Long-term observation of polycaprolactone small-diameter vascular grafts with thickened outer layer and heparinized inner layer in rabbit carotid arteries.

In our previous study, the pristine bilayer small-diameterin situtissue engineered vascular grafts (pTEVGs) were electrospun from a heparinized polycaprolactone (PCL45k) as an inner layer and a non-heparinized PCL80k as an outer layer in the thickness of about 131 µm and 202 µm, respectively. However, the hydrophilic enhancement of inner layer stemmed from the heparinization accelerated the degradation of grafts leading to the early formation of arterial aneurysms in a period of 3 months, severely hindering the perennial observation of the neo-tissue regeneration, host cell infiltration and graft remodeling in those implanted pTEVGs. Herein to address this drawback, the thickness of the outer layers was increased with PCL80k to around 268 µm, while the inner layer remained unchangeable. The thickened TEVGs named as tTEVGs were evaluated in six rabbits via a carotid artery interpositional model for a period of 9 months. All the animals kept alive and the grafts remained patent until explantation except for one whose one side of arterial blood vessels was occluded after an aneurysm occurred at 6 months. Although a significant degradation was observed in the implanted grafts at 9 month, the occurrence of aneurysms was obviously delayed compared to pTEVGs. The tissue stainings indicated that the endothelial cell remodeling was substantially completed by 3 months, while the regeneration of elastin and collagen remained smaller and unevenly distributed in comparison to autologous vessels. Additionally, the proliferation of macrophages and smooth muscle cells reached the maximum by 3 months. These tTEVGs possessing a heparinized inner layer and a thickened outer layer exhibited good patency and significantly delayed onset time of aneurysms.

Azo-Linked Porous Polycalix[n]arenes for the Efficient Removal of Organic Micropollutants from Water.

Developing novel porous adsorbents for efficient wastewater treatment is significant to the environment protection. Herein, three porous polycalix[n]arenes (n = 4, 6, and 8) which had varying cavity sizes of the macrocycle (Azo-CX4P, Azo-CX6P, and Azo-CX8P) were prepared under mild conditions and tested for their potential application in water purification. Azo-CX8P with a larger cavity size of the macrocycle outperformed Azo-CX4P and Azo-CX6P in screening studies involving a range of organic micropollutants. It was proved that Azo-CX8P was especially efficient in the removal of cationic dyes because of its high negative surface charge. In terms of the adsorption of Rhodamine B with Azo-CX8P, the pseudo-second-order rate constant reaches 5.025 g·mg-1·min-1 with the maximum adsorption capacity being 1345 mg·g-1. These values are significantly higher compared with those recorded for most adsorbents. In addition, the easily prepared Azo-CX8P can be reused at least six times without a loss of the adsorption efficiency, demonstrating its potential use in water purification.

Remodeling of structurally reinforced (TPU+PCL/PCL)-Hep electrospun small-diameter bilayer vascular grafts interposed in rat abdominal aortas.

As thermoplastic polyurethane (TPU) elastomers possess good biocompatibility and mechanical properties similar to those of native vascular tissues, they were intended to be co-electrospun with poly(ε-caprolactone) (PCL) onto the outer surface of PCL electrospun small-diameter single-layer vascular grafts (SLVGs) in this study, combining with surface heparinization. In this work, a kind of structurally reinforced TPU+PCL/PCL small-diameter bilayer vascular graft (BLVG) was fabricated via layer-by-layer electrospinning followed by the heparinization of PCL via EDC/NHS chemistry. The resulting (TPU+PCL/PCL)-Hep BLVGs presented excellent mechanical strength and higher compliance, and sustainably released heparin exhibited enhanced anti-coagulation activity. During 6-month implantation in 18 rat abdominal aortas, these vascular prostheses induced the remodeling and regeneration of neovascular tissues, and promoted ECM deposition. Compared to heparinized PCL (PCL-Hep) SLVGs, the formation of aneurysm was completely inhibited and the onset of calcification was significantly delayed in (TPU+PCL/PCL)-Hep BLVGs. Not only vascular cell makers co-expressed by CD206+ cells were identified, but also a high content of elastin was evidenced due to the improvement of mechanical strength and compliance. These results indicated the feasibility and efficacy of inhibiting the aneurysm formation and boosting the vascular remodeling by incorporating TPU into PCL-Hep small-diameter artificial vascular grafts.

Fabrication of heparinized small diameter TPU/PCL bi-layered artificial blood vessels and in vivo assessment in a rabbit carotid artery replacement model.

Increasingly growing problems in vascular access for long-term hemodialysis lead to a considerable demand for synthetic small diameter vascular prostheses, which usually suffer from some drawbacks and are associated to high failure rates. Incorporating the concept of in situ tissue engineering (TE) into synthetic small diameter blood vessels, for example, thermoplastic poly(ether urethane) (TPU) ones, could provide an alternative approach for vascular access that profits from the advantages of excellent mechanical properties of synthetic polymer materials (early cannulation) and unique biointegration regeneration of autologous neovascular tissues (long-term fistulae). In this study, a kind of heparinized small diameter (d = 2.5 mm) TPU/poly(ε-caprolactone) (TPU/PCL-Hep) bi-layered blood vessels was electrospun with an inner layer of PCL and an outer layer of TPU. Afterward, the inner surface heparinization was conducted by coupling H2N-PEG-NH2 to the corroded PCL layer and then heparin to the attached H2N-PEG-NH2 via the EDCI/NHS chemistry. Herein a heparinized PCL inner layer could not only inhibit thrombosis, but also provide sufficient space for the neotissue regeneration via biodegradation with time. Meanwhile, a TPU outer layer could confer the vascular access the good mechanical properties, such as flexibility, viability and fitness of elasticity between the grafts and host blood vessels as evidenced by the adequate mechanical properties, such as compliance (4.43 ± 0.07%/ 100 mmHg), burst pressure (1447 ± 127 mmHg) and suture retention strength (1.26 ± 0.07 N) without blood seepage after implantation. Furthermore, a rabbit carotid aortic replacement model for 5 months was demonstrated 100% animal survival and 86% graft patency. Puncture assay also revealed the puncture resistance and self-sealing (hemostatic time < 2 min). Histological analysis highlighted neotissue regeneration, host cell infiltration and graft remodeling in terms of extracellular matrix turnover. Altogether, these results showed promising aspects of small diameter TPU/PCL-Hep bi-layered grafts for hemodialytic vascular access applications.

Identification of DNA Repair-Related Genes Predicting Clinical Outcome for Thyroid Cancer.

Recent studies have demonstrated the utility and superiority of DNA repair-related genes as novel biomarkers for cancer diagnosis, prognosis, and therapy. Here, we aimed to screen the potential survival-related DNA repair-related genes in thyroid cancer (TC). TCGA datasets were utilized to analyze the differentially expressed DNA repair-related genes between TC and nontumor tissues. The K-M approach and univariate analysis were employed to screen survival-related genes. RT-PCR was employed to examine the expression of DNA repair-related genes in TC samples and matched noncancer samples. CCK-8 analyses were used to determine cellular proliferation. Herein, our team discovered that the expression of four DNA repair-related genes was remarkably upregulated in TC samples in contrast to noncancer samples. Survival assays identified 14 DNA repair-related genes. In our cohort, we observed that the expression of TAF13 and DCTN4 was distinctly elevated in TC specimens in contrast to nontumor specimens. Moreover, knockdown of TAF13 and DCTN4 was observed to inhibit the TC cellular proliferation. Overall, the upregulation of TAF13 and DCTN4 is related to decreased overall survival in TC patients. Therefore, the assessment of TAF13 and DCTN4 expression may be useful for predicting prognosis in these patients.

Hydrogel Complex Electrospun Scaffolds and Their Multiple Functions in In Situ Vascular Tissue Engineering.

Hydrogel complex scaffolds (hydrogel scaffolds) are prepared by coating precursor solutions onto heparin-modified poly(ε-caprolactone) (PCLH) scaffolds followed by subsequent in situ gelation. Here, we show that hydrogel complexation can significantly strengthen the scaffold and slow its degradation. The hydrogel scaffold was implanted into the abdominal aorta of a rat model, and the aneurysm incidence rate of the hydrogel scaffolds sharply decreased compared with that of the hydrogel-free scaffolds. Histological and immunohistological analyses showed that the implanted grafts had good vascular regeneration. The absence of calcification and occurrence of contractile smooth muscle cells (SMCs) at the first month was found in the hydrogel-free PCLH scaffold due to the presence of surface-modified heparin, whereas the hydrogel scaffold exhibited mild calcification and later occurrence of contractile SMCs as the complexed hydrogel covered the fibers and blocked the interaction between heparin and cells. Heparin was further physically encapsulated into the hydrogel before gelation, and its sustainable release was demonstrated by an in vitro release test. A pilot implantation in a rabbit carotid model showed that the encapsulated heparin modulated the scaffold characteristics including anticoagulation, anticalcification, and the early occurrence of contractile SMCs in vivo. Consequently, hydrogel complexation can significantly improve the in vivo regeneration property of the scaffold due to its multiple beneficial characteristics.

Preparation of Small-Diameter Tissue-Engineered Vascular Grafts Electrospun from Heparin End-Capped PCL and Evaluation in a Rabbit Carotid Artery Replacement Model.

Aiming to construct small diameter (ID <6 mm) off-the-shelf tissue-engineered vascular grafts, the end-group heparinizd poly(ε-caprolactone) (PCL) is synthesized by a three-step process and then electrospun into an inner layer of double-layer vascular scaffolds (DLVSs) showing a hierarchical double distribution of nano- and microfibers. Afterward, PCL without the end-group heparinization is electrospun into an outer layer. A steady release of grafted heparin and the existence of a glycocalyx structure give the grafts anticoagulation activity and the conjugation of heparin also improves hydrophilicity and accelerates degradation of the scaffolds. The DLVSs are evaluated in six rabbits via a carotid artery interpositional model for a period of three months. All the grafts are patent until explantation, and meanwhile smooth endothelialization and fine revascularization are observed in the grafts. The composition of the outer layer of scaffolds exhibits a significant effect on the aneurysm dilation after implantation. Only one aneurysm dilation is detected at two months and no calcification is formed in the follow-up term. How to prevent aneurysms remains a challenging topic.

Unexpected Polypseudorotaxanes Formed from the Self-assembly of ß-Cyclodextrins with Poly( N-isopropylacrylamide) Homo- and Copolymers.

Compared with polypseudorotaxanes (PPRs) formed from the self-assembly of ß-cyclodextrins (ß-CDs) with poly(propylene glycol) (PPG) and γ-CDs with poly( N-isopropylacrylamide) (PNIPAAm), the ratio of the inner cavity size of ß-CD to the cross-sectional area of PNIPAAm appears not appropriate for their self-assembly. For a better understanding of the possibility of ß-CDs including PNIPAAm and the crystal structure of PPRs formed therefrom, the PNIPAAm homo- and copolymers were subjected to self-assembly with ß-CDs in an aqueous solution at room temperature. The results revealed that when ß-CDs meet thicker PNIPAAms, the self-assembly takes place, not only giving rise to PPRs by a manner of main-chain inclusion complexation but also presenting the PPRs a matched over-fit crystal structure different from those of either a matched tight-fit ß-CD-PPG PPR or a mismatched over-fit γ-CD-PNIPAAm PPR. This is most likely due to the thicker PNIPAAm adapting its unfavorable main-chain cross-sectional area to fit into the cavity of ß-CDs by changing the side-chain conformations. Based on the X-ray diffraction patterns, a monoclinic crystal system was created from these PPRs and the unit cell parameters calculated were as follows: a = 15.3 Å, b = 10.3 Å, and c = 21.2 Å; ß = 110.3°; and space group P2. It suggested that this matched over-fit crystal structure would possess a Mosaic crystal structure rather than a typical channel-like one.

How Does PHEMA Pass through the Cavity of γ-CDs to Create Mismatched Overfit Polypseudorotaxanes?

A syndiotactic-rich PHEMA oligomer ( rr = 74%, DP = 29, PDI = 1.19) was synthesized and subsequently subjected to self-assembly with a varying amount of γ-CDs in its aqueous solution to create mismatched overfit polypseudorotaxanes (PPRs). The inclusion complexation proceeded in an obvious mismatched manner between the cavity of γ-CDs and the cross-sectional area of an incoming PHEMA chain. The 2D-NOESY NMR analysis provided direct evidence indicating that two adjacent pendant hydroxyethyl groups in PHEMA preferably adopt a curled conformation to pass through the cavity of γ-CDs, giving the PPRs characteristics of a mismatched overfit instead of a matched tight-fit crystal structure. The results suggested that the mutual adaption of pendant side chains of HEMA units with the cavity geometry of γ-CDs would play a dominant role in this unfavorable overfit inclusion complexation besides the size of γ-CDs and the stereoregularity of the PHEMA chain.

Rapidly Recoverable Thixotropic Hydrogels from the Racemate of Chiral OFm Monosubstituted Cyclo(Glu-Glu) Derivatives.

Both chiral OFm monosubstituted cyclo(l-Glu-l-Glu) and cyclo(d-Glu-d-Glu) display a robust gelation ability in a variety of organic solvents and water. In contrast to an individual enantiomer, their racemate can form rapidly recoverable thixotropic hydrogels with a remarkably shorter thixotropic recovery time. This unexpected thixotropic behavior is induced by the random arrangement of d- and l-enantiomers in the cell units, leading to the formation of "pseudoracemate", noncrystalline self-assemblies in the resulting 3D fibrous network.

Ultrasound-induced gelation of fluorenyl-9-methoxycarbonyl-l-lysine(fluorenyl-9-methoxycarbonyl)-OH and its dipeptide derivatives showing very low minimum gelation concentrations.

Four l-Lysine(Lys)-l-glutamic acid(Glu) dipeptide derivatives (1-4) and their precursor-a single fluorenyl-9-methoxycarbonyl(Fmoc)-l-Lys(Fmoc)-OH amino acid (5) were demonstrated as gelators to gelate a variety of alcohols and aromatic solvents under the sonication conditions. Compared to the routine heating-cooling protocol, the ultrasound substantially brought down the minimum gelation concentrations (MGCs) of the resulting organogels. The Fourier transform infrared spectroscopy (FT-IR) and fluorescence studies revealed that the π-π stacking and hydrogen bonding act as major driving forces for the self-assembly of these lysine-based gelators into supramolecular fibrous three dimensional (3D) network, where the more the Fmoc protecting groups, the gelators are more responsive to ultrasound-stimulus and more conducive to an ordered molecular arrangement reinforcing the intermolecular forces. Moreover, the ultrasound-triggered organogels of 5 exhibited the thixotropic property. Upon imposing a mechanical shear, its gels with the fibrous 3D network structure were unraveled into sols. However, after standing quiescently over time, these sols returned to the gels showing a more ordered lamella-like packing structure as evidenced by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses.

Low-Molecular-Weight Organo- and Hydrogelators Based on Cyclo(l-Lys-l-Glu).

Four cyclo(l-Lys-l-Glu) derivatives (3-6) were synthesized from the coupling reaction of protecting l-lysine with l-glutamic acid followed by the cyclization, deprotection, and protection reactions. They can efficiently gelate a wide variety of organic solvents or water. Interestingly, a spontaneous chemical reaction proceeded in the organogel obtained from 3 in acetone exhibiting not only visual color alteration but also increasing mechanical strength with the progress of time due to the formation of Schiff base. Moreover, 6 bearing a carboxylic acid and Fmoc group displayed a robust hydrogelation capability in PBS solution. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed the characteristic gelation morphologies of 3D fibrous network structures in the resulting organo- and hydrogels. FT-IR and fluorescence analyses indicated that the hydrogen bonding and π-π stacking play as major driving forces for the self-assembly of these cyclic dipeptides as low-molecular-weight gelators. X-ray diffraction (XRD) measurements and computer modeling provided information on the molecular packing model in the hydrogelation state of 6. A spontaneous chemical reaction proceeded in the organogel obtained from 3 in acetone exhibiting visual color alteration and increasing mechanical strength. 6 bearing an optimized balance of hydrophilicity to lipophilicity gave rise to a hydrogel in PBS with MGC at 1 mg/mL.

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Riparian zone, the ecological transition buffer between terrestrial and aquatic ecosystems (rivers, lakes, reservoirs, wetlands, and other specific water bodies) with unique eco-hydrological and biogeochemical processes, is the last ecological barrier to prevent ammonium, nitrate and other non-point nitrogen pollutants from adjacent water bodies. Based on a summary of current progress of related studies, we found there were two major mechanisms underpinning the nitrogen retention/removal by the riparian ecosystems: 1) the relative locations of nitrogen in the soil-plant-atmosphere continuum system could be altered by riparian vegetation; 2) nitrogen could also be denitrified and then removed permanently by microorganisms in riparian soil. However, which process is more critical for the nitrogen removal remains elusive. Due to large variances of hydro-dynamic, vegetation, microbial, and soil substrate properties in nitrogen retention and transformation with various watersheds, it's difficult to identify which factor is the most important one driving nitrogen cycle in the riparian ecosystems. It is also found that the limitation of study methods, paucity of data at large spatial and temporal scale, and no consensus on the riparian width, are the three major reasons leading to large variances of the results among studies. In conclusion, it is suggested that further efforts should be focused on: 1) the detailed analysis on the successive environmental factors with long-term; 2) the application of a comprehensive method combining mathematical models, geographic information system, remote sensing and quantified technique (such as the coupled technique of the isotopic tracer and gas exchange measurement); 3) the implementation of studies at large temporal and spatial scales. It is sure that, these efforts can help to optimize the nitrogen removal pathways in the riparian ecosystems and provide scientific basis for ecosystem management.

The fabrication of double layer tubular vascular tissue engineering scaffold via coaxial electrospinning and its 3D cell coculture.

A continuous electrospinning technique was applied to fabricate double layer tubular tissue engineering vascular graft (TEVG) scaffold. The luminal layer was made from poly(ɛ-caprolac-tone)(PCL) ultrafine fibers via common single axial electrospinning followed by the outer layer of core-shell structured nanofibers via coaxial electrospinning. For preparing the outer layernano-fibers, the PCL was electrospun into the shell and both bovine serum albumin (BSA) and tetrapeptide val-gal-pro-gly (VAPG) were encapsulated into the core. The core-shell structure in the outer layer fibers was observed by transmission electron microscope (TEM). The in vitro release tests exhibited the sustainable release behavior of BSA and VAPG so that they provided a better cell growth environment in the interior of tubular scaffold wall. The in vitro culture of smooth muscle cells (SMCs) demonstrated their potential to penetrate into the scaffold wall for the 3D cell culture. Subsequently, 3D cell coculture was conducted. First, SMCs were seeded on the luminal surface of the scaffold and cultured for 5 days, and then endothelial cells (ECs) were also seeded on the luminal surface and cocultured with SMCs for another 2 days. After stained with antibodies, 3D cell distribution on the scaffold was revealed by confocal laser scanning microscopy (CLSM) where ECs were mainly located on the luminal surface whereas SMCs penetrated into the surface and distributed inside the scaffold wall. This double layer tubular scaffold with 3D cell distribution showed the promise to develop it into a novel TEVG for clinical trials in the near future.

Self-assemblies of γ-CDs with pentablock copolymers PMA-PPO-PEO-PPO-PMA and endcapping via atom transfer radical polymerization of 2-methacryloyloxyethyl phosphorylcholine.

Pentablock copolymers PMA-PPO-PEO-PPO-PMA synthesized via atom transfer radical polymerization (ATRP) were self-assembled with varying amounts of γ-CDs to prepare poly(pseudorotaxanes) (PPRs). When the concentration of γ-CDs was lower, the central PEO segment served as a shell of the micelles and was preferentially bent to pass through the γ-CD cavity to construct double-chain-stranded tight-fit PPRs characterized by a channel-like crystal structure. With an increase in the amount of γ-CDs added, they began to accommodate the poly(methyl acrylate) (PMA) segments dissociated from the core of the micelles. When more γ-CDs were threaded and slipped over the segments, the γ-CDs were randomly distributed along the pentablock copolymer chain to generate single-chain-stranded loose-fit PPRs and showed no characteristic channel-like crystal structure. All the self-assembly processes of the pentablock copolymers resulted in the formation of hydrogels. After endcapping via in situ ATRP of 2-methacryloyloxyethyl phosphorylcholine (MPC), these single-chain-stranded loose-fit PPRs were transformed into conformational identical polyrotaxanes (PRs). The structures of the PPRs and PRs were characterized by means of (1)H NMR, GPC, (13)C CP/MAS NMR, 2D (1)H NOESY NMR, FTIR, WXRD, TGA and DSC analyses.

Loose-fit polypseudorotaxanes constructed from γ-CDs and PHEMA-PPG-PEG-PPG-PHEMA.

A pentablock copolymer was prepared via the atom transfer radical polymerization of 2-hydroxyethyl methacrylate (HEMA) initiated by 2-bromoisobutyryl end-capped PPO-PEO-PPO as a macroinitiator in DMF. Attaching PHEMA blocks altered the self-assembly process of the pentablock copolymer with γ-CDs in aqueous solution. Before attaching the PHEMA, the macroinitiator was preferentially bent to pass through the inner cavity of γ-CDs to give rise to tight-fit double-chain stranded polypseudorotaxanes (PPRs). After attaching the PHEMA, the resulting pentablock copolymer was single-chain stranded into the interior of γ-CDs to form more stable, loose-fit PPRs. The results of (1)H NMR, WXRD, DSC, TGA, (13)C CP/MAS NMR and FTIR analyses indicated that γ-CDs can accommodate and slip over PHEMA blocks to randomly distribute along the entire pentablock copolymer chain. This results in unique, single-chain stranded PPRs showing no characteristic channel-type crystal structure.

A pH-sensitive nano drug delivery system of doxorubicin-conjugated amphiphilic polyrotaxane-based block copolymers.

A pH-sensitive nano antitumor drug delivery system was prepared by conjugating doxorubicin (DOX) to amphiphilic polyrotaxane (PR)-based block copolymers through a pH-sensitive cis-aconityl moiety. The resulting polymer-drug conjugates were able to self-assemble into polymeric micelles in an aqueous solution with diameters varying from 297 nm to 178 nm after the conjugation as evidenced by DLS measurements. The pH-sensitive cis-aconityl linkage provided a controlled and sustained release of DOX over a period of more than 5 days in an acidic environment mimicking the tumor microenvironment, and a negligible amount of release in an environment with physiological pH. The nanoparticles had lower cytotoxicity than the free drug and can efficiently transfer and release the drug into HeLa cells. With these promising properties, the PR-based block copolymers have the potential to be carriers for the controlled release of antitumor drugs.

The in vitro and in vivo biocompatibility evaluation of heparin-poly(ε-caprolactone) conjugate for vascular tissue engineering scaffolds.

Poly(ε-caprolactone) (PCL) was conjugated with heparin and fabricated into nonwoven tubular scaffold by electrospinning. The dynamic contact angle analysis revealed the hydrophilicity improvement due to heparin concentrating on the conjugate surface. The microbicinchoninic acid and quartz crystal microbalance measurements implied that the conjugate can significantly reduce the absorption of plasma protein, such as albumin and fibrinogen, indicative of the good blood biocompatibility. As evidenced by Enzyme Linked Immunosorbent Assay, the electrospun conjugate scaffolds possessed a higher loading capability of vascular endothelial growth factor (VEGF) than that of the blank PCL in aqueous solution via static interaction. The viability of loaded VEGF was evaluated by cell culture and adhesion tests. The amount and morphology of cells were substantially improved after VEGF was loaded into scaffolds exhibiting excellent cell biocompatibility. To assess the in vivo biocompatibility, a tubular scaffold (L = 4 cm, D = 2 mm) was transplanted into dog's femoral artery. The scaffold patency was inspected by carotid artery angiography 4 weeks after implantation. The explanted scaffold was also investigated by histological analysis including hematoxyline eosin, Millere Masson (collagen and elastin), and von Kossa (calcium) stain. Furthermore, von Willebrand factor immunohistochemical stain was performed to examine the formation of endothelial layer. The conjugate shows the potential to be used as scaffold materials in vascular tissue engineering.

Formation of a polypseudorotaxane via self-assembly of γ-cyclodextrin with poly(N-isopropylacrylamide).

A polypseudorotaxane (PPR) comprising γ-cyclodextrin (γ-CD) as host molecules and poly(N-isopropylacrylamide) (PNIPAM) as a guest polymer is prepared via self-assembly in aqueous solution. Due to the bulky pendant isopropylamide group, PNIPAM exhibits size-selectivity toward self-assembly with α-, ß-, and γ-CDs. It can fit into the cavity of γ-CD to give rise to a PPR, but cannot pass through α-CD and ß-CD under the same conditions. The ratio of the number of γ-CD molecules to entrapped NIPAM repeat units is kept at 1:2.2 or 1:2.4, determined by (1) H NMR spectroscopy and TGA analysis, respectively, indicating that there are more than 2 but less than 3 NIPAM repeat units included by one γ-CD molecule. This finding opens new avenues to PPR-based supramolecular polymers to be used as solid, stimuli-responsive materials.