Diffusion of NaOH into a protein gel

n-Layer BET adsorption isotherm modeling for multimeric Protein A ligand and its lifetime determination

Langmuir and other single-layer adsorption isotherms show the binding behavior of natural Protein A ligands immobilized on a column. However, no models have been shown in literature to explain the adsorption phenomena on the recombinant high binding capacity Protein A resins. This study has characterized the Protein A binding domain distribution across the ligand with multi-layer adsorption isotherms for a recombinant Protein A resin. The adsorption data was analyzed using the Langmuir, Freundlich, Brunauer-Emmett-Teller (BET) and various other mathematical equations. The best fit of experimental data was obtained with n-layer BET model wherein the isotherms of Protein A exhibited Type IV behavior according to BET classification. Furthermore, the binding capacity was studied throughout the shelf life using the multi-layer adsorption isotherm model. Antibody adsorption isotherms of Protein A resin were obtained at preset duration of caustic incubation. The experiments were carried out for two conditions of sanitization agent, namely, caustic and caustic with salt. Static and dynamic isotherm analysis showed that a new resin had a lower binding capacity and the initial sanitization improved the binding capacity, probably by making the binding domains more accessible. The binding capacity at equilibrium, dynamic breakthrough and batch were also evaluated and reported in this paper. The study modeled the multimeric Protein A ligand and established the requirement of optimization for cleaning regime. This study provides a fundamental understanding of the binding patterns in the recombinant Protein A ligands through a working mathematical equation and improves the current knowledge of Protein A resin lifetimes.

Comparison of the effectiveness of alkaline and enzymatic extraction and the solubility of proteins extracted from carbohydrate-digested rice

Carbohydrate-digested rice (CDR) residue, the production waste of electrolyte drinks, contains high levels of proteins (approximately 50% of dry matter). Methods for effectively extracting protein from CDR were investigated in this study by comparing alkaline and enzymatic extraction. Alkaline extraction was performed using different concentrations of sodium hydroxide (NaOH). Enzymatic extraction was performed with either commercial Alcalase® or Flavourzyme®. Protein recovery and solubility, and total soluble protein obtained via each method were compared to determine extraction effectiveness. In addition, extraction factors affecting protein recovery were adjusted to determine the optimal conditions for each method. Alcalase provided the maximum protein recovery (30.04%), while less protein recovery was achieved with 0.1 N NaOH (55 °C), 1 N NaOH (55 °C), and Flavourzyme. Although the protein recovery achieved by 0.1 N NaOH (27.43%) was close to that of the Alcalase method, protein solubility by extraction with 0.1 N NaOH was much lower (23.46%) than that achieved via the enzymatic method (100%). Hence, the total soluble protein resulting from Alcalase extraction was higher than that obtained using either of the alkaline methods. Consequently, Alcalase extraction was determined to be the most effective method for extracting protein from CDR.

Chemical imaging of protein hydrogels undergoing alkaline dissolution by CARS microscopy

Hydrogels swell, shrink and degrade depending on the solution they are in contact which, strongly affecting their performance. The minimum information needed to validate many published simulations would be the spatial quantification of the solute material with time. In this study we develop a simple methodology to quantify the protein content in heat induced protein hydrogels using a commercial Coherent anti-Stokes Raman Spectroscopy (CARS) microscope. The system is used to quantify the whey protein isolate (WPI) concentration in hydrogels undergoing dissolution at alkaline pH. Quantitative measurements were performed in hydrogels up to depths of ∼600 µm, with an average accuracy of ∼1 wt%. Results show that the protein concentration within the swollen layer is constant with time, confirming the existence of steady state conditions during dissolution. The methodology presented can easily be implemented to other biopolymer hydrogels and foods.

Micromechanical Characterization of Hydrogels Undergoing Swelling and Dissolution at Alkaline pH

The swelling of polyelectrolyte hydrogels usually depends on the pH, and if the pH is high enough degradation can occur. A microindentation device was developed to dynamically test these processes in whey protein isolate hydrogels at alkaline pH 7–14. At low alkaline pH the shear modulus decreases during swelling, consistent with rubber elasticity theory, yet when chemical degradation occurs at pH ≥ 11.5 the modulus decreases quickly and extensively. The apparent modulus was constant with the indentation depth when swelling predominates, but gradients were observed when fast chemical degradation occurs at 0.05–0.1 M NaOH. In addition, these profiles were constant with time when dissolution rates are also constant, the first evidence that a swollen layer with steady state mechanical properties is achieved despite extensive dissolution. At >0.5 M NaOH, we provide mechanical evidence showing that most interactions inside the gels are destroyed, gels were very weak and hardly swell, yet they still dissolve very slowly. Microindentation can provide complementary valuable information to study the degradation of hydrogels.

NaK alloy-induced in vivo tumor ablation therapy

PURPOSE

Alkali metal ablation is newly emerging as an effective, economic and minimally invasive ablation therapy. This study is dedicated to demonstrate the high efficiency of NaK alloy ablation on in vivo tumors with different stages in mice.

MATERIAL AND METHODS

Panc02 tumor cells were injected into 21 female C57B/L mice, which were divided into three groups. Two experimental groups of mice received the same percutaneous NaK alloy injection for a week apart. The inner temperature response and surface temperature distribution were measured using a thermal couple and an infrared camera. After each ablation experiment, two mice in each group were chosen randomly to make pathological sections. The tumor volumes were measured once every two days. At the end, all tumors were cut off to calculate the tumor inhibition rates.

RESULTS

The NaK alloy-induced ablation therapy produced an obvious temperature increase (85 °C) in the ablation region and the high temperature distribution was relatively concentrated. The histopathology sections showed that developing stage tumors received incomplete destruction of the malignant cells compared with early stage tumors. The tumor inhibition rate in the early and developing tumor treatment groups were 88.5% and 67.6%, respectively.

CONCLUSIONS

This technology provides a nearly thorough ablation treatment for early stage tumors and also a palliative treatment for developing tumors.

Effect of solvent addition sequence on lycopene extraction efficiency from membrane neutralized caustic peeled tomato waste

Lycopene is a high value nutraceutical and its isolation from waste streams is often desirable to maximize profits. This research investigated solvent addition order and composition on lycopene extraction efficiency from a commercial tomato waste stream (pH 12.5, solids ∼5%) that was neutralized using membrane filtration. Constant volume dilution (CVD) was used to desalinate the caustic salt to neutralize the waste. Acetone, ethanol and hexane were used as direct or blended additions. Extraction efficiency was defined as the amount of lycopene extracted divided by the total lycopene in the sample. The CVD operation reduced the active alkali of the waste from 0.66 to <0.01M and the moisture content of the pulp increased from 93% to 97% (wet basis), showing the removal of caustic salts from the waste. Extraction efficiency varied from 32.5% to 94.5%. This study demonstrates a lab scale feasibility to extract lycopene efficiently from tomato processing byproducts.