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Herein is an one-pot mechanosynthesis of naloxone covalently linked poly(lactic acid) and nanoparticles (∼600 nm) with a drug loading (∼8.3% w/w).
Biobased reinforcements for poly(lactic acid) (PLA) are needed for more additive manufacturing applications requiring higher strength and sustainability. Flax nanofibrils (FNFs) produced through mechanical refining were explored as a lower energy alternative to cellulose nanofibril (CNF) reinforcements. To compatibilize the FNFs for the PLA matrix, a grafting-through surfactant free emulsion polymerization (SFEP) was performed to functionalize the FNF surface with poly(methyl methacrylate) (PMMA). FNFs produced using different refining energy were functionalized under varying solid contents in suspension. Polymerizations performed at 0.7 wt% FNFs in water yielded the highest degree of PMMA functionality. These optimal conditions were scaled up and the PMMA modified FNFs melt compounded into PLA yielding a 12% increase in tensile strength and 92% increase in the modulus of elasticity as compared to the original PLA. Interestingly, the FNFs with the lowest refining energy yielded the strongest composites using these methods, surpassing the higher refining energy CNF reinforcements. This increase was attributed to improved dispersion of the FNF reinforcements in the PLA matrix that was enabled by the PMMA coating on the FNF surface preventing interfibrillar adhesion and aggregation within the PLA matrix.
Provided herein are graft co-polymers of lignin and poly(lactic acid) (lignin-g-PLA copolymer), thermoset and thermoplastic polymers including them, methods of preparing these polymers, and articles of manufacture including such polymers.
Lamellar patterns and orientations in blends of two crystalline polymers: poly(ethylene oxide) (PEO) and low-molecular-weight poly(L-lactic acid) (PLLA) were investigated using polarizing light optical microscopy (POM), and atomic and scanning electron microscopy (AFM, SEM). Specific etching off of PEO was used to reveal the complex earlier-grown PLLA lamellae patterns with various PEO content in blends. Banding of extremely long pitch (50 μm) in crystallized PLLA spherulites was induced by two kinetic factors: geometry confinement by top cover and introduction of diluent such as PEO. The mechanisms and correlation among the lamellar assembly, ring bands, and cracks are exemplified. Lamellar patterns and ring-band types in blends were found to vary with respect to not only blend compositions, but also confinement of top-cover.
Highlights: • Glucose deprivation induces cell death and autophagy in B16 melanoma cells at neutral pH. • Lactic acid-induced extracellular acidification suppresses both cell death and autophagy. • Neutralization of the acidic environment by sodium bicarbonate may be useful in cancer therapy. In solid tumors, cancer cells survive and proliferate under conditions of microenvironment stress such as poor nutrients and hypoxia due to inadequate vascularization. These stress conditions in turn activate autophagy, which is important for cancer cell survival. However, autophagy has a contrary effect of inducing cell death in cancer cells cultured in vitro under conditions of glucose deprivation. In this study, we hypothesized that supplementation of lactic acid serves as a means of cell survival under glucose-deprived conditions. At neutral pH, cell death of B16 murine melanoma cells by autophagy under glucose-deprived conditions was observed. However, supplementation of lactic acid suppressed cell death and autophagy in B16 melanoma cells when cultured in glucose-deprived conditions. Sodium lactate, which does not change extracellular pH, did not inhibit cell death, while HCl-adjusted acidic pH suppressed cell death under glucose-deprived conditions. These results suggested that an acidic pH is crucial for cell survival under glucose-deprived conditions.
The aim of this study is to investigate the effects of zinc oxide treated halloysite nanotube (HNT-ZnO) on the properties of poly(lactic acid) (PLA) nanocomposites. ZnO was immobilized on HNT using a solvent-free technique. PLA nanocomposites were prepared with different loading of HNT-ZnO (i.e., 3, 5 and 7 wt%) using melt compounding. The properties of the PLA/HNT-ZnO nanocomposites were investigated using tensile test, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, thermogravimetric analysis and UV–visible spectroscopy. In addition, the effects of accelerated weathering (duration 60 days) on the behaviour of PLA/HNT-ZnO nanocomposites were studied. It was found that HNT-ZnO is capable to enhance the reinforcing ability, thermal stability and UV barrier of PLA nanocomposites. The PLA/HNT-ZnO films showed less discoloration and chain scission, indicating its higher photo-stability as compared to PLA/HNT after exposed to accelerated weathering. In summary, this study provides a basis for further development of PLA/HNT-ZnO nanocomposites with desirable mechanical, thermal and UV protection properties for potential outdoor application.
This work is focused on the hydrolysis of cotton fibers from waste textiles to obtain micro and nanofibers to be used as reinforcements in polymer composites. To promote their compatibility with polymeric matrix, hydrolyzed cotton fibers were surface modified with various silane compounds. Thus, these fibers were mixed with commercial poly(lactic acid) (PLA) at 5% w/w loading by melt compounding. Acid treatments caused a decrease of the crystallinity index whereas the thermal stability was significantly improved, especially for cellulose fibers hydrolyzed in two steps. Morphological analysis revealed a reduction of the fibers diameter and a decrease of their length as a consequence of the hydrolysis. NMR analysis confirmed the silanization of the fibers by reaction with the silane agent. Tensile tests revealed that silanization treatments were able to increase the composite Young’s modulus and the stress at break with respect to the neat matrix, indicating that silanization improved the polymer/fiber compatibility interfacial adhesion. The overall results demonstrated that applying suitable surface modification strategies, waste cotton textiles can be effectively recycled as fillers in polymer based composites.
Dairy fermentations are among the oldest food processing applications, aimed at preservation and shelf-life extension through the use of lactic acid bacteria (LAB) starter cultures, in particular strains of Lactococcus lactis, Streptococcus thermophilus, Lactobacillus spp. and Leuconostoc spp. Traditionally this was performed by continuous passaging of undefined cultures from a finished fermentation to initiate the next fermentation. More recently, consumer demands on consistent and desired flavours and textures of dairy products have led to a more defined approach to such processes. Dairy (starter) companies have responded to the need to define the nature and complexity of the starter culture mixes, and dairy fermentations are now frequently based on defined starter cultures of low complexity, where each starter component imparts specific technological properties that are desirable to the product. Both mixed and defined starter culture approaches create the perfect environment for the proliferation of (bacterio)phages capable of infecting these LAB. The repeated use of the same starter cultures in a single plant, coupled to the drive towards higher and consistent production levels, increases the risk and negative impact of phage infection. In this review we will discuss recent advances in tracking the adaptation of phages to the dairy industry, the advances in understanding LAB phage-host interactions, including evolutionary and genomic aspects.
Due to the availability of natural gas, shale gas, and flared gas, there is increased interest in converting methane in these gases into commodity chemicals via cost-effective and sustainable processes. Recently, we have demonstrated an efficient process concept converting methane to lactic acid (LA) by methanotrophic bacteria with high carbon flux, pivoting potentials for commercialization. Herein, we present a first-of-kind conceptual design and a techno-economic analysis (TEA) of a biorefinery process with calculated minimum selling prices. This study includes both sensitivity analysis and scenario analysis for key cost drivers and for projecting path forwards in research and development. The analyses reveal that the conversion efficiency, LA product titer, LA productivity, and gas flow rate have the most significant impacts on cost. The MSP varies from $5.83-$2.17/kg LA depending on these key process attributes. Further, a life cycle assessment of this process concept is evaluated and compared to understand the sustainable aspects. In this TEA study, the bio-upgrading process from natural gas to LA presents a potentially promising approach in terms of the feedstock versatility, economic viability, and environmental impact.
Producing fuels and chemicals from waste is considered economically favorable, due to low feedstock cost, and environmentally favorable, due to avoided emissions from conventional waste management practices. In this study, we evaluate the life cycle greenhouse gas (GHG) emission reduction benefits of renewable natural gas (RNG) and lactic acid (LA) production from four types of wet waste feedstocks (wastewater sludge, food waste, swine manure, and fats, oil, and grease [FOG]) via anaerobic digestion (AD) and LA fermentation, respectively. RNG can be used as an alternative to fossil natural gas, while LA from waste feedstocks can displace conventional LA production pathways (mainly from corn via fermentation). Providing comprehensive life cycle GHG emissions of the combinations of waste feedstocks and products through different routes helps identify the GHG hotspots and show where emissions savings come from. The results show that the carbon intensities (CIs) of waste-derived RNG and LA are much lower than those of their counterparts. We estimated the life cycle GHG emissions for RNG to be between -146 and 27 g carbon dioxide equivalent (CO2e)/MJ, much lower than the CI of fossil fuels. Waste-derived LA pathways also show substantially lower CIs, ranging from -4.2 to -1.4 kgCO2e/kg LA, compared to the CIs of LA from corn and corn stover (1.2 and 0.3 kgCO2e/kg LA, respectively). We will also discuss that the low CIs of waste-derived products can come from low yields leading to high emission credits. Thus, life cycle analysis results presented per weight of treated waste can be used to support decisions about which waste feedstocks and products are to be used for sustainable waste valorization. In addition, we found that monetary emission reduction credits can play an important role in driving waste valorization.
Poly(δ-valerolactone) (PVL) and poly(l-lactic acid) (PLLA) are bioderivable, compostable, and chemically recyclable plastics with synergistic properties for addressing plastic waste accumulation in receiving environments. Though recyclable-by-design polymers often fall short of competing with incumbent materials, blending affords a means to leverage individual component strengths toward ideal tunable properties. Polymer blends are often immiscible, but a range of methodologies are available to promote mixing. Here, we report on the compatibilization of 9 immiscible PVL and PLLA blends with three different compatibilization agents: thermoplastic starch, synthesized PVL-co-PLLA statistical copolymers (SCPs), and synthesized PVL-b-PLLA block-type copolymers. Resulting degrees of compatibilization are observed through scanning electron microscopy, corroborated by thermal and mechanical analyses monitoring performance as a function of microdomain size. Small-angle and wide-angle X-ray scattering experiments are conducted to observe the influence of compatibilizers on individual crystalline phases to further elucidate material behavior. Molecular dynamics simulations provide key insights into the interfacial interactions between homopolymers and compatibilizers. Finally, a suite of end-of-life avenues is established by biodegradation in industrial composting conditions, chemical recycling by deconstruction to hydroxymethyl esters, and direct chemical depolymerization to lactone precursors in mixed feed. Overall, we highlight several promising blends and the counterintuitive SCP compatibilization phenomenon toward high-performance, sustainable materials.
Constant rate compression isotherms of the air–water interfacial Langmuir films of poly(D,L-lactic acid- ran -glycolic acid) (PLGA)show a distinct feature of an exponential increase in surface pressure in the high surface polymer concentration regime. We have previously demonstrated that this abrupt increase in surface pressure is linked to the glass transition of the polymer film, but the detailed mechanism of this process is not understood. In order to obtain a molecular-level understanding of this behavior, we performed extensive characterizations of the surface mechanical, structural and rheological properties of Langmuir PLGA films at the air–water interface, using combined experimental techniques including the Langmuir film balance, X-ray reflectivity and double-wall-ring interfacial rheometry methods.
Hyperoxemic and hypoxemic convulsion effects on sugar, lactic acid, and inorganic phosphorus levels in dog blood and spinal fluid
Advanced biomaterials should also be bioactive with regard to desirable cellular responses, such as selective protein adsorption and cell attachment, proliferation, and differentiation. To enhance cell-material interactions, surface modifications have commonly been performed. Among the various surface modification approaches, atmospheric pressure glow discharge plasma has been used to change a hydrophobic polymer surface to a hydrophilic surface. Poly(L-lactic acid) (PLLA)-derived scaffolds lack cell recognition signals and the hydrophobic nature of PLLA hinders cell seeding. To make PLLA surfaces more conducive to cell attachment and spreading, surface modifications may be used to create cell-biomaterial interfaces that elicit controlled cell adhesion and maintain differentiated phenotypes. In this study, (He) gaseous atmospheric plasma glow discharge was used to change the characteristics of a 3D-type polymeric scaffold from hydrophobic to hydrophilic on both the outer and inner surfaces of the scaffold and the penetration efficiency with fibronectin was investigated. Field-emission scanning electron microscope images showed that some grooves were formed on the PLLA fibers after plasma treatment. X-ray photoelectron spectroscopy data also showed chemical changes in the PLLA structure. After plasma treatment, -CN (285.76 eV) was increased in C1s and -NH{sub 2} (399.70 eV) was increased significantly and –N=CH (400.80 eV) and –NH{sub 3}{sup +} (402.05 eV) were newly appeared in N1s. These changes allowed fibronectin to penetrate into the PLLA scaffold; this could be observed by confocal microscopy. In conclusion, helium atmospheric pressure plasma treatment was effective in modifying the polymeric scaffold, making it hydrophilic, and this treatment can also be used in tissue engineering research as needed to make polymers hydrophilic.
Two commercial mulching films based on aliphatic–aromatic copolyesters, poly(butylene adipate-co-terephthalate) (PBAT) and its blend with poly(lactic acid) (PBAT/PLA) were selected to study their photodegradation and their biodegradation under thermophile conditions. The films were buried in an agricultural field and bacteria were isolated from these. Bacterial strains were characterized with a combination of culture-dependent methods and sequencing of part of the 16S ribosomal RNA gene (rDNA). The most prevalent genus isolated was Bacillus and other related genera were found as well. Consortia of the isolated indigenous bacterial strains, IDN-EF and IDN-EC, and an additional consortia that had been previously isolated from exposed polyethylene, Bacillus-MIX, were prepared to perform the biodegradation assay at 45 °C on highly photodegraded films. Changes in the films were studied using chemiluminescence, ATR–FTIR, contact angle, SEM, GPC, DSC and TGA. A biodegradation assay was also performed on the four monomers that constitute the polymers using Bacillus subtilis and Bacillus licheniformis. Mineralization was evaluated by carbon dioxide measurements using an indirect impedance technique. This technique showed that overall there was a higher mineralization for the photodegraded materials. However, the biodegradation was most efficient when B. subtilis was present in the bacterial consortium and especially when the materials had been previously photodegraded.
Investigation of adsorption of rare earths and a few other elements to an anion-exchange resin from mixed solvents containing lactic acid shows that the lanthanides are absorbed more strongly than from the alpha-hydroxyisobutryric acid system, but with less separation between adjacent members of the series.
The effect of hydration on the molecular structure of amorphous poly(D,L-lactic acid) (PDLLA) with 50:50 L-to-D ratio has been studied by combining experiments with molecular simulations. X-ray diffraction measurements revealed significant changes upon hydration in the structure functions of the copolymer. Large changes in the structure functions at 10 days of incubation coincided with the large increase in the water uptake from {approx} 1 to {approx} 40% and the formation of voids in the film. Computer modeling based on the recently developed TIGER2/TIGER3 mixed sampling scheme was used to interpret these changes by efficiently equilibrating both dry and hydrated models of PDLLA. Realistic models of bulk amorphous PDLLA structure were generated as demonstrated by close agreement between the calculated and the experimental structure functions. These molecular simulations were used to identify the interactions between water and the polymer at the atomic level including the change of positional order between atoms in the polymer due to hydration. Changes in the partial O-O structure functions, about 95% of which were due to water-polymer interactions, were apparent in the radial distribution functions. These changes, and somewhat smaller changes in the C-C and C-O partial structure functions, clearly demonstrated the ability of the model to capture the hydrogen-bonding interactions between water and the polymer, with the probability of water forming hydrogen bonds with the carbonyl oxygen of the ester group being about 4 times higher than with its ether oxygen.
For the past 35 years, radio astronomy has revealed a rich organic chemistry in the interstellar gas, which is exceptionally complex towards active star-forming regions. New solar systems condense out of this gas and may influence the evolution of life on newly formed planets. Much of the biologically important functionality is present among the some 130 gas-phase molecules found to date, including alcohols, aldehydes, ketones, acids, amines, amides and even the simplest sugar - glycolaldehyde. Still, many unidentified interstellar radio signals remain, and their identification relies on further laboratory study. The molecules hydroxyacetone and lactic acid are relatively small organic molecules, but possess rather complex rotational spectra owing to their high asymmetry. Hydroxyacetone is particularly problematic because it possess a very low barrier to internal rotation, and exhibits strong coupling of the free-rotor states with the overall rotation of the molecule. As in the case of acetamide, a full decomposition method was employed to order the resultant eigenstates onto normal asymmetric top eigenvectors.