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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Degradation behavior of hydroxyapatite/poly(lactic-co-glycolic) acid nanocomposite in simulated body fluid

Graphical abstract: In this manuscript, we initiated a systematic study to investigate the effect of HA on thermal properties, inner structure, reduction of mechanical strength, surface morphology and the surface deposit of n-HA/PLGA composite with respect to the soaking time. The results showed that n-HA played an important role in improving the degradation behavior of n-HA/PLGA composite, which can accelerate the degradation of n-HA/PLGA composite and endow it with bioactivity, after n-HA was detached from PLGA during the degradation, so that n-HA/PLGA composite may have a more promising prospect of the clinical application than pure PLGA as bone fracture internal fixation materials, and the results would be of reference significance to predict the in vivo degradation and biological properties. - Highlights: • Effect of n-HA on degradation behavior of n-HA/PLGA composite was investigated. • Degradation behaviors of n-HA/PLGA and PLGA were carried out in SBF for 6 months. • Viscosity, thermal properties, inner structure and bending strength were tested. • n-HA can accelerate the degradation and endows it with bioactivity. - Abstract: To investigate the effect of hydroxyapatite(HA) on the degradation behavior of hydroxyapatite/poly(lactic-co-glycolic) acid (HA/PLGA) nanocomposite, the degradation experiment of n-HA/PLGA composite and pure PLGA were carried out by soaking in simulated body fluid(SBF) at 37 °C for 1, 2, 4 and 6 months. The change of intrinsic viscosity, thermal properties, inner structure, bending strength reduction, surface morphology and the surface deposit of n-HA/PLGA composite and pure PLGA with respect to the soaking time were investigated by means of UbbeloHde Viscometer, differential scanning calorimeter (DSC), scanning electron microscope(SEM), electromechanical universal tester, a conventional camera and X-ray diffraction (XRD). The results showed that n-HA played an important role in improving the degradation behavior of n-HA/PLGA composite, which can accelerate the degradation PLGA and endow it with bioactivity, after n-HA was detached from PLGA during the degradation, so that n-HA/PLGA composite may have a more promising prospect of the clinical application than pure PLGA as bone fracture internal fixation materials.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Poly(lactic-co-glycolic) acid loaded nano-insulin has greater potentials of combating arsenic induced hyperglycemia in mice: Some novel findings

Diabetes is a menacing problem, particularly to inhabitants of groundwater arsenic contaminated areas needing new medical approaches. This study examines if PLGA loaded nano-insulin (NIn), administered either intraperitoneally (i.p.) or through oral route, has a greater cost-effective anti-hyperglycemic potential than that of insulin in chronically arsenite-fed hyperglycemic mice. The particle size, morphology and zeta potential of nano-insulin were determined using dynamic light scattering method, scanning electronic and atomic force microscopies. The ability of the nano-insulin (NIn) to cross the blood–brain barrier (BBB) was also checked. Circular dichroic spectroscopic (CD) data of insulin and nano-insulin in presence or absence of arsenic were compared. Several diabetic markers in different groups of experimental and control mice were assessed. The mitochondrial functioning through indices like cytochrome c, pyruvate-kinase, glucokinase, ATP/ADP ratio, mitochondrial membrane potential, cell membrane potential and calcium-ion level was also evaluated. Expressions of the relevant marker proteins and mRNAs like insulin, GLUT2, GLUT4, IRS1, IRS2, UCP2, PI3, PPARγ, CYP1A1, Bcl2, caspase3 and p38 for tracking-down the signaling cascade were also analyzed. Results revealed that i.p.-injected nano-encapsulated-insulin showed better results; NIn, due to its smaller size, faster mobility, site-specific release, could cross BBB and showed positive modulation in mitochondrial signaling cascades and other downstream signaling molecules in reducing arsenic-induced-hyperglycemia. CD data indicated that nano-insulin had less distorted secondary structure as compared with that of insulin in presence of arsenic. Thus, overall analyses revealed that PLGA nano-insulin showed better efficacy in combating arsenite-induced-hyperglycemia than that of insulin and therefore, has greater potentials for use in nano-encapsulated form. - Highlights: ► PLGA encapsulated nano-insulin attenuates arsenic-induced diabetes in mice. ► Encapsulated insulin acts effectively at nearly 10 fold lesser dose than insulin. ► Injection route is more effective than oral administration route. ► Nano-insulin can cross blood–brain barrier with added physiological implications. ► Nano-insulin acts mainly through regulation of mitochondrial signaling cascade.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1998

Manufacture of porous biodegradable polymer conduits by an extrusion process for guided tissue regeneration

We have fabricated porous, biodegradable tubular conduits for guided tissue regeneration using a combined solvent casting and extrusion technique. The biodegradable polymers used in this study were poly(DL-lactic-co-glycolic acid) (PLGA) and poly(L-lactic acid) (PLLA). A polymer/salt composite was first prepared by a solvent casting process. After drying, the composite was extruded to form a tubular construct. The salt particles in the construct were then leached out leaving a conduit with an open-pore structure. PLGA was studied as a model polymer to analyze the effects of salt weight fraction, salt particle size, and processing temperature on porosity and pore size of the extruded conduits. The porosity and pore size were found to increase with increasing salt weight fraction. Increasing the salt particle size increased the pore diameter but did not affect the porosity. High extrusion temperatures decreased the pore diameter without altering the porosity. Greater decrease in molecular weight was observed for conduits manufactured at higher temperatures. The mechanical properties of both PLGA and PLLA conduits were tested after degradation in vitro for up to 8 weeks. The modulus and failure strength of PLLA conduits were approximately 10 times higher than those of PLGA conduits. Failure strain was similar for both conduits. After degradation for 8 weeks, the molecular weights of the PLGA and PLLA conduits decreased to 38% and 43% of the initial values, respectively. However, both conduits maintained their shape and did not collapse. The PLGA also remained amorphous throughout the time course, while the crystallinity of PLLA increased from 5.2% to 11.5%. The potential of seeding the conduits with cells for transplantation or with biodegradable polymer microparticles for drug delivery was also tested with dyed microspheres. These porous tubular structures hold great promise for the regeneration of tissues which require tubular scaffolds such as peripheral nerve, long bone, intestine, or blood vessel.

NASA Discipline Cell Biology↗
DOE OSTI2023

A metagenome-level analysis of a microbial community fermenting ultra-filtered milk permeate

Fermentative microbial communities have the potential to serve as biocatalysts for the conversion of low-value dairy coproducts into renewable chemicals, contributing to a more sustainable global economy. To develop predictive tools for the design and operation of industrially relevant strategies that utilize fermentative microbial communities, there is a need to determine the genomic features of community members that are characteristic to the accumulation of different products. To address this knowledge gap, we performed a 282-day bioreactor experiment with a microbial community that was fed ultra-filtered milk permeate, a low-value coproduct from the dairy industry. The bioreactor was inoculated with a microbial community from an acid-phase digester. A metagenomic analysis was used to assess microbial community dynamics, construct metagenome-assembled genomes (MAGs), and evaluate the potential for lactose utilization and fermentation product synthesis of community members represented by the assembled MAGs. This analysis led us to propose that, in this reactor, members of the Actinobacteriota phylum are important in the degradation of lactose, via the Leloir pathway and the bifid shunt, and the production of acetic, lactic, and succinic acids. In addition, members of the Firmicutes phylum contribute to the chain-elongation-mediated production of butyric, hexanoic, and octanoic acids, with different microbes using either lactose, ethanol, or lactic acid as the growth substrate. We conclude that genes encoding carbohydrate utilization pathways, and genes encoding lactic acid transport into the cell, electron confurcating lactate dehydrogenase, and its associated electron transfer flavoproteins, are genomic features whose presence in Firmicutes needs to be established to infer the growth substrate used for chain elongation.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Effect of Temperature and pH on Microbial Communities Fermenting a Dairy Coproduct Mixture

Organic-rich industrial residues can serve as renewable feedstocks for the generation of useful products by microbial fermentation. We investigated fermenting communities enriched in a mixture of ultra-filtered milk permeate (UFMP) and acid whey from cottage cheese (CAW), two dairy coproducts rich in lactose. To evaluate how operational pH and temperature affect microbial communities and fermentation products, we operated 12 bioreactors for 140 days, each fed a 1:1 mixture of UFMP and CAW at either 35 °C or 50 °C and at either a pH of 4.8 or 5.5. The bioreactors operated at a pH of 4.8 resulted in the incomplete conversion of lactose, while those operated at a pH of 5.5 consistently fermented lactose, primarily into lactic, acetic, and hexanoic acids. The metagenomic analyses revealed that microbial communities obtained at a pH of 5.5 were dominated by lactic acid-producing organisms. Additionally, an inverse relationship was found between the abundance of chain elongating organisms and lactic acid accumulation, with 50 °C reducing the abundance of these organisms and enhancing lactic acid yields. We conclude that the pH and temperature are important determinants of the fermentation of dairy coproducts with a pH of 5.5 and 50 °C yielding the most promising results for lactic acid production. Additional research is required to better understand the factors affecting functional consistency of the process.

Biotechnology & Applied Microbiology↗
DOE OSTI2017

Investigation on hemolytic effect of poly(lactic co-glycolic) acid nanoparticles synthesized using continuous flow and batch processes

Abstract With the increasing interest in polymeric nanoparticles for biomedical applications, there is a need for continuous flow methodologies that allow for the precise control of nanoparticle synthesis. Poly(lactide-co-glycolic) acid (PLGA) nanoparticles with diameters of 220–250 nm were synthesized using a lab-on-a-chip, exploiting the precise flow control offered by a millifluidic platform. The association and the effect of PLGA nanoparticles on red blood cells (RBCs) were compared for fluorescent PLGA nanoparticles made by this novel continuous flow process using a millifluidic chip and smaller PLGA nanoparticles made by a batch method. Results indicated that all PLGA nanoparticles studied, independent of the synthesis method and size, adhered to the surface of RBCs but had no significant hemolytic effect at concentrations lower than 10 mg/ml.

Libi, Sumit↗
DOE OSTI2025

Research progress on organic acid pretreatment of lignocellulose

Lignocellulosic biomass is a naturally occurring, renewable resource that is utilized to produce a variety of high–value-added products, such as fuels, acids, and building block chemicals. The pretreatment of lignocellulosic biomass is a crucial step in the deconstruction and fractionation of its components. Organic acids, such as formic, acetic, lactic, and maleic acids, have been widely studied for their effectiveness in lignocellulose pretreatment. Organic acid–based pretreatment techniques are gaining increased attention due to their ability to selectively separate hemicellulose and cellulose, promote oligomer formation, and minimize byproducts. This paper presents a comprehensive review of the various advancements in the science and application of organic acids for the pretreatment of lignocellulose. Furthermore, the significant challenges of organic acid recovery after pretreatment are highlighted, and different recovery methods are discussed. In conclusion, the future challenges related to utilizing organic acids for lignocellulose pretreatment are summarized, with a strong emphasis on adopting a sustainable approach to converting valuable bioresources into renewable products.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

The Effect of Cofed Species on the Kinetics of Catalytic Methyl Lactate Dehydration on NaY

The catalytic dehydration of biomass-derived methyl lactate to acrylic acid is a renewable route to a high-value, high-volume monomer, but achieving high selectivity and production rates remains challenging. One roadblock is that the role of the species cofed with methyl lactate, typically water, in the dehydration mechanism over alkali-metal-exchanged zeolites remains unclear. Here, we determined the effects of protic and aprotic cofed species, including water, methanol, and methyl acetate, on the rate and selectivity of methyl lactate dehydration over NaY via kinetic and spectroscopic investigations. We show that water plays multiple competing roles in the mechanism: (1) generating the unselective Brønsted acid sites on NaY leading to acetaldehyde and coke formation; (2) suppressing the activity of the Lewis acid sites responsible for lactate dehydration; and (3) facilitating the displacement of adsorbed sodium acrylate by lactate, leading to the formation of acrylic acid. The first process increases the rate of side product formation, while the second and third processes decrease and increase the dehydration rate, respectively. As a result of these competing roles, the rate-limiting step of methyl lactate dehydration shifts from acrylate product recovery to sodium lactate dehydration as the concentration of water increases.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Identification of a selective inhibitor of human monocarboxylate transporter 4

Highlights: • hMCT4 transporter mediates the transport of metabolites such as l-lactate and pyruvate. • 5-ETZ, a bioisostere of propionate, is recognized by hMCT1 and hMCT4. • Fibrates, a group of isobutyrate derivatives, selectively inhibit hMCT4. • Bindarit might be the first-identified potent and selective inhibitor of hMCT4. The human monocarboxylate transporters (hMCTs/SLC16As) mediate the uptake of various monocarboxylates. Several isoforms of hMCTs are expressed in cancerous tissue as well as in normal tissue. In cancerous tissue, hypoxia induces the expression of hMCT4, which transports the energetic metabolite l-lactate across the plasma membrane. Since hMCT4 is involved in pH regulation and the transport of l-lactate in cancer cells, an hMCT4 inhibitor could function as an anticancer agent. Although several non specific hMCT inhibitors have been developed, a selective hMCT4 inhibitor has not yet been identified. The aim of this study was therefore to identify a selective hMCT4 inhibitor for use as a pharmacological tool for studying hMCT4. The heterologous expression system of the Xenopus oocyte was used to assess the effects of test compounds on hMCT4, whereupon isobutyrate derivatives, fibrates, and bindarit (2-[(1-benzyl-1H-indazol-3-yl)methoxy]-2-methylpropanoic acid) were demonstrated to exhibit selective inhibitory effects against this transporter. It is suggested that the structure formed from the joining of an isobutyrate moiety and two aromatic rings by appropriate linkers is important for acquiring the selective hMCT4-inhibiting activity. These findings provide novel insights into the ligand recognition of hMCT4, and contribute to the development of novel anticancer agents.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Enterococcus faecalis lipoteichoic acid regulates macrophages autophagy via PI3K/Akt/mTOR pathway

Highlights: • We established RAW264.7 expressing mRFP-GFP-LC3 to observe autophagy. • Our data shown Enterococcus faecalis LTA activates macrophage autophagy via PI3K/Akt/mTOR pathway. • Beclin1 is necessary in LTA-stimulated autophagy of macrophage. Enterococcus faecalis (E. faecalis) infection is considered an important etiological factor for the development of persistent apical periodontitis (PAP), but the exact mechanisms of autophagy between E. faecalis and immune cells remain unknown. In this study, we elucidated how E. faecalis lipoteichoic acid (LTA) is associated with macrophages autophagy. We found that E. faecalis LTA apparently activated macrophage autophagy with significant increase of autophagosomes and autophagy relative protein. Meanwhile, we noticed significantly decreasing expression of p-Akt and p-mTOR. However, these effect were absent in macrophages knockdown of Beclin1. In summary, these findings suggested E. faecalis LTA may increased macrophages autophagy via inhibiting PI3K/Akt/mTOR pathway and this process was Beclin1 dependent.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

N-Silylated Benzothiazolium Dye as a Coupling Agent for Polylactic Acid/Date Palm Fiber Bio-composites

This work proposes a benzothiazole derivative bearing a silane moiety as a new coupling agent for polylactic acid (PLA) reinforced by date palm fibers (DPFs). The bio-composites are prepared by solution blending followed by melt compounding. From the samples produced, a complete characterization is performed including morphological, mechanical and thermal properties as a function of fiber content. The results show that the proposed fiber treatment is an easy and effective method to improve the interfacial properties and fiber dispersion leading to better material performance. For example, the addition of only 1 wt% of the dye–IPTMS to the bleached DPF not only improved the thermal stability of the biocomposites, but also led to a significant increase of the Young’s modulus at 7 wt% and higher torsion modulus up to 5 wt% (optimum value).

36 MATERIALS SCIENCE↗
DOE OSTI2014

The chemistry of TALSPEAK: A review of the science

Here, the TALSPEAK Process (Trivalent Actinide Lanthanide Separation with Phosphorus-reagent Extraction from Aqueous Komplexes) was originally developed at Oak Ridge National Laboratory by B. Weaver and F.A. Kappelmann in the 1960s. It was envisioned initially as an alternative to the TRAMEX process (selective extraction of trivalent actinides by tertiary or quaternary amines over fission product lanthanides from concentrated LiCl solutions). TALSPEAK proposed the selective extraction of trivalent lanthanides away from the actinides, which are retained in the aqueous phase as aminopolycarboxylate complexes. After several decades of research and development, the conventional TALSPEAK process (based on di-(2-ethylhexyl) phosphoric acid (extractant) in 1,4-di-isopropylbenzene (diluent) and a concentrated lactate buffer containing diethylenetriamine-N,N,N',N",N"-pentaacetic acid (actinide-selective holdback reagent)) has become a widely recognized benchmark for advanced aqueous partitioning of the trivalent 4f/5f elements. TALSPEAK chemistry has also been utilized as an actinide-selective stripping agent (Reverse TALSPEAK) with some notable success. Under ideal conditions, conventional TALSPEAK separates Am 3+ from Nd 3+ (the usual limiting pair) with a single-stage separation factor of about 100; both lighter and heavier lanthanides are more completely separated from Am 3+ . Despite this apparent efficiency, TALSPEAK has not seen enthusiastic adoption for advanced partitioning of nuclear fuels at process scale for two principle reasons: 1) all adaptations of TALSPEAK chemistry to process scale applications require rigid pH control within a narrow range of pH, and 2) phase transfer kinetics are often slower than ideal. To compensate for these effects, high concentrations of the buffer (0.5-2 M H/Na lactate) are required. Acknowledgement of these complications in TALSPEAK process development has inspired significant research activities dedicated to improving understanding of the basic chemistry that controls TALSPEAK (and related processes based on the application of actinide-selective holdback reagents). In the following report, advances in understanding of the fundamental chemistry of TALSPEAK that have occurred during the past decade will be reviewed and discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Lactiplantibacillus plantarum uses ecologically relevant, exogenous quinones for extracellular electron transfer

Extracellular electron transfer (EET) is a metabolic process that frequently uses quinones to couple intracellular redox reactions with extracellular electron acceptors. The physiological relevance of this metabolism for microorganisms capable of EET but unable to synthesize their own quinones remains to be determined. To address this question, we investigated quinone utilization by Lactiplantibacillus plantarum, a microorganism required for food fermentations, that performs EET and is also a quinone auxotroph. L. plantarum selectively used 1,4-dihydroxy-2-naphthoic acid (DHNA) and more hydrophilic naphthoquinones for EET reduction of insoluble iron (ferrihydrite). However, quinones used for EET also inhibited L. plantarum growth in non-aerated conditions. Transcriptomic analysis showed that DHNA-induced oxidative stress in L. plantarum, but this was alleviated when the electron acceptor, ferric ammonium citrate (FeAC), was included in the growth medium. Although DHNA and FeAC induced L. plantarum EET, this metabolism was still dependent on direct access to environmental electron shuttles. To determine whether quinone-producing food fermentation bacteria could be sources of those electron shuttles, L. plantarum EET was measured after incubation with Lactococcus lactis and Leuconostoc mesenteroides. Quinone-producing L. lactis, but not a quinone-deficient L. lactis ΔmenC mutant, increased L. plantarum ferrihydrite reduction and medium acidification through an EET-dependent mechanism. L. plantarum EET was also stimulated by L. mesenteroides, resulting in greater environmental acidification and transient increases in L. plantarum cell numbers. Our findings show that L. plantarum overcomes the toxic effects of exogenous quinones to use those compounds for EET-conferred, ecological advantages during the early stages of food fermentations.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Blending Novatein{sup ®} thermoplastic protein with PLA for carbon dioxide assisted batch foaming

The convenience of polymeric foams has led to their widespread utilisation in everyday life. However, disposal of synthetic petroleum-derived foams has had a detrimental effect on the environment which needs to be addressed. This study uses a clean and sustainable approach to investigate the foaming capability of a blend of two biodegradable polymers, polylactic acid (PLA) and Novatein® Thermoplastic Protein (NTP). PLA, derived from corn starch, can successfully be foamed using a batch technique developed by the Biopolymer Network Ltd. NTP is a patented formulation of bloodmeal and chemical additives which can be extruded and injection moulded similar to other thermoplastics. However, foaming NTP is a new area of study and its interaction with blowing agents in the batch process is entirely unknown. Subcritical and supercritical carbon dioxide have been examined individually in two uniquely designed pressure vessels to foam various compositions of NTP-PLA blends. Foamed material were characterised in terms of expansion ratio, cell size, and cellular morphology in order to study how the composition of NTP-PLA affects foaming with carbon dioxide. It was found that blends with 5 wt. % NTP foamed using subcritical CO{sub 2} expanded up to 11 times due to heterogeneous nucleation. Morphology analysis using scanning electron microscopy showed that foams blown with supercritical CO{sub 2} had a finer cell structure with consistent cell size, whereas, foams blown with subcritical CO{sub 2} ranged in cell size and showed cell wall rupture. Ultimately, this research would contribute to the production of a biodegradable foam material to be used in packaging applications, thereby adding to the application potential of NTP.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Conductivity of PEO/PLA Doped Liquid Crystal Ionomer Solid Polymer Electrolyte in Mesomorphic Range

A novel polyethylene oxide (PEO)/polylactic acid (PLA) solid polymer electrolyte (SPE) doped with Liquid crystal ionomer (LCI) was prepared by automatic scraping membrane technology and the liquid crystal property of LCI was proposed as an effective strategy to improve the conductivity. The highest conductivity of the SPE with 0.5 wt% LCI achieve a value of 2.19 × 10{sup −4} S/cm at 17 °C which is approximately four orders of magnitude higher than that of the original PEO solid polymer electrolyte, conductivity at room temperature is 10{sup −7}–10{sup −8} S/cm. This is because the crystallinity is reduced by 25.3% compared to the pure PEO host. Differential Scanning Calorimetry (DSC) and polarizing microscope (POM) characterize the structure and properties of LCI. Electrochemical Impedance Spectroscopy (EIS) shows that the conductivity of the polymer electrolyte with 0.5 wt% LCI increased abruptly at 35 °C as the temperature is higher than T{sub g} of LCI, reaching 6.37 × 10{sup −4} S/cm which is 191% higher than that at 17 °C. There ionic conductivity has been improved extremely by continuous channel for efficient ion transportation, especially at the microtherm. And this change is greater at the elevated temperature regions, in line with the VTF equation. In summary, LCI’s liquid crystal performance can be used as an effective strategy to improve the low temperature conductivity of SPE.

36 MATERIALS SCIENCE↗