Removal of Pb pollution using alginate-coupled magnetic sludge biochar: Solidification and stabilization behavior and electron promotion mechanisms.

Environmental and human health problems caused by Pb pollution have attracted much attention, and solidification and stabilization are effective means for its remediation. Improving the ability of biochar to remediate heavy metals through modification is the focus of current biochar research. This study used calcium-alginate gel (GB) and Fe3+ (magnetic) to encapsulate and improve sludge biochar (SB), and explored the adsorption behavior and passivation mechanism of Pb2+ on it from outside to inside. The magnetic-biochar (MB) in magnetic-biochar-gel microspheres (MBGB) showed a homogeneous dispersion and part of the Fe ion was detached from the MB into the three-dimensional pores of the gel. The results of kinetic, isothermal and pH adsorption experiments showed that the MBGB has 108.4 % and 200 % higher Pb2+ adsorption capacity and rate than SB and can be applied to pH 3-9. The adsorption of Pb2+ by MBGB is a multilayer adsorption with both physical and chemical mechanisms. Mineralogical and electrochemical results demonstrate that the cross-linking of the gel with magnetic-biochar (MB) can provide a directional diffusion channel for Pb2+ from the outside to the inside. The electron transfer rate of MBGB was significantly higher than that of SB (222.2 %) after the reaction. The dissolved cations and electrons on the MB guide Pb2+ from the MBGB surface to the internal MB quickly via accelerating the electron transfer and migration rate between Pb2+ and MB. Subsequently, the abundance of PO43- on the MB ensures stable mineral precipitation (Pyromorphite). Moreover, four-step extraction analysis confirmed that most of Pb2+ in MBGB was stable (36.2 % acid-soluble and 47.6 % non-bioavailable). Meanwhile, the Pb adsorption efficiency of MBGB was still >93.0 % after three cycles of adsorption-desorption. Excellent reuse performance and stability guarantee the environmental security of MBGB. The results of the study provide theoretical support for the efficient treatment of Pb2+ polluted water assisted by gel materials.

"3-in-1" Hybrid Biocatalysts: Association of Yeast Cells Immobilized in a Sol-Gel Matrix for Determining Sewage Pollution.

This study presents a novel ″3-in-1″ hybrid biocatalyst design that combines the individual efficiency of microorganisms while avoiding negative interactions between them. Yeast cells of Ogataea polymorpha VKM Y-2559, Blastobotrys adeninivorans VKM Y-2677, and Debaryomyces hansenii VKM Y-2482 were immobilized in an organosilicon material by using the sol-gel method, resulting in a hybrid biocatalyst. The catalytic activity of the immobilized microorganism mixture was evaluated by employing it as the bioreceptor element of a biosensor. Optical and scanning electron microscopies were used to examine the morphology of the biohybrid material. Elemental distribution analysis confirmed the encapsulation of yeast cells in a matrix composed of methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS) (85 and 15 vol %, respectively). The resulting heterogeneous biocatalyst exhibited excellent performance in determining the biochemical oxygen demand (BOD) index in real surface water samples, with a sensitivity coefficient of 50 ± 3 × 10-3·min-1, a concentration range of 0.3-31 mg/L, long-term stability for 25 days, and a relative standard deviation of 3.8%. These findings demonstrate the potential of the developed hybrid biocatalyst for effective pollution monitoring and wastewater treatment applications.

Engineered cell-based therapies in ex vivo ready-made CellDex capsules have therapeutic efficacy in solid tumors.

Encapsulated cell-based therapies for solid tumors have shown promising results in pre-clinical settings. However, the inability to culture encapsulated therapeutic cells prior to their transplantation has limited their translation into clinical settings. In this study, we created a wide variety of engineered therapeutic cells (ThC) loaded in micropore-forming gelatin methacryloyl (GelMA) hydrogel (CellDex) capsules that can be cultured in vitro prior to their transplantation in surgically debulked solid tumors. We show that both allogeneic and autologous engineered cells, such as stem cells (SCs), macrophages, NK cells, and T cells, proliferate within CellDex capsules and migrate out of the gel in vitro and in vivo. Furthermore, tumor cell specific therapeutic proteins and oncolytic viruses released from CellDex capsules retain and prolong their anti-tumor effects. In vivo, ThCs in pre-manufactured Celldex capsules persist long-term and track tumor cells. Moreover, chimeric antigen receptor (CAR) T cell bearing CellDex (T-CellDex) and human SC releasing therapeutic proteins (hSC-CellDex) capsules show therapeutic efficacy in metastatic and primary brain tumor resection models that mimic standard of care of tumor resection in patients. Overall, this unique approach of pre-manufactured micropore-forming CellDex capsules offers an effective off-the-shelf clinically viable strategy to treat solid tumors locally.

In Vitro Models for the Development of Peripheral Nerve Conduits, Part I: Design of a Fibrin Gel-Based Non-Contact Test.

Current clinical strategies to repair peripheral nerve injuries draw on different approaches depending on the extent of lost tissue. Nerve guidance conduits (NGCs) are considered to be a promising, off-the-shelf alternative to autografts when modest gaps need to be repaired. Unfortunately, to date, the implantation of an NGC prevents the sacrifice of a healthy nerve at the price of suboptimal clinical performance. Despite the significant number of materials and fabrication strategies proposed, an ideal combination has not been yet identified. Validation and comparison of NGCs ultimately requires in vivo animal testing due to the lack of alternative models, but in the spirit of the 3R principles, a reliable in vitro model for preliminary screening is highly desirable. Nevertheless, more traditional in vitro tests, and direct cell seeding on the material in particular, are not representative of the actual regeneration scenario. Thus, we have designed a very simple set-up in the attempt to appreciate the relevant features of NGCs through in vitro testing, and we have verified its applicability using electrospun NGCs. To this aim, neural cells were encapsulated in a loose fibrin gel and enclosed within the NGC membrane. Different thicknesses and porosity values of two popular polymers (namely gelatin and polycaprolactone) were compared. Results indicate that, with specific implementation, the system might represent a useful tool to characterize crucial NGC design aspects.

A comparative analytical study on reagent-fused silica gel plate and wax painted paper-based microfluidic device for serological testing.

The detection and identification of body fluids at a crime scene shed light on the events which might have occurred and the people involved in the crime; the techniques used being lengthy, makes the on-scene detection a tough process to carry out and handle. This study aims to develop an on-spot detection method for serological testing using silica gel encapsulation technique and a modified microfluidic paper-based analytical device (µPADs). Kastle-Meyer reagent was incorporated into the µPAD and Silica Gel plate and was subsequently validated for the detection of blood. This study revealed that the µPAD was a better option. The emerging technique of µPADs allows a cost-effective and simple method of detection for body fluids. The fibrous network of the paper is manipulated to fabricate a guided channel for the fluid flow. The guided channels in the modified µPADs were fabricated by patterning a hydrophobic barrier out of wax. The analyte of interest for this study is blood but the principle can be modified to include other biological fluids.

Formation of Spherical Palmelloid Colony with Enhanced Lipid Accumulation by Gel Encapsulation of Chlamydomonas debaryana NIES-2212.

Microalgae such as Chlamydomonas reinhardtii accumulate triacylglycerol (TAG), which is a potential source of biofuels, under stress conditions such as nitrogen deprivation, whereas Chlamydomonas debaryana NIES-2212 has previously been identified and characterized as one of the rare species of Chlamydomonas, which massively accumulates TAG in the stationary phase without external stress. As the high density of the cells in the stationary phase was supposed to act as a trigger for the accumulation of TAG in C. debaryana, in this study, C. debaryana was encapsulated in a Ca2+-alginate gel for the culture with high cell density. We discovered that the growth of the encapsulated cells resulted in the formation of spherical palmelloid colonies with high cell density, where daughter cells with truncated flagella remained wrapped within the mother cell walls. Interestingly, gel encapsulation markedly promoted proliferation of C. debaryana cells, and the encapsulated cells reached the stationary phase earlier than that of the free-living cells. Gel encapsulation also enhanced TAG accumulation. Gene expression analysis revealed that two genes of acyltransferases, DGAT1 and DGTT3, were upregulated in the stationary phase of free-living C. debaryana. In addition, the gene expression of these acyltransferases increased earlier in the encapsulated cells than that in the free-living cells. The enhanced production of TAG by alginate gel encapsulation was not found in C. reinhardtii which is known to use a different repertoire of acyltransferases in lipid accumulation.

Synthesis and encapsulation of V(IV,V) compounds in silica nanoparticles targeting development of antioxidant and antiradical nanomaterials.

The quest for effective treatments of oxidative stress has concentrated over the years on new nanomaterials with improved antioxidant and antiradical activity, thereby attracting broad research interest. In that regard, research efforts in our lab were launched to pursue such hybrid materials involving a) synthesis of silica gel matrices, b) evaluation of the suitability of atoxic matrices as potential carriers for the controlled release of V(IV)(VOSO4), V(V)(NaVO3) compounds and a newly synthesized heterometallic lithium-vanadium(IV,V) tetranuclear compound containing vanadium-bound hydroxycarboxylic 1,3-diamine-2-propanol-N,N,N',N'-tetraacetic acid (DPOT), and c) investigation of structural and textural properties of silica nanoparticles (NPs) by different and complementary characterization techniques, inquiring into the nature of the encapsulated vanadium species and their interaction with the siloxane matrix, collectively targeting novel antioxidant and antiradical nanomaterials biotechnology. The physicochemical characterization of the vanadium-loaded SiO2 NPs led to the formulation of optimized material configuration linked to the delivery of the encapsulated antioxidant-antiradical load. Entrapment and drug release studies showed a) the competence of hybrid nanoparticles with respect to encapsulation efficiency of the vanadium compound (concentration dependence), b) congruence with the physicochemical features determined, and c) a well-defined release profile of NP load. Antioxidant properties and the free radical scavenging capacity of the new hybrid materials (containing VOSO4, NaVO3, and V-DPOT) were demonstrated through a) 2-diphenyl-1-picrylhydrazyl (DPPH) free radical, and b) intracellular-extracellular reactive oxygen species (ROS) assays, through UV-Visible spectroscopy techniques, collectively showing that the hybrid silica NPs (empty-loaded) could serve as an efficient platform for nanodrug formulations counteracting oxidative stress.

Interactions of sol-gel encapsulated acyclovir with silica matrix.

Encapsulation of drugs is promising strategy to improve their pharmacological and consumer properties. The functional properties of the encapsulated drug depend on interactions between the drug and capsule material. Antiviral drug acyclovir (ACV) was encapsulated in silica matrixes using sol-gel technology. The effects of synthesis pH and the silica matrix functionalization by organic groups on the drug - silica matrix interaction were studied. The interactions were investigated using UV/VIS spectroscopy and Fourier-transform infrared (FTIR) spectroscopy. The nature of the interactions in the obtained composites was discussed. It was found that the drug self-association in some composites can be provoked by electrostatic repulsion between the drug and the silica matrix.

Thermal Hyperactivation and Stabilization of ß-Galactosidase from Bacillus circulans through a Silica Sol-Gel Process Mediated by Chitosan-Metal Chelates.

The research of simple and fast enzyme immobilization methods, preserving the enzyme activity and improving the thermal stability, is in the spotlight. The objective of this work is to develop a ß-galactosidase immobilization one-pot route, combining the silica sol-gel encapsulation (SSGE) process with a metal chelation strategy by using chitosan and Ca2+, Zn2+, or Cu2+ cations. The results show that the presence of cations does not affect the encapsulation efficiency (81%) and has positive effects on the maximum catalytic potential, especially at 60 °C and in the presence of Ca2+ ions (MPC = 2203). They enhance the biocatalyst thermal stability and promote hyperactivation with respect to the soluble enzyme at 60 °C (1.6 times higher MPC). The biocatalyst prepared with Zn2+ ions exhibits also thermal hyperactivation in the first 30 min of heating (1.3 times more residual activity), but the enzyme is not stabilized (0.9 times lower MPC); also, the presence of Cu2+ ions does not promote hyperactivation or stabilization of the enzyme (0.3 times lower MPC) at this high temperature. These facts are reflected in the hydrolytic and transgalactosylation activities of the enzyme (33.6-57.4% total lactose conversion), higher than that reported with analogue biocatalysts. The physicochemical characterization of the obtained solid biocatalysts by SEM, TEM, XRF, and XPS indicates that chitosan-metal chelation has an important role in the encapsulation process and that a low metal degree incorporation (8.85 ppm of Ca2+) on the solid biocatalyst favors the thermal hyperactivation and stabilization of the evaluated ß-galactosidase. This work contributes to the understanding of the SSGE process mediated by chitosan-metal chelates, which is a simple and fast one-pot immobilization strategy.

Synthesis of silica-alginate nanoparticles and their potential application as pH-responsive drug carriers.

Composite silica-alginate nanoparticles were prepared via silica sol-gel technique using a water-in-oil microemulsion system. In our system, cyclohexane served as the bulk oil phase into which aqueous solutions of sodium alginate were dispersed as droplets that confined nanoparticle formation after addition of tetraethylorthosilicate (TEOS). Our studies showed that much of the particle growth is completed within the first 24 hours and reaction times up to 120 hours only resulted in an additional 5% increase in particle diameter. Average particle size was found to decrease with increasing water-to-surfactant molar ratio (R) and with increasing cocentration of alginate in the aqueous phase. The potential for drug loading during particle formation was demonstrated using rhodamine B as a model drug. In vitro release studies showed that particles incubated in pH 2.5 phosphate buffer released only about 7% of the drug load in 27 days, while 42% was released in pH 7.5 phosphate buffer over the same period. Analysis of the release profile suggested that rhodamine B was homogeneously distributed throughout the particle and that the drug diffusivity was 40-fold greater in pH 7.5 buffer compared to that at pH 2.5. These results suggest that silica-alginate nanoparticles could be used as a pH-responsive drug carrier for controlled drug release.

Sol-gel encapsulation of pullulanase in the presence of hybrid magnetic (Fe3O4-chitosan) nanoparticles improves thermal and operational stability.

Pullulanase was sol-gel encapsulated in the presence of magnetic chitosan/Fe3O4 nanoparticles. The resulting immobilized pullulanase was characterized by scanning electron microscopy, vibrating sample magnetometry, Fourier transform infrared spectroscopy and thermogravimetric analysis. The results showed that the addition of pullulanase created a more regular surface on the sol-gel matrix and an enhanced magnetic response to an applied magnetic field. The maximal activity retention (83.9%) and specific activity (291.7 U/mg) of the immobilized pullulanase were observed under optimized conditions including an octyltriethoxysilane:tetraethoxysilane (OTES:TEOS) ratio of 1:2 and enzyme concentration of 0.484 mg/mL sol. The immobilized enzyme exhibited good thermal stability. When the temperature was above 60 °C, the immobilized pullulanase showed significantly higher activity than the free enzyme (p < 0.01); enzyme immobilized by simple sol-gel encapsulation and co-immobilized by crosslinking-encapsulation retained 52 and 69% of their initial activity after 5 h at 62 °C, respectively, compared to 11% for the free enzyme. Moreover, the stability of the pullulanase was improved by crosslinking-encapsulation, as the enzyme retained more than 85 and 81% of its original activity after 5 and 6 consecutive reuses, respectively, compared to 80 and 72% of its original activity for simple sol-gel encapsulated enzymes. This indicated the leakage of enzyme molecules through the pores of the gel was substantially abated by cross-linking. Such immobilized pullulanase provides high stability and ease of enzyme recovery, characteristics that are advantageous for applications in the food industry that involve continuous starch processing.

Silica sol-gel encapsulated methylotrophic yeast as filling of biofilters for the removal of methanol from industrial wastewater.

This research suggests the use of new hybrid biomaterials based on methylotrophic yeast cells covered by an alkyl-modified silica shell as biocatalysts. The hybrid biomaterials are produced by sol-gel chemistry from silane precursors. The shell protects microbial cells from harmful effects of acidic environment. Potential use of the hybrid biomaterials based on methylotrophic yeast Ogataea polymorpha VKM Y-2559 encapsulated into alkyl-modified silica matrix for biofilters is represented for the first time. Organo-silica shells covering yeast cells effectively protect them from exposure to harmful factors, including extreme values of pH. The biofilter based on the organic silica matrix encapsulated in the methylotrophic yeast Ogataea polymorpha BKM Y-2559 has an oxidizing power of 3 times more than the capacity of the aeration tanks used at the chemical plants during methyl alcohol production. This may lead to the development of new and effective industrial wastewater treatment technologies.

Utilizing the age-related widening of the gingival crevice as a potential non-invasive vaccination route: Prospects for elderly vaccination.

Gingival crevice (GC) increases with age allowing periodontopathic bacteria and its products to enter. We hypothesize that by mimicking this event we can utilize the GC as a potential vaccination route. Here, we used 20 wk-old (young) and 77 wk-old (old) Sprague-Dawley rats. Initially, we elucidated the difference between oral-administration and oral-supplementation in both young and old rats and, subsequently, we determined the optimal component concentration for xanthan gel-encapsulation. Next, through molecular docking, we simulated xanthan gel-encapsulation of a representative antigen (for this study we used influenza H5N1 hemagglutinin) in order to verify that target epitopes were not blocked. Lastly, we compared the antibody titer among gingival-vaccinated rats (old and young) and, likewise, we evaluated the antibody titer produced via the gingival route as compared to other vaccination routes (intradermal, oral, sublingual). Rat blood serum was collected for further downstream analyses. Throughout the study, we were able to establish the following conditions: higher target components enter old rats via oral-supplementation; 100 µg mL(-1) is the optimal component concentration for xanthan gel-encapsulation; and xanthan gel-encapsulation leaves antibody epitopes exposed. More importantly, we observed that gingival-vaccinated old rats have higher antibody titer as compared to young rats and, likewise, we found that antibody titer elicited via gingival vaccination is comparable to other mucosal vaccination routes. Thus, we propose that the GC has the potential to serve as a non-invasive vaccination route.

Relationship between sol-gel conditions and enzyme stability: a case study with ß-galactosidase/silica biocatalyst for whey hydrolysis.

The sol-gel process has been very useful for preparing active and stable biocatalysts, with the possibility of being reused. Especially those based on silica are well known. However, the study of the enzyme behavior during this process is not well understood until now and more, if the surfactant is involved in the synthesis mixture. This work is devoted to the encapsulation of ß-galactosidase from Bacillus circulans in silica by sol-gel process, assisted by non-ionic Triton X-100 surfactant. The correlation between enzyme activity results for the ß-galactosidase in three different environments (soluble in buffered aqueous reference solution, in the silica sol, and entrapment on the silica matrix) explains the enzyme behavior under stress conditions offered by the silica sol composition and gelation conditions. A stable ß-galactosidase/silica biocatalyst is obtained using sodium silicate, which is a cheap source of silica, in the presence of non-ionic Triton X-100, which avoids the enzyme deactivation, even at 40 °C. The obtained biocatalyst is used in the whey hydrolysis for obtaining high value products from this waste. The preservation of the enzyme stability, which is one of the most important challenges on the enzyme immobilization through the silica sol-gel, is achieved in this study.

Sol-gel encapsulation of binary Zn(II) compounds in silica nanoparticles. Structure-activity correlations in hybrid materials targeting Zn(II) antibacterial use.

In the emerging issue of enhanced multi-resistant properties in infectious pathogens, new nanomaterials with optimally efficient antibacterial activity and lower toxicity than other species attract considerable research interest. In an effort to develop such efficient antibacterials, we a) synthesized acid-catalyzed silica-gel matrices, b) evaluated the suitability of these matrices as potential carrier materials for controlled release of ZnSO4 and a new Zn(II) binary complex with a suitably designed well-defined Schiff base, and c) investigated structural and textural properties of the nanomaterials. Physicochemical characterization of the (empty-loaded) silica-nanoparticles led to an optimized material configuration linked to the delivery of the encapsulated antibacterial zinc load. Entrapment and drug release studies showed the competence of hybrid nanoparticles with respect to the a) zinc loading capacity, b) congruence with zinc physicochemical attributes, and c) release profile of their zinc load. The material antimicrobial properties were demonstrated against Gram-positive (Staphylococcus aureus, Bacillus subtilis, Bacillus cereus) and negative (Escherichia coli, Pseudomonas aeruginosa, Xanthomonas campestris) bacteria using modified agar diffusion methods. ZnSO4 showed less extensive antimicrobial behavior compared to Zn(II)-Schiff, implying that the Zn(II)-bound ligand enhances zinc antimicrobial properties. All zinc-loaded nanoparticles were less antimicrobially active than zinc compounds alone, as encapsulation controls their release, thereby attenuating their antimicrobial activity. To this end, as the amount of loaded zinc increases, the antimicrobial behavior of the nano-agent improves. Collectively, for the first time, sol-gel zinc-loaded silica-nanoparticles were shown to exhibit well-defined antimicrobial activity, justifying due attention to further development of antibacterial nanotechnology.

Trifluorosilane induced structural transitions in beta-lactoglobulin in sol and gel.

Fluoroalcohols such as 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) are strong inducers of protein secondary structure. Here, hydrolyzed (3,3,3-trifluoropropyl)trimethoxysilane (3F) is demonstrated to exhibit greater protein conformation inducing activity than HFIP, which is preserved when 3F is copolymerized in tetraethylorthosilicate (TEOS) sol-gels through protein molecular imprinting. Hydrolyzed 3F formed a pre-polymerization complex with the template protein, ß-lactoglobulin, inducing distinct α-helical structures as evidenced by circular dichroism. Fluorescence resonance energy transfer between tryptophan and the lipophilic probe 1-anilinonaphthalene-8-sulfonic acid showed a sharp molten globule (MG) transition at 0.2M 3F, whereas HFIP induced a broad MG transition centered at 0.6M HFIP. The 3F-induced BLG conformation transitions were retained upon gelation, validating use of the fluorosilane as a conformation directing functional monomer readily incorporated into sol-gels.