Penicillium fellutanum lipase as a green and ecofriendly biocatalyst for depolymerization of poly (ɛ-caprolactone): Biochemical, kinetic, and thermodynamic investigations

Microbial lipases hold a prominent position in biocatalysis by their capability to mediate reactions in aqueous and nonaqueous media. Herein, a lipase from Penicillium fellutanum was biochemically characterized and investigated its potential to degrade poly (ɛ-caprolactone) (PCL). The lipase exhibited stability over a broad pH spectrum and performed best at pH 8.5 and 45 °C. The activation energy was determined to be 66.37 kJ/mol by Arrhenius plot, whereas K_m and V_max for pNPP hydrolysis were 0.75 mM and 83.33 μmol/mL/Min, respectively. A rise in temperature reduced the Gibbs free energy, whereas the enthalpy of thermal unfolding (∆H*) remains the same up to 54 °C following a modest decline at 61 °C. The entropy (∆S*) of the enzyme demonstrated an increasing trend up to 54 °C and dropped at 61 °C. Lipase retained stability by incubation with various industrially relevant organic solvents (benzene, hexanol, ether, and acetone). However, exposure to urea and guanidine hydrochloride influenced its catalytic activity to different extents. Under optimal operating conditions, lipase catalyzed the excellent degradation of PCL film degradation leading to 66% weight loss, increased surface erosion, and crystallinity. Fourier-transform infrared spectrometry, differential scanning calorimetry, and scanning electron microscopy studies monitored the weight loss after enzymatic hydrolysis. The findings indicate that P. fellutanum lipase would be a prospective biocatalytic system for polyesters depolymerization and environmental remediation.

Sustained Simultaneous Delivery of Metronidazole and Doxycycline From Polycaprolactone Matrices Designed for Intravaginal Treatment of Pelvic Inflammatory Disease

Poly(ɛ-caprolactone) (PCL) intravaginal matrices were produced for local delivery of a combination of antibacterials, by rapidly cooling a mixture of drug powders dispersed in PCL solution. Matrices loaded with different combinations of metronidazole (10%, 15%, and 20% w/w) and doxycycline (10% w/w) were evaluated in vitro for release behavior and antibacterial activity. Rapid "burst release" of 8%-15% of the doxycycline content and 31%-37% of the metronidazole content occurred within 24 h when matrices were immersed in simulated vaginal fluid at 37°C. The remaining drug was extracted gradually over 14 days to a maximum of 65%-73% for doxycycline and 62%-71% for metronidazole. High levels of antibacterial activity up to 89%-91% against Gardnerella vaginalis and 84%-92% against Neisseria gonorrhoeae were recorded in vitro for release media collected on day 14, compared to "nonformulated" metronidazole and doxycycline solutions. Based on the in vitro data, the minimum levels of doxycycline and metronidazole released from PCL matrices in the form of intravaginal rings into vaginal fluid in vivo were predicted to exceed the minimum inhibitory concentrations for N. gonorrhea (reported range 0.5-4.0 μg/mL) and G. vaginalis (reported range 2-12.8 μg/mL) respectively, which are 2 of the major causative agents for pelvic inflammatory disease.

Influence of oriented nanofibrous PCL scaffolds on quantitative gene expression during neural differentiation of mouse embryonic stem cells

Neural differentiation of mouse embryonic stem cells in combination with three-dimensional electrospun nanofibers as an artificial extracellular matrix can be utilized to reconstruct a spinal cord defect. In this study, random and parallel-aligned nanofibrous poly ɛ-caprolactone was fabricated using electrospinning. Its hydrophobicity was modified by O2 plasma treatment to facilitate enhanced cell attachment. Embryoid bodies (EBs), which contain all three embryonic germ layers, were cultured on poly ɛ-caprolactone scaffolds to study the effect of fiber orientation on cell morphology and differentiation. Cell morphology and neuron-specific gene and protein expressions were, respectively, evaluated by scanning electron microscopy, real-time polymerase chain reaction, and immunocytochemistry. Although two types of nanofibrous scaffolds showed neural marker expression at the protein level, cells on randomly oriented scaffolds showed short-range topographical guidance and stretched across multiple directions, whereas cells on the parallel scaffolds exhibited long extension with enhanced neuron outgrowth along the fiber, producing oriented extracellular matrix, leading to direct cell migration and nerve regeneration. Quantitative real-time polymerase chain reaction showed that both aligned and random electrospun nanofibers downregulated the precursor neural marker Nestin compared with that in the control group, a gelatin-coated tissue culture plate (T). Analysis also showed higher expression of dorso-ventral neural markers (Isl1/2 and Lim1/2) than motor neuron progenitor markers (Pax6, Nkx6.1, and olig2) in aligned nanofibers than in the T group. Moreover, aligned nanofibers showed higher expression of mature neural specific markers such as β-tub and Map2 than those in the randomly oriented scaffolds. Therefore, we conclude that nanofibers with different orientations can support the neural lineage, but aligned nanofibrous scaffolds are superior candidates to promote the advancement of neural precursors to achieve maturity during the differentiation process.

Poly (epsilon-caprolactone) nanofibrous ring surrounding a polyvinyl alcohol hydrogel for the development of a biocompatible two-part artificial cornea

The study aimed to fabricate and characterize a 2-part artificial cornea as a substitute for penetrating keratoplasty in patients with corneal blindness. The peripheral part of the artificial cornea consisted of plasma-treated electrospun poly (ɛ-caprolactone) (PCL) nanofibers, which were attached to a hydrogel disc of polyvinyl alcohol (PVA) as a central optical part. The physical properties of the prepared artificial cornea, including morphology, mechanical properties, light transmittance, and contact angle, were assessed. Cell attachment and proliferation studies were performed on rabbit limbal stem cells. The SEM image of the polymeric system showed that the peripheral part formed a highly porous scaffold that could facilitate tissue biointegration. Assessment of the mechanical properties of the peripheral nanofibrous part and the hydrogel optical part showed suitable elasticity. Young's modulus values of the electrospun PCL skirt and PVA hydrogel core were 7.5 and 5.3 MPa, respectively, which is in line with the elasticity range of natural human cornea (0.3-7 MPa). The light transmittance of the central part was >85% when measured in the 400-800 nm wavelength range. The plasma-treated PCL nanofibrous scaffold promoted limbal stem cell adhesion and proliferation within 10 days. These results confirmed that the polymeric artificial cornea showed suitable physical properties and good biocompatibility and epithelialization ability.