Effects of process parameters on structure and properties of melt-blown poly(lactic acid) nonwovens for skin regeneration

Skin regeneration requires a three-dimensional (3D) scaffold for cell adhesion, growth and proliferation. A type of the scaffold offering a 3D structure is a nonwoven material produced via a melt-blown technique. Process parameters of this technique can be adapted to improve the cellular response. Polylactic acid (PLA) was used to produce a nonwoven scaffold by a melt-blown technique. The key process parameters, i.e., the head and air temperature, were changed in the range from 180–270 °C to obtain eight different materials (MB1–MB8). The relationships between the process parameters, morphology, porosity, thermal properties and the cellular response were explored in this study. The mean fiber diameters ranged from 3 to 120 µm. The average material roughness values were between 47 and 160 µm, whereas the pore diameters ranged from 5 to 400 µm. The calorimetry thermograms revealed a correlation between the temperature parameters and crystallization. The response of keratinocytes and macrophages exhibited a higher cell viability on thicker fibers. The cell-scaffold interaction was observed via SEM after 7 days. This result proved that the features of melt-blown nonwoven scaffolds depended on the processing parameters, such as head temperature and air temperature. Thanks to examinations, the most suitable scaffolds for skin tissue regeneration were selected

2D-Raman correlation spectroscopy as a method to recognize of the interaction at the interface of carbon layer and albumin

In modern nanomaterial production, including those for medical purposes, carbon based materials are important, due to their inert nature and interesting properties. The essential attribute for biomaterials is their biocompatibility, which indicates way of interactions with host cells and body fluids. The aim of our work was to analyze two types of model carbon layers differing primarily in topography, and developing their interactions with blood plasma proteins. The first layer was formed of pyrolytic carbon C (CVD) and the second was constructed of multi-walled carbon nanotubes obtained by electrophoretic deposition (EPD), both set on a Ti support. The performed complex studies of carbon layers demonstrate significant dissimilarities regarding their interaction with chosen blood proteins, and points to the differences related to the origin of a protein: whether it is animal or human. However the basic examinations, such as: wettability test and nano sctatch tests were not sufficient to explain the material properties. In contrast, Raman microspectroscopy thoroughly decodes the phenomena occurring at the carbon structures in contact with the selected blood proteins. The 2D correlation method selects the most intense interaction and points out the different mechanism of interactions of proteins with the nanocarbon surfaces and differentiation due to the nature of the protein and its source: animal or human. The 2D correlation of the Raman spectra of the MWCNT layer+HSA interphase proves an increase in albumin β-conformation. The presented results explain the unique properties of the Clayers (CVD) in contact with human albumin

Bioresorbable Stent in Anterior Cruciate Ligament Reconstruction

The exact causes of failure of anterior cruciate ligament (ACL) reconstruction are still unknown. A key to successful ACL reconstruction is the prevention of bone tunnel enlargement (BTE). In this study, a new strategy to improve the outcome of ACL reconstruction was analyzed using a bioresorbable polylactide (PLA) stent as a catalyst for the healing process. The study included 24 sheep with 12 months of age. The animals were randomized to the PLA group (n = 16) and control group (n = 8), subjected to the ACL reconstruction with and without the implantation of the PLA tube, respectively. The sheep were sacrificed 6 or 12 weeks post-procedure, and their knee joints were evaluated by X-ray microcomputed tomography with a 50 m resolution. While the analysis of tibial and femoral tunnel diameters and volumes demonstrated the presence of BTE in both groups, the enlargement was less evident in the PLA group. Also, the microstructural parameters of the bone adjacent to the tunnels tended to be better in the PLA group. This suggested that the implantation of a bioresorbable PLA tube might facilitate osteointegration of the tendon graft after the ACL reconstruction. The beneficial e ects of the stent were likely associated with osteogenic and osteoconductive properties of polylactide

Effects of Polylactide Copolymer Implants and Platelet-Rich Plasma on Bone Regeneration within a Large Calvarial Defect in Sheep

The aim of this study was to verify whether L-lactide/DL-lactide copolymer 80/20 (PLDLLA) and platelet-rich plasma (PRP) trigger bone formation within critical-sized calvarial defects in adult sheep ( = 6). Two craniectomies, each ca. 3 cm in diameter, were created in each animal. The first craniectomy was protected with an inner polylactide membrane, filled with PRP-polylactide granules, and covered with outer polylactide membrane. The second control craniectomy was left untreated. The animals were euthanized at 6, 7, 17, 19, 33, and 34 weeks after surgery, and the quality and the rate of reossification were assessed histomorphometrically and microtomographically.The study demonstrated that application of implantsmade of PLDLLA 80/20 combined with an osteopromotive substance (e.g., PRP) may promote bone healing in large calvarial defect in sheep. These promising proof-of-concept studies need to be verified in the future on a larger cohort of animals and over a longer period of time in order to draw definitive conclusions

Search for fibrous aggregates potentially useful in regenerative medicine formed under physiological conditions by self-assembling short peptides containing two identical aromatic amino acid residues

This study investigates the propensity of short peptides to self-organize and the influence of aggregates on cell cultures. The dipeptides were derived from both enantiomers of identical aromatic amino acids and tripeptides were prepared from two identical aromatic amino acids with one cysteine or methionine residue in the C-terminal, N-terminal, or central position. The formation or absence of fibrous structures under physiological conditions was established using Congo Red and Thioflavine T assays as well as by microscopic examination using normal and polarized light. The in vitro stability of the aggregates in buffered saline solution was assessed over 30 days. Materials with potential for use in regenerative medicine were selected based on the cytotoxicity of the peptides to the endothelial cell line EA.hy 926 and the wettability of the surfaces of the films, as well as using scanning electron microscopy. The criteria were fulfilled by H-dPhedPhe-OH, H-dCysdPhedPhe-OH, H-CysTyrTyr-OH, H-dPhedPhedCys-OH, H-TyrTyrMet-OH, and H–TyrMetTyr–OH. Our preliminary results suggest that the morphology and cell viability of L919 fibroblast cells do not depend on the stereochemistry of the self-organizing peptides

Electrospinning for drug delivery systems: potential of the technique

Electrospinning is a technique used to manufacture nano- and submicron fibers based on synthetic or natural polymers. Additionally, biomaterials used in the electrospinning procedure can be modified by bioactive compounds, e.g. peptides or growth factors. The microstructure of the obtained fibrous scaffolds mimics natural extracellular matrix (ECM) environment. The size and the microstructure of the fibrous scaffolds are considered to be suitable for cells adhesion and proliferation. Various design features of the electrospinning device (e.g. the shape of the collector, the shape of the nozzle, the direction of the applied voltage) or electrospinning conditions (e.g. humidity, temperature) allows to control properties of the fibers (their shape, diameter, porosity). Novel structures, such as core-shell fibers, porous fibers attracted wide attention due to their properties and functionalities. Porous fibers or fibers with nanoscaled structures can be obtained in several ways. These methods are mainly focused on using high humidity and highly volatile solvent applied in the electrospinning process. The core-shell structure can be obtained by coaxial electrospinning. That binary fiber has ability to control the release rate of drug enclosed within the shell or core. The drug release profile can be also modified by loading the pharmacological agent either directly to the spinning solution or its post immobilization.This diversity of the electrospun fibers is a reason for non-woven materials to be considered for application as drug carriers. The review of electrospinning methods presented here proves that the control over fibers surface area, morphology and the choice of polymer enable modelling of drug release kinetics

Chemical and physical modifications of electrospun fibers as a method to stimulate tissue regeneration – minireview

Fibrous scaffolds based on (bio)polymers are ob¬served as mimicking the microstructure of the extracel¬lular matrix. Thus, they are considered as an example of a utilitarian scaffold, useful for the regeneration of various types of tissues. The techniques described in the literature are well known to obtain submicrometric and nanometric fibers that, when randomly arranged, mimic the ECM. The biomimetic scaffold criterion might be even better reflected if the cell adhesion sites are present on the surface of such fibers. They promote the formation of the focal adhesion contact or facilitate the formation of a protein film on the fiber surface. Such a process is enhanced by an appropriate physical or chemical modification that activates the protein adsorption and the subsequent cell adhesion. The aim of this paper is to present different methods of physical and/or chemi¬cal modifications of fibrous materials: which can serve as scaffolds to support the regeneration processes of various tissues. In terms of physical methods, only weak interactions between the surface and the modi¬fier were observed. This technique is simple but not durable. Chemisorption used as a second method of fiber modification is possible if a covalent or ionic bond is formed between the fiber and the modifier. Therefo¬re, the chemical adsorption may not be fully reversible and requires a sequence of chemical actions to form a chemical bond. The most commonly used methods are the combined methods where the first step is the physical activation of the fiber surface, which facilitates the chemical modification step

Strategies to Mitigate Biofouling of Nanocomposite Polymer-Based Membranes in Contact with Blood

An extracorporeal blood purification method called continuous renal replacement therapy uses a porous hollow-fiber polymeric membrane that is exposed to prolonged contact with blood. In that condition, like with any other submerged filtration membrane, the hemofilter loses its properties over time and use resulting in a rapid decline in flux. The most significant reason for this loss is the formation of a biofilm. Protein, blood cells and bacterial cells attach to the membrane surface in complex and fluctuating processes. Anticoagulation allows for longer patency of vascular access and a longer lifespan of the membrane. Other preventive measures include the modification of the membrane itself. In this article, we focused on the role of nanoadditives in the mitigation of biofouling. Nanoparticles such as graphene, carbon nanotubes, and silica effectively change surface properties towards more hydrophilic, affect pore size and distribution, decrease protein adsorption and damage bacteria cells. As a result, membranes modified with nanoparticles show better flow parameters, longer lifespan and increased hemocompatibility