Star-Pseudopolyrotaxane Organized in Nanoplatelets for Poly(ε-caprolactone)-Based Nanofibrous Scaffolds with Enhanced Surface Reactivity

Polycaprolactone/α-cyclodextrin polyrotaxanes with cellular uptake enhancing properties

Biodegradable poly(ε-caprolactone) (PCL) was rotaxanated with α-cyclodextrin (α-CD) and an α-CD/2-hydroxypropyl-α-CD (HP-α-CD) mixture. Stoppering was achieved using 2-mercaptosuccinic acid (MSA) via disulfide linkage. The structures of these polymeric supramolecular entities were confirmed by 1H NMR, with 75-80 wt% threaded CD, while the molar mass of the polyrotaxanes was around 18 kDa, determined by gel permeation chromatography. The aqueous solubility was as low as 20.2 ± 1.2 g L-1 for the α-CD-based polyrotaxane but considerably increased to 74.7 ± 6.0 g L-1 by the introduction of threaded HP-α-CD into the polymeric axis. Dethreading of the polyrotaxanes was triggered by the removal of the stopper molecules via disulfide-exchange reactions using glutathione. Additionally, the polyester axis proved to be fully degradable by lipase. Cellular uptake of these polyrotaxanes was investigated by flow cytometry and confocal microscopy. The results showed an almost up to 50-fold higher cellular uptake of polyrotaxanes than free CD. These disulfide end-stoppered polyrotaxanes of biodegradable PCL represent a promising tool for intracellular delivery of CDs and offer novel treatment possibilities for lysosomal storage dysfunctions.

Solvent-Responsive Invisible Photonic Patterns with High Contrast for Fluorescence Emission Regulation and Anti-Counterfeiting

Invisible photonic patterns (IPPs) are photonic materials that can display hidden patterns under external stimulation and are attractive in anti-counterfeiting devices and information storage. In this work, we report a solvent-responsive invisible photonic pattern (SRIPP) with high contrast by polymerizing two monomers of acrylamide (AAm) and poly(ethylene glycol) methacrylate (PEGMA) with different solubility parameters in different regions of poly(hydroxyethyl methacrylate) photonic gels. The two regions with different solvent responsiveness can shrink and swell in the same environment, thus causing the colors of different regions of photonic gel to shift in opposite directions from the initial state. As a result, the contrast of photonic patterns is significantly improved, increasing naked-eye visualization. In addition, by introducing fluorescent substances into the photonic gel and adjusting the photonic band gap (PBG) of photonic gels, we realize the regulation of fluorescence emission and display of fluorescence patterns by utilizing different PBGs on the SRIPP. Dynamic solvent responsiveness patterns and fluorescence patterns are integrated into a photonic gel, showing great potential in information storage and multiple-mode anti-counterfeiting applications.

Thermally induced disassembly mechanism of pseudo-polyrotaxane nanosheets consisting of β-CD and a poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymer

PPRNSs dissolved in two steps during heating owing to the anisotropy of the topological constraint of β-CD by axis polymers.

Polymer-free cyclodextrin and natural polymer-cyclodextrin electrospun nanofibers: A comprehensive review on current applications and future perspectives

The present review discusses the use of cyclodextrins and their derivatives to prepare electrospun nanofibers with specific features. Cyclodextrins, owing to their unique capability to form inclusion complexes with hydrophobic and volatile molecules, can indeed facilitate the encapsulation of bioactive compounds in electrospun nanofibers allowing fast-dissolving products for food, biomedical, and pharmaceutical purposes, filtering materials for wastewater and air purification, as well as a variety of other technological applications. Additionally, cyclodextrins can improve the processability of naturally occurring biopolymers helping the fabrication of "green" materials with a strong industrial relevance. Hence, this review provides a comprehensive state-of-the-art of different cyclodextrins-based nanofibers including those made of pure cyclodextrins, of polycyclodextrins, and those made of natural biopolymer functionalized with cyclodextrins. To this end, the advantages and disadvantages of such approaches and their possible applications are investigated along with the current limitations in the exploitation of electrospinning at the industrial level.

Precise control of cyclodextrin-based pseudo-polyrotaxane lamellar structure via axis polymer composition

Self-assembly of cyclodextrin (CD) with guest polymers has attracted much attention owing to its biocompatibility and accessibility. In this study, we investigate the composition effect of poly(ethylene oxide)m-b-poly(propylene oxide)n-b-poly(ethylene oxide)m (EOmPOnEOm) triblock copolymers on lamellar or plate structures formed by complexation with β-CD. EO5PO29EO5, EO14PO29EO14, and EO75PO29EO75 show periodic lamellar morphology consisting of single-crystalline pseudo-polyrotaxane (PPR) nanosheets with a thickness equal to the central PO length. This is because β-CDs selectively cover the PO component and cause the microphase separation between β-CD and EO layers. The thickness of the EO layers increases linearly with increasing number of EO units, which suggests that the EO chains are constrained into virtual cylinders with the diameter of the β-CD. This means that we can precisely control the thickness of both the crystal (β-CD and PO) and the amorphous (EO) layers in the lamellar structure. In contrast, EO2PO29EO2 forms a thin plate structure, where not only PO but also EO chains are covered with β-CD. Furthermore, the length of the central PO component is necessary to form the lamellar structure with the phase separation between the β-CD and EO layers. These findings provide a more fundamental understanding to enhance the variety and applicability of CD-based self-assembled materials.

Aliphatic Polyester Nanofibers Functionalized with Cyclodextrins and Cyclodextrin-Guest Inclusion Complexes

The fabrication of nanofibers by electrospinning has gained popularity in the past two decades; however, only in this decade, have polymeric nanofibers been functionalized using cyclodextrins (CDs) or their inclusion complexes (ICs). By combining electrospinning of polymers with free CDs, nanofibers can be fabricated that are capable of capturing small molecules, such as wound odors or environmental toxins in water and air. Likewise, combining polymers with cyclodextrin-inclusion complexes (CD-ICs), has shown promise in enhancing or controlling the delivery of small molecule guests, by minor tweaking in the technique utilized in fabricating these nanofibers, for example, by forming core⁻shell or multilayered structures and conventional electrospinning, for controlled and rapid delivery, respectively. In addition to small molecule delivery, the thermomechanical properties of the polymers can be significantly improved, as our group has shown recently, by adding non-stoichiometric inclusion complexes to the polymeric nanofibers. We recently reported and thoroughly characterized the fabrication of polypseudorotaxane (PpR) nanofibers without a polymeric carrier. These PpR nanofibers show unusual rheological and thermomechanical properties, even when the coverage of those polymer chains is relatively sparse (~3%). A key advantage of these PpR nanofibers is the presence of relatively stable hydroxyl groups on the outer surface of the nanofibers, which can subsequently be taken advantage of for bioconjugation, making them suitable for biomedical applications. Although the number of studies in this area is limited, initial results suggest significant potential for bone tissue engineering, and with additional bioconjugation in other areas of tissue engineering. In addition, the behaviors and uses of aliphatic polyester nanofibers functionalized with CDs and CD-ICs are briefly described and summarized. Based on these observations, we attempt to draw conclusions for each of these combinations, and the relationships that exist between their presence and the functional behaviors of their nanofibers.

Electrospun Fibers of Cyclodextrins and Poly(cyclodextrins)

Cyclodextrins (CDs) can endow electrospun fibers with outstanding performance characteristics that rely on their ability to form inclusion complexes. The inclusion complexes can be blended with electrospinnable polymers or used themselves as main components of electrospun nanofibers. In general, the presence of CDs promotes drug release in aqueous media, but they may also play other roles such as protection of the drug against adverse agents during and after electrospinning, and retention of volatile fragrances or therapeutic agents to be slowly released to the environment. Moreover, fibers prepared with empty CDs appear particularly suitable for affinity separation. The interest for CD-containing nanofibers is exponentially increasing as the scope of applications is widening. The aim of this review is to provide an overview of the state-of-the-art on CD-containing electrospun mats. The information has been classified into three main sections: (i) fibers of mixtures of CDs and polymers, including polypseudorotaxanes and post-functionalization; (ii) fibers of polymer-free CDs; and (iii) fibers of CD-based polymers (namely, polycyclodextrins). Processing conditions and applications are analyzed, including possibilities of development of stimuli-responsive fibers.

The study of the pseudo-polyrotaxane architecture as a route for mild surface functionalization by click chemistry of poly(ε-caprolactone)-based electrospun fibers

PCL fibers with pseudopolyrotaxanes at their surface are functionalized with bicyclononyne clickable groups making possible an easy bioconjugation in water and without copper catalysts for biomedical applications.