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A series of random copolymers were synthesized via the copolymerization of a carbohydrate lactone, acetic acid 5-acetoxy-6-oxotetrahydropyran-2-yl methyl ester (1), and ε-caprolactone. The copolymers were characterized by nuclear magnetic resonance (NMR) spectroscopy, size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). Copolymers (P1–P4) were produced with typical carbohydrate ester compositions of 1–4 mol %. These copolymers are semicrystalline and can be processed into thin films with Young’s moduli of 300–420 MPa, values that exceed that for polycaprolactone (PCL). The copolymers were processed using supercritical carbon dioxide (scCO2, 35 °C, 200 bar) into foamed, porous scaffolds, which were characterized by dynamic mechanical thermal analyses (DMTA), mercury porosimetry, and scanning electron microscopy (SEM). The copolymer foams showed increased pore size with increasing carbohydrate ester content. The average pore size increased from 71 μm (PCL) to 319 μm (P4). The foamed scaffolds have normalized storage moduli ranging from 37 MPa cm3 g–1 (P4) to 109 MPa cm3 g–1 (P1). A representative copolymer foamed scaffold, tested according to ISO 10993-5 criteria, was cytocompatible for cell culture. MC3T3 cells cultured on a film of this copolymer showed increased relative metabolic activities compared to cells cultured on a PCL film. When primary bovine chondrocytes were cultured on the foamed scaffolds, increased cell penetration into the random copolymer foam was observed compared to PCL foams.

Airborne dust can cause engine wear and contribute to engine gas emission. This study developed a novel submicro-fiber filter medium to provide protection to engines against dust. The wet-laid submicro-fiber medium was prepared by a dual-layer paper machine, and its dust loading performance was compared with other filter media during laboratory and field tests. During the laboratory tests, the dust holding capacity of the wet-laid submicro-fiber medium was 48% and 10% higher than that of the standard heavy-duty medium and electrospun submicro-fiber medium, respectively. During the field tests, the pressure drop of the wet-laid submicro-fiber filter was 45% lower than that of the standard heavy-duty filter after 10,000 km of operation. It was found that there were two crucial ways to design a better filter medium for protection against dust. Firstly, the surface loading rather than the depth loading was preferred for dust filtration. The submicro-fiber layer kept large amounts of dust particles from penetrating into the depth of filter medium. Secondly, particles were captured preferably by fibers rather than pores. The unique fibrous structure of the wet-laid submicro-fiber medium made more particle deposition take place on fibers via interception and inertial impaction.

Geometric cues have been used for a variety of cell regulation and tissue regenerative applications. While the function of geometric cues is being recognized, their stability and degradation behaviors are not well known. Here, we studied the influence of degradation on uniaxial-stretch-induced poly(ε-caprolactone) (UX-PCL) ridge/groove arrays and further cellular responses. Results from accelerated hydrolysis in vitro showed that UX-PCL ridge/groove arrays followed a surface-controlled erosion, with an overall geometry remained even at ∼45% film weight loss. Compared to unstretched PCL flat surfaces and/or ridge/groove arrays, UX-PCL ridge/groove arrays achieved an enhanced morphological stability against degradation. Over the degradation period, UX-PCL ridge/groove arrays exhibited an "S-shape" behavior of film weight loss, and retained more stable surface hydrophilicity and higher film mechanical properties than those of unstretched PCL surfaces. Human mesenchymal stem cells (MSCs) aligned better toward UX-PCL ridge/groove arrays when the geometries were remained intact, and became sensitive with gradually declined nucleus alignment and elongation to the geometric degradation of ridges. We speculate that uniaxial stretching confers UX-PCL ridge/groove arrays with enhanced stability against degradation in erosive environment. This study provides insights of how degradation influences geometric cues and further cell responses, and has implications for the design of biomaterials with stability-enhanced geometric cues for long-term tissue regeneration.

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