Poly L-lactic Acid Nanofibers Research Articles

The Effect of MultilayeredElectrospun PLLA Nanofibers Coated with Human Amnion or Bladder ECM Proteins on Epithelialization and Smooth Muscle Regeneration in the Rabbit Bladder.

Nanofibrous scaffolds have attracted much attention in bladder reconstruction approaches due to their excellent mechanical properties. In addition, their biological properties can be improved by combination with biological materials. Taking into account the advantages of nanofibrous scaffolds and decellularized extracellular matrix (dECM) in tissue engineering, scaffolds of poly-L-lactic acid (PLLA) coated with decellularized human amnion membrane (hAM) or sheep bladder (SB)-derived ECM proteins are developed (amECM-coated PLLA and sbECM-coated PLLA, respectively). The bladder regenerative potential of modified electrospun PLLA scaffolds is investigated in rabbits. The presence of ECM proteins is confirmed on the nanofibers' surface. Coating the surface of the PLLA nanofibers improves cell adhesion and proliferation. Histological and immunohistochemical evaluations show that rabbits subjected to cystoplasty with a multilayered PLLA scaffold show de novo formation and maturation of the multilayered urothelial layer. However, smooth muscle bundles (myosin heavy chain [MHC] and α-smooth muscle actin [α-SMA] positive) are detected only in ECM-coated PLLA groups. All groups show no evidence of a diverticulumor fistula in the urinary bladder. These results suggest that the biofunctionalization of electrospun PLLA nanofibers with ECM proteins can be a promising option for bladder tissue engineering. Furthermore, hAM can also replace animal-sourced ECM proteins in bladder tissue regeneration approaches.

Post-modification of PLLA nanofiber nonwovens by various solvent treatments

Abstract Degradable polymeric Biomaterials, such as polylactic acid, are widely used in medical field as bioresorbable implant coatings. More recently, stent covers, implantable tubes or wound dressings made from electrospun nanofibers have been developed. In order to tailor the material for specific applications, dedicated fine-tuning procedures are required. To modify fiber interconnection or porosity, solvents or their dilutions are applicable. In this work, the effect of differently diluted protic and aprotic-polar solvents on electrospun poly-L-lactic acid (PLLA) nonwovens was investigated via immersion or vapor exposure. Fiber adhesion was observed with protic solvents. Fiber destruction and increased polymer crystallinity was observed with aprotic polar solvents. The immersion duration revealed to be far more irrelevant than solvent dilution. None of the tested solvents affected molecular weight. This opens up significant research potential to replace halogenated solvents as a cornerstone of eco-friendly “green” electrospinning processes. The results of this study are suggesting that biomaterials with desired properties can be produced in a targeted manner.

Characterization of Electrospun BDMC-Loaded PLA Nanofibers with Drug Delivery Function and Anti-Inflammatory Activity.

Controlled drug release systems are the subject of many investigations to achieve the therapeutic effect of drugs. They have numerous advantages, such as localized effects, lower side effects, and less onset of action. Among drug-delivery systems, electrospinning is a versatile and cost-effective method for biomedical applications. Furthermore, electrospun nanofibers are promising as drug carrier candidates due to their properties that mimic the extracellular matrix. In this work, electrospun fibers were made of Poly-L-lactic acid (PLA), one of the most widely tested materials, which has excellent biocompatible and biodegradable properties. A curcuminoid, bisdemethoxycurcumin (BDMC) was added in order to complete the drug delivery system. The PLA/BDMC membranes were characterized, and biological characteristics were examined in vitro. The results show that the average fiber diameter was reduced with the drug, which was mainly released during the first 24 h by a diffusion mechanism. It was seen that the use of our membranes loaded with BDMC enhanced the rate of proliferation in Schwann cells, the main peripheral neuroglial cells, and modulated inflammation by reducing NLRP3 inflammasome activation. Considering the results, the prepared PLA/BDMC membranes hold great potential for being used in tissue engineering applications.

A new insight into the mechanical properties of nanobiofibers and vibrational behavior of atomic force microscope beam considering them as the samples

Nowadays, the utilization and production of polymeric nanofibers are expanding rapidly due to their unique and exclusive properties. The current study examined silk fibroin nanofibers, poly-L lactic acid (PLLA), and polycaprolactone (PCL) as three widely-used biopolymers. In the first section, the mechanical properties of nanobiofibers, including elastic modulus as the first research variable, were investigated using atomic force microscopy (AFM)-based nanoindentation and tensile testing (through a universal testing machine). The results indicated that increasing the concentration of the biopolymer solution increased its elastic modulus. The total amount of elastic modulus for silk fibroin (SF), PCL, and PLLA nanofibers with random and aligned scaffold formats ranged from 1.207 MPa to 3.71 MPa. Based on the molecular weight and concentrations of the solutions, PLLA, PCL, and silk fibroin nanofibers yielded the highest elastic modulus, respectively. In addition, the elastic modulus was greater in an aligned scaffold as opposed to a random format and in retraction as opposed to an extended stroke. During the second section of the study, resonant frequencies as the second research variable and the amplitude of the FRF of the AFM beam's vertical movements using nanobiopolymers with various scaffolds as the samples were investigated theoretically (using the Finite Element Method [FEM]) and experimentally (using AFM). For the first to third modes, the resonant frequency of the AFM beam considering biopolymer nanofibers as samples varied from 12658.43 Hz to 241208.4 Hz. The results revealed that increasing the elastic modulus of the samples increases the resonant frequency. The mechanical and vibrational properties of nanofibers calculated by various methods were subsequently compared separately. Overall, the comparison indicated good agreement between the properties.

Synergistic Effect of Reinforced Multiwalled Carbon Nanotubes and Boron Nitride Nanosheet-Based Hybrid Piezoelectric PLLA Scaffold for Efficient Bone Tissue Regeneration.

Electrospun poly(l-lactic acid) nanofibers (PLLANFs) have been receiving considerable attention in bone tissue engineering (BTE) due to their tunable biodegradability and remarkable in vitro and in vivo biocompatibility. However, deterioration in the mechanical strength of PLLANFs during the regeneration process leads to low osteoinductive performances. Additionally, their high hydrophobicity and limited piezoelectric properties have to be addressed concerning BTE. Herein, we report an efficient approach for fabricating high-performance PLLANF hybrid scaffolds for BTE by reinforcing amphiphilic triblock copolymer pluronic F-127 (PL)-functionalized nanofillers (PL-functionalized carboxylated multiwalled carbon nanotubes (PL-cMWCNTs) and PL-functionalized exfoliated boron nitride nanosheets (PL-EBN)). The synergistic reinforcement effect from one-dimensional (1D) electrically conducting PL-cMWCNTs and two-dimensional (2D) piezoelectric PL-EBN was remarkable in PLLANFs, and the obtained PL-Hybrid (PL-cMWCNTs + PL-EBN) reinforced scaffolds have outperformed the mechanical strength, wettability, and piezoelectric performances of pristine PLLANFs. Consequently, in vitro biocompatibility results reveal the enhanced proliferation of MC3T3-E1 cells on PL-Hybrid nanofiber scaffolds. Furthermore, the ALP activity, ARS staining, and comparable osteogenic gene expression results demonstrated significant osteogenic differentiation of MC3T3-E1 cells on PL-Hybrid nanofiber scaffolds than on the pristine PLLANF scaffold. Thus, the reported approach for constructing high-performance piezoelectric biodegradable scaffolds for BTE by the synergistic effect of PL-cMWCNTs and PL-EBN holds great promise in tissue engineering applications.

Effects of nanofiber scaffolds coated with nanoparticulate and micro-particulate FDBA on the morphology, adhesion and proliferation of human mesenchymal stem cells.

Background:Freeze dried bone allograft nanoparticles on a nanofiber membrane may serve as an ideal scaffold for bone regeneration. This study aimed to assess the biological behavior of human MSCs in terms of proliferation and adhesion to nanoparticulate and microparticulate FDBA scaffolds on PLLA nanofiber membrane. Methods:In this experimental study, PLLA nanofiber scaffolds were synthesized by the electrospinning method. The FDBA nanoparticles were synthesized mechanically. The FDBA nanoparticles and microparticles were loaded on the surface of PLLA nanofiber membrane. A total of 64 scaffold samples in four groups of n-FDBA/PLLA, FDBA/PLLA, PLLA and control were placed in 24-well polystyrene tissue culture plates; 16 wells were allocated to each group. Data were analyzed using one-way ANOVA and Bonferroni test. Results:The proliferation rate of MSCs was significantly higher in the nanoparticulate group compared to the microparticulate group at five days (p = 0.034). Assessment of cell morphology at 24 hours revealed spindle-shaped cells with a higher number of appendages in the nanoparticulate group compared to other groups. Conclusion:MSCs on n-FDBA/PLLA scaffold were morphologically more active and flatter with a higher number of cellular appendages, as compared to FDBA/PLLA. It seems that the nanoparticulate scaffold is superior to the microparticulate scaffold in terms of proliferation, attachment, and morphology of MSCs in vitro.

Stemness Maintenance and Massproduction of Neural Stem Cells on Poly L-Lactic Acid Nanofibrous Membrane Based on Piezoelectriceffect.

Neural stem cells (NSCs) therapy is promising for treating neurodegenerative disorders and neural injuries. However, the limited in vitro expansion, spontaneous differentiation, and decrease in stemness obstruct the acquisition of high quantities of NSCs, restricting the clinical application of cell-based therapies and tissue engineering. This article reports a facile method of promoting NSCs expansion and maintaining stemness using wireless electrical stimulation triggered by piezoelectric nanomaterials. A nanofibrous membrane of poly L-lactic acid (PLLA) is prepared by electrostatic spinning, and the favorable piezoelectric property of PLLA facilitates the freeing of electrons after transformation. These self-powered electric signals generated by PLLA significantly enhance NSCs proliferation. Further, an undifferentiated cellular state is maintained in the NSCs cultured on the surfaces of PLLA nanofibers exposed to ultrasonic vibration. In addition, the neural differentiation potencies and functions of NSCs expanded by piezoelectric-driven localized electricity are not attenuated. Moreover, cell stemness can be maintained by wireless electric stimulation. Taken together, the electronic signals mediated by PLLA nanofibers facilitate NSCs proliferation. This efficient and simple strategy can maintain the stemness of NSCs during proliferation, which is essential for their clinical application, and opens up opportunities for the mass production of NSCs for use in cell therapy.

Aligned Poly-l-lactic Acid Nanofibers Induce Self-Assembly of Primary Cortical Neurons into 3D Cell Clusters.

Relative to two-dimensional (2D) culture, three-dimensional (3D) culture of primary neurons has yielded increasingly physiological responses from cells. Electrospun nanofiber scaffolds are frequently used as a 3D biomaterial support for primary neurons in neural tissue engineering, while hydrophobic surfaces typically induce aggregation of cells. Poly-l-lactic acid (PLLA) was electrospun as aligned PLLA nanofiber scaffolds to generate a structure with both qualities. Primary cortical neurons from E18 Sprague-Dawley rats cultured on aligned PLLA nanofibers generated 3D clusters of cells that extended highly aligned, fasciculated neurite bundles within 10 days. These clusters were viable for 28 days and responsive to AMPA and GABA. Relative to the 2D culture, the 3D cultures exhibited a more developed profile; mass spectrometry demonstrated an upregulation of proteins involved in cortical lamination, polarization, and axon fasciculation and a downregulation of immature neuronal markers. The use of artificial neural network inference suggests that the increased formation of synapses may drive the increase in development that is observed for the 3D cell clusters. This research suggests that aligned PLLA nanofibers may be highly useful for generating advanced 3D cell cultures for high-throughput systems.

Multifunctional modified polylactic acid nanofibrous scaffold incorporating sodium alginate microspheres decorated with strontium and black phosphorus for bone tissue engineering

Polylactic acid (PLA) nanofibrous scaffolds have received extensive attention in the field of tissue engineering due to their excellent degradability, biocompatibility and the biomimetic extracellular matrix (ECM) topographies. However, the cell affinity and osteogenic activity of PLA scaffolds is not satisfactory because of their intrinsic hydrophobicity, the absence of cell recognition sites and the nucleation sites of the in vivo biomineralization. Furthermore, effective anti-inflammatory activity for the in vivo scaffold could not be ignored, so a strategy to develop a multifunctional PLLA (poly-L-lactic acid) nanofibrous scaffold with improved hydrophilicity, osteoinductivity, excellent near-infrared photothermal-responsive drug release capacity and anti-inflammatory activity via incorporating sodium alginate microspheres decorated with strontium and ibuprofen-loaded black phosphorus (BP + IBU@SA microspheres) into aminated modified PLLA nanofiber network is proposed in this study. Scanning electron microscopy (SEM) observation showed that the BP + IBU@SA microspheres were homogeneously dispersed into the modified PLLA matrix with uniform nanofiber structure and the chemical composition of the as-prepared scaffolds was confirmed by X-ray diffraction analysis (XRD) and elemental mapping. The photothermal property of the scaffolds was assessed under near-infrared (NIR) light irradiation, the results manifested that the entrapment of BP nanosheets endowed PLLA nanofibrous scaffold with significantly high photothermal conversion efficiency and optical cycle stability. Meanwhile, the scaffold also displayed an excellent photothermal-responsive intelligent drug release performance toward Sr2+ and ibuprofen. Moreover, the in vitro studies revealed that the as-developed scaffolds possessed a good biocompatibility for cell adhesion and proliferation and an improved bioactivity to induce apatite formation. All these results indicated the potential of the fabricated scaffolds in tissue engineering applications.

Coating biodegradable magnesium alloys with electrospun poly-L-lactic acid-åkermanite-doxycycline nanofibers for enhanced biocompatibility, antibacterial activity, and corrosion resistance

Magnesium alloys are attracting increasing attention for orthopedic applications on account of their superior biocompatibility and biodegradability. However, such applications have been limited by their high degradation rate and inadequate antibacterial performance. The present study illustrates the use of a poly-L-lactic acid (PLLA)-åkermanite (AKT)-doxycycline (DOXY) nanofiber coating, created using the electrospinning method, to enhance the corrosion resistance, antibacterial performance, and cytocompatibility of Mg alloys. The experimental results show the PLLA-based nanofiber coatings are smooth and uniform with fiber diameters ranging from 300 to 350 nm. PLLA nanofibers containing AKT have a higher bonding strength (11.8 MPa) than PLLA nanofibers, owing to the significant effect of AKT on the PLLA structure. An in vitro drug release profile of PLLA-AKT nanofibers containing DOXY shows that the nanofibers allow rapid release of drug in the initial stage to provide antibacterial effects as well as sustained release over the long term to prevent infection. The implants coated with PLLA-AKT nanofibers containing DOXY have excellent antibacterial performance against Gram-positive (Staphylococcus aureus, ATCC 12600) and Gram-negative (Escherichia coli, ATCC 9637) bacteria; those coated with PLLA and PLLA-AKT without DOXY have poor antibacterial performance. Cytotoxicity tests show that PLLA and PLLA-AKT nanofiber coatings considerably enhance the cytocompatibility of Mg alloys, while incorporation of a high concentration of DOXY (10% wt.) into the PLLA-AKT coating has adverse effects on cytocompatibility. Thus, PLLA-AKT nanofiber coatings containing low concentrations of DOXY can be employed to control the degradation rate and enhance the antibacterial performance and biocompatibility of Mg alloys as applied to bone infection treatments. The results of this study represent essential information to direct the development of future orthopedic applications.

Fabrication and Electrospinning of 3D Biodegradable Poly-l-Lactic Acid (PLLA) Nanofibers for Clinical Application.

Poly-L-lactic acid (PLLA) is a biodegradable synthetic polyester synthesized by polymerization or polycondensation. PLLA hydrolytically degrades into lactic acid, a biocompatible metabolic by-product, making it suitable for clinical applications. PLLA scaffolds or nanofibers have been used in various regenerative medicine and drug delivery applications. These scaffolds impart biocompatible properties of high surface area, hydrophobicity, native extracellular properties, and mechanical strength for an organ system. Moreover, PLLA nanofibers hold great promise as drug delivery systems, where fabrication parameters and drug-PLA compatibility greatly affect the drug release kinetics. In this chapter, we present the protocols to fabricate, electrospinning, and validation of 3D PLLA nanofibrous scaffolds for tissue engineering application and offer perspectives on their future use.

Electrospun poly-l-lactic acid nanofibers decorated with melt-derived S53P4 bioactive glass nanoparticles: The effect of nanoparticles on proliferation and osteogenic differentiation of human bone marrow mesenchymal stem cells in vitro

S53P4 bioactive glass nanoparticles (BGn) were prepared by the melting-quenching method at 1400 °C followed by ball milling. The prepared glass nanoparticles were used for surface decoration of poly-l-lactic acid (PLLA) nanofibers fabricated by electrospinning method. The microstructure, morphology and chemical functional groups of the nanomaterials were characterized by XRD, FESEM, and FTIR techniques. The results confirmed the successful synthesis of amorphous glass nanoparticles with the diameter ranged from ~ 100 to 800 nm and PLLA nanofibers with an average diameter of 500 nm. PLLA/BGn nanocomposites showed a uniform distribution of the BGn on the surface of PLLA nanofibers. The growth, viability, and proliferation of the cultured human bone marrow mesenchymal stem cells (hMSCs) on the prepared nanomaterials were examined using various biological assays, including MTT cytotoxicity, ALP activity, calcium biomineralization, Alizarin red staining, and gene expression. The biological results clearly showed that the growth, proliferation and osteogenic ability of hMSCs were significantly improved due to the surface modification of PLLA nanofibers with BGn. It was concluded that the 3D structure, optimum porosity and balanced dissolution rate of PLLA/BGn nanocomposites led to the promoted cellular activity.

Electrically polarized PLLA nanofibers as neural tissue engineering scaffolds with improved neuritogenesis.

Tissue engineering is evolving towards the production of smart platforms exhibiting stimulatory cues to guide tissue regeneration. This work explores the benefits of electrical polarization to produce more efficient neural tissue engineering platforms. Poly (l-lactic) acid (PLLA)-based scaffolds were prepared as solvent cast films and electrospun aligned nanofibers, and electrically polarized by an in-lab built corona poling device. The characterization of the platforms by thermally stimulated depolarization currents reveals a polarization of 60 × 10-10C cm-2 that is stable on poled electrospun nanofibers for up to 6 months. Further in vitro studies using neuroblastoma cells reveals that platforms' polarization potentiates Retinoic Acid-induced neuronal differentiation. Additionally, in differentiating embryonic cortical neurons, poled aligned nanofibers further increased neurite outgrowth by 30% (+70 μm) over non-poled aligned nanofibers, and by 50% (+100 μm) over control conditions. Therefore, the synergy of topographical cues and electrical polarization of poled aligned nanofibers places them as promising biocompatible and bioactive platforms for neural tissue regeneration. Given their long lasting induced polarization, these PLLA poled nanofibrous scaffolds can be envisaged as therapeutic devices of long shelf life for neural repair applications.

5,10,15,20-Tetrakis (4-carboxyphenyl) porphin-conjugated poly(l-lactic) acid/polyethylene oxide nanofiber membranes for photodynamic therapy

In this work, a poly(l-lactic) acid (PLLA)/polyethylene oxide (PEO) nanofiber membrane was prepared by electrospinning as a carrier for the photosensitizer 5,10,15,20-tetrakis (4-carboxyphenyl) porphin (TCPP) to study the effects of singlet oxygen (1O2) on tumor cells. Scanning electron microscopy and confocal laser scanning microscopy images showed that the fiber surface was smooth and that TCPP was evenly dispersed in the nanofibers. TCPP, PLLA, and PEO were mixed with nanofibers without the formation of new chemical bonds, as shown by Fourier transform infrared spectroscopy. The addition of PEO improved the hydrophilicity of the nanofibers, making the contact angle of the PLLA nanofiber membrane change from 93.3° to near 0° and resulting in good cell compatibility. The sustained release experiment showed that when the amount of TCPP was 3%, the cumulative release concentration after 72h was close to saturation in the test system. Electron spin resonance spectroscopy confirmed that TCPP produced 1O2 at light irradiation (532nm). The results of in vitro cell experiments showed that TCPP@PLLA/PEO nanofiber membranes did not affect the normal growth of HeLa cells but had cytotoxic effects on cancer cells under light irradiation.

Hardystonite-Coated Poly(l-lactide) Nanofibrous Scaffold and Efficient Osteogenic Differentiation of Adipose-Derived Mesenchymal Stem Cells.

In this study, a ceramic-coated nanofibrous scaffold has been fabricated to biomimic the microstructure of natural extracellular matrix and the stiffening inorganic compartment of bone. Poly-l-lactic acid (PLLA) nanofibers were electrospun and exposed to oxygen plasma to induce hydrophilicity and promote ceramic adsorption. Hardystonite (HS), which possesses superior osteoinduction potential over hydroxyapatite, was coated on plasma-treated PLLA nanofibers by drenching the nanofibers in HS suspension. Pure and composite PLLA-based scaffolds were characterized in terms of physical and biological properties. In vitro cultivation of adipose-derived mesenchymal stem cells (AMSCs) on the scaffolds displayed that the composite scaffold is able to further support cell attachment and proliferation. In case of osteogenic differentiation of AMSCs, HS coating significantly increased the synthesis and activity of alkaline phosphate over 21 days period. In addition, the composite scaffold showed improved mineralization. The expression level of osteonectin and osteocalcin genes was significantly enhanced by HS coating of nanofibers. The biological improvement of PLLA nanofibrous matrix in the presence of HS nanoparticles could either be attributed to the release and stimulatory effect of constituent ions of HS or to the modification of chemico-physical properties of the resultant ceramic by silicon and zinc present in HS.

Enhanced Skin Regeneration by Herbal Extract-Coated Poly-L-Lactic Acid Nanofibrous Scaffold.

The wound healing process is directly related to the type of treatment. Existing methods of treatment are not responsive enough for severe wounds. The aim of this study was the potential capacity investigation of poly-L-lactic acid (PLLA) nanofibrous scaffolds coated by aloe vera gel for wound dressing applications. In this study, electrospinning method was used for preparing PLLA nanofibers, and after characterization by SEM and MTT, its influence on the wound healing process was investigated with and without aloe vera gel as a wound dressing in full-thickness skin defect in mice. Band-Aids were used as a positive control and vaseline gauze as a negative control. SEM and MTT assays confirmed the nanometer size and biocompatibility of fabricated nanofibers. Macroscopic and histopathological characteristics were evaluated at theend of days 7, 12, and 17 and their results showed that the gel-coated scaffold accelerated the wound-healing process compared with other groups. At the end of the experiment, it was shown that during the whole time of study, gel-coated scaffold had the highest overall repair score. Therefore, gel-coated PLLA scaffold would be an ideal construct for wound healing and skin regenerative medicine application.

Osteogenic differentiation of mesenchymal stem cells cultured on PLLA scaffold coated with Wharton's Jelly.

Poly-L-lactic acid (PLLA) electrospun nanofiber scaffold is one of the most commonly used synthetic polymer scaffolds for bone tissue engineering application. However, PLLA is hydrophobic in nature, hence does not maintain proper cell adhesion and tissue formation, moreover, it cannot provide the osteo-inductive environment due to inappropriate surface characteristic and the lack of surface motives participating in the first cellular events. To modify these shortcomings different approaches have been used, among those the most commonly used one is coating of the surface of the electrospun nanofiber with natural materials. In this work Wharton's jelly (WJ), a tissue which surrounds the umbilical cord vessels, reaches in high amounts of extracellular matrix (ECM) components mainly; collagen, hyaluronic acid and several sulphated glycosaminoglycans (GAGs) were used to cover the surface of electrospun PLLA nanofiber scaffolds. The surface morphology of the nanofiber scaffold was evaluated via scanning electron microscope, and the in vitro osteogenic differentiation potential was determined by MTT assay and common osteogenic marker tests such as alkaline phosphatase (ALP) activity and calcium deposition tests. Coating of WJ could not change the surface morphology and diameter of the nanofibers. However, WJ-PLLA scaffolds showed higher proliferation of human mesenchymal stem cells (MSC) than tissue culture plate (TCP) and pristine PLLA scaffolds, moreover, WJ-PPLA scaffold demonstrated significant alkaline phosphatase activity and calcium mineralization than either TCP or PLLA nanofiber scaffolds.

A Method for the Immunohistochemical Identification and Localization of Osterix in Periosteum-Wrapped Constructs for Tissue Engineering of Bone.

A novel immunohistochemistry (IHC) approach has been developed to label and localize osterix, a bone-specific transcription factor, within formalin-fixed, paraffin-embedded, tissue-engineered constructs uniquely containing synthetic polymers and human periosteal tissue. Generally, such specimens consisting in part of polymeric materials and mineral are particularly difficult for IHC identification of proteins. Samples here were fabricated from human periosteum, electrospun poly-l-lactic acid (PLLA) nanofibers, and polycaprolactone/poly-l-lactic acid (PCL/PLLA, 75/25) scaffolds and harvested following 10 weeks of implantation in athymic mice. Heat-induced and protease-induced epitope retrieval methods from selected existing protocols were examined to identify osterix. All such protease-induced techniques were unsuccessful. Heat-induced retrieval gave positive results for osterix immunohistochemical staining in sodium citrate/EDTA/Tween 20 with high heat (120C) and pressure (~30 psi) for 10 min, but the heat and pressure levels resulted in tissue damage and section delamination from slides that limited protocol effectiveness. Heat-induced epitope retrieval led to other osterix-positive staining results achieved with minimal impact on structural integrity of the tissue and polymers in sodium citrate/EDTA/Tween 20 buffer at 60C and normal pressure (14.5 psi) for 72 hr. The latter approach identified osterix-positive cells by IHC within periosteal tissue, layers of electrospun PLLA nanofibers, and underlying PCL/PLLA scaffolds of the tissue-engineered constructs.

Highly aligned core-shell structured nanofibers for promoting phenotypic expression of vSMCs for vascular regeneration.

This study was designed to assess the efficacy of hyaluronan (HA) functionalized well-aligned nanofibers of poly-l-lactic acid (PLLA) in modulating the phenotypic expression of vascular smooth muscle cells (vSMCs) for blood vessel regeneration. Highly aligned HA/PLLA nanofibers in core-shell structure were prepared using a novel stable jet electrospinning approach. Formation of a thin HA-coating layer atop each PLLA nanofiber surface endowed the uni-directionally oriented fibrous mats with increased anisotropic wettability and mechanical compliance. The HA/PLLA nanofibers significantly promoted vSMC to elongation, orientation, and proliferation, and also up-regulated the expression of contractile genes/proteins (e.g., α-SMA, SM-MHC) as well as the synthesis of elastin. Six weeks of in vivo scaffold replacement of rabbit carotid arteries showed that vascular conduits made of circumferentially aligned HA/PLLA nanofibers could maintain patency and promoted oriented vSMC regeneration, lumen endothelialization, and capillary formation. This study demonstrated the synergistic effects of nanotopographical and biochemical cues in one biomimetic scaffold design for efficacious vascular regeneration.

Electrospun PLA/MWCNTs composite nanofibers for combined chemo- and photothermal therapy

Carbon nanotubes are effective thermal generators by absorbing near-infrared radiation (NIR). In this study, multiwalled carbon nanotubes (MWCNTs) and doxorubicin (DOX) were successfully electrospun into the poly-l-lactic acid (PLLA) nanofibers. It is confirmed that NIR radiation could not only initiate burst release of DOX from the fibers due to the relatively low glass transition temperature (Tg) of PLLA, but also significantly increase the temperature of fibers-covering tumor site. The multifunctional fibers showed increased cytotoxicity both in vitro and in vivo by the combination of photothermal induced hyperthermia and chemotherapy with DOX. This drug delivery system could be very useful and convenient in future clinical applications for localized cancer therapy. Statement of SignificanceCombination of chemo- and photothermal therapy has been widely researched owing to its enhanced cancer treatment efficacy. In this study, chemotherapy and photothermal therapy were integrated into one single system using electrospun DOX/MWCNTs loaded PLLA nanofiber mats and the anti-cancer efficacy of the fibers was studied in vivo for the first time. The effective NIR irradiation control showed a typical switch on/off effect on the release behavior of drug. As local delivery system, the fibers maximize the drug concentration in tumor and keep the MWCNTs in the surroundings of tumor, thus allowing a repeated localized heating. The high porosity of nanofibers is easy for cell binding, which may present an attractive alternative for local hyperthermia treatment of easily metastasizing tumors.