Process study, development and degradation behavior of different size scale electrospun poly(caprolactone) and poly(lactic acid) fibers

An osteoporosis bone defect regeneration strategy via three-dimension short fibers loaded with alendronate modified hydroxyapatite

Osteoporotic bone defect has become clinic challenge due to its morbid bone microenvironment. Overactive bone resorption and limited bone formation lead to unstable combination between bone tissue and scaffolds. Electrospinning has been widely used in guide tissue membrane, but its barrier property results in limited application. In order to optimize the structure and add anti-bone resorption function of electrospinning fibers, we exploited the application of short fibers generated by homogenization at osteoporotic tibial bone defect. The modified nano-hydroxyapatite (m-HA) was loaded with alendronate. It overcame the problem that hydrophilic drugs were difficult to distribute uniformly in hydrophobic fibers. We confirmed that m-HA was loaded into polycaprolactone (PCL) short fibers. PCL short fibers with m-HA (PCL/m-HA) continuously released ALN, provided stable structure and showed good cytocompatibility. In vitro, PCL/m-HA increased the activity of alkaline phosphatase (ALP), promoted extracellular matrix mineralization and upregulated the expression of osteogenesis-related genes, Col 1, Alp, osteopontin (Opn) and runt-related transcription factor 2 (Runx2). In vivo, PCL/m-HA short fibers accelerated the new bone formation, inhibited the bone resorption and rebalanced the bone microenvironment through regulating osteoprotegerin (OPG) /receptor activator of NF-kB (RANKL) ratio. The above results confirmed that the PCL/m-HA short fibers achieved the application of three-dimension osteoporotic bone defect and had potential prospects in bone tissue scaffolds.

Hydrolytic Degradation and Bioactivity of Electrospun PCL-Mg-NPs Fibrous Mats

In this work, the in vitro degradation behavior of nanofibers was investigated in phosphate buffer solution (PBS) and simulated body fluid (SBF) to study their degradation behavior, as well as their bioactivity. The degradation was studied at different immersion times in order to evaluate how the presence of Mg-based nanoparticles can affect the degradation in terms of morphology, crystallinity, degradation rate and pH changes, and finally to evaluate the bioactivity of PCL-based electrospun nanofibers. We found that the degradation of the materials takes more than 3 months; however, the presence of nanoparticles seems to have an accelerating effect on the degradation of the electrospun nanofibers based on PCL. In fact, a reduction in diameter of almost 50% was observed with the highest content of both types of nanoparticles and an increase in crystallinity after 296 days of immersion in PBS. Moreover, the carbonyl index was calculated from an FTIR analysis, and a reduction of 20-30% was observed due to the degradation effect. Additionally, the bioactivity of PCL-based electrospun nanofibers was studied and the formation of crystals on the nanofibers surface was detected, except for neat electrospun PCL related to the formation of NaCl and apatites, depending on the amount and type of nanoparticles. The presence of apatites was confirmed by an XRD analysis and FT-IR analysis observing the characteristic peaks; furthermore, the EDX analysis demonstrated the formation of apatites than can be reconducted to the presence of HA when 20 wt% of nanoparticles is added to the PCL electrospun fibers.

Aloe vera incorporated starch-64S bioactive glass-quail egg shell scaffold for promotion of bone regeneration

Simultaneous promotion of osteoconductive and osteoinductive characteristics through combining bioactive glasses with natural polymers is still a challenge in bone tissue engineering. Starch, 64S bioactive glass (BG), aloe vera (AV) and quail eggshell powder (QE) were utilized to achieve biodegradable, bioactive, biocompatible and mechanically potent multifunctional scaffolds, using freeze-drying mechanism. Cell viability for starch-BG-AV-QE scaffolds at 3 and 7 day intervals was reported to be over 95 %. Acridine orange staining was employed to study live/dead cells cultured on the scaffolds. The high sufficiency of starch-BG-AV-QE scaffolds in osteogenic differentiation and extracellular matrix mineralization was confirmed through alkaline phosphatase activity and alizarin red staining assessments after 7 and 14 days of cell culture. High compressive strength, managed biodegradability and expression of osteocalcin and osteopontin as late markers of osteogenic differentiation were also reached in the range of 30-75 % for starch-BG-AV-QE scaffolds. Hence, starch-BG-AV-QE scaffolds with ideal physico-mechanical and biological characteristics can be considered as promising candidates for promotion of bone regeneration.

Impact of the solvent composition on the structural and mechanical properties of customizable electrospun poly(vinylpyrrolidone) fiber mats

The performance of fibrous membrane composites fabricated via electrospinning is strongly influenced by the solution's properties, process variables and ambient conditions, although a precise mechanism for controlling the properties of the resulting composite has remained elusive. In this work, we focus on the fabrication of electrospun poly(vinylpyrrolidone) (PVP) fibers, by varying both the polymer concentration and the mixture of ethanol (EtOH) and dimethylformamide (DMF) used as solvent. The impact of the solvent composition on the structural properties is assessed by a combined experimental and theoretical approach, employing scanning electron microscopy (SEM), differential scanning calorimetry (DSC), rheology, Fourier-transform infrared spectroscopy (FTIR) and stress-strain curves obtained from tensile tests to characterize the fibrous membranes produced, and density functional theory (DFT) calculations to explain the solvent's affect on PVP crystallization. We establish a morphological phase diagram, and propose a possible mechanism based on the measured fiber diameter distribution, the viscoelastic properties of the precursor solution, the correlation between the functional groups and the mechanical properties, the thermal transitions and the degree of crystallinity. We also employ DFT calculations to model the polymer coverage at equilibrium of a PVP polymer chain in the presence of EtOH/DMF solvent mixtures to corroborate the crucial role their O or -OH groups play in achieving high PVP coverages and promoting the stability of the resulting fiber. These findings will be valuable to researchers interested in predicting, modulating, and controlling both a fiber's morphology and its concomitant physico-chemical properties.

Docosahexaenoic Acid-Loaded Polylactic Acid Core-Shell Nanofiber Membranes for Regenerative Medicine after Spinal Cord Injury: In Vitro and In Vivo Study

Spinal cord injury (SCI) is associated with disability and a drastic decrease in quality of life for affected individuals. Previous studies support the idea that docosahexaenoic acid (DHA)-based pharmacological approach is a promising therapeutic strategy for the management of acute SCI. We postulated that a nanostructured material for controlled delivery of DHA at the lesion site may be well suited for this purpose. Toward this end, we prepare drug-loaded fibrous mats made of core-shell nanofibers by electrospinning, which contained a polylactic acid (PLA) shell for encapsulation of DHA within the core, for delivery of DHA in situ. In vitro study confirmed sustained DHA release from PLA/DHA core-shell nanofiber membrane (CSNM) for up to 36 days, which could significantly increase neurite outgrowth from primary cortical neurons in 3 days. This is supported by the upregulation of brain-derived neurotropic factor (BDNF) and neurotrophin-3 (NT-3) neural marker genes from qRT-PCR analysis. Most importantly, the sustained release of DHA could significantly increase the neurite outgrowth length from cortical neuron cells in 7 days when co-cultured with PLA/DHA CSNM, compared with cells cultured with 3 μM DHA. From in vivo study with a SCI model created in rats, implantation of PLA/DHA CSNM could significantly improve neurological functions revealed by behavior assessment in comparison with the control (no treatment) and the PLA CSNM groups. According to histological analysis, PLA/DHA CSNM also effectively reduced neuron loss and increased serotonergic nerve sprouting. Taken together, the PLA/DHA CSNM may provide a nanostructured drug delivery system for DHA and contribute to neuroprotection and promoting neuroplasticity change following SCI.

Biocompatible chemical network of α-cellulose-ESBO (epoxidized soybean oil) scaffold for tissue engineering application

Despite many desirable properties, the use of α-cellulose in biomedical applications is limited because of its poor processability. Here we demonstrate that the chemical network of α-cellulose and epoxidized soybean oil (ESBO) can be adequately processed into biocompatible, self-standing, highly-porous scaffolds for tissue engineering applications. First, α-cellulose was dissolved in N-Methylmorpholine N-oxide monohydrate (NMMO.MH) and chemically crosslinked by ESBO. Then, the porous scaffolds of α-cellulose-ESBO were fabricated by solvent exchange and freeze-drying techniques. The scaffolds were evaluated for morphology, thermal and mechanical stability, and in vitro cell attachment and cell viability. Scanning electron microscopy images and Brunauer-Emmett-Teller results suggested that porous scaffolds provide a good surface and internal structure for cell adhesion and growth. Specifically, the α-cellulose-ESBO scaffolds support the homogeneous attachment and proliferation of MG63 cells. Overall, our results suggest that α-cellulose-ESBO chemically crosslinked networks are biocompatible and demonstrate a remarkable capacity for the development of tissue engineering platforms.

Material Characterization of PCL:PLLA Electrospun Fibers Following Six Months Degradation In Vitro

The annulus fibrosus-one of the two tissues comprising the intervertebral disc-is susceptible to injury and disease, leading to chronic pain and rupture. A synthetic, biodegradable material could provide a suitable scaffold that alleviates this pain and supports repair through tissue regeneration. The transfer of properties, particularly biomechanical, from scaffold to new tissue is essential and should occur at the same rate to prevent graft failure post-implantation. This study outlines the effect of hydrolytic degradation on the material properties of a novel blend of polycaprolactone and poly(lactic acid) electrospun nanofibers (50:50) over a six-month period following storage in phosphate buffered saline solution at 37 °C. As expected, the molecular weight distribution for this blend decreased over the 180-day period. This was in line with significant changes to fiber morphology, which appeared swollen and merged following observation using Scanning Electron Microscopy. Similarly, hydrolysis resulted in considerable remodeling of the scaffolds' polymer chains as demonstrated by sharp increases in percentage crystallinity and tensile properties becoming stiffer, stronger and more brittle over time. These mechanical data remained within the range reported for human annulus fibrosus tissue and their long-term efficacy further supports this novel blend as a potential scaffold to support tissue regeneration.