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A semi-automatic image analysis program, SMART, was used to analyze transmission electron microscopy (TEM) images from four laboratories that participated in an interlaboratory comparison study by Meija et al. on CNC particle size measurement by TEM using conventional manual image analysis approaches. Detailed image-to-image comparisons found that the percentage of “correctly” identified CNCs by SMART was 58% to 78%, while manual was 70% to 87%, depending on TEM image quality from a given laboratory. SMART was able to parameterize image quality, and it was found that SMART had difficulties in CNC identification for images with a combination of higher noise, lower contrast, and higher CNC density. Overall, the SMART image analysis was consistent with the manual approach. SMART showed lower laboratory-laboratory variation as compared to manual, suggesting that the variability of analyst bias of manual approach was removed and demonstrates an opportunity with SMART to improve the standardization of CNC size characterization. An approach to estimate the likelihood of reaching a representative measurement for CNC particle size was developed. SMART area analysis found that less than 10% of CNCs were used in morphology characterization; to assess more CNC material, SMART was used to analyze CNC agglomerates as a proof-of-concept demonstration. The total SMART image analysis time for each laboratory, having between 115 and 244 images, was less than 15 min, after selection of appropriate parameters. The SMART code is now available for the public to use for free at Github™.

Pulp fibre as reinforcement in non-structural building material, such as fibre cement, could be a forerunner in mitigating the carbon dioxide (CO2) footprint of cement-based residential and commercial structures. However, one of the major bottlenecks in increasing the content of reinforcement in fibre cement has been their poor chemical stability in the strongly alkaline cement matrix. To date, probing the health of pulp fibre-cement is a lengthy and laborious process, requiring mechanical and chemical separations. In this study, we have demonstrated that it is possible to understand more of the chemical interactions at the fibre-cement interfaces by probing lignin, which could act as the indicator of the severity of the cement matrix’s alkalinity. Multidimensional fluorometry is shown here for the first time to be a highly sensitive and versatile platform technology to understand the lignin degradation in fibre cement.

Utilizing a novel processing method of PEEK foam that produces hierarchical mesoporosity, we explore the use of hydroxyapatite (HA)/PEEK composites for mimicking the structure of human bone. The effect of HA content and processing parameters on the porosity, and interconnective network are studied with respect to the corresponding morphology, mechanical properties, and ultimately the cell viability. Having achieved hierarchical structuration with pore sizes ranging from approx. a hundred nanometers all the way to a few hundred microns, the HA/PEEK composites produced desirable mechanical properties and promising cell proliferation. A strong correlation was not seen with HA loading and the resulting properties, but a combination of the HA loading and variance in porosity is shown to be significant. The development and analysis of this bone mimic structure opens up the potential for this processing method and material as a treatment to bone injuries and bone diseases.

Properties of cellulose nanocrystals (CNCs) depend upon their supramolecular structures, which are important to understand in order to optimize their applications. In this investigation, the structures of CNCs produced upon 48–64% H2SO4 hydrolysis of hydrothermally-treated poplar, bleached kraft pulp, cotton microcrystalline cellulose, bacterial cellulose, tunicin, and cladophora cellulose were comparatively analyzed. TEM provided information on the morphological aspects. Raman, MAS-NMR, and XRD provided information on one aspect of the supramolecular organization, namely, crystallinity (CrI). Other characteristics of supramolecular structure were analyzed by various Raman methods, namely, accessibility to water, exocyclic CH2OH conformation ratio, and chain conformation disorder (CCONDIS)—the last method was developed in the present study. In general, CNCs retained the crystallinity of the starting material irrespective of the measurement method of CrI. Additionally, it was found that crystallite size and supramolecular organization influenced CrI as well. These analyses further indicated that poplar- and pulp-CNCs had significantly higher water accessibility as compared with CNCs from cladophora, bacterial, tunicin, and cotton MCC CNCs, implying higher molecular disorder, which was also reflected in measurements of CH2OH conformation ratio and CCONDIS. The findings indicate that significant differences among the CNCs seem to arise largely from differences between the starting materials. Additionally, considering that CNCs can have very different morphologies and structural properties depending upon how they are produced, the analyses carried out here can characterize such CNCs and estimate their applications.

Polymers that can be repaired after being damaged are attractive, because this feature can improve the reliability, functionality, and lifetime of these materials. We report here light-healable nanocomposites based on a telechelic poly(ethylene-co-butylene) that was functionalized with hydrogen-bonding ureidopyrimidone (UPy) and cellulose nanocrystals (CNCs) decorated with the same binding motif. These nanocomposites show significantly improved mechanical properties when compared to the supramolecular polymer alone. When these materials are exposed to ultraviolet radiation, the UPy motifs are excited and the absorbed energy is converted into heat. This causes temporary disengagement of the hydrogen-bonding motifs, concomitant with a reversible decrease of the supramolecular polymers’ molecular weight and viscosity. As a result, deliberately introduced defects can be healed quickly and efficiently, even at a filler content of 20% w/w, that is, in compositions that exhibit high strength and stiffness.

Carbonated hydroxyapatite (CHAp) adsorbent material was prepared from Achatina achatina snail shells and phosphate-containing solution using a wet chemical deposition method. The CHAp adsorbent material was investigated to adsorb aqua Fe(II) complex; [Fe(H2O)6]2+ from simulated iron contaminated water for potential iron remediation application. The CHAp was characterized before and after adsorption using infrared (IR) and Raman spectroscopy. The IR and the Raman data revealed that the carbonate functional groups of the CHAp adsorbent material through asymmetric orientation in water bonded strongly to the aqua Fe(II) complex adsorbate. The adsorption behaviour of the adsorbate onto the CHAp adsorbent correlated well to pseudo-second-order kinetics model, non-linear Langmuir and Freundlich model at room temperature of a concentration (20–100 mg L−1) and contact time of 180 min. The Langmuir model estimated the maximum adsorption capacity to be 45.87 mg g−1 whereas Freundlich model indicated an S-type isotherm curvature which supported the spectroscopy revelation.

This work reports on the use of low-cost pineapple leaf fiber (PALF) as an alternative reinforcing material to the established, commonly used material for prosthetic socket fabrication which is carbon-fiber-reinforced composite (CFRC) due to the high strength and stiffness of carbon fiber. However, the low range of loads exerted on a typical prosthetic socket (PS) in practice suggests that the use of CFRC may not be appropriate because of the high material stiffness which can be detrimental to socket-limb load transfer. Additionally, the high cost of carbon fiber avails opportunities to look for an alternative material as a reinforcement for composite PS development. PALF/Methyl Methacrylate-based (MMA) composites with 0°, 45° and 90° fiber orientations were made with 5–50 v/v fiber volume fractions. The PALF/MMA composites were subjected to a three-point flexural test to determine the effect of fiber volume fraction and fiber orientation on the flexural properties of the composite. The results showed that 40% v/v PALF/MMA composite with 0° fiber orientation recorded the highest flexural strength (50 MPa) and stiffness (1692 MPa). Considering the average load range exerted on PS, the flexural performance of the novel composite characterized in this work could be suitable for socket-limb load transfer for PS fabrication.

This study analyzes and evaluates the use of cellulose nanocrystals (CNCs), stiff nanosized natural materials that have been modified to mimic heparin. These CNCs are simple polysaccharides with a similar backbone structure to heparin, which when modified reduces coagulation and potentially the long-term effects of solution-based anticoagulants. Thus, CNCs represent an ideal foundation for generating materials biocompatible with blood. In this study, we developed a biocompatible material that inhibits blood clotting through surface functionalization to mimic heparin. Surface chemistry of CNCs was modified from "plain" CNCs (70 mmol SO3-/kg) to 500 mmol COO-/kg (TEMPO-oxidized CNCs) and 330 mmol SO3-/kg CNCs (sulfonated CNCs). Platelet adherence and blood assays show that changes in functionalization reduce coagulation. By utilizing and modifying CNCs reactive functional groups, we create a material with unique and favorable mechanical properties while also reducing clotting.

In this work, photosensitive alginate and cellulose-based hydrogels with interpenetrating polymer networks were successfully prepared from alginate, TEMPO-oxidized cellulose nanofibers (TEMPO-CNFs) and polyacrylamide, crosslinked by both Fe3+ and N,N′-methylenebis-acrylamide. The obtained hydrogels showed a clear relationship between the mechanical properties and the content of the TEMPO-CNFs. The results indicated that the mechanical properties of crosslinked hydrogels were enhanced with the mass ratio of TEMPO-CNFs and alginate increased from 1/2 to 2. Moreover, the crosslinked ionic alginate and cellulose-based hydrogels with various TEMPO-CNFs contents exhibited an interconnected porous morphology with an average pore size of ca. 130 µm, and demonstrated an increased cumulative release amount of BSA drugs under the ultraviolet irradiation. This study demonstrated that the as-prepared photoresponsive hydrogels would have a potential application as local drug release systems for wound dressings.

We demonstrate the reinforcement of a previously inaccessible norbornene-silane with a stiff, bio-based nanofiller. Poly(5-triethoxysilyl-2-norbornene) (PTESN), a glassy and thermally stable polymer, was combined with cellulose nanocrystals (CNCs) and solvent cast from toluene to form reinforced materials. Composite films showed excellent translucency and no visible aggregation, which was supported by scanning electron micrographs that showed no signs of CNC aggregation within the polymer matrix. Reinforcement was evident at the moderate loading of 5 wt% CNC, showing a statistically significant enhancement for Young's modulus and even greater reinforcement for 20 wt% CNC loading for Young's modulus (540 MPa vs. 970 MPa) and storage modulus at 25 °C (400 MPa vs. 1200 MPa). We suspect that there is a strong interaction between the polymer and CNC filler based upon the increase of thermal degradation temperature of the CNCs increasing, for example from 278 °C to 295 °C at 10 wt% CNCs. These interactions were probed via solid-state NMR, which suggests that no covalent bonding occurs between the triethoxylsilyl substituents of the polymer and the CNCs. We therefore hypothesize that hydrogen bonding interactions between PTESN and CNCs are responsible for the increased thermal stability and reinforcement of the polymer material.

Understanding the crystallization kinetics and microstructure that result after an imposed shear flow in an additive-containing polymeric system is imperative for the development of robust polymer composites suitable for advanced engineering applications. Both nucleating agents and flow accelerate the crystallization kinetics as well as alter the ultimate polymer microstructure. During melt processing, polymers are subject to shear flow prior to the solidification of the melt. As an unsheared baseline in this study, the addition of 5 wt % cellulose nanocrystals (CNC) into quiescent polyamide 12 (PA 12) revealed that CNCs act as a natural nucleating agent to the quiescent PA 12 during slow cooling and at high temperatures, as measured by standard differential scanning calorimetry. To evaluate the role of shear work in promoting flow-induced crystallization, both neat and PA 12/CNC composite were subjected to known amounts of shear work. Then fast scanning calorimetry was used to differentiate the nucleation activity from both flow-induced precursors and CNC particles during isothermal crystallization across a wide temperature range. It was found that the addition of the CNC accelerated crystallization in the heterogeneous nucleation regime (T > 100 °C) in the quiescent material. With the addition of shear, the neat system displayed a reduced crystallization peak time with increasing shear history. In the nanocomposite system, the CNCs are an extremely efficient nucleating agent, achieving a saturating limit for nucleation of crystallization, such that shear was only a factor at low supercooling, specifically at temperatures greater than 140 °C.

We introduce a novel method of solvent exchanges and drying poly(ether ether ketone) (PEEK) that result in a hierarchical nanoporous structure. Traditional processing of porous PEEK typically consists of dry mixing with salt beads as porogens and compression molding or employing drying methods of solvent casted PEEK such as freeze-drying or supercritical drying. These processes however come with their drawbacks of either being too expensive or not supporting the porous network throughout the drying process due to solvent crystallization. The fabrication method proposed in this work utilizes ethanol as an intermediate solvent, which coupled with the following drying process provides a gradient porous network through the sample. The PEEK samples displayed mostly nanoporosity with an overall mesoporosity of approximately 2% and a measurable density of 0.84 g/cm3 ± 0.18, which is higher than that of aerogels produced using traditional methods. Therefore, the compressive strength displayed by the porous PEEK samples prepared with varying drying methods were higher to that of aerogels prepared through traditional methods. Herein, we show a promising, and relatively inexpensive, alternative method to fabricate mechanically robust porous PEEK with control over structuration, porosity and surface area through ethanol solvent exchange.

Cellulose nanocrystal nanocomposites (CNC) with metallic nanoparticles (NP) are used for applications ranging from environmental remediation to smart electronics such as conductive films. To optimi...

The aspect ratio (AR) of filler particles is one of the most critical determinants for the mechanical properties of particle-reinforced polymer composites. However, it has been challenging to solely study the effect of particle AR due to the difficulties of controlling AR without altering the physical and chemical properties of the particle. Herein, we synthesized PCN-222, a zirconium-based porphyrinic metal-organic framework (MOF) with preferential longitudinal growth as a series of particles with ARs increasing from 3.4 to 54. The synthetic MOF conditions allowed for the chemical properties of the particles to remain constant over the series. The particles were employed as reinforcers for poly(methyl methacrylate) (PMMA). MOF-polymer composite films were fabricated using doctor-blading techniques, which facilitated particle dispersion and alignment in the PMMA matrix, as revealed by optical microscopy and wide-angle X-ray diffraction. Mechanical measurements showed that both elastic and dynamic moduli increased with particle AR and particle concentrations but started to decrease as particle loading increased beyond 0.5 wt % (1.12 vol %). The data obtained at low particle loadings were fitted well with the Halpin-Tsai model. In contrast, the percolation model and the Cox model were unable to adequately fit the data, indicating the mechanical reinforcement in our system mainly originated from efficient load transfer between particles and the matrix in the particle orienting direction. Finally, we showed that the thermal stability of composite films increased with the addition of MOF particles because of the high thermal degradation temperature and restricted polymer chain mobility.

A novel nanocomposite comprised of cellulose nanocrystals (CNCs) and 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) oxidized cellulose nanofibers (TOCNFs) was prepared through solution casting to evaluate potential improvements of the mechanical performance compared to individual reinforcements alone. Such materials can be implemented as mechanical reinforcements in polymer composites, especially when less weight is desired. Dissipative particle dynamics (DPD) simulations, in combination with polarized light microscopy and atomic force microscopy, were analyzed to evaluate the morphology of these combined cellulose nanomaterial (CNM) films. Our results indicate that TOCNFs provide enhanced translational mobility to CNCs which become incorporated near the crystalline domains of TOCNFs. This mobility enables CNCs to increase the rigidity of the network without sacrificing elongation and toughness. The combination of these materials provides improved ultimate tensile strength and elongation without sacrificing the Young's modulus. Therefore, a combination of these materials can be used to develop nanocomposites with enhanced mechanical properties.

The 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) oxidation of cellulose, when mediated with Oxone® (KHSO5), can be performed simply and under mild conditions. Furthermore, the products of the reaction can be isolated into two major components: Oxone®-mediated TEMPO-oxidized cellulose nanomaterials Form I and Form II (OTO-CNM Form I and Form II). This study focuses on the characterization of the properties of OTO-CNMs. Nanoparticle-sized cellulose fibers of 5 and 16 nm, respectively, were confirmed through electron microscopy. Infrared spectroscopy showed that the most carboxylation presented in Form II. Conductometric titration showed a two-fold increase in carboxylation from Form I (800 mmol/kg) to Form II (1600 mmol/kg). OTO-CNMs showed cellulose crystallinity in the range of 64–68% and crystallite sizes of 1.4–3.3 nm, as shown through XRD. OTO-CNMs show controlled variability in hydrophilicity with contact angles ranging from 16 to 32°, within or below the 26–47° reported in the literature for TEMPO-oxidized CNMs. Newly discovered OTO-CNM Form II shows enhanced hydrophilic properties as well as unique crystallinity and chemical functionalization in the field of bio-sourced material and nanocomposites.

Characterization of cellulose nanocrystals (CNCs) is often complex and tedious. With their increased use for biological materials, polymer reinforcing agents, and other applications, better characterization methods of CNCs are needed to ensure product quality. However, because of their small size, hydrogen bonding, and low electron density, individual CNCs are difficult to image with high resolution and magnification using electron microscopy. Methods to help counter these challenges include staining for increased contrast and techniques to increase dispersion. This work tested several stains, dispersing agents, and sample supports to find a consistent method of individualizing CNCs and providing good contrast for imaging in transmission electron microscopy (TEM). The most consistent method found uses a low concentration of CNCs, bovine serum albumin as a dispersing agent, and Nanovan® as the contrasting stain on a silicon monoxide-coated Formvar TEM grid.

The pistachio nut (pistacia vera) is a common food source. The shell of the nut has few known applications and is considered a waste product of the agriculture industry (agro waste). In this paper, we show a method for isolating cellulose nanocrystals (CNCs) from the pistachio shell. CNCs are well known for having very good mechanical properties which have shown themselves to be effective in many different polymer based nano-composites. We show that common methods of purifying and hydrolyzing cellulose will result in useable CNCs. We found a yield of 50 ± 14 wt%, which is rather high for an agro waste product. We found an aspect ratio of 17 ± 3 , a crystallinity of 66%, and a surface charge density of 90 ± 12 mmol/kg. These numbers compare well with other common commercial sources of CNCs.

As the world's population exponentially grows, so does the need for the production of food, with cereal production growing annually from an estimated 1.0 billion to 2.5 billion tons within the last few decades. This rapid growth in food production results in an ever increasing amount of agricultural wastes, of which already occupies nearly 50% of the total landfill area. For example, is the billions of dry tons of cellulose-containing spent coffee grounds disposed in landfills annually. This paper seeks to provide a method for isolating cellulose nanocrystals (CNCs) from spent coffee grounds, in order to recycle and utilize the cellulosic waste material which would otherwise have no applications. CNCs have already been shown to have vast applications in the polymer engineering field, mainly utilized for their high strength to weight ratio for reinforcement of polymer-based nanocomposites. A successful method of purifying and hydrolyzing the spent coffee grounds in order to isolate usable CNCs was established. The CNCs were then characterized using current techniques to determine important chemical and physical properties. A few crucial properties determined were aspect ratio of 12 +/- 3, crystallinity of 74.2%, surface charge density of (48.4 +/- 6.2) mM/kg cellulose, and the ability to successfully reinforce a polymer based nanocomposite. These characteristics compare well to other literature data and common commercial sources of CNCs.

Dioclea reflexa bioactive compounds have been shown to contain antioxidant properties. The extracts from the same plant are used in traditional medical practices to treat various diseases with impressive outcomes. In this study, ionic mobility in Saccharomyces cerevisiae cells in the presence of D. reflexa seed extracts was monitored using electrochemical detection methods to link cell death to ionic imbalance. Cells treated with ethanol, methanol, and water extracts were studied using cyclic voltammetry and cell counting to correlate electrochemical behavior and cell viability, respectively. The results were compared with cells treated with pore-forming Amphotericin b (Amp b), as well as Fluconazole (Flu) and the antimicrobial drug Rifampicin (Rif). The D. reflexa seed water extract (SWE) revealed higher anodic peak current with 58% cell death. Seed methanol extract (SME) and seed ethanol extract (SEE) recorded 31% and 22% cell death, respectively. Among the three control drugs, Flu revealed the highest cell death of about 64%, whereas Amp b and Rif exhibited cell deaths of 35% and 16%, respectively, after 8 h of cell growth. It was observed that similar to SWE, there was an increase in the anodic peak current in the presence of different concentrations of Amp b, which also correlated with enhanced cell death. It was concluded from this observation that Amp b and SWE might follow similar mechanisms to inhibit cell growth. Thus, the individual bioactive compounds from the water extracts of D. reflexa seeds could further be purified and tested to validate their potential therapeutic application. The strategy to link electrochemical behavior to biochemical responses could be a simple, fast, and robust screening technique for new drug targets and to understand the mechanism of action of such drugs against disease models. Published version

The aspect ratio of nanoparticles governs their percolation threshold in polymer composites, and thus exerts a significant influence on the materials properties. We explored how the combination of two rod-like particle types with different aspect ratio, but otherwise similar characteristics, affects the properties of nanocomposites. Using experimental data of composites made with two different cellulose nanocrystal (CNC) types, we show that a substantial fraction of the high-aspect-ratio CNCs can be substituted with the low-aspect-ratio nanoparticles without significantly affecting the properties. Exploring the boundary limits of aspect ratios, where random contact criterions and mean field approximations are valid, we formulated a generalized theoretical model that permits predicting the modulus of nanocomposites with two rod-like nanoparticle types having different length distributions. The model shows that the modulus of such nanocomposites is strongly weighted by the particles with higher aspect ratio.

Milling of microcrystalline cellulose (gMCC) and poly(vinyl acetate) (gPVAc) was performed, and the milled samples were pre-mixed prior to melt-mixing. Ground samples that were pre- and subsequently melt-mixed (gPVAc/gMCC) showed similar reinforcement (modulus of ∼3 GPa at 25 °C, ∼9 MPa at 90 °C) compared to the directly mixed composites containing cellulose nanocrystals isolated by acid hydrolysis from cotton (PVAc/CNC, modulus of ∼3 GPa at 25 °C and ∼10 MPa at 90 °C). Highly concentrated masterbatches (up to 60 wt% of gMCC) are shown for the first time with cellulosic filler. These additive concentrates can be first prepared using a solution casting approach, aiding in efficient transport, and then diluted by melt-mixing when needed. Using DMF and water as solvents for preparation, melt-processing schemes that are easier to scale-up and exploit industrially were evaluated in this work.

Thin-film nanocomposite membranes (TFNs) are a recent class of materials that use nanoparticles to provide improvements over traditional thin-film composite (TFC) reverse osmosis membranes by addressing various design challenges, e.g., low flux for brackish water sources, biofouling, etc. In this study, TFNs were produced using as-received cellulose nanocrystals (CNCs) and 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanocrystals (TOCNs) as nanoparticle additives. Cellulose nanocrystals are broadly interesting due to their high aspect ratios, low cost, sustainability, and potential for surface modification. Two methods of membrane fabrication were used in order to study the effects of nanoparticle dispersion on membrane flux and salt rejection: a vacuum filtration method and a monomer dispersion method. In both cases, various quantities of CNCs and TOCNs were incorporated into a polyamide TFC membrane via in-situ interfacial polymerization. The flux and rejection performance of the resulting membranes was evaluated, and the membranes were characterized via attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The vacuum filtration method resulted in inconsistent TFN formation with poor nanocrystal dispersion in the polymer. In contrast, the dispersion method resulted in more consistent TFN formation with improvements in both water flux and salt rejection observed. The best improvement was obtained via the monomer dispersion method at 0.5 wt% TOCN loading resulting in a 260% increase in water flux and an increase in salt rejection to 98.98 &plusmn, 0.41% compared to 97.53 &plusmn, 0.31% for the plain polyamide membrane. The increased flux is attributed to the formation of nanochannels at the interface between the high aspect ratio nanocrystals and the polyamide matrix. These nanochannels serve as rapid transport pathways through the membrane, and can be used to tune selectivity via control of particle/polymer interactions.

Dioclea reflexa bioactive compounds have been shown to contain antioxidant properties. The extracts from the same plant are used in traditional medical practices to treat various diseases with impressive outcomes. In this study, ionic mobility in Saccharomyces cerevisiae cells in the presence of D. reflexa seed extracts was monitored using electrochemical detection methods to link cell death to ionic imbalance. Cells treated with ethanol, methanol, and water extracts were studied using cyclic voltammetry and cell counting to correlate electrochemical behavior and cell viability, respectively. The results were compared with cells treated with pore-forming Amphotericin b (Amp b), as well as Fluconazole (Flu) and the antimicrobial drug Rifampicin (Rif). The D. reflexa seed water extract (SWE) revealed higher anodic peak current with 58% cell death. Seed methanol extract (SME) and seed ethanol extract (SEE) recorded 31% and 22% cell death, respectively. Among the three control drugs, Flu revealed the highest cell death of about 64%, whereas Amp b and Rif exhibited cell deaths of 35% and 16%, respectively, after 8 h of cell growth. It was observed that similar to SWE, there was an increase in the anodic peak current in the presence of different concentrations of Amp b, which also correlated with enhanced cell death. It was concluded from this observation that Amp b and SWE might follow similar mechanisms to inhibit cell growth. Thus, the individual bioactive compounds from the water extracts of D. reflexa seeds could further be purified and tested to validate their potential therapeutic application. The strategy to link electrochemical behavior to biochemical responses could be a simple, fast, and robust screening technique for new drug targets and to understand the mechanism of action of such drugs against disease models.

Disc degeneration affects 12% to 35% of a given population, based on genetics, age, gender, and other environmental factors, and usually occurs in the lumbar spine due to heavier loads and more strenuous motions. Degeneration of the extracellular matrix (ECM) within reduces mechanical integrity, shock absorption, and swelling capabilities of the intervertebral disc. When severe enough, the disc can bulge and eventually herniate, leading to pressure build up on the spinal cord. This can cause immense lower back pain in individuals, leading to total medical costs exceeding $100 billion. Current treatment options include both invasive and noninvasive methods, with spinal fusion surgery and total disc replacement (TDR) being the most common invasive procedures. Although these treatments cause pain relief for the majority of patients, multiple challenges arise for each. Therefore, newer tissue engineering methods are being researched to solve the ever-growing problem. This review spans the anatomy of the spine, with an emphasis on the functions and biological aspects of the intervertebral discs, as well as the problems, associated solutions, and future research in the field. Published version

As cellulose nanocrystals (CNCs) are increasing in production, establishing safe workplace practices in industry will be paramount to their continued use and growth. Particles other than CNCs with similar high aspect ratios have exhibited toxicity on inhalation. Safeguards are needed to monitor concentrations of CNCs in air in industrial and laboratory settings to protect workers. However, because of their size, morphology, and chemical makeup, CNCs are difficult to characterize and differentiate from other dust and cellulose products. This work is focused on developing an effective method of characterizing the concentration of airborne ultrafine CNCs that may deposit in the respiratory tract. CNCs were tagged with rhodamine b (RhB-CNCs) for improved visualization and characterized using UV-vis spectroscopy (UV-vis), transmission electron microscopy (TEM), and dynamic light scattering (DLS), then aerosolized and collected via a novel method using plastic impingers. Concentration of RhB-CNCs was measured using UV-vis and scanning mobility particle sizer (SMPS). The plastic impinger with 3D-printed nozzle collected airborne CNCs at an efficiency that improves upon commercially available impingers for relevant particle sizes.

Effective therapeutic delivery of peptide and protein drugs is challenged by short in vivo half-lives due to rapid degradation. Sustained release formulations of αCT1, a 25 amino acid peptide drug, would afford lower dosing frequency in indications that require long term treatment, such as chronic wounds and cancers. In this study, rhodamine B (RhB) was used as a model drug to develop and optimize a double emulsion-solvent evaporation method of poly(lactic-co-glycolic acid) (PLGA) nanoparticle synthesis. Encapsulation of αCT1 in these nanoparticles (NPs) resulted in a sustained in vitro release profile over three weeks, characterized by an initial burst release of approximately 50% of total encapsulated drug over the first three days followed by sustained release over the remaining two and a half weeks. NP uptake by glioblastoma stem cells was through endocytosis and RhB and αCT1 were observed in cells after at least 4 days.

The stability and longevity of recordings obtained from intracortical microelectrodes continues to remain an area of concern for neural interfacing applications. The limited longevity of microelectrode performance has been associated with the integrity of the blood brain barrier (BBB) and the neuroinflammatory response to the microelectrode. Here, we report the investigation of an additive approach that targets both mechanical and chemical factors believed to contribute to chronic BBB instability and the neuroinflammatory response associated with implanted intracortical microelectrodes. The implants investigated were based on a mechanically adaptive, compliant nanocomposite (NC), which reduces the tissue response and tissue strain. This material was doped with various concentrations of the antioxidant resveratrol with the objective of local and rapid delivery. In vitro analysis of resveratrol release, antioxidant activity, and cytotoxicity suggested that a resveratrol content of 0.01% was optimal for in vivo assessment. Thus, probes made from the neat NC reference and probes containing resveratrol (NC Res) were implanted into the cortical tissue of rats for up to sixteen weeks. Histochemical analysis suggested that at three days post-implantation, neither materials nor therapeutic approaches (independently or in combination) could alter the initial wound healing response. However, at two weeks post-implantation, the NC Res implant showed a reduction in activated microglia/macrophages and improvement in neuron density at the tissue-implant interface when compared to the neat NC reference. However, sixteen weeks post-implantation, when the antioxidant was exhausted, NC Res and the neat NC reference exhibited similar tissue responses. The data show that NC Res provides short-term, short-lived benefits due to the antioxidant release, and a long-term reduction in neuroinflammation on account of is mechanical adaptive, compliant nature. Together, these results demonstrate that local delivery of resveratrol can provide an additive advantage by providing a consistent reduction in the tissue response.

Articular cartilage serves as a low-friction cushion in synovial joints and is vital for mammalian skeletal movements. Due to its avascular nature and the low cell density, the tissue has a limited ability to regenerate, and damage due to injury, wear and tear, or disease usually requires surgical intervention. While articular cartilage had been predicted to be one of the first tissues to be successfully engineered, it proved to be challenging to reproduce the complex architecture and biomechanical properties of the native tissue. Here we report the fabrication of multi-layer polymer nanocomposite scaffolds that mimic the structural design, chemical cues, and mechanical characteristics of mature articular cartilage. These scaffolds guide the morphology, orientation, and phenotypic state of cultured chondrocytes in a spatially controlled manner, support the growth of tissue with features that are reminiscent of the natural analogue, and promote localized hydroxyapatite formation to permit integration with the subchondral bone.

The present study aimed at developing new thermally responsive shape-memory composites, that were fabricated by compacting mats of electrospun poly(vinyl alcohol) (PVA) fibers and sheets of a thermoplastic polyether block amide elastomer (PEBA). This design was based on the expectation that the combination of the rubber elasticity of the PEBA matrix and the mechanical switching exploitable through the reversible glass transition temperature (Tg) of the PVA filler could be combined to create materials that display shape memory characteristics as an emergent effect. Dynamic mechanical analyses (DMA) show that, upon introduction of 10-20% w/w PVA fibers, the room-temperature storage modulus (E') increased by a factor of 4-5 in comparison to the neat PEBA, and they reveal a stepwise reduction of E' around the Tg of PVA (85 °C). This transition could indeed be utilized to fix a temporary shape and recover the permanent shape. At low strain, the fixity was 66 ± 14% and the recovery was 98 ± 2%. Overall, the data validate a simple and practical strategy for the fabrication of shape memory composites that involves a melt compaction process and employs two commercially available polymers.

We investigated how different processing methods affect the morphology and mechanical properties of nanocomposites made from poly(vinyl acetate) (PVAc) and cellulose nanocrystals (CNCs). Homogeneously mixed reference PVAc/CNC nanocomposites of various compositions were first prepared by solution casting. These materials were post-processed by mixing in a roller blade mixer (RBM) or a twin-screw extruder (TSE) and subsequent compression molding. Transmission electron microscopy was used to elucidate the dispersion and size distribution of the CNCs and these data were correlated with the materials' mechanical properties. While RBM processed composites are virtually indistinguishable from the solution-cast reference materials, TSE processing led to mechanical degradation of the CNCs and resulted materials with inferior mechanical properties. Direct RBM mixing of PVAc and CNCs was also explored. This process afforded materials that are much stiffer than the neat matrix, but did not reach the levels of the reference series.