Biocompatible electrospun tactic poly(methyl methacrylate) blend fibers

Uniform and beads free fibers of pristine syndiotactic PMMA (s-PMMA), isotactic PMMA (i-PMMA), and their blends in the ratio of s:i = 3:1, 1:1 and 1:3 were successfully prepared using the electrospinning technique. The tactic PMMA blend fibers showed unique thermal stability and glass transition temperatures compared to their pristine counterparts. An interesting endotherm peak was observed for the s:i = 1:3 electrospun fibers, which might indicate a complex formation between the two tactic PMMAs. Systematic surface functionalities study by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) revealed the interactions between these two tactic PMMAs. Biocompatibility of tactic PMMA and their blend fibers was first time comparably investigated using HeLa as the model mammalian cell line; an intriguing observance was first revealed that the blend fibers showed better biocompatibility than both pristine ones, though the behind mechanism is not well understood yet.     

Nanoporous poly(methyl methacrylate)-quantum dots nanocomposite fibers toward biomedical applications

In this work, poly(methyl methacrylate) (PMMA)-CdSe/ZnS quantum dots (QDs) nanocomposite fibers were fabricated via a simple electrospinning method. The parameters including concentration of PMMA, feed rate, applied voltage and working distance between the needle tip and the fiber collecting electrode were investigated and optimized to acquire large quantity, uniform and defect-free PMMA and its QD nanocomposite fibers. The surface morphology of the fibers was characterized by scanning electron microscopy (SEM), while the fluorescence emission characteristics of the polymer nanocomposite (PNC) fibers were analyzed with fluorescence microscopy. The thermal properties of the PMMA-QDs PNC fibers were explored by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). In comparison to the pristine PMMA fibers, the PNC fibers with only 0.1 wt% QD loading showed an improved thermal stability by 15 °C for the midpoint and onset degradation temperature. Surface chemical structure and functionalities were probed by a combination of attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). New vibration bands were observed in the PNC fibers in the ATR-FTIR spectra, while the binding energy for both high resolution C 1s and O 1s spectra in the PNC fibers showed an apparent shift toward lower field. Rheological studies revealed a pseudoplastic behavior of both pristine PMMA and PMMA-QDs solutions. Moreover, the formed nanoporous PMMA-QDs fiber media exhibited an excellent biocompatibility as evidenced by the model Chinese hamster ovary (CHO) cell culturing test. The CHO cells demonstrated good adhesion, growth and viability in the reported testing.     

Magnetic electrospun fluorescent polyvinylpyrrolidone nanocomposite fibers

Magnetic nanoparticles (MNPs) were synthesized from facile thermodecomposition of iron pentacarbonyl and the subsequent silica coating on the MNP surface was achieved via a modified Stöber process to obtain the core–shell composite structured particles (MNPs-SiO₂). MNPs-SiO₂ were then incorporated into polyvinylpyrrolidone (PVP) to form nanocomposite fibers via an electrospinning process with optimized operational parameters such as polymer concentration, applied electrical voltage, feed rate and tip-to-collector distance. All these parameters show an unusual effect on the produced fiber diameter. Contrary to the conventional observation, i.e., increasing the applied voltage and feed rate or decreasing the distance could increase the fiber diameter; a reduced average fiber diameter was observed in this study and could be explained from the stretching and contraction force balance within the fiber during electrospinning. The size of the resulting PVP fibers is correlated to the corresponding rheological behaviors of the PVP solutions with different concentrations. The MNPs-SiO₂/PVP nanocomposite fibers exhibit a similar thermal decomposition temperature (386.3 °C) as that (387.8 °C) of pure PVP. Meanwhile, unique fluorescent and magnetic properties have been incorporated simultaneously in the nanocomposite fibers with the addition of small amount of MNPs-SiO₂ nanoparticles.     

Ionic liquid assisted electrospinning of quantum dots/elastomer composite nanofibers

Quantum dots (QDs)/elastomer (VM) composite nanofibers have been fabricated via electrospinning method with the assistance of small amount (1 wt%) of ionic liquid. Without ionic liquid, polymer solution underwent an electrospraying process within the electric field and only individual droplets rather than continuous fibers were observed. Both fixed electrode and rotating disk electrode were used to collect the products. The latter one turned out to be much more advanced in collecting separated, aligned and narrow-size distributed composite nanofibers. With fixed electrode, even though nanofibers were obtained initially, the as-spun fibers were easily to merge together due to the flexible non-crystalline nature of the VM chains and finally formed a condensed thin film. Strong fluorescent emission was observed in the composite nanofibers with a QD loading of 3 and 5 wt%, respectively. The optical property of QDs was not degraded after dispersing in the polymer solution as evidenced by the UV-Vis absorption at 562 nm and 592 nm, and strong photoluminescent emission at 612 nm. In addition, differential scanning calorimetry (DSC) analysis revealed a strong interaction between ionic liquid and the polymer chains, which well explains the function of the ionic liquid on producing fiber structure of VM. An enhanced thermal stability of the elastomer in the composite nanofibers is observed as compared to that of the pure elastomer fibers.