Hybrid Nanomat: Copolymer Template CdSe Quantum Dots In Situ Stabilized and Immobilized within Nanofiber Matrix

Abstract

Fabrication and characterization of hybrid nanomats containing quantum dots can play a prominent role in the development of advanced biosensors and bio-based semiconductors. Owing to their size-dependent properties and controlled nanostructures, quantum dots (QDs) exhibit distinct optical and electronic characteristics. However, QDs include heavy metals and often require stabilizing agents which are toxic for biological applications. Here, to mitigate the use of toxic ligands, cadmium selenide quantum dots (CdSe QDs) were synthesized in situ with polyvinylpyrrolidone (PVP) at room temperature. The addition of PVP polymer provided size regulation, stability, and control over size distribution of CdSe QDs. The characterization of the optical properties of the CdSe QDs was performed using fluorescence and ultraviolet–visible (UV-Vis) spectroscopy. CdSe QDs exhibited a typical absorbance peak at 280 nm and a photoluminescence emission peak at 580 nm. Transmission electron microscopy (TEM) micrographs demonstrated that CdSe QDs having an average size of 6±4 nm were obtained via wet chemistry method. CdSe QDs were immobilized in a blend of PVP and poly(L-lactide-co-ε-caprolactone) (PL-b-CL) copolymer that was electrospun to produce nanofibers. Scanning electron microscopy (SEM), thermal analyses and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) were used to characterize properties of fabricated nanofibers. Both pristine and hybrid nanofibers possessed cylindrical geometry and rough surface features, facilitating increased surface area. Infrared absorption spectra showed a slight shift in absorbance peaks due to interaction of PVP-coated CdSe QDs and nanofiber matrix. The presence of CdSe QDs influenced the fiber diameter and their thermal stability. Further, in vitro biological analyses of hybrid nanofibers showed promising antibacterial effect and decline in cancer cell viability. This study offers a simple approach to obtain hybrid nanomats immobilized with size-controlled PVP-coated CdSe QDs, which have potential applications as biosensors and antibacterial and anticancer cell agents.

Dendronized Ag/Au Nanomats: Antimicrobial Scaffold for Wound Healing Bandages

“…Using ATR‐FTIR analysis, the absorption spectra of nanofibers were obtained to determine the influence of the addition of AuNPs in the matrix ( Figure 4 ). The observed spectra contained the standard peaks for a combination of co polymer PL‐b‐CL and PVP homopolymer [ 35 ] after electrospinning. As seen in Figure 4, the ─OH stretching [ 42,43 ] vibration due to the presence of PVP could be observed at 3454 cm −1 in the case of pristine nanofibers.…”

“…[ 46 ] CH 2 wagging or twisting could be observed at 1272 cm −1 , [ 47 ] along with symmetric and asymmetric C─O─C stretching (amorphous) present at 1181 and 1129 cm −1 , respectively. [ 35,46 ] Finally, C─C breathing observed through absorbance at 754 cm −1 in pristine nanofibers was restricted in AuNPs functionalized nanofibers, and the peak was red shifted to 736 cm −1 . [ 48 ] The N─CO bend absorbance peak between 650 and 533 cm −1 was observed in both samples.…”

“…After that, the cells were treated for 24 h with UV‐sterilized nanofibers (nanofibers with an area of ≈9 cm 2 to cover the surface of the well). [ 35 ] After 24 h incubation, the nanofibers were removed, cells were washed three times with PBS, they were harvested by trypsinization, and centrifuged. The pellet was resuspended in 100 µL 1×binding buffer (50 m m HEPES, 700 m m NaCl, 12.5 m m, and CaCl 2 , pH 7.4), and then, incubated with 5 µL of PI (propidium iodide) and 5 µL of Annexin V at room temperature for 15 min in the dark.…”

“…After that, the cells were treated for 24 h with UV-sterilized nanofibers (nanofibers with an area of ≈9 cm 2 to cover the surface of the well). [35] After 24 h incubation, the nanofibers were removed, cells were washed three times with PBS, they were harvested by trypsinization, and centrifuged.…”

Optical Properties of Electrospun Nanofiber Mats

“…Measurements of the optical properties of such nanofiber mats are usually performed by spectrophotometric methods, often applying a UV-visible (UV/Vis) spectrometer, besides other techniques such as diffuse reflectance spectroscopic (DRS) measurements, etc. [26][27][28]. However, many more specialized methods are available and will be described in the next sections.…”