Synthesis, characterization, and antimicrobial properties of novel double layer nanocomposite electrospun fibers for wound dressing applications

PVA/Chitosan/Silver Nanoparticles Electrospun Nanocomposites: Molecular Relaxations Investigated by Modern Broadband Dielectric Spectroscopy

In this study, we used broadband dielectric spectroscopy to analyze polymer nanofibers of poly(vinyl alcohol)/chitosan/silver nanoparticles. We also studied the effect of incorporating silver nanoparticles in the polymeric mat, on the chain motion dynamics and their interactions with chitosan nanofibers, and we calculated the activation energies of the sub-T_g relaxation processes. Results revealed the existence of two sub-T_g relaxations, the first gets activated at very low temperature (-90 °C) and accounts for motions of the side groups within the repeating unit such as ⁻NH₂, ⁻OH, and ⁻CH₂OH in chitosan and poly(vinyl alcohol). The second process gets activated around -10 °C and it is thought to be related to the local main chain segments' motions that are facilitated by fluctuations within the glycosidic bonds of chitosan. The activation energy for the chitosan/PVA/AgNPs nanocomposite nanofibers is much higher than that of the chitosan control film due to the presence of strong interactions between the amine groups and the silver nanoparticles. Kramers⁻Krönig integral transformation of the ε'' vs. f spectra in the region of the chitosan T_g helped resolve this relaxation and displayed the progress of its maxima with increasing temperature in the regular manner.

Electrospun PCL/mupirocin and chitosan/lidocaine hydrochloride multifunctional double layer nanofibrous scaffolds for wound dressing applications

Background

An ideal wound dressing should exhibit good biocompatibility, minimize pain and infection, absorb excess exudates, and maintain a moist environment. However, few clinical products meet all these needs. Therefore, the aim of this study was to fabricate a multifunctional double layer nanofibrous scaffolds (DLS) as a potential material for wound dressing.

Materials and methods

The scaffold was formed from mupirocin and lidocaine hydrochloride homogeneously incorporated into polycaprolactone as the first layer of scaffolds and chitosan as the second layer of scaffolds nanofibers through electrospinning. The fabricated nanofibrous scaffolds were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and measurement of swelling ratio, contact angle, drug release, and mechanical properties. Furthermore, antibacterial assessment, live/dead cell assays, and MTT assays were used to investigate the antibacterial activity and cytotoxicity of the nanofibrous scaffolds.

Results

The morphology of the nanofibrous scaffolds was studied by scanning electron microscopy, showing successful nanofibrous scaffolds. Fourier transform infrared spectroscopy demonstrated the successful incorporation of the material used to produce the produced nanofibrous scaffolds. Thermal studies with thermogravimetric analysis and differential scanning calorimetry indicated that the DLS had high thermal stability. The DLS also showed good in vitro characteristics in terms of improved swelling ratio and contact angle. The mechanical results revealed that the DLS had an improved tensile strength of 3.88 MPa compared with the second layer of scaffold (2.81 MPa). The release of drugs from the scaffold showed different profiles for the two drugs. Lidocaine hydrochlo ride exhibited an initial burst release (66% release within an hour); however, mupirocin exhibited only a 5% release. Furthermore, the DLS nanofibers displayed highly effective antibacterial activities against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa and were nontoxic to fibroblasts.

Conclusion

The fabricated DLS exhibited excellent hydrophilicity, cytocompatibility, sustained drug release, and antibacterial activity, which are favorable qualities for its use as a multifunctional material for wound dressing applications.

Colon-specific pulsatile drug release provided by electrospun shellac nanocoating on hydrophilic amorphous composites

Background

Colon-specific pulsatile drug release, as a combined drug controlled-release model, is a useful drug delivery manner for a series of diseases. New nanomedicines and related preparation methods are highly desired.

Methods

With diclofenac sodium (DS) as a model drug, a new type of structural nanocomposite (SC), in which composite polyvinylpyrrolidone (PVP)-DS core was coated by shellac, was fabricated via modified coaxial electrospinning. For comparison, traditional PVP-DS monolithic hydrophilic nanocomposites (HCs) were generated using a traditional blending process. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared (ATR-FTIR), water contact angle (WCA), and in vitro dissolution and ex vivo permeation tests were conducted to characterize the composites.

Results

SEM images demonstrated that both composites were linear nanofibers with smooth surface morphology and cross sections. TEM disclosed that the SCs had a thin shellac sheath layer of approximately 12 nm. XRD and ATR-FTIR results demonstrated that the crystalline DS was converted into amorphous composites with PVP because of favorable secondary interactions. WCA and in vitro dissolution tests demonstrated that the sheath shellac layers in SC could resist acid conditions and provide typical colon-specific pulsatile release, rather than a pulsatile release of HC under acid conditions. Ex vivo permeation results demonstrated that the SCs were able to furnish a tenfold drug permeation rate than the DS particles on the colon membrane.

Conclusion

A new SC with a shellac coating on hydrophilic amorphous nanocomposites could furnish a colon-specific pulsatile drug release profile. The modified coaxial process can be exploited as a useful tool to create nanocoatings.