while the zeta-potential was -27.5 mV. An optical tweezers study has demonstrated the possibility of manipulation with microgel using external magnetic fields. Loading of the composite microgel with doxorubicin did not lead to any change in particle size and colloidal stability. Magnetic-driven interaction of the drug-loaded microgel with model cell membranes was demonstrated by fluorescence microscopy. The described magnetic microgels demonstrate the potential for the controlled delivery of biologically active substances.

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.

Improved art bioactivity by encapsulation within cyclodextrin carboxylate

Artemisinin (Art) is a natural sesquiterpene lactone that is claimed to exhibit various bioactivities. The poor solubility of Art in both water and oil hinders its application in formulations intended for oral administration. In this study, we investigated the potential of forming a host-guest complex between Art and succinic acid modified cyclodextrin (SACD) to improve its solubility characteristics. Art-SACD inclusion complexes (2:1 M ratio) were successfully formed in water, which was attributed to the relatively large cavity size of SACD, as well as the intermolecular interactions between the Art and succinic acid branches in the cavity. The thermal stability of the Art was retained after incorporation into the Art-SACD complexes, which may be useful for applications such as pasteurization or cooking. The encapsulated Art showed antibacterial activity against both Gram-positive and Gram-negative bacteria. Such encapsulation technology allows Art to be introduced into oral delivery systems in a bioactive form.

Preformulation Studies and Bioavailability Enhancement of Curcumin with a 'Two in One' PEG-β-Cyclodextrin Polymer

Drug delivery systems are used to improve the biopharmaceutical properties of curcumin. Our aim was to investigate the effect of a water-soluble 'two in one' polymer containing covalently bonded PEG and βCD moieties (βCPCD) on the solubility and bioavailability of curcumin and compare it to a polymeric β-cyclodextrin (βCDP) cross-linked with epichlorohydrin. Phase-solubility and dynamic light scattering (DLS) experiments showed that the solubility of curcumin increased significantly in 10 m/m % βCPCD and βCDP solutions, but βCPCD-curcumin particles had higher hydrodynamic volume. The formation of the βCPCD-curcumin complex in solution and sedimented phase was confirmed by NMR spectroscopy. Biocompatibility and permeability experiments were performed on Caco-2 cells. Polymers did not show cytotoxicity up to 10 m/m % and βCPCD significantly increased the permeability of curcumin. DLS measurements revealed that among the interaction of polymers with mucin, βCPCD formed bigger aggregates compared to βCDP. Curcumin complexes were lyophilized into capsules and structurally characterized by micro-CT spectroscopy. Drug release was tested in a pH 1.2 medium. Lyophilized complexes had a solid porous matrix and both βCPCD and βCDP showed rapid drug release. βCPCD provides an opportunity to create a swellable, mucoadhesive matrix system for oral drug delivery.

A Fluorescence Study of the Interaction of Anticancer Drug Molecule Doxorubicin Hydrochloride in Pluronic P123 and F127 Micelles

Drug delivery systems for the sustained and target delivery of doxorubicin to tumor cells are a topic of interest due to the efficacy of the doxorubicin in cancer treatment. The use of polymers such as Pluronic is being studied widely for the formulation of doxorubicin hydrochloride. However, the basic understanding of the physicochemical properties of pluronic micelles in presence of doxorubicin hydrochloride is a very essential topic of study. Doxorubicin hydrochloride is fluorescent; this helped us to study its sensitivity towards the Pluronic microenvironment using the fluorescence technique. In this work, the interaction and place of location of doxorubicin hydrochloride in Pluronic F127 and P123 micelles has been studied extensively using steady-state fluorescence intensity, dynamic fluorescence lifetime, quenching studies, dynamic light scattering, and zeta potential measurements, at different Pluronic concentrations. Using a fluorescence quenching experiment, doxorubicin hydrochloride was found to reside near the hydrophilic PEO corona region of the Pluronic micelles. For both the Pluronic, in the concentration range of study, the micellar size was found to be below 30 nm; this may have a greater advantage for various applications.

Cyclodextrin Cationic Polymer-Based Nanoassemblies to Manage Inflammation by Intra-Articular Delivery Strategies

Injectable nanobioplatforms capable of locally fighting the inflammation in osteoarticular diseases, by reducing the number of administrations and prolonging the therapeutic effect is highly challenging. β-Cyclodextrin cationic polymers are promising cartilage-penetrating candidates by intra-articular injection due to the high biocompatibility and ability to entrap multiple therapeutic and diagnostic agents, thus monitoring and mitigating inflammation. In this study, nanoassemblies based on poly-β-amino-cyclodextrin (PolyCD) loaded with the non-steroidal anti-inflammatory drug diclofenac (DCF) and linked by supramolecular interactions with a fluorescent probe (adamantanyl-Rhodamine conjugate, Ada-Rhod) were developed to manage inflammation in osteoarticular diseases. PolyCD@Ada-Rhod/DCF supramolecular nanoassemblies were characterized by complementary spectroscopic techniques including UV-Vis, steady-state and time-resolved fluorescence, DLS and ζ-potential measurement. Stability and DCF release kinetics were investigated in medium mimicking the physiological conditions to ensure control over time and efficacy. Biological experiments evidenced the efficient cellular internalization of PolyCD@Ada-Rhod/DCF (within two hours) without significant cytotoxicity in primary human bone marrow-derived mesenchymal stromal cells (hMSCs). Finally, polyCD@Ada-Rhod/DCF significantly suppressed IL-1β production in hMSCs, revealing the anti-inflammatory properties of these nanoassemblies. With these premises, this study might open novel routes to exploit original CD-based nanobiomaterials for the treatment of osteoarticular diseases.

Temozolomide-Doxorubicin Conjugate as a Double Intercalating Agent and Delivery by Apoferritin for Glioblastoma Chemotherapy

We designed a conjugated compound by coupling temozolomide (TMZ) with doxorubicin (DOX) via an acylhydrazone linkage as a potential prodrug used for glioblastoma multiforme (GBM) treatment. Viscosity and spectroscopic studies revealed that the drug conjugate could act as a nonclassical double intercalating agent. Although free TMZ is an inefficient DNA binder in comparison to DOX, the TMZ moiety interacted with DNA as an induced intercalator, arising from the synergistic effect of DOX moiety that mediated conformational changes of the DNA helix. Two binding modes were proposed to interpret the double intercalating effect of the drug conjugate on intra- and inter-DNA interactions that could cause DNA cross-linking and fibril aggregates. We also developed a delivery nanoplatform with a loading efficiency of 83% using copper-bound apoferritin as a nanocarrier. In sharp contrast to the short half-life of free TMZ, the nanocomposite was stable under physiological conditions without detectable drug decomposition after a 2 week storage, and drug release was activatable in the presence of glutathione at millimolar levels. The antitumor effect of the drug conjugate and nanocomposite against GBM cells was reported to demonstrate the potential therapeutic applications of double intercalating materials.

Combination Therapy Strategies for the Treatment of Malaria

Malaria is a vector- and blood-borne infection that is responsible for a large number of deaths around the world. Most of the currently used antimalarial therapeutics suffer from drug resistance. The other limitations associated with the currently used antimalarial drugs are poor drug bioavailability, drug toxicity, and poor water solubility. Combination therapy is one of the best approaches that is currently used to treat malaria, whereby two or more therapeutic agents are combined. Different combination therapy strategies are used to overcome the aforementioned limitations. This review article reports two strategies of combination therapy; the incorporation of two or more antimalarials into polymer-based carriers and hybrid compounds designed by hybridization of two antimalarial pharmacophores.

Functionalized β-Cyclodextrin Immobilized on Ag-Embedded Silica Nanoparticles as a Drug Carrier

Cyclodextrins (CDs) have beneficial characteristics for drug delivery, including hydrophobic interior surfaces. Nanocarriers with β-CD ligands have been prepared with simple surface modifications as drug delivery vehicles. In this study, we synthesized β-CD derivatives on an Ag-embedded silica nanoparticle (NP) (SiO₂@Ag NP) structure to load and release doxorubicin (DOX). Cysteinyl-β-CD and ethylenediamine-β-CD (EDA-β-CD) were immobilized on the surface of SiO₂@Ag NPs, as confirmed by transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) spectrophotometry, and Fourier transform infrared (FTIR) spectroscopy. DOX was introduced into the β-CD on the SiO₂@Ag NPs and then successfully released. Neither cysteinyl-β-CD and EDA-β-CD showed cytotoxicity, while DOX-loaded cysteinyl-β-CD and EDA-β-CD showed a significant decrease in cell viability in cancer cells. The SiO₂@Ag NPs with β-CD provide a strategy for designing a nanocarrier that can deliver a drug with controlled release from modified chemical types.

Linear polymers of β and γ cyclodextrins with a polyglutamic acid backbone as carriers for doxorubicin

Cyclodextrins have been used to encapsulate drugs improving their stability and efficiently regulating their release. Polymeric nanoparticles containing cyclodextrins are currently undergoing clinical trials as nanotherapeutics. In this context, we have synthesized new linear polymers based on polyglutamic acid with pendant β- or γ-cyclodextrins, using a high yield reaction route. The new polymers with an average number of about 17 cyclodextrin cavities were characterized (NMR, MALDI-MS, DLS) and tested as carriers of doxorubicin in human tumor cells. They can include doxorubicin, and the inclusion complexes show antiproliferative activity in human tumor cells.

Cyclodextrin-based nanocarriers containing a synergic drug combination: A potential formulation for pulmonary administration of antitubercular drugs

Tuberculosis (TB) remains a major global health problem. The use of ethionamide (ETH), a main second line drug, is associated to severe toxic side-effects due to its low therapeutic index. In this challenging context, "booster" molecules have been synthetized to increase the efficacy of ETH. However, the administration of ETH/booster pair is mostly hampered by the low solubility of these drugs and the tendency of ETH to crystallize. Here, ETH and a poorly water-soluble booster, so-called BDM43266, were simultaneously loaded in polymeric β-cyclodextrin nanoparticles (pβCyD NPs) following a "green" protocol. The interaction of ETH and BDM43266 with pβCyD NPs was investigated by complementary techniques. Remarkably, the inclusion of ETH and BDM43266 pβCyD NPs led to an increase of their apparent solubility in water of 10- and 90-fold, respectively. Competition studies of ETH and BDM43266 for the CyD cavities of pβCyD NPs corroborated the fact that the drugs did not compete with each other, confirming the possibility to simultaneously co-incorporate them in NPs. The drug-loaded NP suspensions could be filtered through 0.22μm filters. Finally, the drug-loaded NPs were passed through a Microsprayer^® to evaluate the feasibility to administer pβCyD NPs by pulmonary route. Each spray delivered a constant amount of both drugs and the NPs were totally recovered after passage through the Microsprayer^®. These promising results pave the way for a future use of pβCyD NPs for the pulmonary delivery of the ETH/BDM43266 pair.

Design of Drug Delivery Systems Containing Artemisinin and Its Derivatives

Artemisinin and its derivatives have been reported to be experimentally effective for the treatment of highly aggressive cancers without developing drug resistance, they are useful for the treatment of malaria, other protozoal infections and they exhibit antiviral activity. However, they are limited pharmacologically by their poor bioavailability, short half-life in vivo, poor water solubility and long term usage results in toxicity. They are also expensive for the treatment of malaria when compared to other antimalarials. In order to enhance their therapeutic efficacy, they are incorporated onto different drug delivery systems, thus yielding improved biological outcomes. This review article is focused on the currently synthesized derivatives of artemisinin and different delivery systems used for the incorporation of artemisinin and its derivatives.

Sensitization of multidrug-resistant malignant cells by liposomes co-encapsulating doxorubicin and chloroquine through autophagic inhibition

Adenosine triphosphate (ATP)-binding cassette (ABC) transporters play a key role in the development of multidrug resistance (MDR) in cancer cells. P-glycoprotein (P-gp) and multidrug resistance-associated protein 1 (MRP1) are important proteins in this superfamily which are widely expressed on the membranes of multidrug resistance (MDR) cancer cells. Besides, upregulation of cellular autophagic responses is considered a contributing factor for MDR in cancer cells. We designed a liposome system co-encapsulating a chemotherapeutic drug (doxorubicin hydrochloride, DOX) and a typical autophagy inhibitior (chloroquine phosphate, CQ) at a weight ratio of 1:2 and investigated its drug resistance reversal mechanism. MTT assay showed that the IC₅₀ of DOX/CQ co-encapsulated liposome in DOX-resistant human breast cancer cells (MCF7/ADR) was 4.7 ± 0.2 μM, 5.7-fold less than that of free DOX (26.9 ± 1.9  μM), whereas it was 19.5-fold in doxorubicin-resistant human acute myelocytic leukemia cancer cells (HL60/ADR) (DOX/CQ co-encapsulated liposome 1.2 ± 0.1 μM, free DOX 23.4 ± 2.8 μM). The cellular uptake of DOX increased upon addition of free CQ, indicating that CQ may interact with P-gp and MRP1; however, the expressions of P-gp and MRP1 remained unchanged. In contrast, the expression of the autophagy-related protein LC3-II increased remarkably. Therefore, the mechanism of MDR reversal may be closely related to autophagic inhibition. Evaluation of anti-tumor activity was achieved in an MCF-7/ADR multicellular tumor spheroid model and transgenic zebrafish model. DOX/CQ co-encapsulated liposome exerted a better anti-tumor effect in both models than that of liposomal DOX or DOX alone. These findings suggest that encapsulating CQ with DOX in liposomes significantly improves the sensitivity of DOX in DOX-resistant cancer cells.

A vision for cyclodextrin nanoparticles in drug delivery systems and pharmaceutical applications

Cyclodextrins (CDs) have brought a revolution in the pharmaceutical field over the last decade. Natural and modified CDs (α-CD and β-CD) have been studied and some have gained US FDA approval or achieved 'Generally Regarded as Safe' (GRAS) status. Another characteristic of CDs is the ease with which they can be induced to form supramolecular structures for its use in drug delivery. CDs, grafted or crosslinked with polymers, are now being developed into 'smart' systems for efficient targeted drug delivery, especially for hydrophobic drugs. Amphiphilic CDs have the ability to form nanospheres or nanocapsules via a simple nanoprecipitation technique. This review deals with different types of CDs, and their efficacy, physicochemical properties and transformation into nanoparticles with interesting in vitro and in vivo applications.

Photoactivable platforms for nitric oxide delivery with fluorescence imaging

The multifaceted role nitric oxide (NO) plays in human physiology and pathophysiology has stimulated a massive interest on NO-releasing compounds for therapeutic purposes. A main issue associated with use of NO donors is the precise spatiotemporal control of the NO release, as its effects are strictly site- and dose-dependent. NO photochemical precursors permit surmounting this difficulty since triggering with light offers an exquisite control of location and timing of NO delivery. On the other hand, the combination of NO photodonors with fluorescent components remains an urgent need for image-guided phototherapeutic treatments based on the use of NO. Fluorescence techniques permit not only an easy tracking of the photoprecursor in a biological environment but also the real-time quantification of the NO photoreleased therein in a non-invasive fashion. In this Focus Review we seek to provide an overview of recent advances in photoactivable platforms developed in our and other laboratories which combine the photoregulated release of NO with fluorescent functionalities. We shall focus attention on NO photoreleasing systems exhibiting 1) persistent fluorescence and 2) photoactivable fluorescence signals, highlighting their logical design and potential developments for phototheranostics.

Unusual self-assembly of a hydrophilic β-cyclodextrin inclusion complex into vesicles capable of drug encapsulation and release

A hydrophilic β-cyclodextrin bis-inclusion complex forms supramolecular vesicles which can be loaded with the anti-cancer drug doxorubicin. The loaded drug can be released upon addition of a competitive inclusion binder such as adamantane carboxylate.

Novel amino-cyclodextrin cross-linked oligomer as efficient carrier for anionic drugs: a spectroscopic and nanocalorimetric investigation

The amino groups of a novel oligomer of amino-cyclodextrins play a relevant role in the recognition process of diclofenac and this highlights the potential of short polymeric chains as new drug carriers.

Host-guest interactions in Fe(III)-trimesate MOF nanoparticles loaded with doxorubicin

Doxorubicin (DOX) entrapment in porous Fe(III)-trimesate metal organic frameworks (MIL-100(Fe)) nanoparticles was investigated in neutral Tris buffer via UV-vis absorption, circular dichroism (CD), and fluorescence. The binding constants and the absolute spectra of the DOX-MIL-100(Fe) complexes were determined via absorption and fluorescence titrations. A binding model where DOX associates as monomer to the dehydrated Fe3O (OH)(H2O)2 [(C6H3)(CO2)3]2 structural unit in 1:1 stoichiometry, with apparent association constant of (1.1 to 1.8) × 10(4) M(-1), was found to reasonably fit the experimental data. Spectroscopic data indicate that DOX binding occurs via the formation of highly stable coordination bonds between one or both deprotonated hydroxyl groups of the aglycone moiety and coordinatively unsaturated Fe(III) centers. Complete quenching of the DOX fluorescence and remarkable thermal and photochemical stability were observed for DOX incorporated in the MIL-100(Fe) framework.

Citric acid-γ-cyclodextrin crosslinked oligomers as carriers for doxorubicin delivery

Two citric acid crosslinked γ-cyclodextrin oligomers (pγ-CyD) with a MW of 21-33 kDa and 10-15 γ-CyD units per molecule were prepared by following green chemistry methods and were fully characterized. The non-covalent association of doxorubicin (DOX) with these macromolecules was investigated in neutral aqueous medium by means of circular dichroism (CD), UV-vis absorption and fluorescence. Global analysis of multiwavelength spectroscopic CD and fluorescence titration data, taking into account the DOX monomer-dimer equilibrium, evidenced the formation of 1 : 1 and 1 : 2 pγ-CyD unit-DOX complexes. The binding constants are 1-2 orders of magnitude higher than those obtained for γ-CyD and depend on the characteristics of the oligomer batch used. The concentration profiles of the species in solution evidence the progressive monomerization of DOX with increasing oligomer concentration. Confocal fluorescence imaging and spectral imaging showed a similar drug distribution within the MCF-7 cell line incubated with either DOX complexed to pγ-CyD or free DOX. In both cases DOX is taken up into the cell nucleus without any degradation.

Fluorescent cyclodextrin carriers for a water soluble ZnII pyrazinoporphyrazine octacation with photosensitizer potential

Novel, negatively charged, fluorescent cyclodextrin oligomers form highly stable complexes with a water soluble, octacationic porphyrazine photosensitizer in dimeric form.

Noncovalent interaction-assisted polymeric micelles for controlled drug delivery

Various individual or synergistic noncovalent interactions were employed to mediate polymeric micelles for controlled drug delivery.