Control of the Colloidal and Adsorption Behaviors of Chitin Nanocrystals and an Oppositely Charged Surfactant at Solid, Liquid, and Gas Interfaces

Chitin has a unique hierarchical structure, spanning the macro- and nanoscales, and presents chemical characteristics that make it a suitable component of multiphase systems. Herein, we elucidate the colloidal interactions between partially deacetylated chitin nanocrystals (cationic ChNC) and an anionic surfactant, sodium dodecyl sulfate (SDS). We investigate charge neutralization and association (electrophoretic mobility, surface tensiometry, and quartz crystal microgravimetry) and their role in the stabilization of Pickering emulsions. We find SDS adsorption and association with ChNC under distinctive regimes: At low SDS concentration, submonolayer assemblies form on ChNC, driven by the hydrophobic effect and electrostatic interactions. With the increased SDS concentration, bilayers or patchy bilayers form, followed by adsorbed hemimicelles and micelles. We further suggested the role of hydrophobic effects in the observed colloidal transitions and complex conformations. At the highest SDS concentration tested, charge neutralization and SDS/ChNC flocculation take place. Remarkably, at given concentrations, adsorbed SDS endows the chitin nanoparticles with an effective hydrophobicity that opens the opportunity to achieve tailorable Pickering stabilization. Hence, a facile route is proposed by in situ modification by SDS physisorption, which extends the potential of renewable nanoparticles in the formulation of complex fluids, for instance, those relevant to household and healthcare products.

Multifunctioning of carboxylic-cellulose nanocrystals on the reinforcement of compressive strength and conductivity for acrylic-based hydrogel

Simultaneously having competitive compressive properties, fatigue-resistant stability, excellent conductivity and sensitivity has still remained a challenge for acrylic-based conductive hydrogels, which is critical in their use in the sensor areas where pressure is performed. In this work, an integrated strategy was proposed for preparing a conductive hydrogel based on acrylic acid (AA) and sodium alginate (SA) by addition of carboxylic-cellulose nanocrystals (CNC-COOH) followed by metal ion interaction to reinforce its compressive strength and conductivity simultaneously. The CNC-COOH played a multifunctional role in the hydrogel by well-dispersing SA and AA in the hydrogel precursor solution for forming a uniform semi-interpenetrating network, providing more hydrogen bonds with SA and AA, more -COOH for metal ion interactions to form uniform multi-network, and also offering high modulus to the final hydrogel. Accordingly, the as-prepared hydrogels showed simultaneous excellent compressive strength (up to 3.02 MPa at a strain of 70 %) and electrical conductivity (6.25 S m-1), good compressive fatigue-resistant (93.2 % strength retention after 1000 compressive cycles under 50 % strain) and high sensitivity (gauge factor up to 14.75). The hydrogel strain sensor designed in this work is capable of detecting human body movement of pressing, stretching and bending with highly sensitive conductive signals, which endows it great potential for multi-scenario strain sensing applications.

The pre-addition of "blocking" proteins decreases subsequent cellulase adsorption to lignin and enhances cellulose hydrolysis

The pre-adsorption of non-catalytic/blocking proteins onto the lignin component of pretreated biomass has been shown to significantly increase the effectiveness of subsequent enzyme-mediated hydrolysis of the cellulose by limiting non-productive enzyme adsorption. Layer-by-layer adsorption of non-catalytic proteins and enzymes onto lignin was monitored using Quartz Crystal Micro balancing combined with Dissipation monitoring (QCM-D) and conventional protein adsorption. These methods were used to assess the interaction between soft/hardwood lignins, cellulases and the three non-catalytic proteins BSA, lysozyme and ovalbumin. The QCM-D analysis showed higher adsorption rates for all of the non-catalytic proteins onto the lignin films as compared to cellulases. This suggested that the "blocking" proteins would preferentially adsorb to the lignin rather than the enzymes. Pre-incubation of the lignin films with blocking proteins resulted in reduced adsorption of cellulases onto the lignin, significantly enhancing cellulose hydrolysis.

Pickering emulgels reinforced with host-guest supramolecular inclusion complexes for high fidelity direct ink writing

Direct ink writing (DIW) of Pickering emulsions offers great potential for constructing on-demand objects. However, the rheological properties of fluid emulsions greatly undermines the shape fidelity and structural integrity of 3D-printed structures. We solve here these challenges and realize a new route towards complex constructs for actual deployment. A dynamic, supramolecular host-guest hydrogel based on poly(ethylene glycol) and α-cyclodextrin was synthesized in the continuous phase of cellulose nanocrystal-stabilized Pickering emulsions. The storage modulus of the obtained emulgels could reach up to ∼113 kPa, while being shear thinning and yielding precise printability. Diverse complex architectures were possible with high shape fidelity and structural integrity. The printed objects, for example a double-wall cylinder with 75 layers, demonstrated excellent dimensional stability (shrinkage of 7 ± 2% after freeze-drying). With the merits of a simple fabrication process and the high biocompatibility of all the components, the concept of dynamic supramolecular hydrogel-reinforced emulgels represent a potentially versatile route to construct new materials and structures VIA DIW for use in bioproducts and biomedical devices.

Three-Dimensional Printed Cell Culture Model Based on Spherical Colloidal Lignin Particles and Cellulose Nanofibril-Alginate Hydrogel

Three-dimensional (3D) printing has been an emerging technique to fabricate precise scaffolds for biomedical applications. Cellulose nanofibril (CNF) hydrogels have attracted considerable attention as a material for 3D printing because of their shear-thinning properties. Combining cellulose nanofibril hydrogels with alginate is an effective method to enable cross-linking of the printed scaffolds in the presence of Ca²⁺ ions. In this work, spherical colloidal lignin particles (CLPs, also known as spherical lignin nanoparticles) were used to prepare CNF-alginate-CLP nanocomposite scaffolds. High-resolution images obtained by atomic force microscopy (AFM) showed that CLPs were homogeneously mixed with the CNF hydrogel. CLPs brought antioxidant properties to the CNF-alginate-CLP scaffolds in a concentration-dependent manner and increased the viscosity of the hydrogels at a low shear rate, which correspondingly provide better shape fidelity and printing resolution to the scaffolds. Interestingly, the CLPs did not affect the viscosity at high shear rates, showing that the shear thinning behavior typical for CNF hydrogels was retained, enabling easy printing. The CNF-alginate-CLP scaffolds demonstrated shape stability after printing, cross-linking, and storage in Dulbecco's phosphate buffer solution (DPBS +) containing Ca²⁺ and Mg²⁺ ions, up to 7 days. The 3D-printed scaffolds showed relative rehydration ratio values above 80% after freeze-drying, demonstrating a high water-retaining capability. Cell viability tests using hepatocellular carcinoma cell line HepG2 showed no negative effect of CLPs on cell proliferation. Fluorescence microscopy indicated that HepG2 cells grew not only on the surfaces but also inside the porous scaffolds. Overall, our results demonstrate that nanocomposite CNF-alginate-CLP scaffolds have high potential in soft-tissue engineering and regenerative-medicine applications.

Three-Dimensional Printed Cell Culture Model Based on Spherical Colloidal Lignin Particles and Cellulose Nanofibril-Alginate Hydrogel

Three-dimensional (3D) printing has been an emerging technique to fabricate precise scaffolds for biomedical applications. Cellulose nanofibril (CNF) hydrogels have attracted considerable attention as a material for 3D printing because of their shear-thinning properties. Combining cellulose nanofibril hydrogels with alginate is an effective method to enable cross-linking of the printed scaffolds in the presence of Ca2+ ions. In this work, spherical colloidal lignin particles (CLPs, also known as spherical lignin nanoparticles) were used to prepare CNF-alginate-CLP nanocomposite scaffolds. High-resolution images obtained by atomic force microscopy (AFM) showed that CLPs were homogeneously mixed with the CNF hydrogel. CLPs brought antioxidant properties to the CNF-alginate-CLP scaffolds in a concentration-dependent manner and increased the viscosity of the hydrogels at a low shear rate, which correspondingly provide better shape fidelity and printing resolution to the scaffolds. Interestingly, the CLPs did not affect the viscosity at high shear rates, showing that the shear thinning behavior typical for CNF hydrogels was retained, enabling easy printing. The CNF-alginate-CLP scaffolds demonstrated shape stability after printing, cross-linking, and storage in Dulbecco's phosphate buffer solution (DPBS +) containing Ca2+ and Mg2+ ions, up to 7 days. The 3D-printed scaffolds showed relative rehydration ratio values above 80% after freeze-drying, demonstrating a high water-retaining capability. Cell viability tests using hepatocellular carcinoma cell line HepG2 showed no negative effect of CLPs on cell proliferation. Fluorescence microscopy indicated that HepG2 cells grew not only on the surfaces but also inside the porous scaffolds. Overall, our results demonstrate that nanocomposite CNF-alginate-CLP scaffolds have high potential in soft-tissue engineering and regenerative-medicine applications.

Production of bacterial nanocellulose (BNC) and its application as a solid support in transition metal catalysed cross-coupling reactions

Bacterial nanocellulose (BNC) emerged as an attractive advanced biomaterial that provides desirable properties such as high strength, lightweight, tailorable surface chemistry, hydrophilicity, and biodegradability. BNC was successfully obtained from a wide range of carbon sources including sugars derived from grass biomass using Komagataeibacter medellinensis ID13488 strain with yields up to 6 g L^-1 in static fermentation. Produced BNC was utilized in straightforward catalyst preparation as a solid support for two different transition metals, palladium and copper with metal loading of 20 and 3 wt%, respectively. Sustainable catalysts were applied in the synthesis of valuable fine chemicals, such as biphenyl-4-amine and 4'-fluorobiphenyl-4-amine, used in drug discovery, perfumes and dye industries with excellent product yields of up to 99%. Pd/BNC catalyst was reused 4 times and applied in two consecutive reactions, Suzuki-Miyaura cross-coupling reaction followed by hydrogenation of nitro to amino group while Cu/BNC catalyst was examined in Chan-Lam coupling reaction. Overall, the environmentally benign process of obtaining nanocellulose from biomass, followed by its utilisation as a solid support in metal-catalysed reactions and its recovery has been described. These findings reveal that BNC is a good support material, and it can be used as a support for different catalytic systems.

Anaerobic treatment of cassava starch extraction wastewater using a horizontal flow filter with bamboo as support

Small-scale sour starch agroindustry in Colombia suffer from absence of water treatment. Although starch processing plants produce diluted wastewater, it is a source of pollution and cause environmental problems to the nearby rural population. A laboratory scale anaerobic horizontal flow filter packed with bamboo pieces was evaluated for the treatment of cassava starch extraction wastewater. The wastewater used in the experimentation was the draining water of the starch sedimentation basin. The reactor was operated for 6 months. It was inoculated with a semi-granular sludge from an anaerobic UASB reactor of a slaughterhouse. Maximum organic loading rate (OLR) applied was 11.8g COD/L d without dilution of the wastewater. At steady state and maximum OLR applied, 87% of the COD was removed and a gas productivity of 3.7L/L d was achieved. The average biogas yield was 0.36L/g COD removed. Methane content in the biogas was in the range of 69-81%. The total suspended solids (TSS) removed were 67%. The relative high lactic acid content did not negatively influence the performance of the reactor. No perturbation due to cyanide (3-5mg/L) was observed during the reactor operation. The results obtained indicated that the anaerobic horizontal flow filter could be used efficiently for the treatment of wastewater from Colombian starch processing small-scale agroindustry.

Active spleno-femoral shunt avoids splanchnic congestion during portal triad occlusion: an experimental study

Portal triad occlusion (PTO) is often performed during hepatic resections for trauma or malignancies to minimize intraoperative blood loss. The pringle maneuver is also regularly required during liver transplantation. This maneuver leads to temporary hepatic ischemia and may be associated with splanchnic blood flow congestion, promoting undesirable hemodynamic disturbances in some patients. Veno-venous bypass is a useful, easily performed technique that may avoid those deleterious hemodynamic effects of PTO. We tested the hypothesis that an active spleno-femoral shunt maintains hemodynamic stability and promotes complete decompression of the mesenteric bed, avoiding intestinal mucosal blood congestion, during PTO.

METHODS

Seven dogs (17.2 +/- 0.9 kg) were subjected to 45 minutes of hepatic ischemia during which there was an active spleno-femoral shunt. Systemic hemodynamics were evaluated through Swan-Ganz and arterial catheters. Splanchnic perfusion was assessed by portal vein blood flow and hepatic artery blood flow (PVBF and HABF, ultrasonic flowprobe), intestinal mucosal-arterial pCO(2) gradient (D(t-a)pCO(2), tonometry), and regional O(2)-derived variables.

RESULTS

No significant changes in systemic and regional parameters were observed during the ischemia period. During reperfusion, a significant decrease in mean arterial pressure, PVBF, and arterial pH was observed. A significant increase in ALT and D(t-a)pCO(2) (4.8 +/- 2.5 to 18.9 +/- 3 mm Hg) was also observed following hepatic blood flow restoration.

CONCLUSION

Spleno-femoral shunt maintains systemic hemodynamic stability, with an effective decompression of the splanchnic bed during portal triad occlusion. The deleterious hemodynamic and metabolic effects observed during reperfusion period, such as transitory hypotension, high D(t-a)pCO(2), and acidemia, were associated with an isolated hepatic ischemia-reperfusion injury, not with the blood congestion in the splanchnic bed.

Ethyl-2-cyanoacrylate fixation of the cranial bone flap after craniotomy

BACKGROUND

This procedure was done in order to evaluate the efficacy and safety of ethylcyanoacrylate as an adhesive for fixation of the bone flap.

METHODS

One hundred consecutive craniotomies in patients older than 16 years in which the bone flap was fixed with ethyl-2-cyanoacrylate were studied. The osteosynthesis and any complications in all cases were followed clinically and radiologically for 3 months.

RESULTS

Clinical and radiographic observation demonstrated that osteosynthesis was produced in 100% of the cases with no complications related to this procedure.

CONCLUSION

This technique proved to be safe, fast, and easy to accomplish, with immediate stability of the bone flap and excellent cosmetic results.

Laparoscopic repair of pleural laceration produced during truncal vagotomy: case report

A partial pneumothorax developed in a patient undergoing laparoscopic truncal vagotomy when a small pleural laceration was accidentally produced. Changes in oxygen saturation and PETCO2 were immediately detected by the anesthesiologist and measures were taken to maintain the patient's ventilatory stability. The pleural laceration was repaired laparoscopically, and the pneumothorax was corrected by ventilatory manipulation, avoiding the placement of a chest tube. The procedure was completed uneventfully. Literature about the causes of pneumothorax during laparoscopic procedures as well as preventive and therapy viewed.

[Malignant pleural mesotheliomas]

An increase in incidence of malignant pleural mesotheliomas has been noted recently. In order to assess our own experience, we reviewed all medical records and biopsies of patients who were seen with this diagnosis in Hospital Maria Ferrer between January 1986 and December 1997. Clinical data of 17 patients were analyzed. Mean age was 59 years, 76% were male. Industrial or environmental exposure to asbestos was established in 9 patients (53%). Most common symptoms at presentation were dyspnea (88%) and chest pain (65%). Pleural thickening with or without effusion was the usual finding in chest X rays and CAT scans. Biochemical analysis of pleural fluids was consistent with exudate. Diagnosis was performed by thoracotomy (47%), needle biopsy (23.5%) and videothoracoscopy (29.5%). Histological samples were available for review in 16 of the 17 patients: they were epithelial (10), sarcomatoid (2) and mixed tumors (4). Treatment reflected varying approaches. Palliative methods (pleurodesis, chemotherapy and radiotherapy) were preferred at the beginning while more aggressive interventions are performed nowadays. Pleuroneumonectomy alone or in combination with other therapies was carried out in 5 patients with no operative mortality although some complications occurred such as empyema, bronchopleural fistula and severe chest pain. Survival rate for all groups was 10.5 +/- 5.9 months. However, the mean survival of patients who underwent surgery was 17.5 +/- 2.1 months (p < 0.04) with an associated improvement in quality of life. Therefore, we consider that surgery associated with other therapies offers at present, the best therapeutic option for this bad prognosis condition.

Implication of beta 1- and beta 2-adrenergic receptors in the antinociceptive effect of tricyclic antidepressants

Tricyclic antidepressants have been shown to be useful for the treatment of pain of varying etiology. Monoaminergic systems seem to be implicated in this phenomenon. In this study, the influence of the selective beta 1- (CGP 20712A) and beta 2- (ICI 118551) adrenergic blockers on the antinociceptive effect of desipramine and nortriptyline was studied in mice using physical and chemical nociceptive tests that implicate different levels of sensory-motor integration in the central nervous system (CNS). An activity test was performed to detect "false positive" or "false negative" results. Results obtained show that both CGP 20712A and ICI 118551 are able to antagonize the antinociceptive effect of these antidepressants in physical tests (hot-plate and tail-flick). However, in chemical tests (acetic acid and formalin), the analgesic effect of the antidepressants used was only antagonized by CGP 20712A. These results suggest that the analgesic effect of desipramine and nortriptyline is mediated by beta-adrenoceptors. The beta-adrenoceptor involved depends on the type of nociceptive stimulus: beta 1 and beta 2 are both implicated when the stimulus is physical, but only beta 1 is involved when the stimulus is chemical.

[Tuberculin reactivity in the elderly. Comparison of PPD-RT23 and PPD-CT68]

BACKGROUND

Tuberculin reactivity varies on the basis of the PPD lot and the population studied.

AIMS

To compare tuberculin reactivity in the elderly following successive applications of PPD from 2 different lots.

POPULATION

Elderly nursing-home residents, from the province of Guadalajara, Spain.

METHODS

The elderly were randomly selected and administered with a first Mantoux intradermoreaction of 2 UT of PPD-RT23 or 2 UT of PPD-CT68. The study was performed in a scaled basis, eliminating the reactors (transversal induration > or = 5 mm at 72 h). The non reactors were restudied with a second and third test in alternative arms at a 7-day interval with the same lot and initial dosis of PPD. At one year the scaled study was repeated with 2 UT of PPD-CT68.

RESULTS

Eight hundred and thirty elderly persons (79 +/- 9 years) were studied, with 410 receiving PPD-RT23 and 420 receiving PPD-CT68. No differences were observed in the percentage of initial reactors (31% vs 29%; p = 0.26) or in the booster reactors (23% vs 20%; p = 0.16). The PPD-RT23 was found to trigger more intensive reactions than the PPD-CT68 leading to a greater frequency of indurations > 14 mm. After one year, the percentage of stable reactions was similar in both groups (50.5% vs 49.5%; NS).

CONCLUSIONS

1) In elderly nursing-home residents 2 UT of PPD-RT23 and 2 UT of PPD-CT68 showed similar results in regard to the number of reactors and the frequency of booster reactions. 2) The proportion of intense reactions was greater with 2 UT of PPD-RT23 than with 2 UT of PPD-CT68. 3) The stability of the reactions at one year was independent of the lot used in the first phase.

[Usefulness of the PCR technique (polymerase chain reaction) in the follow-up of patients infected with hepatitis C virus. Preliminary communication]

In the study we show the usefulness of PCR (polymerase chain reaction) to follow patients with chronic hepatitis, infected with hepatitis C virus (HCV) of Centro Médico de Caracas. The study included 14 patients: 12 anti-HCV positive, 1 with chronic autoimmune hepatitis and 1 classified as non B-non C hepatitis. The patients were divided in 3 groups: Group 1 (5 pretreatment patients, anti-HCV+), 4 with increase in ALT and PCR positive, 1 with normal ALT and PCR negative. Group 2 (7 treated with recombinant interferon alpha 2b), 4 without normalization of ALT and PCR positive, 3 with normalization of ALT and PCR negative. Group 3 (control) 2 patients anti-HCV negative and PCR negative. Two posttreatment patients could be genotyped: one patient was infected with 1a and showed an early relapse with treatment and the other was infected with genotype 1b, which is reported to be more refractory to antiviral treatment.

CONCLUSIONS

the results show a 100% correlation between biochemical markers of HCV infected patients and the presence of viral RNA detected by PCR. the usefulness of determination of genotype to assess any prognostic value of this parameter in Venezuela is discussed.

[Biomedical aspects of 4 cases of snake bites by Lachesis muta (Ophidia: Viperidae) in Costa Rica]

Three out of four cases of snake bite by Lachesis muta stenophrys (Bushmaster) in Costa Rica were fatal and one recovered after a long period of hospitalization. Initial symptoms were similar to those of bothropic envenomation: intense pain, nausea, vomiting, sweating, and excitability, but differing in the magnitude of a tremendous edema and in the absence of intensive bleeding and phlyctenae. We found important alterations in arterial blood pressure and in the activity and concentration of coagulation factors. All patients showed infections, and necrosis was found in at least three of them.

Replacement of the trachea with dura mater. Experimental work

Results in a series of 30 dogs subjected to tracheal resection and repair are described. The dogs were divided into three groups. Seven to ten rings of the trachea were resected and then were replaced by a prosthesis made of dura mater and stainless steel wire. Different aspects of the procedures for respiratory support in the three groups are evaluated, as are the different kinds of prostheses used. Our results with ventilatory studies showed taht the mose effective means of respiratory support was insertion of an endotracheal tube after thoracotomy. Among the prostheses, the one used in the third group of dogs, a stainless steel spring covered with only one layer of dura mater, allowed a longer survival period but eventually caused late scarring and stenosis.