Non-Stoichiometric Polymer-Cyclodextrin Inclusion Compounds: Constraints Placed on Un-Included Chain Portions Tethered at Both Ends and Their Relation to Polymer Brushes

Preparation of the Heterogeneous Saponified Poly(Vinyl Alcohol)/Poly(Methyl Methacrylate-Methallyl Alcohol) Blend Film

For the first time, poly(vinyl alcohol) (PVA)/poly(methyl methacrylate-methallyl alcohol) (P(MMA-MAA)) (9:1, 7:3, 5:5) blend films were made simultaneously using the saponification method in a heterogeneous medium from poly(vinyl acetate) (PVAc)/poly(methyl methacrylate) (PMMA) (9:1, 7:3, 5:5) blend films, respectively. The surface morphology and characteristics of the films were investigated using optical microscopy (OM), atomic force microscopy (AFM), X-ray diffractometer (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Moreover, the effect of the PVAc content on the degree of saponification (DS) of the PVAc/PMMA films were evaluated and revealed that the obtained DS value increased with the increase in PVAc content in the PVAc/PMMA blend films. According to the OM results, the saponified films demonstrated increased surface roughness compared with the unsaponified films. The AFM images revealed morphological variation among the saponified PVAc/PMMA blend films with different mass ratios of 9:1, 7:3, and 5:5. According to the DSC and TGA results, all blend film types exhibited higher thermal property after the saponification treatment. The XRD and FTIR results confirmed the conversion of the PVAc/PMMA into PVA/P(MMA-MAA) films. Thus, our present work may give a new idea for making blend film as promising medical material with significant surface properties based on hydrophilic/hydrophobic strategy.

Nanoscale Restructuring of Polymer Materials to Produce Single Polymer Composites and Miscible Blends

I summarize work conducted in our laboratories over the past 30 years using small host molecules to restructure polymer materials at the nanometer level. Certain small molecules, such as the cyclic starches cyclodextrins (CDs) and urea (U) can form non-covalent crystalline inclusion compounds (ICs) with a range of guest molecules, including many polymers. In polymer-CD- and -U-ICs, guest polymer chains reside in narrow channels created by the host molecule crystals, where they are separated and highly extended. When the host crystalline lattice is carefully removed, the guest polymer chains coalesce into a bulk sample with an organization that is distinct from that normally produced from its melt or from solution. Amorphous regions of such coalesced polymer samples have a greater density, likely with less chain entanglement and more chain alignment. As a consequence, after cooling from their melts, coalesced amorphous polymers show glass-transition temperatures (T_gs) that are elevated above those of samples prepared from their solutions or melts. Upon cooling from their melts, coalesced samples of crystallizable polymers show dramatically-increased abilities to crystallize more rapidly and much closer to their melting temperatures (T_ms). These unique behaviors of polymers coalesced from their CD- and U-ICs are unexpectedly resistant to extended annealing above their T_gs and T_ms. Taking advantage of this behavior permits us to create polymer materials with unique and improved properties. Among these are amorphous polymers with elevated T_gs and semi-crystalline polymers with finer more uniform morphologies. Improved mechanical properties can be achieved through self-nucleation with small amounts of the same polymer made rapidly crystallizable through coalescence from its CD- or U-IC. This can lead to single polymer composites with as-received polymer matrices and self-nucleated reinforcements. Through simultaneous formation and subsequent coalescence from their common CD–ICs, stable well-mixed blends can be achieved between any two or more polymers, despite their inherent immiscibilities. Such coalesced and well-mixed blends are also resistant to phase segregation when heated for extensive periods well above their T_gs and T_ms.

Polymers Containing Non-Covalently Bound Cyclodextrins

We summarize and review the formation, characterization, behaviors, and possible uses of polymers that are threaded through, but only partially covered by cyclodextrins (CDs), which we call non-stoichiometric polymer–CD inclusion compounds (ICs) or non-stoichiometric (n-s) polymer–CD ICs. Emphasis is placed on comparison of the behaviors of unthreaded neat polymers with those that are threaded through and partially covered by CDs. These comparisons lead to several suggested uses for (n-s) polymer–CD ICs.

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.

Evaluation of host-guest system to enhance the tamoxifen efficiency

Hydrophobic drugs can absorb as guest molecules inside the cavity of cyclodextrins as host sites. So, forming the drug-cyclodextrin complex can exert a profound effect on the physicochemical and biological properties of the drugs. According to these advantages, in this study, we synthesized the tamoxifen (TMX) loaded cyclodextrin (CD)-conjugated MNPs to evaluate simultaneously the cytotoxicity and sustained release as well as hepatoprotective effect of this nanomedicine. The average size of Fe₃O₄-DPA-PEG-CD-TMX NPs was approximately 31 nm. By energy-dispersive X-ray spectroscopy (EDS), it was revealed that Fe₃O₄ constitutes 14.34% of the composition of modified MNPs. In the other words, nearly 85% of Fe₃O₄-DPA-PEG-CD NPs are made of dopamine (DPA), polyethylene glycol (PEG) and β-cyclodextrin (β-CD). The TMX loaded MNPs (with entrapment efficiency of 33 mg TMX per unit CD (mg) and loading efficiency of 87.5%) showed sustained liberation of TMX molecules (with 91% release in 120 h). Cytotoxicity assay and apoptosis assay by TUNEL analysis revealed that the engineered Fe₃O₄-DPA-PEG-CD-TMX NPs were able to significantly inhibit the MCF-7 breast cancer cells. According to effect of CD on TMX sustained release, it was found that CD can decrease the hepatotoxicity induced by TMX nearly 30%. Based upon these findings, we suggest the Fe₃O₄-DPA-PEG-CD-TMX NPs as an effective multifunctional nanomedicine with simultaneous therapeutic and hepatoprotective effects.