Cyclodextrin-based supramolecular systems for drug delivery: recent progress and future perspective

Photoelectron spectroscopy and computational investigations of the electronic structures and noncovalent interactions of cyclodextrin-closo-dodecaborate anion complexes χ-CD·B12X122− (χ = α, β, γ; X = H, F)

We report a joint negative ion photoelectron spectroscopy and computational study on the electronic structures and noncovalent interactions of a series of cyclodextrin-closo-dodecaborate dianion complexes, χ-CD·B₁₂X₁₂²⁻ (χ = α, β, γ; X = H, F).

Fluorescent glycoconjugates and their applications

Fluorescent glycoconjugates are discussed for their applications in biology in vitro, in cell assays and in animal models. Advantages and limitations are presented for each design using a fluorescent core conjugated with glycosides, or vice versa.

Smart regioselectivity towards mono 6-hydroxyl α-cyclodextrin amphiphilic derivatives

Following the trend of eco-friendly development, a smart regioselective modification is described herein, for mono 6-hydroxyl and penta-alkyl coexistence on the primary face of α-cyclodextrins with no additional catalysis or no enzyme process, just via the adjustment of the ratio of alkali to alkylation agent, with good yields. The novel procedure minimized the tedious protection, deprotection steps and provided useful intermediates for further cutting edge research. Thus, the scope of green and economical access is extended from penta-pentenyl substitution to C₄–C₆ alkyl group substitution. It was speculated that the mechanism might be controlled by the concentration of alkali in the system and the steric effects of the electrophilic reagent RBr.

A smart regioselective CD modification is described. For mono 6-hydroxyl and penta-alkyl coexistence on the primary face of α-CD, no additional catalysis or enzyme process are needed, just via adjustment of the ratio of alkali to alkylation agent.

α-Cyclodextrin-Based Polypseudorotaxane Hydrogels

Supramolecular hydrogels that are based on inclusion complexes between α-cyclodextrin and (co)polymers have gained significant attention over the last decade. They are formed via dynamic noncovalent bonds, such as host-guest interactions and hydrogen bonds, between various building blocks. In contrast to typical chemical crosslinking (covalent linkages), supramolecular crosslinking is a type of physical interaction that is characterized by great flexibility and it can be used with ease to create a variety of "smart" hydrogels. Supramolecular hydrogels based on the self-assembly of polypseudorotaxanes formed by a polymer chain "guest" and α-cyclodextrin "host" are promising materials for a wide range of applications. α-cyclodextrin-based polypseudorotaxane hydrogels are an attractive platform for engineering novel functional materials due to their excellent biocompatibility, thixotropic nature, and reversible and stimuli-responsiveness properties. The aim of this review is to provide an overview of the current progress in the chemistry and methods of designing and creating α-cyclodextrin-based supramolecular polypseudorotaxane hydrogels. In the described systems, the guests are (co)polymer chains with various architectures or polymeric nanoparticles. The potential applications of such supramolecular hydrogels are also described.

Guanidinocalix[5]arene for sensitive fluorescence detection and magnetic removal of perfluorinated pollutants

Perfluorinated alkyl substances, such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), are toxic materials that are known to globally contaminate water, air, and soil resources. Strategies for the simultaneous detection and removal of these compounds are desired to address this emerging health and environmental issue. Herein, we develop a type of guanidinocalix[5]arene that can selectively and strongly bind to PFOS and PFOA, which we use to demonstrate the sensitive and quantitative detection of these compounds in contaminated water through a fluorescent indicator displacement assay. Moreover, by co-assembling iron oxide nanoparticle with the amphiphilic guanidinocalix[5]arene, we are able to use simple magnetic absorption and filtration to efficiently remove PFOS and PFOA from contaminated water. This supramolecular approach that uses both molecular recognition and self-assembly of macrocyclic amphiphiles is promising for the detection and remediation of water pollution.

Bio-orthogonal Supramolecular Latching inside Live Animals and Its Application for in Vivo Cancer Imaging

Here, we demonstrate a supramolecular latching tool for bio-orthogonal noncovalent anchoring of small synthetic molecules in live animal models using a fully synthetic high-affinity binding pair between cucurbit[7]uril (CB[7]) and adamantylammonium (AdA). This supramolecular latching system is small (∼1 kDa), ensuring efficient uptake into cells, tissues, and whole organisms. It is also chemically robust and resistant to enzymatic degradation and analogous to well-characterized biological systems in terms of noncovalent binding. Occurrence of fluorescence resonance energy transfer (FRET) between cyanine 3-CB[7] (Cy3-CB[7]) and boron-dipyrromethene 630/650X-AdA (BDP630/650-AdA) inside a live worm (Caenorhabditis elegans) indicates efficient in situ high-affinity association between AdA and CB[7] inside live animals. In addition, selective visualization of a cancer site of a live mouse upon supramolecular latching of cyanine 5-AdA (Cy5-AdA) on prelocalized CB[7]-conjugating antibody on the cancer site demonstrates the potential of this synthetic system for in vivo cancer imaging. These findings provide a fresh insight into the development of new chemical biology tools and medical therapeutic systems.

Fatty acid profile of Romanian's common bean (Phaseolus vulgaris L.) lipid fractions and their complexation ability by β-cyclodextrin

The goal of the present study was the evaluation of the fatty acid (FA) profile of lipid fraction from dry common beans (Phaseolus vulgaris L.) (CBO) harvested from North-East (NE) and South-West (SW) of Romania and to protect against thermal and oxidative degradation of the contained omega-3 and omega-6 polyunsaturated fatty acid (PUFA) glycerides by β-cyclodextrin (β-CD) nanoencapsulation, using kneading method. The most abundant FAs in the CBO samples were PUFAs, according to gas chromatography-mass spectrometry (GC-MS) analysis. Linoleic acid (methyl ester) was the main constituent, having relative concentrations of 43.4 (±1.95) % and 35.23 (±0.68) % for the lipid fractions separated from the common beans harvested from the NE and SW of Romania, respectively. Higher relative concentrations were obtained for the omega-3 α-linolenic acid methyl ester at values of 13.13 (±0.59) % and 15.72 (±0.30) % for NE and SW Romanian samples, respectively. The omega-3/omega-6 ratio consistently exceeds the lower limit value of 0.2, from where the PUFA glyceride mixture is valuable for the human health. This value was 0.32 (±0.02) for the NE samples and significantly higher for the CBO-SW samples, 0.51 (±0.01). These highly hydrophobic mixtures especially consisting of PUFA triglycerides provide β-CD complexes having higher thermal and oxidative stability. Kneading method allowed obtaining β-CD/CBO powder-like complexes with higher recovery yields of >70%. Thermal analyses of complexes revealed a lower content of hydration water (3.3–5.8% up to 110°C in thermogravimetry (TG) analysis and 154–347 J/g endothermal effect in differential scanning calorimetry (DSC) analysis) in comparison with the β-CD hydrate (12.1% and 479.5–480 J/g, respectively). These findings support the molecular inclusion process of FA moieties into the β-CD cavity. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analysis reveals the formation of the β-CD/CBO inclusion complexes by restricting the vibration and bending of some bonds from the host and guest molecules. Moreover, powder X-ray diffractometry (PXRD) analysis confirm the formation of the host-guest complexes by modifying the diffractograms for β-CD/CBO complexes in comparison with the β-CD and β-CD + CBO physical mixtures. A significant reduction of the level of crystallinity from 93.3 (±5.3) % for β-CD to 60–60.9% for the corresponding β-CD/CBO complexes have been determined. The encapsulation efficiency (EE), the profile of FAs, as well as the controlled release of the encapsulated oil have also been evaluated. The EE was >40% in all cases, the highest value being obtained for β-CD/CBO-SW complex. The SFA content increased, while the unsaturated FA glycerides had lower relative concentrations in the encapsulated CBO samples. It can be emphasized that the main omega-3 FA (namely α-linolenic acid glycerides) had close concentrations in the encapsulated and raw CBOs (13.13 (±0.59) % and 14.04 (±1.54) % for non-encapsulated and encapsulated CBO-NE samples, 15.72 (±0.30) % and 12.41 (±1.95) % for the corresponding CBO-SW samples, respectively). The overall unsaturated FA content significantly decreased after complexation (from 19.03–19.16% for the raw CBOs to 17.3–17.7% for encapsulated oils in the case of MUFAs, and from 55.7–58.8% to 35.13–43.36% for PUFAs). On the other hand, the omega-3/omega-6 ratio increased by β-CD nanoencapsulation to 0.51 (±0.07) and 0.76 (0.26) for β-CD/CBO-NE and β-CD/CBO-SW complexes, respectively. As a conclusion, the lipid fractions of the Romanian common beans are good candidates for β-CD complexation and they can be protected against thermal and oxidative degradation in common beans based food products such as functional foods or food supplements using natural CDs.

Stimulus-Responsive Supramolecular Host-Guest Assembly of a Cationic Pyrene Derivative with Sulfated β-Cyclodextrin

In general, aggregation-prone organic molecules are prevented from self-aggregation in the presence of macrocyclic hosts like β-cyclodextrin because of their preference for the formation of inclusion complex with guest molecules. On the contrary, sulfate-laced β-cyclodextrin has been recently reported to induce the aggregation of some of the non-aggregation-prone organic dyes, which have been subsequently utilized for biosensing applications. In the present contribution, we report the interaction of a cationic organic probe molecule, 1-pyrene methyl amine (PMA), which belongs to one of the most useful families of organic fluorescent probes, that is, pyrene, with a sulfated β-cyclodextrin derivative (SCD). Interaction of a cationic probe with a β-cyclodextrin derivative was studied using a variety of photophysical methods such as ground-state absorption, steady-state emission, and time-resolved emission techniques. Detailed photophysical investigations have revealed that SCD induces the ground-state association of PMA molecules. This SCD-induced aggregation of PMA molecules has been attributed to the charge neutralization of the cationic probe by negatively charged sulfate groups, which subsequently lead to their association because of the close proximity on the rims of cyclodextrin. This monomer-dimer equilibrium of the PMA-SCD system is found to be extremely responsive to external chemical stimuli like temperature, pH, ionic strength of the medium, and organic solvent (dimethyl sulfoxide), which projects them as potential platforms for various sensing applications including bioanalytes. The supramolecular assembly has been demonstrated to sense arginine.

Cyclodextrin-Derived Intrinsically Bioactive Nanoparticles for Treatment of Acute and Chronic Inflammatory Diseases

Inflammation is a common cause of many acute and chronic inflammatory diseases. A major limitation of existing anti-inflammatory therapeutics is that they cannot simultaneously regulate pro-inflammatory cytokine production, oxidative stress, and recruitment of neutrophils and macrophages. To overcome this limitation, nanoparticles (NPs) with multiple pharmacological activities are synthesized, using a chemically modified cyclic oligosaccharide. The manufacture of this type of bioactive, saccharide material-based NPs (defined as LCD NP) is straightforward, cost-effective, and scalable. Functionally, LCD NP effectively inhibits inflammatory response, oxidative stress, and cell migration for both neutrophils and macrophages, two major players of inflammation. Therapeutically, LCD NP shows desirable efficacies for the treatment of acute and chronic inflammatory diseases in mouse models of peritonitis, acute lung injury, and atherosclerosis. Mechanistically, the therapeutic benefits of LCD NP are achieved by inhibiting neutrophil-mediated inflammatory macrophage recruitment and by preventing subsequent pro-inflammatory events. In addition, LCD NP shows good safety profile in a mouse model. Thus, LCD NP can serve as an effective anti-inflammatory nanotherapy for the treatment of inflammatory diseases mainly associated with neutrophil and macrophage infiltration.

PEGylated β-cyclodextrins: Click synthesis and in vitro biological insights

We present three easily rationalized star-shaped PEGylated β-cyclodextrin (βCD) derivatives synthesized via conjugation of different molecular weight PEG chains (5000, 2000, and 550 Da) to the βCD primary face by click chemistry (βCD-PEG₅₀₀₀, βCD-PEG₂₀₀₀, βCD-PEG₅₅₀ respectively). βCDPEG systems are envisioned to further carry bioactive molecules, therefore, their interactions with biological interfaces must be determined at an early stage of development. Hence, the effect of βCDPEGs chain length on cell viability was investigated. To this aim, three models were selected: Vero cells for their fibroblast-like features; HeLa cells that are commonly used for preliminary viability screening; and human peripheral monocytes which are macrophage precursors. Of the three pegylated derivatives, βCD-PEG₅₅₀ was the one that significantly affected HeLa cells and human monocytes viability. Despite the popularity of PEGylation approach, our results underscore the importance of careful and systematic PEGylated materials design for their future success in drug delivery systems.

Biomaterials for Interfacing Cell Imaging and Drug Delivery: An Overview

This feature article provides an overview of different kinds of futuristic biomaterials which have the potential to be used for fluorescent imaging and drug delivery, often simultaneously. The synthesis route or preparation process, fluorescence property, release profile, biocompatibility, bioimaging, and mechanistic approaches are vividly discussed. These include bioimaging with fluorescently doped quantum dots, mesoporous silica, noble metals, metal clusters, hydrophilic/hydrophobic polymers, semiconducting polymer dots, carbon/graphene dots, dendrimers, fluorescent proteins, and other nanobiomaterials. Another section discusses the controlled and targeted drug, gene, or biologically active material delivery using various vehicles such as micelles, 2D nanomaterials, organic nanoparticles, polymeric nanohybrids, and chemically modified polymers. In the last section, we discuss biomaterials, which can deliver biologically active molecules, and imaging the cell/tissue.

Clinical and pharmaceutical applications of affinity ligands in capillary electrophoresis: A review

Affinity capillary electrophoresis (ACE) is a separation technique that combines a biologically-related binding agent with the separating power and efficiency of capillary electrophoresis. This review will examine several classes of binding agents that have been used in ACE and applications that have been described for the resulting methods in clinical or pharmaceutical analysis. Binding agents that will be considered are antibodies, aptamers, lectins, serum proteins, carbohydrates, and enzymes. This review will also describe the various formats in which each type of binding agent has been used in CE, including both homogeneous and heterogeneous methods. Specific areas of applications that will be considered are CE-based immunoassays, glycoprotein/glycan separations, chiral separations, and biointeraction studies. The general principles and formats of ACE for each of these applications will be examined, along with the potential advantages or limitations of these methods.

Cyclodextrin-Based Nanosystems as Drug Carriers for Cancer Therapy

BACKGROUND AND OBJECTIVE

Cyclodextrins have been of great interest as excellent candidates for fabricating versatile nano-drug delivery systems due to their commercial availability, easy functionalization, low immunogenicity, biocompatibility and safety. The possibility of reversible inclusion complex formation between cyclodextrins and various guest molecules in association with versatile exclusive properties of cyclodextrins offer a route towards the fabrication of highly sophisticated nanostructures with enormous potential for cancer treatment.

METHODS AND RESULTS

The current review discusses important recent advances in the fabrication and development of cyclodextrin-based nanostructures for cancer therapy. Firstly, the formation of inclusion complexes between cyclodextrin derivatives and anticancer compounds, as well as their application, are summarized. Secondly, the cyclodextrins -based nanosystems including cyclodextrin-containing polymers, cyclodextrin-based supramolecular necklaces, which consist of polyrotaxanes and polypseudorotaxanes and cyclodextrin based hydrogels accompanied by their applications in cancer treatment are highlighted. In the end, the future perspective of this field is discussed.

CONCLUSION

Numerous investigations in this area pave the way for the flourishing of the next generation of nano-therapeutics towards enhanced cancer therapy.

Complexation of Danube common nase (Chondrostoma nasus L.) oil by β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin

β-Cyclodextrin- and 2-hydroxypropyl-β-cyclodextrin/Danube common nase (Chondrostoma nasus L.) oil complexes (β-CD- and HP-β-CD/CNO) have been obtained for the first time. The fatty acid (FA) profile of the CNO indicates an important content of polyunsaturated fatty acids, the most important being eicosapentaenoic acid (EPA, 6.3%) and docosahexaenoic acid (DHA, 1.6%), both ω-3 FAs. The complexes have been obtained by kneading method. The moisture content and successful of molecular encapsulation have been evaluated by thermal and spectroscopic techniques. Thermogravimetry and differential scanning calorimetry analyses reveals that the moisture content of CD/CNO complexes significantly decreased, compared to starting CDs. On the other hand, the crystallinity index was for the first time determined for such type of complexes, the β-CD/CNO complex having values of 43.9(±18.3)%, according to X-ray diffractometry. FA profile and CD/CNO characteristics sustain the use of these ω-3 based complexes for food supplements or functional food products, but further studies are needed.

Inclusion Complexes of Melphalan with Gemini-Conjugated β-Cyclodextrin: Physicochemical Properties and Chemotherapeutic Efficacy in In-Vitro Tumor Models

β-cyclodextrin (βCD) has been widely explored as an excipient for pharmaceuticals and nutraceuticals as it forms stable host–guest inclusion complexes and enhances the solubility of poorly soluble active agents. To enhance intracellular drug delivery, βCD was chemically conjugated to an 18-carbon chain cationic gemini surfactant which undergoes self-assembly to form nanoscale complexes. The novel gemini surfactant-modified βCD carrier host (hereafter referred to as 18:1βCDg) was designed to combine the solubilization and encapsulation capacity of the βCD macrocycle and the cell-penetrating ability of the gemini surfactant conjugate. Melphalan (Mel), a chemotherapeutic agent for melanoma, was selected as a model for a poorly soluble drug. Characterization of the 18:1βCDg-Mel host–guest complex was carried out using 1D/2D ¹H NMR spectroscopy and dynamic light scattering (DLS). The 1D/2D NMR spectral results indicated the formation of stable and well-defined 18:1βCDg-Mel inclusion complexes at the 2:1 host–guest mole ratio; whereas, host–drug interaction was attenuated at greater 18:1βCDg mole ratio due to hydrophobic aggregation that accounts for the reduced Mel solubility. The in vitro evaluations were performed using monolayer, 3D spheroid, and Mel-resistant melanoma cell lines. The 18:1βCDg-Mel complex showed significant enhancement in the chemotherapeutic efficacy of Mel with 2–3-fold decrease in Mel half maximal inhibitory concentration (IC₅₀) values. The findings demonstrate the potential applicability of the 18:1βCDg delivery system as a safe and efficient carrier for a poorly soluble chemotherapeutic in melanoma therapy.

AIE Supramolecular Assembly with FRET Effect for Visualizing Drug Delivery

Here, we constructed a nanostructured pH/redox dual-responsive supramolecular drug carrier with both aggregation-induced emission (AIE) and Forster resonance energy transfer (FRET) effects, which enabled selective drug release and monitoring drug delivery and release processes. Taking the hyperbranched polyamide amine (H-PAMAM) with intrinsic AIE effects as the core, poly(ethylene glycol) (PEG) was bridged on its periphery by dithiodipropionic acid. Then, through the host-guest interaction of PEG and α-cyclodextrin, the supramolecular nanoparticles with AIE effects were constructed to load the anticancer drug doxorubicin (DOX). The supramolecular assembly has sufficiently large DOX loading due to the abundant cavities formed by branched structures. The hyperbranched core H-PAMAM has strong fluorescence, and the dynamic track of drug carriers and the dynamic drug release process can be monitored by the AIE and FRET effects between H-PAMAM and DOX, respectively. Furthermore, the introduction of disulfide bonds and the pH sensitivity of H-PAMAM enable the achievement of rapid selective release of loaded DOX at the tumor while remaining stable under normal physiological conditions. In vitro cytotoxicity indicates that the drug-loaded supramolecular assembly has a good therapeutic effect on cancer. In addition, the H-PAMAM core is different from the traditional AIE functional group, which has no conjugated structure, such as a benzene ring, thereby providing better biocompatibility. This technology will have broad applications as a new drug delivery system.

Therapeutic gene regulation using pyrrole-imidazole polyamides

Recent innovations in cutting-edge sequencing platforms have allowed the rapid identification of genes associated with communicable, noncommunicable and rare diseases. Exploitation of this collected biological information has facilitated the development of nonviral gene therapy strategies and the design of several proteins capable of editing specific DNA sequences for disease control. Small molecule-based targeted therapeutic approaches have gained increasing attention because of their suggested clinical benefits, ease of control and lower costs. Pyrrole-imidazole polyamides (PIPs) are a major class of DNA minor groove-binding small molecules that can be predesigned to recognize specific DNA sequences. This programmability of PIPs allows the on-demand design of artificial genetic switches and fluorescent probes. In this review, we detail the progress in the development of PIP-based designer ligands and their prospects as advanced DNA-based small-molecule drugs for therapeutic gene modulation.

Gas-Phase Fragmentation of Cyclic Oligosaccharides in Tandem Mass Spectrometry

Modern mass spectrometry, including electrospray and MALDI, is applied for analysis and structure elucidation of carbohydrates. Cyclic oligosaccharides isolated from different sources (bacteria and plants) have been known for decades and some of them (cyclodextrins and their derivatives) are widely used in drug design, as food additives, in the construction of nanomaterials, etc. The peculiarities of the first- and second-order mass spectra of cyclic oligosaccharides (natural, synthetic and their derivatives and modifications: cyclodextrins, cycloglucans, cyclofructans, cyclooligoglucosamines, etc.) are discussed in this minireview.

A Multifunctional Nanotherapy for Targeted Treatment of Colon Cancer by Simultaneously Regulating Tumor Microenvironment

Colitis-associated colon cancer (CAC) is a widely recognized cancer, while treatment with the existing chemotherapeutic drugs affords limited clinical benefits. Herein we proposed a site-specific, combination nanotherapy strategy for targeted treatment of CAC by the oral route. Methods: A reactive oxygen species (ROS)-responsive and hydrogen peroxide-eliminating material OCD was synthesized, which was further produced into a functional nanoparticle (OCD NP). The antioxidative stress and anti-inflammatory effects of OCD NP were examined by in vitro and in vivo experiments. By packaging an anticancer drug camptothecin-11 (CPT-11) into OCD NP, a ROS-responsive nanotherapy CPT-11/OCD NP was obtained, and its antitumor activity was evaluated by both in vitro and in vivo studies. Preliminary safety studies were also performed for CPT-11/OCD NP in mice. Results: OCD NP significantly attenuated oxidative stress and inhibited inflammatory response in different cells and mice with induced colitis. CPT-11/OCD NP could selectively release drug molecules under intestinal pH conditions and at high levels of ROS. In C26 murine colon carcinoma cells, this nanotherapy showed significantly higher antitumor activity compared to free CPT-11 and a non-responsive CPT-11 nanotherapy. Correspondingly, oral delivery of CPT-11/OCD NP notably inhibited tumorigenesis and tumor growth in mice with induced CAC. By combination therapy with the nanovehicle OCD NP in the inflammatory phase, more desirable therapeutic effects were achieved. Furthermore, CPT-11/OCD NP displayed excellent safety profile for oral administration at a dose that is 87.3-fold higher than that employed in therapeutic studies. Conclusions: Anticancer nanotherapies derived from intrinsic anti-inflammatory nanocarriers are promising for targeted combination treatment of inflammation-associated tumors by simultaneously shaping pro-inflammatory microenvironment toward a relatively normal niche sensitive to chemotherapy.

Complex systems that incorporate cyclodextrins to get materials for some specific applications

Cyclodextrins (CDs) are a family of biodegradable cyclic hydrocarbons composed of α-(1,4) linked glucopyranose subunits, the more common containing 6, 7 or 8 glucose units are named α, β and γ-cyclodextrins respectively. Since the discovery of CDs, they have attracted interest among scientists and the first studies were about the properties of the native compounds and in particular their use as catalysts of organic reactions. Characteristics features of different types of cyclodextrins stimulated investigation in different areas of research, due to its non-toxic and non-inmunogenic properties and also to the development of an improved industrial production. In this way, many materials with important properties have been developed. This mini-review will focus on chemical systems that use cyclodextrins, whatever linked covalently or mediated by the non covalent interactions, to build complex systems developed mainly during the last five years.

Host-Guest Chemistry in Supramolecular Theranostics

Macrocyclic hosts, such as cyclodextrins, calixarenes, cucurbiturils, and pillararenes, exhibit unparalleled advantages in disease diagnosis and therapy over the past years by fully taking advantage of their host-guest molecular recognitions. The dynamic nature of the non-covalent interactions and selective host-guest complexation endow the resultant nanomaterials with intriguing properties, holding promising potentials in theranostic fields. Interestingly, the differences in microenvironment between the abnormal and normal cells/tissues can be employed as the stimuli to modulate the host-guest interactions, realizing the purpose of precise diagnosis and specific delivery of drugs to lesion sites. In this review, we summarize the progress of supramolecular theranostics on the basis of host-guest chemistry benefiting from their fantastic topological structures and outstanding supramolecular chemistry. These state-of-the-art examples provide new methodologies to overcome the obstacles faced by the traditional theranostic systems, promoting their clinical translations.

Integrating Stimuli-Responsive Properties in Host-Guest Supramolecular Drug Delivery Systems

Host-guest motifs are likely the most recognizable manifestation of supramolecular chemistry. These complexes are characterized by the organization of small molecules on the basis of preferential association of a guest within the portal of a host. In the context of their therapeutic use, the primary application of these complexes has been as excipients which enhance the solubility or improve the stability of drug formulations, primarily in a vial. However, there may be opportunities to go significantly beyond such a role and leverage key features of the affinity, specificity, and dynamics of the interaction itself toward "smarter" therapeutic designs. One approach in this regard would seek stimuli-responsive host-guest recognition, wherein a complex forms in a manner that is sensitive to, or can be governed by, externally applied triggers, disease-specific proteins and analytes, or the presence of a competing guest. This review will highlight the general and phenomenological design considerations governing host-guest recognition and the specific types of chemistry which have been used and are available for different applications. Finally, a discussion of the molecular engineering and design approaches which enable sensitivity to a variety of different stimuli are highlighted. Ultimately, these molecular-scale approaches offer an assortment of new chemistry and material design tools toward improving precision in drug delivery.

Paclitaxel interaction with cucurbit [7]uril and acyclic Cucurbit[4]uril nanocontainers: A computational approach

Paclitaxel (PTX) is a natural terpenoid compound that has been broadly studied for its antitumor activities and widely used as a chemotherapy medication. The treatment efficacy of PTX is affected by its low aqueous solubility, thus causing a subject of extensive research. In recent years, synthetic molecular containers such as cucurbit[n]urils (CB[n]s) and their derivatives have been significantly developing because of their remarkable ability to bind hydrophobic and cationic drugs. Recent experimental studies have shown that acyclic CB[n]-type containers (aCB[n]s), as new derivatives of the family of CB[n]s, increase the solubility of insoluble pharmaceuticals. However, the nature by which the drug interacts with carriers remains largely unknown. In this study, molecular docking and molecular dynamics (MD) simulation were performed to understand how CB[7] and aCB[4] nanocontainers interact with PTX which affect its aqueous solubility. The results clarify how the flexibility of containers is influenced by their structure and how this affects their interactions with PTX. Our results reveal that although both CB[7] and aCB[4] are capable of binding to PTX, the affinity to aCB[4] is higher than that of CB[7]. It has also been shown that the binding to both CB[7] and aCB[4] is probably an entropy-driven process. This research supports the potential use of the cucurbit[n]urils and their acyclic derivatives as drug delivery systems.

Colloidal-electrochemical fabrication strategies for functional composites of linear polyethylenimine

Colloidal-electrochemical fabrication strategies have been developed for the deposition of linear polyethylenimine (LPEI) composite materials. Electrophoretic deposition (EPD) allowed for the fabrication of composite films containing Mn₃O₄ and ZnO nanoparticles, as well as advanced flame retardant materials, such as halloysite nanotubes and memory-type Al-Mg-Zr complex hydroxide (AMZ) in the matrix of the water-insoluble LPEI. A liquid-liquid extraction method has been designed for the agglomerate-free processing of AMZ particles. Efficient extraction was achieved using decylphosphonic acid as an extractor. A conceptually new polymer complex (PC)-EPD method has been developed, which is based on the use of LPEI-metal ion complexes. Proof-of-concept studies involved the fabrication of LPEI-Ni(OH)₂ and LPEI-MnOx nanocomposites. The composites showed valuable flame retardant and charge-storage properties. The analysis of basic EPD and PC-EPD mechanisms as well as complexing properties of LPEI has driven the development of new strategies for the fabrication of organic composites. Hemoglobin was used as a model protein for the fabrication of composite films. Another important finding was the fabrication of composites, containing cyclodextrin, which is a unique carrier of various functional organic molecules. EPD and PC-EPD are versatile methods, which allow for the deposition of novel LPEI based composites containing various functional materials.

3D-printable self-healing and mechanically reinforced hydrogels with host-guest non-covalent interactions integrated into covalently linked networks

Natural polymer hydrogels are one of the best biomaterials for soft tissue repair because of their excellent biocompatibility, biodegradability and low immune rejection. However, they lack mechanical strength matching that of natural tissue and desired functionality (e.g. self-healing and 3D-printability). To solve this problem, we developed a host-guest supramolecule (HGSM) with three arms covalently crosslinked with a natural polymer to construct a novel hydrogel with non-covalent bonds integrated in a covalently crosslinked network. The unique structure enabled the hydrogel to bear improved mechanical properties and show both self-healing and 3D printing capabilities. The three-armed HGSM was first prepared via the efficient non-covalent host-guest inclusion interactions between isocyanatoethyl acrylate-modified β-cyclodextrin (β-CD-AOI₂) and acryloylated tetra-ethylene glycol-modified adamantane (A-TEG-Ad). Subsequently, a host-guest supramolecular hydrogel (HGGelMA) was obtained through copolymerization between the arms of HGSM and gelatin methacryloyl (GelMA) to form a covalently crosslinked network. The HGGelMA was robust, fatigue resistant, reproducible and rapidly self-healing. In HGGelMA, the covalent crosslinking maintained its overall shape whereas the weak reversible non-covalent host-guest interactions reinforced its mechanical properties and enabled it to rapidly self-heal upon fracturing. The reversible non-covalent interactions could be re-established upon breaking, so as to heal the hydrogel and dissipate energy to prevent catastrophic fracture propagation. Furthermore, the precursors of the HGGelMA were sufficiently viscous and could be rapidly photocrosslinked to produce a robust scaffold with an exquisite internal structure through 3D printing. The 3D-printed HGGelMA hydrogel scaffold was biocompatible, promoted cell adhesion and proliferation, and supported tissue in-growth. Our strategy of integrating non-covalently linked HGSM in a covalently linked hydrogel network represents a new approach to the development of natural polymers into biocompatible hydrogels with improved strength as well as desired self-healing and 3D-printability.

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.

Macromolecules as targeted drugs delivery vehicles: an overview

Targeted drug delivery system improves the efficiency and safety of the therapeutic agents by managing the pharmacokinetics and pharmacodynamics of drugs. Currently, numerous drug carrier systems have been developed with different sizes, architectures and characteristics surface properties. Among different systems, macromolecules have a wide range of applications in targeted drug delivery system. The optimal drug loading potential, smooth drug releasing ability and biocompatibility are the distinguishing features that ensure the drugs delivery ability of macromolecules. This review briefly introduces some of the most commonly studied macromolecules which have been recommended as drugs delivery vehicles.

Nanocarriers and Their Loading Strategies

Nanocarriers are of paramount significance for drug delivery and nanomedicine technology. Given the imperfect systems and nonideal therapeutic effects, there are works to be done in synthesis as much as in biological studies, if not more so. Building the foundation of synthesis would offer more tools and deeper insights for exploring the biological systems with extreme complexity. This review aims at a broad-scope summary and classification of nanocarriers for drug delivery, with focus on the synthetic strategy and structural implications. The nanocarriers are divided into four categories according to the loading principle: molecular-level loading, surface loading, matrix loading, and cavity loading systems. Making comparisons across diverse nanocarrier systems would make it easier to see the fundamental characteristics, from where the weakness can be addressed and the strengths combined. The systematic comparisons may also inspire new ideas and methods.