disentangling-high-strength-copolymer-aramid-fibers-to-enable

Disentangling High Strength Copolymer Aramid Fibers to Enable the Determination of Their Mechanical Properties

Traditionally, soft body armor has been made from poly(p-phenylene terephthalamide) (PPTA) and ultra-high molecular weight polyethylene. However, to ...

solution-blow-spinning-polymeric-nano-composite-fibers-for-personal

Solution Blow Spinning of Polymeric Nano-Composite Fibers for Personal Protective Equipment

Light-weight, protective armor systems typically consist of high modulus (&#62;109 MPa) and high-strength polymeric fibers held in place with an elastic ...

a-synthetic-methodology-for-preparing-impregnated-grafted-amine-based

A Synthetic Methodology for Preparing Impregnated and Grafted Amine-Based Silica Composites for Carbon Capture

Recently, there has been a significant effort towards reducing or mitigating CO2 emissions through the use of carbon capture materials for point source or ...

University of Maryland

Material Measurement Laboratory, National Institute of Standards and Technology

Theiss Research

National Institute of Standards and Technology (NIST)

In vitro and in vivo experimentation of various synthetic polymer hydrogels was conducted to establish some of the integral material properties that influence hemostasis. In vitro swelling experiments suggested that positive electrostatic charge was a key determinant of the ability of a polymer hydrogel to absorb physiological fluids, e.g. human plasma and blood. In vitro testing using unadulterated sheep blood suggested positive electrostatic charge and crosslink density were key determinants of the ability of a material to induce or enhance clot formation. Hydrogel formulations composed of higher amounts of positive electrostatic charge and lower crosslink density were able to effectively induce and enhance clot formation in the presence of a coagulation cascade activator. In vivo experimentation confirmed that hydrogels containing higher electrostatic charge and low crosslink density are more effective at fostering the formation of a robust hemostatic plug to control blood loss.

In vitro and in vivo evaluation of polymer hydrogels for hemorrhage control.

Designing of drug nanocarriers to aid delivery of therapeutics is an expanding field that can improve medical treatments. Nanocarriers are often functionalized with elements that recognize cell-surface molecules involved in subcellular transport to improve targeting and endocytosis of therapeutics. Combination-targeting using several affinity elements further modulates this outcome. The most studied example is endothelial targeting via multiple cell adhesion molecules (CAMs), which mimics the strategy of leukocytes to adhere and traverse the vascular endothelium. Yet, the implications of this strategy on intracellular transport and in vivo biodistribution remain uncharacterized. We examined this using nanocarriers functionalized for dual- or triple-targeting to intercellular, platelet-endothelial, and/or vascular CAMs (ICAM-1, PECAM-1, VCAM-1). These molecules differ in expression level, location, pathological stimulation, and/or endocytic pathway. In endothelial cells, binding of PECAM-1/VCAM-1-targeted nanocarriers was intermediate to single-targeted counterparts and enhanced in disease-like conditions. ICAM-1/PECAM-1-targeted nanocarriers surpassed PECAM-1/VCAM-1 in control, but showed lower selectivity toward disease-like conditions. Triple-targeting resulted in binding similar to ICAM-1/PECAM-1 combination and displayed the highest selectivity in disease-like conditions. All combinations were effectively internalized by the cells, with slightly better performance when targeting receptors of different endocytic pathways. In vivo, ICAM-1/PECAM-1-targeted nanocarriers outperformed PECAM-1/VCAM-1 in control and disease-like conditions, and triple-targeted counterparts slightly enhanced this outcome in some organs. As a result, delivery of a model therapeutic cargo (acid sphingomyelinase, deficient in Niemann-Pick disease A-B) was enhanced to all affected organs by triple-targeted nanocarriers, particularly in disease-like conditions. Therefore, multi-CAM targeting may aid the optimization of some therapeutic nanocarriers, where the combination and multiplicity of the affinity moieties utilized allow modulation of targeting performance. 

Combination-targeting to multiple endothelial cell adhesion molecules modulates binding, endocytosis, and in vivo biodistribution of drug nanocarriers and their therapeutic cargoes.

Nanocarriers (NCs) help improve the performance of therapeutics, but their removal by phagocytes in the liver, spleen, tissues, etc. diminishes this potential. Although NC functionalization with polyethylene glycol (PEG) lowers interaction with phagocytes, it also reduces interactions with tissue cells. Coating NCs with CD47, a protein expressed by body cells to avoid phagocytic removal, offers an alternative. Previous studies showed that coating CD47 on non-targeted NCs reduces phagocytosis, but whether this alters binding and endocytosis of actively-targeted NCs remains unknown. To evaluate this, we used polymer NCs targeted to ICAM-1, a receptor overexpressed in many diseases. Co-coating of CD47 on anti-ICAM NCs reduced macrophage phagocytosis by ∼50% for up to 24 h, while increasing endothelial-cell targeting by ∼87% over control anti-ICAM/IgG NCs. Anti-ICAM/CD47 NCs were endocytosed via the CAM-mediated pathway with efficiency similar (0.99-fold) to anti-ICAM/IgG NCs. Comparable outcomes were observed for NCs targeted to PECAM-1 or transferrin receptor, suggesting broad applicability. When injected in mice, anti-ICAM/CD47 NCs reduced liver and spleen uptake by ∼30-50% and increased lung targeting by ∼2-fold (∼10-fold over IgG NCs). Therefore, co-coating NCs with CD47 and targeting moieties reduces macrophage phagocytosis and improves targeted uptake. This strategy may significantly improve the efficacy of targeted drug NCs.

Co-coating of receptor-targeted drug nanocarriers with anti-phagocytic moieties enhances specific tissue uptake versus non-specific phagocytic clearance.

We have developed novel photopolymer gels to function as separators in blood collection tubes. By incorporating antioxidants such as α-tocopherol and nitroxides (TEMPO and TEMPOL), the new formulation can be sterilized with electron beam or gamma rays at a dose level of 17 kGy, without inducing premature curing of the photopolymers. For the blood separator gels that contain α-tocopherol, our results show that α-tocopherol plays a decisive role in impeding C-centered free radical propagation reactions through an Htransfer mechanism. This mechanism involves the transfer of an H-atom from the hydroxyl group (OH) of α-tocopherol to the propagating C-centered radical leading to the termination of the polymerization. The sterilization radiation-induced premature curing of the photopolymer was also prevented in the blood separator gel containing nitroxides. For the gels containing TEMPO or TEMPOL, inhibition of the premature curing was achieved through an addition reaction or an H-transfer reaction, respectively. Our results also show that while α-tocopherol is not a contributing factor in the subsequent (time-of-use) UV curing of the gels, nitroxides enhance the UV curing process through nitroxide-mediated living free radical polymerization reactions leading to a decrease in UV curing time. The photopolymer separator gels are shown to function advantageously in clinical laboratory testing, especially for cell-free DNA measurements in blood.

Sterilizing photocurable materials by irradiation: preserving UV-curing properties of photopolymers following E-beam, gamma, or X-ray exposure.

Nanocellulose is a high value material that has gained increasing attention because of its high strength, stiffness, unique photonic and piezoelectric properties, high stability and uniform structure. Through utilization of a biorefinery concept, nanocellulose can be produced in large volumes from wood at relatively low cost via ionizing radiation processing. Ionizing radiation causes significant break down of the polysaccharide and leads to the production of potentially useful gaseous products such as H and CO. The application of radiation processing to the production of nanocellulose from woody and non-wood sources, such as field grasses, bio-refining byproducts, industrial pulp waste, and agricultural surplus materials remains an open field, ripe for innovation and application. Elucidating the mechanisms of the radiolytic decomposition of cellulose and the mass generation of nanocellulose by radiation processing is key to tapping into this source of nanocelluose for the growth of nanocellulostic-product development. More importantly, understanding the structural break-up of the cell walls as a function of radiation exposure is a key goal and only through careful, detailed characterization and dimensional metrology can this be achieved at the level of detail that is needed to further the growth of large scale radiation processing of plant materials. This work is resulting from strong collaborations between NIST and its academic partners who are pursuing the unique demonstration of applied ionizing radiation processing to plant materials as well as the development of manufacturing metrology for novel nanomaterials.

Ionizing radiation processing and its potential in advancing biorefining and nanocellulose composite materials manufacturing.

In order to test the effectiveness of oxalate-based polymeric adsorbents in the recovery of uranium from seawater, diallyl oxalate (DAOx) was grafted onto nylon 6 fabrics by exposing the fabric, immersed in pure liquid DAOx or in a surfactant-stabilized dispersion of DAOx in water, to electron beam or gamma radiation. Following drying and weighing to determine the degree of grafting (DoG), the presence of oxalate in the fabrics was verified using XPS. Zeta potential measurements showed the fabric surfaces to be negatively charged. The fabrics were tested by rotating them for 7 days in a rotary agitator with actual seawater spiked with 0.2 or 1.0 mg∙L uranium. The fraction of uranium in the solution which was removed due to uptake on the fabrics was found to rise with increasing DoG at both uranium concentrations. EDS measurements were used to map the distribution of adsorbed uranium on the polymeric fibers.

Uranium removal from seawater by means of polymeric fabrics grafted with diallyl oxalate through a single-step, solvent-free process.

This work demonstrates the synergy between the thermo-mechanical and humidity induced degradation as well as the oxidation reactions in the kink-banded areas of ultra-high molar mass polyethylene (UHMMPE) fiber-based laminates used in body armor. For aged materials, the energy-dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) results reveal high concentrations of oxygen containing products, and the EPR results demonstrate the presence of the peroxyl radicals (RO ) in the kink-banded areas. After one year of dark ambient storage, very long-lived RO radicals were observed primarily in the samples exposed to ageing conditions of elevated temperatures, humidity, and mechanical stress. The total percentage of crystallinity, as measured by differential scanning calorimetry, of the kinkbanded fibers was unchanged, indicating that the degradation occurs primarily in the amorphous region, and may also involve recrystallization processes of the degraded chains. However, the most abundant orthorhombic crystalline phase decreases from 77 % to 70 %. This decrease in the orthorhombic structure leads to more diffusion of oxygen into the kink-banded region, enhancing the oxidation processes. No changes are observed in the monoclinic phase of the kinked fibers, which remained constant and constituted ~2 % of the total crystallinity.

Oxidation Reactions in Kink Banded Regions of UHMMPE Fiber-Based Laminates Used in Body Armor: A Mechanistic Study.

To improve properties such as thermal conductivity, low temperature thermal strain, and creep resistance of ultra-high molar mass polyethylene (UHMMPE) fibers, several researchers have previously undertaken efforts to crosslink these fibers using radiation. Ionizing radiation is commonly used to crosslink bulk UHMMPE in other applications, such as artificial joints. However, UHMMPE fibers differ from bulk UHMMPE in that they have a higher crystallinity (approximately 85% to 90%) and are very highly oriented during manufacturing in which the fibers are stretched 50 to 100 times their original length. Thus, the amorphous fraction of the UHMMPE fibers is also highly ordered. Several experiments were conducted to crosslink the UHMMPE fibers using both low dose rate (gamma) and high dose rate (electron beam) irradiation, all in the absence of oxygen. In all cases, the tensile strength of the fiber was greatly reduced by the irradiation. The oxidation index was also measured for the irradiated samples, and oxidation was not found to play a major role in the reduction of tensile strength in the fibers after irradiation. While this work did not achieve the desired result of improving the mechanical properties of the UHMMPE fiber, a significant result was found. The electron paramagnetic resonance (EPR) spectrum of the UHMMPE fibers was measured shortly after irradiation, and a mixture of allyl and alkyl radicals were detected. The irradiated samples were stored in dark ambient conditions for at least six years, then reexamined using EPR for free radical characterization. Surprisingly, the gamma-irradiated samples showed clear evidence of long-lived polyenyl radicals present in the material. Free radicals are very reactive species that will typically migrate to the surface of the crystalline domain and decay in a relatively short time through various reactions in the amorphous regions. It is hypothesized herein that due to the high crystallinity and large anisotropy of the highly drawn UHMMPE fiber, the polyenyl radicals were trapped in the crystal phase and were unable to migrate and decay. An experiment was performed to test this hypothesis, by which samples of the irradiated fibers were heated to temperatures above first the alpha relaxation and then melting point of polyethylene, and EPR measurements were taken. Results showed that the polyenyl radical signal persisted below the , but was rapidly eliminated upon melting of the crystals. These experiments support the hypothesis that the long-lived polyenyl radicals are trapped in the crystalline region of the polyethylene fibers.

Effect of Irradiation and Detection of Long-Lived Polyenyl Radicals in Highly Crystalline Ultra-High Molar Mass Polyethylene (UHMMPE) Fibers.

The construction of ballistic-resistant body armor is experiencing an increasing use of flexible unidirectional (UD) composite laminates that comprise multiple layers. Each UD layer contains hexagonally packed high-performance fibers with a very low modulus matrix (sometimes referred to as binder resins). Laminates are then made from orthogonal stacks of these layers, and these laminate-based armor packages offer significant performance advantages over standard woven materials. When designing any armor system, the long-term reliability of the armor materials is critical, particularly with regard to stability with exposure to temperature and humidity, as these are known causes of degradation in commonly used body armor materials. To better inform future armor designers, this work investigates the tensile behavior of an ultra-high molar mass polyethylene (UHMMPE) flexible UD laminate that was aged for at least 350 d at two accelerated conditions: 70 °C at 76% relative humidity (RH) and 70 °C in a desiccator. Tensile tests were performed at two different loading rates. The mechanical properties of the material after ageing demonstrated less than 10% degradation in tensile strength, indicating high reliability for armor made from this material.

ArticleTotal : 3	Year
Publication title Cited by 4	2018
Publication title Cited by 5	2021
Publication title Cited by 5	2023

Article	Year
In vitro and in vivo evaluation of polymer hydrogels for hemorrhage control. Journal of biomaterials science. Polymer edition\| PubMed ID: 23742132	2013
Combination-targeting to multiple endothelial cell adhesion molecules modulates binding, endocytosis, and in vivo biodistribution of drug nanocarriers and their therapeutic cargoes. Journal of controlled release : official journal of the Controlled Release Society\| PubMed ID: 24933603	2014
Co-coating of receptor-targeted drug nanocarriers with anti-phagocytic moieties enhances specific tissue uptake versus non-specific phagocytic clearance. Biomaterials\| PubMed ID: 28923682	2017
Sterilizing photocurable materials by irradiation: preserving UV-curing properties of photopolymers following E-beam, gamma, or X-ray exposure. Journal of materials science. Materials in medicine\| PubMed ID: 29039618	2017
Ionizing radiation processing and its potential in advancing biorefining and nanocellulose composite materials manufacturing. Radiation physics and chemistry (Oxford, England : 1993)\| PubMed ID: 29230084	2018
Uranium removal from seawater by means of polymeric fabrics grafted with diallyl oxalate through a single-step, solvent-free process. Industrial & engineering chemistry research\| PubMed ID: 29720786	2016
Oxidation Reactions in Kink Banded Regions of UHMMPE Fiber-Based Laminates Used in Body Armor: A Mechanistic Study. Polymer degradation and stability\| PubMed ID: 30996496	2018
Effect of Irradiation and Detection of Long-Lived Polyenyl Radicals in Highly Crystalline Ultra-High Molar Mass Polyethylene (UHMMPE) Fibers. Polymers\| PubMed ID: 31137768	2019
Effect of Aging on Unidirectional Composite Laminate Polyethylene for Body Armor. Polymers\| PubMed ID: 36987127	2023

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