Polymeric Core-Shell Assemblies Mediated by Host-Guest Interactions: Versatile Nanocarriers for Drug Delivery

Expanding the arsenal against pulmonary diseases using surface-functionalized polymeric micelles: breakthroughs and bottlenecks

Pulmonary diseases such as lung cancer, asthma and tuberculosis have remained one of the common challenges globally. Polymeric micelles (PMs) have emerged as an effective technique for achieving targeted drug delivery for a local as well as a systemic effect. These PMs encapsulate and protect hydrophobic drugs, increase pulmonary targeting, decrease side effects and enhance drug efficacy through the inhalation route. In the current review, emphasis has been placed on the different barriers encountered by the drugs given via the pulmonary route and the mechanism of PMs in achieving drug targeting. The applications of PMs in different pulmonary diseases have also been discussed in detail.

Gelation Based on Host-Guest Interactions Induced by Multi-Functionalized Nanosheets

Host–guest interaction, being reversible and stimuli-responsive, is ideal to be applied to the design of hydrogels. We created a gelation system based on the host–guest interactions between the adamantyl groups and β-cyclodextrin (β-CD) polymer. N,N,N-trimethyl-1-adamantylammonium hydroxide (TriMAA) cations were attached to the pre-exfoliated α-zirconium phosphate (α-ZrP) nanosheets by ionic bonding through a displacement reaction with the exfoliating agents. The exfoliated α-ZrP nanosheets with adamantyl groups directly or indirectly attached to the surface act as reversible high-functionality crosslinkers within the β-CD polymer. The gelation occurred at a host-to-guest ratio of 1:10 or 1:5 at room temperature within minutes. The agents used to exfoliate α-ZrP can tailor the surface of the resultant α-ZrP nanosheets and the ionic strength of the system, which directly affects the further gelation results. Plus, the exfoliating agent cations may generate a host-and-guest interaction with the β-CD polymer as well. This gelation process without covalent bonding formation should help fellow researchers to better understand the gelation system and host–guest interactions.

Bio-multifunctional noncovalent porphyrin functionalized carbon-based nanocomposite

Herein, in a one-pot method, the reduced graphene oxide layers with the assistance of multiwalled carbon nanotubes were decorated to provide a suitable space for the in situ growth of CoNi₂S₄, and the porphyrins were incorporated into the layers as well to increase the sensitivity of the prepared nanostructure. The prepared nanocomposite can establish π-π interactions between the genetic material and on the surface of porphyrin rings. Also, hydrogen bonds between genetic domains and the porphyrin' nitrogen and the surface hydroxyl groups are probable. Furthermore, the potential donor-acceptor relationship between the d⁷ transition metal, cobalt, and the genetic material provides a suitable way to increase the interaction and gene loading , and transfections. The reason for this phenomenon was optimized to increase the EGFP by up to 17.9%. Furthermore, the sensing ability of the nanocomposite towards H₂O₂ was investigated. In this regard, the limit of detection of the H₂O₂ obtained 10 µM. Also, the in situ biosensing ability in the HEK-293 and PC12 cell lines was evaluated by the addition of PMA. The nanocomposite showed the ability to detect the released H₂O₂ after adding the minimum amount of 120 ng/mL of the PMA.

Controlling the Stacking Modes of Metal-Organic Framework Nanosheets through Host-Guest Noncovalent Interactions

The tuning of metal-organic framework (MOF) nanosheet stacking modes from molecular level was rarely explored although it significantly affected the properties and applications of nanosheets. Here, the different stacking modes of Zr-1, 3, 5-(4-carboxylphenyl)-benzene framework nanosheets were synthesized through the induction of different host-guest noncovalent interactions. The solvents of methyl benzene and ethyl acetate induced twisted stacking of nanosheets with the specific rotation angles of 12°, 18°, 24° and 6°, 18°, 24°, 30°, respectively, which was in agreement with theoretical calculations. Meanwhile, the alkanes were likely to vertically enter the pores of Zr-BTB nanosheets because of steric hindrance and hydrophobic interactions, resulting in the untwisted stacking of nanosheets. The untwisted ordered nanopores showed the excellent gas chromatographic separations of benzene derivative isomers, which was better than twisted nanosheets stacking and commercial columns. This work uncovers a rational strategy to control the stacking of two-dimensional MOF nanosheets.

Emerging Supramolecular Therapeutic Carriers Based on Host-Guest Interactions

Recent advances in host-guest chemistry have significantly influenced the construction of supramolecular soft biomaterials. The highly selective and non-covalent interactions provide vast possibilities of manipulating supramolecular self-assemblies at the molecular level, allowing a rational design to control the sizes and morphologies of the resultant objects as carrier vehicles in a delivery system. In this Focus Review, the most recent developments of supramolecular self-assemblies through host-guest inclusion, including nanoparticles, micelles, vesicles, hydrogels, and various stimuli-responsive morphology transition materials are presented. These sophisticated materials with diverse functions, oriented towards therapeutic agent delivery, are further summarized into several active domains in the areas of drug delivery, gene delivery, co-delivery and site-specific targeting deliveries. Finally, the possible strategies for future design of multifunctional delivery carriers by combining host-guest chemistry with biological interface science are proposed.

Preparation of poly(cyclooctene)-g-poly(ethylene glycol) (PCOE-g-PEG) graft copolymers with tunable PEG side chains via ROMP and its protein adsorption and platelet adhesion properties

In our previous work [H. Shi, D. Shi et al., Polymer Chemistry 2(2011)679-684], polycyclooctene-g-PEG (PCOE-g-PEG) copolymers were synthesized via ring opening metathesis polymerization (ROMP) from PEG functionalized cyclic olefin macromonomers and cyclooctene. The grafting degree and the grafting site were easily controlled through the "grafting through" approach. The PCOE-g-PEG film surface was imparted excellent anti-protein adsorption properties. In that work, the molecular weight of PEG side chain was fixed at 750 g/mol and the neat PEG content in the copolymer was lower than 50 wt.%. In this work, both the effects of PEG side chain lengths (350 to 1000 g/mol) at a fixed PEG content (50 wt.%) and the neat PEG content (30 wt.% to 70 wt.%) at a fixed PEG molecular weight (750 g/mol) on the anti-protein adsorption and anti-platelet adhesion properties are studied. It is shown that the copolymer with 60 wt.% PEG side chains of 750 g/mol, where both PEG and PCOE form continuous morphology, is optimal to reduce the adsorption of both the bovine serum albumin (BSA) and platelet. When the PEG content reaches 70 wt.%, phase inversion happens. PEG is the continuous phase but PCOE becomes the dispersed phase. The surface roughness of the casting PCOE-g-PEG film increases. In this case, both BSA adsorption and platelet adhesion will slightly increase comparing to the sample with 60 wt.% PEG.