Static secondary ion mass spectrometry for the surface characterisation of individual nanofibres of polycaprolactone functionalised with an antibacterial additive

Abstract

Electrospinning (ES) of polymer solutions generates non-woven webs of nanofibres. The fibre diameter ranges between 10 nm and 1 μm depending on the operating conditions. Surface functionalisation can be performed by the use of suitable additives. Detailed characterisation of the molecular composition at the fibre surface is a key issue. Biodegradable nanowebs with potential antibacterial activity have been prepared by ES of solutions containing polycaprolactone (PCL) and a functionalising additive with PCL segments and hexyldimethylammonium groups (PCLhexaq). Static secondary ion mass spectrometry with Bi(3)(+) projectiles has been applied to individual nanofibres. The positive ion mass spectra contain several signals with high structural specificity allowing the presence of PCLhexaq to be traced back in spite of its low concentration (0.16-1.4% w/w relative to PCL) and its structural similarity to the PCL fibre matrix. Imaging of structural ions visualises the homogeneous distribution of PCLhexaq over the fibre surface. Quantifying the surface concentration of PCLhexaq relative to that of PCL reveals electric field-driven surface enrichment of the additive during ES. Finally, nanofibres subjected to leaching in water for up to 72 h have been analysed. The PCLhexaq surface concentration decreases almost linearly with time at a rate of 0.6% h(-1).

Blending chitosan‐g‐poly(caprolactone) with poly(caprolactone) by electrospinning to produce functional fiber mats for tissue engineering applications

“…A hollow pipe‐like structure was imaged indicating that amino functionalities of CS‐g‐PCL were concentrated at the fibers' surface rather than at the fibers' core, resulting in a relative enrichment of the polar amine functionalities at the nonpolar fibers' surface. This observation is commonly known in the literature for other systems, however, could have also been due to a hydrophobic core of the fibers, which did not allow the hydrophilic biopolymer to penetrate into the fibers completely. This possible explanation, however, was rejected based on the XPS results (see below).…”

“…This might be due to the electrospinning process itself, which leads to a phase separation resulting in “pure” PCL phases and phases of graft‐copolymer during the drying process of the fibers. Such processes of enrichment of certain phases are well known in the literature . The unprocessed materials however showed two melting peaks, indicating two distinct crystalline phases.…”

“…To improve electrospun PCL fiber mats for biomedical applications, blending of PCL with polymers like CS appears promising but is challenging to implement successfully. According to the literature, the CS amino groups should enrich at the fibers' surface and therefore improve cell adhesion and allow to deposit drug‐delivery systems . However, the compatibility of PCL with CS is low .…”

“…An easier and more direct method to functionalize electrospun fibers would be directly blending PCL with CS‐g‐PCL in the spinning process. Blending is well established in the field of electrospinning as well as the fact that blending of polar additives to a nonpolar matrix in the electrospinning process may result in an enrichment of polar groups at the fibers' surface . Therefore, it could be expected to find the polar chitosan moieties of CS‐g‐PCL at the fiber surface and the blending of CS‐g‐PCL in the electrospinning process should result in a similar fiber surface as a modification without the necessity of additional process steps.…”

Stable poly(St-co-BA) nanoemulsion polymerization for high performance antibacterial coatings in the presence of dioctyldimethylammonium chloride

“…However, their high cost is a disadvantage. (3) Organic bactericides include isothiazolinone, organic amine, and formaldehyde [21][22][23]. This classification can quickly sterilize pathogenic microorganisms.…”