Mechanical behavior of polylactic acid/polycaprolactone porous layered functional composites

Biopolymeric porous devices exhibiting graded properties can play a crucial role in several fields, such as tissue engineering or controlled drugs release. In this context, the gradient of a specific property can be achieved by developing porous laminates composed by different types of materials. This work presents for the first time a multi-phasic porous laminate based on polycaprolactone (PCL) and polylactic acid (PLA) prepared by combining melt mixing, compression molding and particle leaching. All the materials were characterized from a morphological and a mechanical point of view. The results put into evidence the possibility to tune and to predict the mechanical properties by controlling the process parameters together with geometrical features

Poly-L-Lactic Acid (PLLA)-Based Biomaterials for Regenerative Medicine: A Review on Processing and Applications

Synthetic biopolymers are effective cues to replace damaged tissue in the tissue engineering(TE) field, both for in vitro and in vivo application. Among them, poly-L-lactic acid (PLLA) has beenhighlighted as a biomaterial with tunable mechanical properties and biodegradability that allowsfor the fabrication of porous scaffolds with different micro/nanostructures via various approaches.In this review, we discuss the structure of PLLA, its main properties, and the most recent advancesin overcoming its hydrophobic, synthetic nature, which limits biological signaling and proteinabsorption. With this aim, PLLA-based scaffolds can be exposed to surface modification or combinedwith other biomaterials, such as natural or synthetic polymers and bioceramics. Further, variousfabrication technologies, such as phase separation, electrospinning, and 3D printing, of PLLA-basedscaffolds are scrutinized along with the in vitro and in vivo applications employed in various tissuerepair strategies. Overall, this review focuses on the properties and applications of PLLA in theTE field, finally affording an insight into future directions and challenges to address an effectiveimprovement of scaffold properties

Innovative, ecofriendly biosorbent-biodegrading biofilms for bioremediation of oil- contaminated water

Immobilization of microorganisms capable of degrading specific contaminants significantly promotes bioremediation processes. In this study, innovative and ecofriendly biosorbent-biodegrading biofilms have been developed in order to remediate oil-contaminated water. This was achieved by immobilizing hydrocarbon-degrading gammaproteobacteria and actinobacteria on biodegradable oil-adsorbing carriers, based on polylactic acid and polycaprolactone electrospun membranes. High capacities for adhesion and proliferation of bacterial cells were observed by scanning electron microscopy. The bioremediation efficiency of the systems, tested on crude oil and quantified by gas chromatography, showed that immobilization increased hydrocarbon biodegradation by up to 23 % compared with free living bacteria. The resulting biosorbent biodegrading biofilms simultaneously adsorbed 100 % of spilled oil and biodegraded more than 66 % over 10 days, with limited environmental dispersion of cells. Biofilm-mediated bioremediation, using eco-friendly supports, is a low-cost, low-impact, versatile tool for bioremediation of aquatic systems

Innovative ready to use carrier-bacteria devices for bioremediation of oil contaminated water

Bioremediation, that uses microorganisms to remove environmental pollutants, is the best way of restoring the environment due to its low cost and sustainability. Immobilization of microorganisms capable of degrading specific contaminants significantly promotes bioremediation processes. An innovative ready to use bioremediation system to clean up oil-contaminated water was developed immobilizing highly performant marine and soil HC degrading bacteria, on biodegradable oil-absorbing carriers. Two soil Actinobacteria (Gordonia sp. SoCg, Nocardia sp. SoB) and two marine Gammaproteobacteria (Alcanivorax sp. SK2, Oleibacter sp.5), were immobilized on biopolymeric membranes prepared by electrospinning (polylactic acid, PLA and polycaprolactone, PCL). These carriers are characterized by high uptake capacity, oil retention, buoyancy, durability, reusability and recoverability of the oil absorbed. The morphology of the carriers and microbial adhesion and proliferation were evaluated using scanning electron microscopy (SEM). A high capacity of adhesion and proliferation of bacterial cells was observed on membranes after 5 days. The bioremediation efficiency of the carrier-bacteria systems was tested on crude oil by GC-FID analysis and compared whit planktonic cells. The bacterial immobilization on PLA and PCL membranes was a promoting factor for biodegradation, increasing hydrocarbon removal up to 20%, in respect to planktonic cells. Biofilm-mediated bioremediation is a versatile tool to be developed for in situ and ex situ bioremediation of aquatic systems. Several applications can be designed to exploit both the high oil uptake capacity of the carriers, and the biodegradation potential of autochtonous microrganisms and/or of selected microorganisms that are immobilized on the carriers before exposure to the contaminated site

Galvanic deposition of Chitosan-AgNPs as antibacterial coating

Thanks to mechanical properties similar human bones, metallic materials represent the best choice for fabrication of orthopedic implants. Although metals could be widely used in the field of biomedical implants, corrosion phenomena could occur, causing metal ions releasing around periprosthetic tissues leading, in the worst cases, to the development of infections. In these cases, patients need prolonged antibiotic therapies that may cause bacterial resistance. Preventing bacterial colonization of biomedical surfaces is the key to limiting the spread of infections. Antibacterial coatings have become a very active field of research, strongly stimulated by the increasing urgency of identifying alternatives to the traditional administration of antibiotics. Nowadays, the research was focused on coating science to deal with these issues. In particular, the development of the antibacterial composite coatings could be a viable way to provide not only a corrosion resistance but also an antibacterial action and biocompatibility. Chitosan is a great biomaterial used in medicine. It is a natural bioactive polymer and is the second most abundant in nature polysaccharide after cellulose. Chitosan comes from the deacetylation of chitin, a homopolymer of beta-(1-4)-N-acetyl-D-glucosamine, derived from exoskeleton of crustaceans. It is high biocompatible and it is also used in drug delivery. In addition, chitosan has chelating properties due to the amino groups of polysaccharide that are responsible of selective chelation with metal ions. In particular, the attention has been paid to silver nanoparticles for their high stability, low toxicity, biocompatibility and antibacterial properties. These ones are incorporated in polymeric matrix (e.g. chitosan) and they are capable to interact physically with cell walls of bacteria. In this study Chitosan-Silver nanoparticles composite coating on AISI 304L was investigated. These coatings were realized by an alternative method of deposition respect to traditional ones based on galvanic coupling. This process doesn’t request any external power supply and is very easy to carried out. The difference of the electrochemical redox potential between the substrate (cathode) and a sacrificial anode is the pivotal role of the process. Deposition rate is controlled by the ratio of cathodic and anodic area. In practice, electrons generated by anode corrosion flow towards to more noble metal thanks to a short-circuit. As soon electrons arrive to the cathode, the base electrogeneration reactions of nitrate ions and water molecules occur. Production of hydroxyl ions causes an increasing of pH at substrate/solution interface. Hence, deprotonation of amine group leads precipitation of chitosan (pKa=6.4) onto surface. At the same time, silver nanoparticles are incorporated in polymeric matrix of chitosan. Physical-chemical characterizations of the coatings were carried out in order to investigate morphology and chemical composition. In addition, corrosion tests (potentiodynamic polarization and electrochemical impedance spectroscopy) were executed in a simulated body fluid to scrutinize the corrosion resistance. Furthermore, the release of silver nanoparticles from coating in SBF were studied

Galvanic Deposition of Calcium Phosphate/Bioglass Composite Coating on AISI 316L

Calcium phosphate/Bioglass composite coatings on AISI 316L were investigated with regard to their potential role as a beneficial coating for orthopedic implants. These coatings were realized by the galvanic co-deposition of calcium phosphate compounds and Bioglass particles. A different amount of Bioglass 45S5 was used to study its effect on the performance of the composite coatings. The morphology and chemical composition of the coatings were investigated before and after their aging in simulated body fluid. The coatings uniformly covered the AISI 316L substrate and consisted of a brushite and hydroxyapatite mixture. Both phases were detected using X-ray diffraction and Raman spectroscopy. Additionally, both analyses revealed that brushite is the primary phase. The presence of Bioglass was verified through energy-dispersive X-ray spectroscopy, which showed the presence of a silicon peak. During aging in simulated body fluid, the coating was subject to a dynamic equilibrium of dissolution/reprecipitation with total conversion in only the hydroxyapatite phase. Corrosion tests performed in simulated body fluid at different aging times revealed that the coatings made with 1 g/L of Bioglass performed best. These samples have a corrosion potential of −0.068V vs. Ag/AgCl and a corrosion current density of 8.87 × 10−7 A/cm2. These values are better than those measured for bare AISI 316L (−0.187 V vs. Ag/AgCl and 2.52 × 10−6 A/cm2, respectively) and remained superior to pure steel for all 21 days of aging. This behavior indicated the good protection of the coating against corrosion phenomena, which was further confirmed by the very low concentration of Ni ions (0.076 ppm) released in the aging solution after 21 days of immersion. Furthermore, the absence of cytotoxicity, verified through cell viability assays with MC3T3-E1 osteoblastic cells, proves the biocompatibility of the coatings

Integrated production of biopolymers with industrial wastewater treatment: Effects of OLR on process yields, biopolymers characteristics and mixed microbial community enrichment

The production of polyhydroxyalkanoates (PHA) using industrial wastewaters as feedstocks is a current and challenging topic. This study investigated the production of biopolymers by a mixed microbial culture under different OLRs equal to 1 kgCOD m-3d-1 (Period 1), 2 kgCOD m-3d-1 (Period 2) and 3 kgCOD m-3d-1 (Period 3). The maximum PHA content was achieved in Period 2 (0.38 gPHA gTSS-1), whereas lower values were obtained in Period 1 (0.13 gPHA gTSS-1) and Period 3 (0.26 gPHA gTSS-1). Overall, the maximum PHA productivity resulted equal to 0.08 gPHA L-1h-1 (P2), 0.05 gPHA L-1h-1 (P1) and 0.04 gPHA L-1h-1 (P3), respectively. The molecular weight of the PHA increased from Period 1 (250 kDa) to Period 2 (417 KDa) and Period 3 (463 KDa), although resulting in a slight decrease of crystallinity degree. Microbial community analysis, revealed a reduction in bacterial diversity and a progressive shift of the microbial community with the increasing OLR. Alpha-diversity indexes based on Operational Taxonomic Units (OTUs) at 99% identity revealed higher species richness (Taxa (S) 280) and diversity (Shannon (H) 4,06) in Period 1, whereas Period 3 was characterized by reduced richness and diversity and higher dominance (Taxa (S) 133, Shannon (H) 2,40). Based on the results obtained, it was pointed out that the OLR variation determined significant effects on the process performances, as well as on the productivity and quality of the biopolymers. This means that OLR is a key control parameter to maximize the PHA production and control the physical-chemical characteristics of the polymers

Green and Integrated Wearable Electrochemical Sensor for Chloride Detection in Sweat

Wearable sensors for sweat biomarkers can provide facile analyte capability and monitoring for several diseases. In this work, a green wearable sensor for sweat absorption and chloride sensing is presented. In order to produce a sustainable device, polylactic acid (PLA) was used for both the substrate and the sweat absorption pad fabrication. The sensor material for chloride detection consisted of silver-based reference, working, and counter electrodes obtained from upcycled compact discs. The PLA substrates were prepared by thermal bonding of PLA sheets obtained via a flat die extruder, prototyped in single functional layers via CO2 laser cutting, and bonded via hot-press. The effect of cold plasma treatment on the transparency and bonding strength of PLA sheets was investigated. The PLA membrane, to act as a sweat absorption pad, was directly deposited onto the membrane holder layer by means of an electrolyte-assisted electrospinning technique. The membrane adhesion capacity was investigated by indentation tests in both dry and wet modes. The integrated device made of PLA and silver-based electrodes was used to quantify chloride ions. The calibration tests revealed that the proposed sensor platform could quantify chloride ions in a sensitive and reproducible way. The chloride ions were also quantified in a real sweat sample collected from a healthy volunteer. Therefore, we demonstrated the feasibility of a green and integrated sweat sensor that can be applied directly on human skin to quantify chloride ions

Sudden Unexpected Deaths and Vaccinations during the First Two Years of Life in Italy: A Case Series Study

Background The signal of an association between vaccination in the second year of life with a hexavalent vaccine and sudden unexpected deaths (SUD) in the two days following vaccination was reported in Germany in 2003. A study to establish whether the immunisation with hexavalent vaccines increased the short term risk of SUD in infants was conducted in Italy. Methodology/Principal Findings The reference population comprises around 3 million infants vaccinated in Italy in the study period 1999–2004 (1.5 million received hexavalent vaccines). Events of SUD in infants aged 1–23 months were identified through the death certificates. Vaccination history was retrieved from immunisation registries. Association between immunisation and death was assessed adopting a case series design focusing on the risk periods 0–1, 0–7, and 0–14 days after immunisation. Among the 604 infants who died of SUD, 244 (40%) had received at least one vaccination. Four deaths occurred within two days from vaccination with the hexavalent vaccines (RR = 1.5; 95% CI 0.6 to 4.2). The RRs for the risk periods 0–7 and 0–14 were 2.0 (95% CI 1.2 to 3.5) and 1.5 (95% CI 0.9 to 2.4). The increased risk was limited to the first dose (RR = 2.2; 95% CI 1.1 to 4.4), whereas no increase was observed for the second and third doses combined. Conclusions The RRs of SUD for any vaccines and any risk periods, even when greater than 1, were almost an order of magnitude lower than the estimates in Germany. The limited increase in RRs found in Italy appears confined to the first dose and may be partly explained by a residual uncontrolled confounding effect of age

Three-layered porous device in PCL/PEG blend for interface tissue engineering

Tissue interfaces, such as cartilage-to-bone, exhibit anisotropic structural properties, which gradually vary from one tissue to another. Consequently a regenerative scaffold designed for interface tissues should exhibit a gradient in composition, structure and mechanical features, mimicking those of the native zones. In particular, the architecture of pores plays a central role. Indeed, a biomedical implant should be designed with porosityand pore size gradients simulating the structure of the two interface tissues. One of the most common techniques to prepare porous scaffolds is the particulate leaching method, which involves the selective leaching of a mineral or organic compound as porogen agents. The main advantage of particulate leaching methods is the effective control of porosity and pore size by variation of the amount and size of leachable particles