A comprehensive study of the spontaneous formation of nanoassemblies in water by a “lock-and-key” interaction between two associative polymers

Supramolecular red-light-photosensitized nitric oxide release with fluorescence self-reporting within biocompatible nanocarriers

The strict dependence of the biological effects of nitric oxide (NO) on its concentration and generation site requires this inorganic free radical to be delivered with precise spatiotemporal control. Light-activation by suitable NO photoprecursors represents an ideal approach. Developing strategies to activate NO release using long-wavelength excitation light in the therapeutic window (650-1300 nm) is challenging. In this contribution, we demonstrate that NO release by a blue-light activatable NO photodonor (NOPD) with self-fluorescence reporting can be triggered catalytically by the much more biocompatible red light exploiting a supramolecular photosensitization process. Different red-light absorbing photosensitizers (PSs) are co-entrapped with the NOPD within different biocompatible nanocarriers such as Pluronic® micelles, microemulsions and branched cyclodextrin polymers. The intra-carrier photosensitized NO release, involving the lowest, long-lived triplet state of the PS as the key intermediate and its quenching by the NOPD, is competitive with that by molecular oxygen. This allows NO to be released with good efficacy, even under aerobic conditions. Therefore, the adopted general strategy provides a valuable tool for generating NO from an already available NOPD, otherwise activatable with the poorly biocompatible blue light, without requiring any chemical modification and using sophisticated and expensive irradiation sources.

Stepwise Nitric Oxide Release and Antibacterial Activity of a Nitric Oxide Photodonor Hosted within Cyclodextrin Branched Polymer Nanocarriers

A hydrophobic nitric oxide (NO) photodonor integrating both nitroso and nitro functionalities within its chromophoric skeleton has been synthesized. Excitation of this compound with blue light triggers the release of two NO molecules from the nitroso and the nitro functionalities via a stepwise mechanism. Encapsulation of the NO photodonor within biocompatible neutral, cationic, and anionic β-cyclodextrin branched polymers as suitable carriers leads to supramolecular nanoassemblies, which exhibit the same nature of the photochemical processes but NO photorelease performances enhanced by about 1 order of magnitude when compared with the free guest. Antibacterial tests carried out with methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii demonstrate an effective antibacterial activity exclusively under light activation and point out a differentiated role of the polymeric nanocarriers in determining the outcome of the antibacterial photodynamic action.

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.

Mixed β-γ-Cyclodextrin Branched Polymer with Multiple Photo-Chemotherapeutic Cargos

The achievement of biocompatible platforms for multimodal therapies is one of the major challenges in the burgeoning field of nanomedicine. Here, we report on a mixed β- and γ-cyclodextrin-based branched polymeric material (βγCD-NOPD) covalently integrating a nitric oxide (NO) photodonor (NOPD) within its macromolecular scaffold, and its supramolecular ensemble with a singlet oxygen (1O2) photosensitizer (PS) Zn(II) phthalocyanine (ZnPc) and the chemodrug Lenvatinib (LVB). This polymer is highly water-soluble and generates NO under visible blue light stimuli with an efficiency of more than 1 order of magnitude higher than that of the single NOPD. The PS, which in an aqueous solution is aggregated and non-photoresponsive, can be entangled in the polymeric network as a photoresponsive monomeric species. In addition, the poorly water-soluble LVB can be co-encapsulated within the polymeric host, which increases the drug solubility by more than 30-fold compared to the free drug and more than 2-fold compared with a similar branched polymer containing only βCD units. The supramolecular nanoensemble, ca. 15 nm in diameter, retains well the photochemical properties of both the NOPD and PS, which can operate in parallel under light stimuli of different energies. Irradiation with blue and red light results in the photogeneration of NO and 1O2 associated with red fluorescence emission, without inducing any photodegradation of LVB. This result is not trivial and is due to the absence of significant, mutual interactions between the NOPD, the PS and LVB both in the ground and excited states, despite these components are confined in the same host. The proposed polymeric nanoplatform may represent a potential trimodal nanomedicine for biomedical research studies, since it combines the double photodynamic action of NO and 1O2, two species that do not suffer multidrug resistance, with the therapeutic activity of a conventional chemodrug.

A Supramolecular Nanoassembly of Lenvatinib and a Green Light-Activatable NO Releaser for Combined Chemo-Phototherapy

The chemotherapeutic Lenvatinib (LVB) and a nitric oxide (NO) photodonor based on a rhodamine antenna (RD-NO) activatable by the highly compatible green light are supramolecularly assembled by a β-cyclodextrin branched polymer (PolyCD). The poorly water-soluble LVB and RD-NO solubilize very well within the polymeric host leading to a ternary supramolecular nanoassembly with a diameter of ~55 nm. The efficiency of the NO photorelease and the typical red fluorescence of RD-NO significantly enhance within the polymer due to its active role in the photochemical and photophysical deactivation pathways. The co-presence of LVB within the same host does not affect either the nature or the efficiency of the photoinduced processes of RD-NO. Besides, irradiation of RD-NO does not lead to the decomposition of LVB, ruling out any intermolecular photoinduced process between the two guests despite sharing the same host. Ad-hoc devised Förster Resonance Energy Transfer experiments demonstrate this to be the result of the not close proximity of the two guests, which are confined in different compartments of the same polymeric host. The supramolecular complex is stable in a culture medium, and its biological activity has been evaluated against HEP-G2 hepatocarcinoma cell lines in the dark and under irradiation with visible green light, using LVB at a concentration well below the IC₅₀. Comparative experiments performed using the polymeric host encapsulating the individual LVB and RD-NO components under the same experimental conditions show that the moderate cell mortality induced by the ternary complex in the dark increases significantly upon irradiation with visible green light, more likely as the result of synergism between the NO photogenerated and the chemotherapeutic.

Green Synthesis of Near-Infrared Plasmonic Gold Nanostructures by Pomegranate Extract and Their Supramolecular Assembling with Chemo- and Photo-Therapeutics

Au nanostructures exhibiting a localized surface plasmon resonance in the near-infrared spectral window are obtained in a single, green step at room temperature by pomegranate extract in the presence of a highly biocompatible β-cyclodextrin branched polymer, without the need of preformed seeds, external reducing and sacrificial agents, and conventional surfactants. The polymeric component makes the Au nanostructures dispersible in water, stable for weeks and permits their supramolecular assembling with the chemotherapeutic sorafenib and a nitric oxide (NO) photodonor (NOPD), chosen as representative for chemo- and photo-therapeutics. Irradiation of the plasmonic Au nanostructures in the therapeutic window with 808 nm laser light results in a good photothermal response, which (i) is not affected by the presence of either the chemo- or the phototherapeutic guests and (ii) does not lead to their photoinduced decomposition. Besides, irradiation of the hybrid Au nanoassembly with the highly biocompatible green light results in the NO release from the NOPD with efficiency similar to that observed for the free guest. Preliminary biological experiments against Hep-G2 hepatocarcinoma cell lines are also reported.

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.

Applications of Photoinduced Phenomena in Supramolecularly Arranged Phthalocyanine Derivatives: A Perspective

This review focuses on the description of several examples of supramolecular assemblies of phthalocyanine derivatives differently functionalized and interfaced with diverse kinds of chemical species for photo-induced phenomena applications. In fact, the role of different substituents was investigated in order to tune peculiar aggregates formation as well as, with the same aim, the possibility to interface these derivatives with other molecular species, as electron donor and acceptor, carbon allotropes, cyclodextrins, protein cages, drugs. Phthalocyanine photo-physical features are indeed really interesting and appealing but need to be preserved and optimized. Here, we highlight that the supramolecular approach is a versatile method to build up very complex and functional architectures. Further, the possibility to minimize the organization energy and to facilitate the spontaneous assembly of the molecules, in numerous examples, has been demonstrated to be more useful and performing than the covalent approach.

Intrinsic Antibacterial Activity of Nanoparticles Made of β-Cyclodextrins Potentiates Their Effect as Drug Nanocarriers against Tuberculosis

Multi-drug-resistant tuberculosis (TB) is a major public health problem, concerning about half a million cases each year. Patients hardly adhere to the current strict treatment consisting of more than 10 000 tablets over a 2-year period. There is a clear need for efficient and better formulated medications. We have previously shown that nanoparticles made of cross-linked poly-β-cyclodextrins (pβCD) are efficient vehicles for pulmonary delivery of powerful combinations of anti-TB drugs. Here, we report that in addition to being efficient drug carriers, pβCD nanoparticles are endowed with intrinsic antibacterial properties. Empty pβCD nanoparticles are able to impair Mycobacterium tuberculosis (Mtb) establishment after pulmonary administration in mice. pβCD hamper colonization of macrophages by Mtb by interfering with lipid rafts, without inducing toxicity. Moreover, pβCD provoke macrophage apoptosis, leading to depletion of infected cells, thus creating a lung microenvironment detrimental to Mtb persistence. Taken together, our results suggest that pβCD nanoparticles loaded or not with antibiotics have an antibacterial action on their own and could be used as a carrier in drug regimen formulations effective against TB.

A phototherapeutic fluorescent β-cyclodextrin branched polymer delivering nitric oxide

A water soluble b-CD-branched polymer covalently binds a fluorescein moiety for imaging and a NO photodonor for therapy that can be operated in parallel upon visible light excitation.

Combination therapy for tuberculosis treatment: pulmonary administration of ethionamide and booster co-loaded nanoparticles

Tuberculosis (TB) is a leading infectious cause of death worldwide. The use of ethionamide (ETH), a main second line anti-TB drug, is hampered by its severe side effects. Recently discovered "booster" molecules strongly increase the ETH efficacy, opening new perspectives to improve the current clinical outcome of drug-resistant TB. To investigate the simultaneous delivery of ETH and its booster BDM41906 in the lungs, we co-encapsulated these compounds in biodegradable polymeric nanoparticles (NPs), overcoming the bottlenecks inherent to the strong tendency of ETH to crystallize and the limited water solubility of this Booster. The efficacy of the designed formulations was evaluated in TB infected macrophages using an automated confocal high-content screening platform, showing that the drugs maintained their activity after incorporation in NPs. Among tested formulations, "green" β-cyclodextrin (pCD) based NPs displayed the best physico-chemical characteristics and were selected for in vivo studies. The NPs suspension, administered directly into mouse lungs using a Microsprayer®, was proved to be well-tolerated and led to a 3-log decrease of the pulmonary mycobacterial load after 6 administrations as compared to untreated mice. This study paves the way for a future use of pCD NPs for the pulmonary delivery of the [ETH:Booster] pair in TB chemotherapy.

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.

Spontaneous Self-Assembly of Polymeric Nanoparticles in Aqueous Media: New Insights From Microfluidics, In Situ Size Measurements, and Individual Particle Tracking

Supramolecular cyclodextrin-based nanoparticles (CD-NPs) mediated by host-guest interactions have gained increased popularity because of their "green" and simple preparation procedure, as well as their versatility in terms of inclusion of active molecules. Herein, we showed that original CD-NPs of around 100 nm are spontaneously formed in water, by mixing 2 aqueous solutions of (1) a CD polymer and (2) dextran grafted with benzophenone moieties. For the first time, CD-NPs were instantaneously produced in a microfluidic interaction chamber by mixing 2 aqueous solutions of neutral polymers, in the absence of organic solvents. Whatever the mixing conditions, CD-NPs with narrow size distributions were immediately formed upon contact of the 2 polymeric solutions. In situ size measurements showed that the CD-NPs were spontaneously formed. Nanoparticle tracking analysis was used to individually follow the CD-NPs in their Brownian motions, to gain insights on their size distribution, concentration, and stability on extreme dilution. Nanoparticle tracking analysis allowed to establish that despite their non-covalent nature, and the CD-NPs were remarkably stable in terms of concentration and size distribution, even on extreme dilution (concentrations as low as 100 ng/mL).

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.

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.

A multi-photoresponsive supramolecular hydrogel with dual-color fluorescence and dual-modal photodynamic action

We have developed an engineered supramolecular hydrogel, formed in the absence of any toxic solvents or reagents, by the self-assembly of four different components: a poly-β-cyclodextrin polymer, a hydrophobically modified dextran, a commercial zinc phthalocyanine and a tailored nitric oxide photodonor. The formation of this supramolecular assembly is based on a "lock-and-key" mechanism in which the alkyl side chains of the modified dextran form inclusion complexes with the cyclodextrin cavities of the poly-β-cyclodextrin polymer. The multivalent character of the interactions between all the components ensures the stability of the hydrogel and the negligible leaching of the photoactive components from the gel network under physiological conditions, even in the absence of protective coating agents. The combination of steady-state and time-resolved spectroscopic techniques together with photoamperometric measurements shows that the two chromo-fluorogenic components do not interfere with each other while being enclosed in their supramolecular matrix and can thus be operated in parallel under the control of light stimuli. Specifically, excitation with visible light results in the red and green fluorescence emission typical of the two photoactive centers and in their capability to generate singlet oxygen and nitric oxide, two cytotoxic species playing a key role in photodynamic cancer and bacterial therapies.

A multi-photoresponsive molecular-hybrid for dual-modal photoinactivation of cancer cells

A bichromophoric molecular conjugate combines red fluorescence with the simultaneous photogeneration of singlet oxygen and nitric oxide, inducing amplified photomortality on melanoma cancer cells.

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

The association of doxorubicin (DOX) and artemisinin (ART) to a β-CyD-epichlorohydrin crosslinked polymer (pβ-CyD), organized in nanoparticles of ca. 15 nm size, was investigated in neutral aqueous medium by circular dichroism (CD), UV-vis absorption and fluorescence. The stability constants and the absolute CD spectra of the drug complexes were determined by global analysis of multiwavelength data from spectroscopic titrations. The polymer pβ-CyD proved able to disrupt the DOX dimer when the latter is the predominant form of DOX in solution. The spectroscopic and photophysical properties of the complexes evidenced an alcohol-like environment for ART and an improved inherent emission ability for DOX in the nanoparticle frame.