The α-linkage in funoran and agarose could be hydrolyzed by a GH96 family enzyme: Discovery of the α-funoranase

Agarans represent a group of galactans extracted from red algae. Funoran and agarose are the two major types and commercially applied polysaccharides of agaran. Although the glycoside hydrolases targeting β-glycosidic bonds of agaran have been widely investigated, those capable of degrading α-glycosidic bonds of agarose were limited, and the enzyme degrading α-linkages of funoran has not been reported till now. In this study, a GH96 family enzyme BiAF96A_Aq from a marine bacterium Aquimarina sp. AD1 was heterologously expressed in Escherichia coli. BiAF96A_Aq exhibited dual activities towards the characteristic structure of funoran and agarose, underscoring the multifunctionality of GH96 family members. Glycomics and NMR analysis revealed that BiAF96A_Aq hydrolyzed the α-1,3 glycosidic bonds between 3,6-anhydro-α-l-galactopyranose (LA) and β-d-galactopyranose-6-sulfate (G6S) of funoran, as well as LA and β-d-galactopyranose (G) of agarose, through an endo-acting manner. The end products of BiAF96A_Aq were majorly composed of disaccharides and tetrasaccharides. The identification of the activity of BiAF96A_Aq on funoran indicated the first discovery of the funoran hydrolase for α-1,3 linkage. Considering the novel catalytic reaction, we proposed to name this activity as "α-funoranase" and recommended the assignment of a dedicated EC number for its classification.

Design and Development of Transient Sensing Devices for Healthcare Applications

With the ever-growing requirements in the healthcare sector aimed at personalized diagnostics and treatment, continuous and real-time monitoring of relevant parameters is gaining significant traction. In many applications, health status monitoring may be carried out by dedicated wearable or implantable sensing devices only within a defined period and followed by sensor removal without additional risks for the patient. At the same time, disposal of the increasing number of conventional portable electronic devices with short life cycles raises serious environmental concerns due to the dangerous accumulation of electronic and chemical waste. An attractive solution to address these complex and contradictory demands is offered by biodegradable sensing devices. Such devices may be able to perform required tests within a programmed period and then disappear by safe resorption in the body or harmless degradation in the environment. This work critically assesses the design and development concepts related to biodegradable and bioresorbable sensors for healthcare applications. Different aspects are comprehensively addressed, from fundamental material properties and sensing principles to application-tailored designs, fabrication techniques, and device implementations. The emerging approaches spanning the last 5 years are emphasized and a broad insight into the most important challenges and future perspectives of biodegradable sensors in healthcare are provided.

Form Factor-Free Boron Nitride Nanotube-Agarose Composites for Neutron Shielding

Boron nitride nanotubes (BNNTs) have remarkable mechanical and thermal properties and are suitable for neutron shielding due to boron. Because BNNTs exist in bundled and stiff shapes, limiting their practical applications, however, it is essential to improve their formability and processability. In this study, we demonstrate form-factor-free BNNTs and agarose composites for use in neutron shielding for the first time; they are fabricated by mixing hydrophilic agarose with noncovalently functionalized water-soluble BNNTs (p-BNNTs). The mechanical properties of the agarose/p-BNNT composite films surpass those of conventional commodity plastics. When the p-BNNT concentration increased, the neutron linear attenuation coefficient of the composite film increases from 0.574 ± 0.010 to 0.765 ± 0.062 mm-1, which is comparable to that of conventional rigid shielding materials. In particular, the addition of 10 wt % p-BNNTs to agarose results in excellent form-factor flexibility, neutron shielding, and mechanical properties, thus rendering it a promising candidate for the nuclear industry.

T7 phage-assisted evolution of riboswitches using error-prone replication and dual selection

Leveraging riboswitches, non-coding mRNA fragments pivotal to gene regulation, poses a challenge in effectively selecting and enriching these functional genetic sensors, which can toggle between ON and OFF states in response to their cognate inducers. Here, we show our engineered phage T7, enabling the evolution of a theophylline riboswitch. We have replaced T7's DNA polymerase with a transcription factor controlled by a theophylline riboswitch and have created two types of host environments to propagate the engineered phage. Both types host an error-prone T7 DNA polymerase regulated by a T7 promoter along with another critical gene-either cmk or pifA, depending on the host type. The cmk gene is necessary for T7 replication and is used in the first host type for selection in the riboswitch's ON state. Conversely, the second host type incorporates the pifA gene, leading to abortive T7 infections and used for selection in the riboswitch's OFF state. This dual-selection system, termed T7AE, was then applied to a library of 65,536 engineered T7 phages, each carrying randomized riboswitch variants. Through successive passage in both host types with and without theophylline, we observed an enrichment of phages encoding functional riboswitches that conferred a fitness advantage to the phage in both hosts. The T7AE technique thereby opens new pathways for the evolution and advancement of gene switches, including non-coding RNA-based switches, setting the stage for significant strides in synthetic biology.

SURE gel electrophoresis: A method for improved detection and purification of dilute nucleic acid samples

Agarose gel electrophoresis is performed routinely by molecular biologists as both an analytical and a preparative method for characterization of nucleic acids. Gel analysis of highly dilute DNA solutions is challenging because of the limited sensitivity of detection available with conventional methods. In this study a new approach is described for concentrating samples directly within gels called SURE (successive reloading) electrophoresis. The approach involves loading of dilute samples multiple times into a single well, with each loading followed by a brief pulse of electrical current before the next sample is loaded. The procedure generates single bands created by molecular stacking that exhibit strongly enhanced signal intensities and minimal band broadening. Using optimized voltages and time intervals as many as 20 successive loadings could be performed and up to 800 μL could be loaded into a single well. Gel extraction and fluorescent quantitation demonstrated that approximately 97 % of the DNA from each loading was incorporated into the resultant band. Highly dilute DNA samples (<0.0007 ng per microliter) could be readily detected after six loadings. The method produced good results with either TAE or TBE as electrophoresis buffers, using loading dyes with or without SDS, and in both minigels and large gels.

Mucosa-Inspired Electro-Responsive Lubricating Supramolecular-Covalent Hydrogel

Enabling the living capability of secreting liquids dynamically triggered by external stimuli while maintaining the bulk frame is a significant challenge for mucosa-inspired hydrogels. A mucosa-inspired electro-responsive hydrogel is developed in this study using the synergy between electro-responsive silk fibroin supramolecular non-covalent networks and covalent polyacrylamide and polyvinyl alcohol polymer networks. The formed supramolecular-covalent hydrogel exhibits a partial gel-sol transition upon the application of an electric field, and the liquid layer on the hydrogel surface near the cathode is used to mimic the mucus-secreting capability to regulate lubrication. The electro-responsive lubricating process can operate under a safe voltage and exhibits good reversibility. It is also a universal strategy to construct an electro-responsive hydrogel by introducing an electro-responsive supramolecular network into the polymer network. This mucosa-inspired electro-responsive supramolecular-covalent hydrogel offers a promising method for designing soft actuators or robots that can regulate lubrication using an electric strategy.

Sialylation and Sulfation of Anionic Glycoconjugates Are Common in the Extracellular Polymeric Substances of Both Aerobic and Anaerobic Granular Sludges

Anaerobic and aerobic granular sludge processes are widely applied in wastewater treatment. In these systems, microorganisms grow in dense aggregates due to the production of extracellular polymeric substances (EPS). This study investigates the sialylation and sulfation of anionic glyconconjugates in anaerobic and aerobic granular sludges collected from full-scale wastewater treatment processes. Size exclusion chromatography revealed a wide molecular weight distribution (3.5 to >5500 kDa) of the alkaline-extracted EPS. The high-molecular weight fraction (>5500 kDa), comprising 16.9-27.4% of EPS, was dominant with glycoconjugates. Mass spectrometry analysis and quantification assays identified nonulosonic acids (NulOs, e.g., bacterial sialic acids) and sulfated groups contributing to the negative charge in all EPS fractions. NulOs were predominantly present in the high-molecular weight fraction (47.2-84.3% of all detected NulOs), while sulfated glycoconjugates were distributed across the molecular weight fractions. Microorganisms, closely related to genera found in the granular sludge communities, contained genes responsible for NulO and sulfate group synthesis or transfer. The similar distribution patterns of sialylation and sulfation of the anionic glycoconjugates in the EPS samples indicate that these two glycoconjugate modifications commonly occur in the EPS of aerobic and anaerobic granular sludges.

3D Bioprinting of Hyaline Articular Cartilage: Biopolymers, Hydrogels, and Bioinks

The musculoskeletal system, consisting of bones and cartilage of various types, muscles, ligaments, and tendons, is the basis of the human body. However, many pathological conditions caused by aging, lifestyle, disease, or trauma can damage its elements and lead to severe disfunction and significant worsening in the quality of life. Due to its structure and function, articular (hyaline) cartilage is the most susceptible to damage. Articular cartilage is a non-vascular tissue with constrained self-regeneration capabilities. Additionally, treatment methods, which have proven efficacy in stopping its degradation and promoting regeneration, still do not exist. Conservative treatment and physical therapy only relieve the symptoms associated with cartilage destruction, and traditional surgical interventions to repair defects or endoprosthetics are not without serious drawbacks. Thus, articular cartilage damage remains an urgent and actual problem requiring the development of new treatment approaches. The emergence of biofabrication technologies, including three-dimensional (3D) bioprinting, at the end of the 20th century, allowed reconstructive interventions to get a second wind. Three-dimensional bioprinting creates volume constraints that mimic the structure and function of natural tissue due to the combinations of biomaterials, living cells, and signal molecules to create. In our case-hyaline cartilage. Several approaches to articular cartilage biofabrication have been developed to date, including the promising technology of 3D bioprinting. This review represents the main achievements of such research direction and describes the technological processes and the necessary biomaterials, cell cultures, and signal molecules. Special attention is given to the basic materials for 3D bioprinting-hydrogels and bioinks, as well as the biopolymers underlying the indicated products.

Functionalized agarose hydrogel with in situ Ag nanoparticles as highly recyclable heterogeneous catalyst for aromatic organic pollutants

In the present research work, a highly recyclable catalyst of Ag-based agarose (HRC-Ag/Agar) hydrogel was successfully fabricated through a simple and efficient in situ reduction method without the aid of additional surface active agent. The interaction between the rich hydroxyl functional (-OH) groups in agarose and Ag can effectively control the growth and dispersion of Ag nanoparticles (NPs) in the HRC-Ag/Agar hydrogel and keep Ag NPs free from chemical contamination, which also guarantees the reusability of HRC-Ag/Agar hydrogel as catalysts. HRC-Ag/Agar hydrogel without freeze drying and calcination was investigated for their potential applications as highly active/recyclable catalysts in reducing aromatic organic pollutants (p-nitrophenol (4-NP), methylene blue (MB) and rhodamine B (RhB)) by KBH₄. The optimal HRC-Ag/Agar-1.9 hydrogel can complete the catalytic reduction of 4-NP within 11 min. Moreover, HRC-Ag/Agar-1.9 hydrogel achieves the high conversion rate (> 99%) through ten catalytic runs. Similarly, HRC-Ag/Agar-1.9 hydrogel was able to achieve a reduction efficiency of RhB at 98% within 17 min and that of MB at 95% within 40 min. The advantages of simple synthetic procedure, no secondary pollution, strong stability and easily separated make the HRC-Ag/Agar hydrogel have great potential prospect for environmental applications.

Low Throughput Direct Cycle Sequencing of Polymerase Chain Reaction (PCR) Products

Polymerase Chain Reaction (PCR) products have been traditionally characterized by cloning and cycle sequencing. However, when quick sequencing data are required, the cloning step may be omitted and PCR products can be sequenced directly. We describe here a sequencing protocol that involves the gold standard Big Dye chemistry in a low throughput format using one of the latest sequencing platforms the ABI Seqstudio. Our cycle sequencing protocol follows the following steps: (1) purification of the PCR product with a spin column-based kit; (2) quality & quantity assessment of the PCR product with the use of spectrophotometry & gel electrophoresis; (3) setup and amplification of the cycle sequencing reaction; (4) Capillary Electrophoresis; (5) Sequence Data Analysis.

Cytophilic Agarose-Epoxide-Amine Cryogels Engineered with Granulated Microstructures

Inherent cytophobicity of agarose limits its direct use for the growth of anchorage-dependent cells. Here, we report a simple strategy allowing the development of agarose-based hydrogels entailed with both cytophilicity and microstructured morphology. Through the reaction of water-soluble 1,4-butanediol diglycidyl ether (BDDE) with trifunctional polyetheramine Jeffamine T403 in agarose solution followed by cryogelation of the mixtures, a series of macroporous agarose-epoxide-amine cryogels were prepared readily. Results from fluorescent labeling and energy-dispersive X-ray elemental mapping showed the formation of granulated microstructures in the cryogels. Such features closely correlated to the phase separation of BDDE-T403 polymers within the agarose matrix. Cytophilicity of the microstructured cryogels due to the integrated amine moieties was demonstrated through the adhesion of fibroblasts. Functional enrichment of the cryogels was further highlighted by leveraging the granulates as micro-reservoirs for polyphenol proanthocyanidin to enable antioxidation and protection of fibroblasts from H₂O₂-induced cytotoxic effect in vitro.

Spontaneous and Electrically Induced Anisotropy of Composite Agarose Gels

Agarose gels containing and not bacteriorhodopsin purple membranes (incorporated before gelling) manifest spontaneous optical anisotropy. The dependencies of the anisotropy on the agarose concentration and time have been studied. The rise in the anisotropy is explained by the predominant orientation of the agarose fibers during the gelling and subsequent deformation of the gel net. In the electric field, additional optical anisotropy rises, which is caused by the orientation of the membranes. A procedure has been developed to separate electrically induced and spontaneous anisotropy in composite gels. The isoelectric points and surface electric potential of bacteriorhodopsin trimer and purple membranes are calculated by the method of protein electrostatics to explain their electric asymmetry, which leads to perpendicular orientation in the direct electric field and longitudinal in the kilohertz sinusoidal field. The results allow for an increase in the separation capability of composite gels of electrophoresis for macromolecules with different sizes by applying an appropriate electric field to modulate the effective pore size.

Diffusion mechanisms of DNA in agarose gels: NMR studies and Monte Carlo simulations

We report on the diffusion mechanism of short, single-stranded DNA molecules with up to 100 nucleobases in agarose gels with concentrations of up to 2.0% with the aim to characterize the DNA–agarose interaction. The diffusion coefficients were measured directly, i.e., without any model assumptions, by pulsed field gradient nuclear magnetic resonance (PFG-NMR). We find that the diffusion coefficient decreases, as expected, with an increase in both DNA strand length and gel concentration. In addition, we performed Monte Carlo simulations of particle diffusion in a model network of polymer chains, considering our experimental conditions. Together, the Monte Carlo simulations and the PFG-NMR results show that the decrease in diffusion coefficients in the presence of the agarose gel is due to a temporary adhesion of the DNA molecules to the surface of gel fibers. The average adhesion time to a given gel fiber increases with the length of the DNA strands but is independent of the number of gel fibers. The corresponding magnitude of the binding enthalpies of DNA strands to gel fibers indicates that a mixture of van der Waals interactions and hydrogen bonding contributes to the decreased diffusion of DNA in agarose gels.

Paper-based genetic assays with bioconjugated gold nanorods and an automated readout pipeline

Paper-based biosensors featuring immunoconjugated gold nanoparticles have gained extraordinary momentum in recent times as the platform of choice in key cases of field applications, including the so-called rapid antigen tests for SARS-CoV-2. Here, we propose a revision of this format, one that may leverage on the most recent advances in materials science and data processing. In particular, we target an amplifiable DNA rather than a protein analyte, and we replace gold nanospheres with anisotropic nanorods, which are intrinsically brighter by a factor of ~ 10, and multiplexable. By comparison with a gold-standard method for dot-blot readout with digoxigenin, we show that gold nanorods entail much faster and easier processing, at the cost of a higher limit of detection (from below 1 to 10 ppm in the case of plasmid DNA containing a target transgene, in our current setup). In addition, we test a complete workflow to acquire and process photographs of dot-blot membranes with custom-made hardware and regression tools, as a strategy to gain more analytical sensitivity and potential for quantification. A leave-one-out approach for training and validation with as few as 36 sample instances already improves the limit of detection reached by the naked eye by a factor around 2. Taken together, we conjecture that the synergistic combination of new materials and innovative tools for data processing may bring the analytical sensitivity of paper-based biosensors to approach the level of lab-grade molecular tests.

Polymeric Hydrogels for In Vitro 3D Ovarian Cancer Modeling

Ovarian cancer (OC) grows and interacts constantly with a complex microenvironment, in which immune cells, fibroblasts, blood vessels, signal molecules and the extracellular matrix (ECM) coexist. This heterogeneous environment provides structural and biochemical support to the surrounding cells and undergoes constant and dynamic remodeling that actively promotes tumor initiation, progression, and metastasis. Despite the fact that traditional 2D cell culture systems have led to relevant medical advances in cancer research, 3D cell culture models could open new possibilities for the development of an in vitro tumor microenvironment more closely reproducing that observed in vivo. The implementation of materials science and technology into cancer research has enabled significant progress in the study of cancer progression and drug screening, through the development of polymeric scaffold-based 3D models closely recapitulating the physiopathological features of native tumor tissue. This article provides an overview of state-of-the-art in vitro tumor models with a particular focus on 3D OC cell culture in pre-clinical studies. The most representative OC models described in the literature are presented with a focus on hydrogel-based scaffolds, which guarantee soft tissue-like physical properties as well as a suitable 3D microenvironment for cell growth. Hydrogel-forming polymers of either natural or synthetic origin investigated in this context are described by highlighting their source of extraction, physical-chemical properties, and application for 3D ovarian cancer cell culture.

Capillary Sodium Dodecyl Sulfate Agarose Gel Electrophoresis of Proteins

Capillary sodium dodecyl sulfate gel electrophoresis has long been used for the analysis of proteins, mostly either with entangled polymer networks or translationally cross-linked gels. In this paper capillary agarose gel electrophoresis is introduced for the separation of low molecular weight immunoglobulin subunits. The light (LC~24 kDa) and heavy (HC~50 kDa) chain fragments of a monoclonal antibody therapeutic drug were used to optimize the sieving matrix composition of the agarose/Tris-borate-EDTA (TBE) systems. The agarose and boric acid contents were systematically varied between 0.2–1.0% and 320–640 mM, respectively. The influence of several physical parameters such as viscosity and electroosmotic flow were also investigated, the latter to shed light on its effect on the electrokinetic injection bias. Three dimensional Ferguson plots were utilized to better understand the sieving performance of the various agarose/TBE ratio gels, especially relying on their slope (retardation coefficient, K_R) value differences. The best resolution between the LC and non-glycosylated HC IgG subunits was obtained by utilizing the molecular sieving effect of the 1% agarose/320 mM boric acid composition (ΔK_R = 0.035). On the other hand, the 0.8% agarose/640 mM boric acid gel showed the highest separation power between the similar molecular weight, but different surface charge density non-glycosylated HC and HC fragments (ΔK_R = 0.005). It is important to note that the agarose-based gel-buffer systems did not require any capillary regeneration steps between runs other than simple replenishment of the sieving matrix, significantly speeding up analysis cycle time.

A facile biosynthesis strategy of plasmid DNA-derived nanowires for readable microRNA logic operations

Multiple microRNAs (miRNAs) logical assays have attracted wide attention recently, which can be applied to mimic and reveal cellular events at the molecular level. However, it remains challenging to develop...

A Laboratory Exercise Simulating Antibody and Antigen Reactions of the Ouchterlony Double Immunodiffusion Assay Using Inorganic Salts

The Ouchterlony double immunodiffusion assay is a serological technique used in the detection of antibodies and antigens for diagnostic purposes and also used in immunology laboratory courses as a common teaching assay where students observe the geometrical precipitation line patterns that form in the agarose, elucidating degrees of homology between antigens. In this classical technique, students must wait several hours to days to obtain results when protein antigens and antibodies are used. Furthermore, these proteins degrade over time if not frozen or stored in the refrigerator and are the most expensive consumables of the laboratory exercise. In this study, inexpensive and commonly used inorganic ionic salt solutions that are stable and can be stored at room temperature for several years were used to mimic antigens and antibodies. The precipitation lines started to form in the agarose plates after 15 min and fully developed within an hour, showing different geometrical precipitation patterns and spur formations that could be identified by students as full identity, partial identity, and nonidentity between the simulated (inorganic) antigens. Students conducting this exercise in a combined lecture and laboratory immunology course were able to finish the exercise as well as record and discuss results within class time, and tvhey showed increased interest in the laboratory exercise and had a better understanding of antibody-antigen reactions. Thus, this simulated laboratory experiment is an inexpensive, safe, and fast exercise that allows students to observe precipitations reactions of the Ouchterlony assay within the class session time.

Convenient Agarose Preparation with Hydrogen Peroxide and Desulfation Process Analysis

Agarose is a natural seaweed polysaccharide and widely used in the medicine, food, and biological fields because of its high gel strength, non-toxicity, and electrical neutrality. The sulfate group is one of the main charged groups that affect the performance of agarose. In the present study, a simple, eco-friendly, and efficient method was explored for agarose preparation. After desulfation with hydrogen peroxide (H₂O₂), the sulfate content of agar reached 0.21%. Together with gel strength, electroendosmosis, gelling and melting temperature, the indicators of desulfated agar met the standards of commercially available agarose. Notably, the desulfated agar can be used as an agarose gel electrophoresis medium to separate DNA molecules, and the separation effect is as good as that of commercially available agarose. Further, the H₂O₂ desulfation process was analyzed. The addition of a hydroxyl radical (HO•) scavenger remarkably decreased the H₂O₂ desulfation rate, indicating that HO• has a certain role in agar desulfation. Sulfate content detection indicated that sulfur was removed from agar molecules in the form of sulfate ions (SO₄²⁻) and metal sulfate. The band absence at 850 cm⁻¹ indicated that the sulfate groups at C-4 of D-galactose in sulfated galactan were eliminated.

In-Gel Isolation and Characterization of Large (and Other) Phages

We review some aspects of the rapid isolation of, screening for and characterization of jumbo phages, i.e., phages that have dsDNA genomes longer than 200 Kb. The first aspect is that, as plaque-supporting gels become more concentrated, jumbo phage plaques become smaller. Dilute agarose gels are better than conventional agar gels for supporting plaques of both jumbo phages and, prospectively, the even larger (>520 Kb genome), not-yet-isolated mega-phages. Second, dilute agarose gels stimulate propagation of at least some jumbo phages. Third, in-plaque techniques exist for screening for both phage aggregation and high-in-magnitude, negative average electrical surface charge density. The latter is possibly correlated with high phage persistence in blood. Fourth, electron microscopy of a thin section of a phage plaque reveals phage type, size and some phage life cycle information. Fifth, in-gel propagation is an effective preparative technique for at least some jumbo phages. Sixth, centrifugation through sucrose density gradients is a relatively non-destructive jumbo phage purification technique. These basics have ramifications in the development of procedures for (1) use of jumbo phages for phage therapy of infectious disease, (2) exploration of genomic diversity and evolution and (3) obtaining accurate metagenomic analyses.

Extraction and Modification of Macroalgal Polysaccharides for Current and Next-Generation Applications

Marine macroalgal (seaweed) polysaccharides are highly promising for next-generation applications in several industries. However, despite the reported comprehensive potential of these polysaccharides, commercial products are scarce on the market. Seaweed cultivations are increasing in number and production quantity, owing to an elevated global trend of utilization interest in seaweed. The extraction of polysaccharides from seaweed generally generates low yields, but novel methods are being developed to facilitate and improve the extraction processes. Current areas of applications for seaweed polysaccharides mainly take advantage of the physicochemical properties of certain polysaccharides, such as gelling, thickening and emulsifying. However, many of the numerous bioactivities reported are still only at research level and lack clinical evidence for commercialization. It has been suggested the construction of smaller units may generate better defined molecules that are more suitable for biomedical applications. Enzymatic modification is a promising tool for the generation of more defined, targeted biomolecules. This review covers; structural differences between the most predominant marine algal polysaccharides, extraction processes, modification alternatives, as well as a summary of current and potential next-generation application areas.

Cyclodextrin functionalized agarose gel with low gelling temperature for controlled drug delivery systems

Conventional agaroses with high gelling temperature are limited to apply to the field of drug delivery. In this study, β-cyclodextrin (βCD) functionalized agarose (CFA) with low gelling temperature was successfully prepared from ethylenediamine-functionalized agarose using mono-succinyl βCD. The gelling temperature of CFA dramatically decreased to 26.7 °C from 65 °C and the melting temperature declined from 95 °C to 66.1 °C. Upon drug loading, CFA can be used at 30 °C because of its low gelling temperature compared to agarose. CFA gel could be used both for bovine serum albumin as a full release, and for the doxorubicin (DOX) for sustained release, via inclusion complexation of βCD. Furthermore, cytotoxicity tests revealed that CFA was noncytotoxic. DOX in the CFA gel could retain the anti-cancer activity. Newly synthesized CFA with low gelling temperature offer a new means for the development of hydrogel-based delivery systems for a variety of therapeutic drugs.

Hydrogels as a water bolus during hyperthermia treatment

The feasibility of using hydrogels as a water bolus during hyperthermia treatment was assessed. Three types of gels, high methoxyl (HM) pectin/alginate, xanthan/locust bean gum (LBG) and xanthan/LBG/agarose were evaluated based on their dielectric, rheological and mechanical properties. The most suitable, xanthan/LBG/agarose gel was further used as a water bolus in a hyperthermia array applicator. The gels composed of polysaccharides carrying low charge displayed dielectric properties close to those of water, while the dielectric properties of HM pectin/alginate gel was deemed unsuitable for the current application. The mechanical examination shows that the xanthan/LBG gel has a non-brittle behaviour at room temperature, in contrast to the agarose gel. The moduli of the xanthan/LBG gel weaken however considerably between the temperature range of 40 °C and 50 °C, reducing its potential to be used as water bolus. The ternary system of xanthan/LBG/agarose had advantageous behaviour as it was dominated by the thermal hysteresis typical of agarose upon temperature increase, but governed by the typical non-brittle behaviour of the xanthan/LBG at low temperatures. The final evaluation within the hyperthermia applicator showed excellent signal transmission from the antennas. The agarose/xanthan/LBG gel reduced the scattering of electromagnetic waves, enabled a tight closure between the body and the antennas, and offered a less bulky solution than the currently used water-filled plastic bags. The results presented here open up a new application area for hydrogels in improving heat delivery during hyperthermia treatment and other near-field microwave applications.

Preparation and Application in Drug Storage and Delivery of Agarose Nanoparticles

In this work, monodisperse agarose gel nanoparticles were prepared using a W/O microemulsion as a template to control the size of the obtained particles. The combination of this template method with a temperature-induced gelling and a solvent exchange methodology has allowed preparing stable aqueous dispersions of monodisperse agarose gel nanoparticles in water. The average size, measured as an apparent hydrodynamic diameter, of the obtained particles was around 150 nm. The ability of the obtained hydrogel particles for the encapsulation and release of a synthetic insecticide (azamethiphos) was tested. The results evidence that the insecticide molecules encapsulated in the fabricated nanoparticles are released following a diffusion-controlled mechanism. These results combined with the biodegradability of the agarose provide the bases for the design of a new vector with application in the control of parasites in water reservoirs.

Controlling Dispersion during Single-Cell Polyacrylamide-Gel Electrophoresis in Open Microfluidic Devices

New tools for measuring protein expression in individual cells complement single-cell genomics and transcriptomics. To characterize a population of individual mammalian cells, hundreds to thousands of microwells are arrayed on a polyacrylamide-gel-coated glass microscope slide. In this "open" fluidic device format, we explore the feasibility of mitigating diffusional losses during lysis and polyacrylamide-gel electrophoresis (PAGE) through spatial control of the pore-size of the gel layer. To reduce in-plane diffusion-driven dilution of each single-cell lysate during in-microwell chemical lysis, we photopattern and characterize microwells with small-pore-size sidewalls ringing the microwell except at the injection region. To reduce out-of-plane-diffusion-driven-dilution-caused signal loss during both lysis and single-cell PAGE, we scrutinize a selectively permeable agarose lid layer. To reduce injection dispersion, we photopattern and study a stacking-gel feature at the head of each <1 mm separation axis. Lastly, we explore a semienclosed device design that reduces the cross-sectional area of the chip, thus reducing Joule-heating-induced dispersion during single-cell PAGE. As a result, we observed a 3-fold increase in separation resolution during a 30 s separation and a >2-fold enhancement of the signal-to-noise ratio. We present well-integrated strategies for enhancing overall single-cell-PAGE performance.

Multi-component hybrid hydrogels - understanding the extent of orthogonal assembly and its impact on controlled release

This paper reports self-assembled multi-component hybrid hydrogels including a range of nanoscale systems and characterizes the extent to which each component maintains its own unique functionality, demonstrating that multi-functionality can be achieved by simply mixing carefully-chosen constituents. Specifically, the individual components are: (i) pH-activated low-molecular-weight gelator (LMWG) 1,3;2,4-dibenzylidenesorbitol-4',4''-dicarboxylic acid (DBS-COOH), (ii) thermally-activated polymer gelator (PG) agarose, (iii) anionic biopolymer heparin, and (iv) cationic self-assembled multivalent (SAMul) micelles capable of binding heparin. The LMWG still self-assembles in the presence of PG agarose, is slightly modified on the nanoscale by heparin, but is totally disrupted by the micelles. However, if the SAMul micelles are bound to heparin, DBS-COOH self-assembly is largely unaffected. The LMWG endows hybrid materials with pH-responsive behavior, while the PG provides mechanical robustness. The rate of heparin release can be controlled through network density and composition, with the LMWG and PG behaving differently in this regard, while the presence of the heparin binder completely inhibits heparin release through complexation. This study demonstrates that a multi-component approach can yield exquisite control over self-assembled materials. We reason that controlling orthogonality in such systems will underpin further development of controlled release systems with biomedical applications.

Real-Space, in Situ Maps of Hydrogel Pores

We characterize the porosity of hydrogels by imaging the displacement trajectories of embedded tracer particles. This offers the possibility of characterizing the size and projected shape of individual pores as well as direct, real-space maps of heterogeneous porosity and its distribution. The scheme shows that when fluorescent spherical particles treated to avoid specific adsorption are loaded into the gel, their displacement trajectories from Brownian motion report on the size and projected shape in which the pore resides, convoluted by the particle size. Of special interest is how pores and their distribution respond to stimuli. These ideas are validated in agarose gels loaded with latex particles stabilized by adsorbed bovine serum albumin. Gels heated from room temperature produced an increasingly more monodisperse pore size distribution because increasing temperature preferentially enlarges smaller pores, but this was irreversible upon cooling, and shearing agarose gels beyond the yield point destroyed larger pores preferably. The method is considered to be generalizable beyond the agarose system presented here as proof of concept.

New design of hydrogels with tuned electro-osmosis: a potential model system to understand electro-kinetic transport in biological tissues

A series of charged polymer gels with precisely controlled magnitude and direction of electro-osmotic flow was prepared and opens up the possibility for understanding the contribution of electro-osmosis to transport phenomenon in native biological tissues.

An ultra melt-resistant hydrogel from food grade carbohydrates

We have formulated an ultra melt-resistant composite hydrogel with tailorable rheology over a range of temperatures.

NMR analysis of weak molecular interactions using slice-selective experiments via study of concentration gradients in agar gels

Weak molecular interactions can be localized and quantified using a single NMR experiment analysing concentration gradients generated in agar gels.

Gel mesh as "brake" to slow down DNA translocation through solid-state nanopores

Agarose gel is introduced onto the cis side of silicon nitride nanopores by a simple and low-cost method to slow down the speed of DNA translocation. DNA translocation speed is slowed by roughly an order of magnitude without losing signal to noise ratio for different DNA lengths and applied voltages in gel-meshed nanopores. The existence of the gel moves the center-of-mass position of the DNA conformation further from the nanopore center, contributing to the observed slowing of translocation speed. A reduced velocity fluctuation is also noted, which is beneficial for further applications of gel-meshed nanopores. The reptation model is considered in simulation and agrees well with the experimental results.

Hydrogel-derived non-precious electrocatalysts for efficient oxygen reduction

The development of highly active, cheap and robust oxygen reduction reaction (ORR) electrocatalysts to replace precious metal platinum is extremely urgent and challenging for renewable energy devices. Herein we report a novel, green and especially facile hydrogel strategy to construct N and B co-doped nanocarbon embedded with Co-based nanoparticles as an efficient non-precious ORR catalyst. The agarose hydrogel provides a general host matrix to achieve a homogeneous distribution of key precursory components including cobalt (II) acetate and buffer salts, which, upon freeze-drying and carbonization, produces the highly active ORR catalyst. The gel buffer containing Tris base, boric acid and ethylenediaminetetraacetic acid, commonly adopted for pH and ionic strength control, plays distinctively different roles here. These include a green precursor for N- and B-doping, a salt porogen and a Co²⁺ chelating agent, all contributing to the excellent ORR activity. This hydrogel-based process is potentially generalizable for many other catalytic materials.

Modification of gel architecture and TBE/TAE buffer composition to minimize heating during agarose gel electrophoresis

Agarose gel electrophoresis of DNA and RNA is routinely performed using buffers containing either Tris, acetate, and EDTA (TAE) or Tris, borate, and EDTA (TBE). Gels are run at a low, constant voltage (∼10 V/cm) to minimize current and asymmetric heating effects, which can induce band artifacts and poor resolution. In this study, alterations of gel structure and conductive media composition were analyzed to identify factors causing higher electrical currents during horizontal slab gel electrophoresis. Current was reduced when thinner gels and smaller chamber buffer volumes were used, but was not influenced by agarose concentration or the presence of ethidium bromide. Current was strongly dependent on the amount and type of EDTA used and on the concentrations of the major acid-base components of each buffer. Interestingly, resolution and the mobilities of circular versus linear plasmid DNAs were also affected by the chemical form and amount of EDTA. With appropriate modifications to gel structure and buffer constituents, electrophoresis could be performed at high voltages (20-25 V/cm), reducing run times by up to 3-fold. The most striking improvements were observed with small DNAs and RNAs (10-100 bp): high voltages and short run times produced sharper bands and higher resolution.

Facile fabrication of graphene composite microwires via drying-induced size reduction of hydrogel filaments

Graphene composite microwires with good electrical conductivities are formed by extrusion of a graphene oxide–agarose suspension followed by drying and reduction of graphene oxide to graphene.

Integration of nanoporous membranes into microfluidic devices: electrokinetic bio-sample pre-concentration

The integration of nanoporous membranes into microfluidic devices allows a wide range of analytical and biochemical applications such as stable concentration gradient generation, sample pre-concentration, and ion and biomolecule filtration in a controllable manner. However, further applications of nanoporous membranes in microfluidic devices require rapid and controllable fabrication methods of various nanoporous precursor materials; currently, few such methods exist. Here, we describe simple and robust methods that can be used for microfabricating four different precursor materials as leakage-tight membranes in a microfluidic channel network. The methods consist of a common integration process and individual solidification processes such as solvent evaporation, UV-curing, and temperature treatment. We demonstrate that the fabricated membranes can be used for electrokinetic, nanofluidic pre-concentration of bio-samples such as proteins, cells, and microspheres on either the anodic or cathodic side of the membranes. In addition, we not only characterize the physicochemical properties of the membranes such as conductance of membrane-integrated microchannels, relative permselectivity, and pre-concentration ability, but also compare fabrication availability, membrane robustness, surface charge density tunability and biocompatibility with buffer solutions. The methods are versatile for many nanoporous precursor materials and easy to control the location and dimension of the membranes. Hence, the methods developed and the characterized properties of the membranes tested in this work could be widely employed for further applications of nanoporous membranes in microfluidic systems.

Sustained delivery of bioactive TGF-β1 from self-assembling peptide hydrogels induces chondrogenesis of encapsulated bone marrow stromal cells

Tissue engineering strategies for cartilage defect repair require technology for local targeted delivery of chondrogenic and anti-inflammatory factors. The objective of this study was to determine the release kinetics of transforming growth factor β1 (TGF-β1) from self-assembling peptide hydrogels, a candidate scaffold for cell transplant therapies, and stimulate chondrogenesis of encapsulated young equine bone marrow stromal cells (BMSCs). Although both peptide and agarose hydrogels retained TGF-β1, fivefold higher retention was found in peptide. Excess unlabeled TGF-β1 minimally displaced retained radiolabeled TGF-β1, demonstrating biologically relevant loading capacity for peptide hydrogels. The initial release from acellular peptide hydrogels was nearly threefold lower than agarose hydrogels, at 18% of loaded TGF-β1 through 3 days as compared to 48% for agarose. At day 21, cumulative release of TGF-β1 was 32-44% from acellular peptide hydrogels, but was 62% from peptide hydrogels with encapsulated BMSCs, likely due to cell-mediated TGF-β1 degradation and release of small labeled species. TGF-β1 loaded peptide hydrogels stimulated chondrogenesis of young equine BMSCs, a relevant preclinical model for treating injuries in young human cohorts. Self-assembling peptide hydrogels can be used to deliver chondrogenic factors to encapsulated cells making them a promising technology for in vivo, cell-based regenerative medicine.

Microfluidic impact printer with interchangeable cartridges for versatile non-contact multiplexed micropatterning

Biopatterning has been increasingly used for well-defined cellular microenvironment, patterned surface topology, and guided biological cues; however, it meets challenges on biocompatibility, thermal and chemical sensitivity, as well as limited availability of reagents. In this paper, we aim at combining the desired features from non-contact inkjet printing and dot-matrix impact printing to establish a versatile multiplexed micropatterning platform, referred to as Microfluidic Impact Printer (MI-Printer), for emerging biomedical applications. Using this platform, we can achieve the distinct features of no cross-contamination, sub-microliter ink loading with a minimal dead volume, high-throughput printing, biocompatible non-contact processing, sequential patterning with self-alignment, wide adaptability for complex media (e.g., cell suspension or colloidal solutions), interchangeable/disposable cartridge design, and simple assembly and configuration, all highly desirable towards laboratory-based research and development. Specifically, the printing resolution of the MI-printer platform has been experimentally characterized and theoretically analysed. Optimal printing resolution of 80 μm has been repeatedly obtained. Furthermore, two useful functions of the MI-printer, multiplexed printing and combinatorial printing, have been experimentally demonstrated with less than 10 μm misalignment. Moreover, molecular and biological patterning, utilizing the multiplexed and combinatorial printing, has been implemented to illustrate the utility of this versatile printing technique for emerging biomedical applications.

Adsorption of peptides and small proteins with control access polymer permeation to affinity binding sites. Part I: Polymer permeation-immobilized metal ion affinity chromatography separation adsorbents with polyethylene glycol and immobilized metal ions

Despite the many efforts to develop efficient protein purification techniques, the isolation of peptides and small proteins on a larger than analytical scale remains a significant challenge. Recovery of small biomolecules from diluted complex biological mixtures, such as human serum, employing porous adsorbents is a difficult task mainly due to the presence of concentrated large biomolecules that can add undesired effects in the system such as blocking of adsorbent pores, impairing diffusion of small molecules, or competition for adsorption sites. Adsorption and size exclusion chromatography (AdSEC) controlled access media, using polyethylene glycol (PEG) as a semi-permeable barrier on a polysaccharide matrix, have been developed and explored in this work to overcome such effects and to preferentially adsorb small molecules while rejecting large ones. In the first part of this work, adsorption studies were performed with small peptides and proteins from synthetic mixtures using controlled access polymer permeation adsorption (CAPPA) media created by effectively grafting PEG on an immobilized metal affinity chromatography (IMAC) agarose resin, where chelating agents and immobilized metal ions were used as the primary affinity binding sites. Synthetic mixtures consisted of bovine serum albumin (BSA) with small proteins, peptides, amino acids (such as histidine or Val⁴-Angiotensin III), and small molecules-spiked human serum. The synthesized hybrid adsorbent consisted of agarose beads modified with iminodiacetic (IDA) groups, loaded with immobilized Cu(II) ions, and PEG. These CAPPA media with grafted PEG on the interior and exterior surfaces of the agarose matrix were effective in rejecting high molecular weight proteins. Different PEG grafting densities and PEG of different molecular weight were tested to determine their effect in rejecting and controlling adsorbent permeation properties. Low grafting density of high molecular weight PEG was found to be as effective as high grafting density of low molecular weight PEG in the rejecting properties of the semi-permeable synthesized media.

Probing and controlling fluorescence blinking of single semiconductor nanoparticles

In this review we present an overview of the experimental and theoretical development on fluorescence intermittency (blinking) and the roles of electron transfer in semiconductor crystalline nanoparticles. Blinking is a very interesting phenomenon commonly observed in single molecule/particle experiments. Under continuous laser illumination, the fluorescence time trace of these single nanoparticles exhibit random light and dark periods. Since its first observation in the mid-1990s, this intriguing phenomenon has attracted wide attention among researchers from many disciplines. We will first present the historical background of the discovery and the observation of unusual inverse power-law dependence for the waiting time distributions of light and dark periods. Then, we will describe our theoretical modeling efforts to elucidate the causes for the power-law behavior, to probe the roles of electron transfer in blinking, and eventually to control blinking and to achieve complete suppression of the blinking, which is an annoying feature in many applications of quantum dots as light sources and fluorescence labels for biomedical imaging.