@article{fritz_salas_jameel_rojas_2017, title={Self-association and aggregation of kraft lignins via electrolyte and nonionic surfactant regulation: stabilization of lignin particles and effects on filtration}, volume={32}, number={4}, journal={Nordic Pulp & Paper Research Journal}, author={Fritz, C. and Salas, C. and Jameel, H. and Rojas, O. J.}, year={2017}, pages={572–585} }
 @article{el-naggar_abdelgawad_salas_rojas_2016, title={Curdlan in fibers as carriers of tetracycline hydrochloride: Controlled release and antibacterial activity}, volume={154}, ISSN={["1879-1344"]}, DOI={10.1016/j.carbpol.2016.08.042}, abstractNote={Curdlan (CURD) and polyethylene oxide were used to synthesize nanofibers as carriers of hydro soluble tetracycline hydrochloride (TCH). The viscosity, surface tension and conductivity of the precursor multicomponent aqueous solutions were determined and adjusted to produce defect-free fiber webs. Except for a slight increase in diameter, the addition of TCH did not affect the original morphology of the CURD/PEO nanofibers, as determined by FE-SEM imaging. However, the thermal stability of the system was enhanced (TGA and DSC). Moreover, water resistance, as measured with 24-h immersion tests, was observed upon crosslinking with glutaraldehyde. In-vitro activity measurements indicated a sustained and controlled TCH time-release pattern and excellent antibacterial activity against E. coli, as assessed by UV-vis spectroscopy and viable cell counting, respectively. Overall, we propose nanofibers based on CURD as promising platforms for scaffolds for wound dressing and drug delivery.}, journal={CARBOHYDRATE POLYMERS}, author={El-Naggar, Mehrez E. and Abdelgawad, Abdelrahman M. and Salas, Carlos and Rojas, Orlando J.}, year={2016}, month={Dec}, pages={194–203} }
 @article{lenze_peksa_sun_hoeger_salas_hubbe_2016, title={Intact and broken cellulose nanocrystals as model nanoparticles to promote dewatering and fine-particle retention during papermaking}, volume={23}, ISSN={["1572-882X"]}, DOI={10.1007/s10570-016-1077-9}, number={6}, journal={CELLULOSE}, author={Lenze, Connor J. and Peksa, Caryn A. and Sun, Weimin and Hoeger, Ingrid C. and Salas, Carlos and Hubbe, Martin A.}, year={2016}, month={Dec}, pages={3951–3962} }
 @article{ferrer_salas_rojas_2016, title={Physical, thermal, chemical and rheological characterization of cellulosic microfibrils and microparticles produced from soybean hulls}, volume={84}, ISSN={["1872-633X"]}, DOI={10.1016/j.indcrop.2016.02.014}, abstractNote={Soybean hulls were used to isolate cellulosic microfibrils (SMF) and brick-like microparticles (SMP) by combining chemical and mechanical pretreatments. The key physical and chemical features of SMF and SMP were compared with those of micro and nanofibrillated cellulose (MNFC) obtained from fully bleached wood fibers. SMF and SMP chemical composition includes residual polysaccharides and lignin that endow such biologically-derived materials with properties typical of nanocellulosics. Compared to MNFC, SMF and SMP exhibit enhanced crystallinity (∼ > 10% higher) and thermal stability (onset degradation temperature >295 °C and maximum degradation at 361 and 355 °C). Such observations make SMF and SMP suitable for reinforcement in thermoplastic composites. A strong shear thinning behavior was observed for aqueous dispersions of SMF and SMP, revealing that these cellulose microstructures are of interest for rheology modification, coatings and films. Overall, the availability and low cost of biomass from residual soybean hulls constitutes a viable option for their use as a feedstock for the production and development of novel materials from SMF and SMP.}, journal={INDUSTRIAL CROPS AND PRODUCTS}, author={Ferrer, Ana and Salas, Carlos and Rojas, Orlando J.}, year={2016}, month={Jun}, pages={337–343} }
 @article{ferrer_salas_rojas_2015, title={Dewatering of MNFC containing microfibrils and microparticles from soybean hulls: mechanical and transport properties of hybrid films}, volume={22}, ISSN={["1572-882X"]}, DOI={10.1007/s10570-015-0768-y}, number={6}, journal={CELLULOSE}, author={Ferrer, Ana and Salas, Carlos and Rojas, Orlando J.}, year={2015}, month={Dec}, pages={3919–3928} }
 @article{fritz_ferrer_salas_jameel_rojas_2015, title={Interactions between Cellulolytic Enzymes with Native, Autohydrolysis, and Technical Lignins and the Effect of a Polysorbate Amphiphile in Reducing Nonproductive Binding}, volume={16}, ISSN={["1526-4602"]}, DOI={10.1021/acs.biomac.5b01203}, abstractNote={Understanding enzyme-substrate interactions is critical in designing strategies for bioconversion of lignocellulosic biomass. In this study we monitored molecular events, in situ and in real time, including the adsorption and desorption of cellulolytic enzymes on lignins and cellulose, by using quartz crystal microgravimetry and surface plasmon resonance. The effect of a nonionic surface active molecule was also elucidated. Three lignin substrates relevant to the sugar platform in biorefinery efforts were considered, namely, hardwood autohydrolysis cellulolytic (HWAH), hardwood native cellulolytic (MPCEL), and nonwood native cellulolytic (WSCEL) lignin. In addition, Kraft lignins derived from softwoods (SWK) and hardwoods (HWK) were used as references. The results indicated a high affinity between the lignins with both, monocomponent and multicomponent enzymes. More importantly, the addition of nonionic surfactants at concentrations above their critical micelle concentration reduced remarkably (by over 90%) the nonproductive interactions between the cellulolytic enzymes and the lignins. This effect was hypothesized to be a consequence of the balance of hydrophobic and hydrogen bonding interactions. Moreover, the reduction of surface roughness and increased wettability of lignin surfaces upon surfactant treatment contributed to a lower affinity with the enzymes. Conformational changes of cellulases were observed upon their adsorption on lignin carrying preadsorbed surfactant. Weak electrostatic interactions were determined in aqueous media at pH between 4.8 and 5.5 for the native cellulolytic lignins (MPCEL and WSCEL), whereby a ∼20% reduction in the enzyme affinity was observed. This was mainly explained by electrostatic interactions (osmotic pressure effects) between charged lignins and cellulases. Noteworthy, adsorption of nonionic surfactants onto cellulose, in the form cellulose nanofibrils, did not affect its hydrolytic conversion. Overall, our results highlight the benefit of nonionic surfactant pretreatment to reduce nonproductive enzyme binding while maintaining the reactivity of the cellulosic substrate.}, number={12}, journal={BIOMACROMOLECULES}, author={Fritz, Consuelo and Ferrer, Ana and Salas, Carlos and Jameel, Hasan and Rojas, Orlando J.}, year={2015}, month={Dec}, pages={3878–3888} }
 @article{song_salas_rojas_2015, title={Role of textile substrate hydrophobicity on the adsorption of hydrosoluble nonionic block copolymers}, volume={454}, ISSN={["1095-7103"]}, DOI={10.1016/j.jcis.2015.04.061}, abstractNote={The adsorption of polyalkylene glycols and co-polymers of ethylene oxide and propylene oxide on substrates relevant to textiles with varying surface energies (cellulose, polypropylene, nylon and polyester) was studied by using quartz crystal microgravimetry. Langmuirian-type isotherms were observed for the adsorption profiles of nonionic block polymers of different architectures. The affinity with the surfaces is discussed based on experimental observations, which highlights the role of hydrophobic effects. For a given type of block polymer, micellar and monomeric adsorption is governed by the balance of polymer structure (mainly, chain length of hydrophobic segments) and substrate's surface energy.}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={Song, Junlong and Salas, Carlos and Rojas, Orlando J.}, year={2015}, month={Sep}, pages={89–96} }
 @misc{salas_nypeloe_rodriguez-abreu_carrillo_rojas_2014, title={Nanocellulose properties and applications in colloids and interfaces}, volume={19}, ISSN={["1879-0399"]}, DOI={10.1016/j.cocis.2014.10.003}, abstractNote={In this review we introduce recent advances in the development of cellulose nanomaterials and the construction of high order structures by applying some principles of colloid and interface science. These efforts take advantage of natural assemblies in the form of fibers that nature constructs by a biogenetic bottom-up process that results in hierarchical systems encompassing a wide range of characteristic sizes. Following the reverse process, a top-down deconstruction, cellulose materials can be cleaved from fiber cell walls. The resulting nanocelluloses, mainly cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC, i.e., defect-free, rod-like crystalline residues after acid hydrolysis of fibers), have been the subject of recent interest. This originates from the appealing intrinsic properties of nanocelluloses: nanoscale dimensions, high surface area, morphology, low density, chirality and thermo-mechanical performance. Directing their assembly into multiphase structures is a quest that can yield useful outcomes in many revolutionary applications. As such, we discuss the use of non-specific forces to create thin films of nanocellulose at the air–solid interface for applications in nano-coatings, sensors, etc. Assemblies at the liquid–liquid and air–liquid interfaces will be highlighted as means to produce Pickering emulsions, foams and aerogels. Finally, the prospects of a wide range of hybrid materials and other systems that can be manufactured via self and directed assembly will be introduced in light of the unique properties of nanocelluloses.}, number={5}, journal={CURRENT OPINION IN COLLOID & INTERFACE SCIENCE}, author={Salas, Carlos and Nypeloe, Tiina and Rodriguez-Abreu, Carlos and Carrillo, Carlos and Rojas, Orlando J.}, year={2014}, month={Oct}, pages={383–396} }
 @article{salas_ago_lucia_rojas_2014, title={Synthesis of soy protein-lignin nanofibers by solution electrospinning}, volume={85}, ISSN={["1873-166X"]}, DOI={10.1016/j.reactfunctpolym.2014.09.022}, abstractNote={Nanofibers were produced by electrospinning aqueous alkaline solutions containing different mass ratios of soy protein and lignin in the presence of poly(ethylene glycol) coadjutant, all of which presented shear thinning behavior. SEM revealed that the addition of polyethylene oxide as a coadjutant indeed facilitated the formation of defect-free fibers whose diameter increased with lignin concentration, in the range between ≈ 124 and ≈ 400 nm. Favorable interactions between lignin and soy protein were identified from data provided by differential scanning calorimetry. In addition, an increased hydrogen bonding and the loss of secondary structure of the proteins as the lignin concentration increased were observed from the disappearance of amide II (∼1500 cm−1) and III (∼1400–1200 cm−1) bands and a red shift of amide I band in the FT-IR spectrum. The unfolding of the protein contributed to a better interaction with lignin macromolecules, which further improved the electrospinning process. It is concluded that mixtures of lignin and soy proteins, two major renewable resources with interesting chemical features, are suitable for the development of composite sub-micron fibers.}, journal={REACTIVE & FUNCTIONAL POLYMERS}, author={Salas, Carlos and Ago, Mariko and Lucia, Lucian A. and Rojas, Orlando J.}, year={2014}, month={Dec}, pages={221–227} }
 @article{salas_rojas_lucia_hubbe_genzer_2013, title={On the Surface Interactions of Proteins with Lignin}, volume={5}, ISSN={1944-8244 1944-8252}, url={http://dx.doi.org/10.1021/am3024788}, DOI={10.1021/am3024788}, abstractNote={Lignins are used often in formulations involving proteins but little is known about the surface interactions between these important biomacromolecules. In this work, we investigate the interactions at the solid-liquid interface of lignin with the two main proteins in soy, glycinin (11S) and β-conglycinin (7S). The extent of adsorption of 11S and 7S onto lignin films and the degree of hydration of the interfacial layers is quantified via Quartz crystal microgravimetry (QCM) and surface plasmon resonance (SPR). Solution ionic strength and protein denaturation (2-mercaptoethanol and urea) critically affect the adsorption process as protein molecules undergo conformational changes and their hydrophobic or hydrophilic amino acid residues interact with the surrounding medium. In general, the adsorption of the undenatured proteins onto lignin is more extensive compared to that of the denatured biomolecules and a large amount of water is coupled to the adsorbed molecules. The reduction in water contact angle after protein adsorption (by ~40° and 35° for undenatured 11S and 7S, respectively) is explained by strong nonspecific interactions between soy proteins and lignin.}, number={1}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Salas, Carlos and Rojas, Orlando J. and Lucia, Lucian A. and Hubbe, Martin A. and Genzer, Jan}, year={2013}, month={Jan}, pages={199–206} }
 @article{salas_genzer_lucia_hubbe_rojas_2013, title={Water-Wettable Polypropylene Fibers by Facile Surface Treatment Based on Soy Proteins}, volume={5}, ISSN={["1944-8252"]}, DOI={10.1021/am401065t}, abstractNote={Modification of the wetting behavior of hydrophobic surfaces is essential in a variety of materials, including textiles and membranes that require control of fluid interactions, adhesion, transport processes, sensing, etc. This investigation examines the enhancement of wettability of an important class of textile materials, viz., polypropylene (PP) fibers, by surface adsorption of different proteins from soybeans, including soy flour, isolate,glycinin, and β-conglycinin. Detailed investigations of soy adsorption from aqueous solution (pH 7.4, 25 °C) on polypropylene thin films is carried out using quartz crystal microbalance (QCM) and surface plasmon resonance (SPR). A significant amount of protein adsorbs onto the PP surfaces primarily due to hydrophobic interactions. We establish that adsorption of a cationic surfactant, dioctadecyldimethylammonium bromide (DODA) onto PP surfaces prior to the protein deposition dramatically enhances its adsorption. The adsorption of proteins from native (PBS buffer, pH 7.4, 25 °C) and denatured conditions (PBS buffer, pH 7.4, 95 °C) onto DODA-treated PP leads to a high coverage of the proteins on the PP surface as confirmed by a significant improvement in water wettability. A shift in the contact angle from 128° to completely wettable surfaces (≈0°) is observed and confirmed by imaging experiments conducted with fluorescence tags. Furthermore, the results from wicking tests indicate that hydrophobic PP nonwovens absorb a significant amount of water after protein treatment, i.e., the PP-modified surfaces become completely hydrophilic.}, number={14}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Salas, Carlos and Genzer, Jan and Lucia, Lucian A. and Hubbe, Martin A. and Rojas, Orlando J.}, year={2013}, month={Jul}, pages={6541–6548} }
 @article{salas_rojas_lucia_hubbe_genzer_2012, title={Adsorption of Glycinin and beta-Conglycinin on Silica and Cellulose: Surface Interactions as a Function of Denaturation, pH, and Electrolytes}, volume={13}, ISSN={["1526-4602"]}, DOI={10.1021/bm2014153}, abstractNote={Soybean proteins have found uses in different nonfood applications due to their interesting properties. We report on the kinetics and extent of adsorption on silica and cellulose surfaces of glycinin and β-conglycinin, the main proteins present in soy. Quartz crystal microgravimetry (QCM) experiments indicate that soy protein adsorption is strongly affected by changes in the physicochemical environment. The affinity of glycinin and the mass adsorbed on silica and cellulose increases (by ca. 13 and 89%, respectively) with solution ionic strength (as it increases from 0 to 100 mM NaCl) due to screening of electrostatic interactions. In contrast, β-conglycinin adsorbs on the same substrates to a lower extent and the addition of electrolyte reduces adsorption (by 25 and 57%, respectively). The addition of 10 mM 2-mercaptoethanol, a denaturing agent, reduces the adsorption of both proteins with a significant effect for glycinin. This observation is explained by the cleavage of disulfide bonds which allows unfolding of the molecules and promotes dissociation into subunits that favors more compact adsorbed layer structures. In addition, adsorption of glycinin onto cellulose decreases with lowering the pH from neutral to pH 3 due to dissociation of the macromolecules, resulting in flatter adsorbed layers. The respective adsorption isotherms fit a Langmuir model and QCM shifts in energy dissipation and frequency reveal multiple-step kinetic processes indicative of changes in adlayer structure.}, number={2}, journal={BIOMACROMOLECULES}, author={Salas, Carlos and Rojas, Orlando J. and Lucia, Lucian A. and Hubbe, Martin A. and Genzer, Jan}, year={2012}, month={Feb}, pages={387–396} }