With the rapid development of biomimetic polymers for cell-based assays and tissue engineering, crosslinking electrospun nanofibrous biopolymer constructs is of great importance for achieving sustainable and efficient three-dimensional scaffold constructs. Uncrosslinked electrospun gelatin nanofibrous constructs immediately and completely dissolved in aqueous solutions due to their aqueous solubility and poor storage stability. Here, a novel and versatile approach for the fabrication and crosslinking of electrospun gelatin construct with tunable porosity and high aspect ratio nanofibers is presented. Uncrosslinked electrospun gelatin/genipin nanofibrous and pure gelatin nanofibrous constructs exhibited smooth surfaces that were well-defined, with a diameter in the range of 448 ± 364 nm and 257 ± 57 nm, respectively. Dehydrothermal, genipin-EDC/Sulfo-NHS, and EDC/Sulfo-NHS crosslinking approaches were examined to achieve insoluble gelatin nanofibrous constructs that were suitable for cell-based assays. Mechanical characterization demonstrated that the pure gelatin nanofibrous construct crosslinked via EDC/Sulfo-NHS exhibited an increased mechanical strength and stiffness and showed no dissolution in aqueous solutions and retained its fiber morphology. An excellent 1 month storage stability was demonstrated at 22, 4, -20, and -80°C (dehydrated) and at 4°C (hydrated). The as-crosslinked gelatin nanofibrous construct was highly biocompatible (90% cell viability), as demonstrated by the promoted proliferation of PC12 cells.

Biofuel cells have been widely used to generate bioelectricity. Early biofuel cells employ a semi-permeable membrane to separate the anodic and cathodic compartments. The impact of different membrane materials and compositions has also been explored. Some membrane materials are employed strictly as membrane separators, while some have gained significant attention in the immobilization of enzymes or microorganisms within or behind the membrane at the electrode surface. The membrane material affects the transfer rate of the chemical species (e.g., fuel, oxygen molecules, and products) involved in the chemical reaction, which in turn has an impact on the performance of the biofuel cell. For enzymatic biofuel cells, Nafion, modified Nafion, and chitosan membranes have been used widely and continue to hold great promise in the long-term stability of enzymes and microorganisms encapsulated within them. This article provides a review of the most widely used membrane materials in the development of enzymatic and microbial biofuel cells.

Degradable polyethylene glycol (PEG) hydrogels are excellent vehicles for sustained drug release due to their biocompatibility, tunable physical properties, and customizable degradation. However, protein therapeutics are unstable under physiological conditions and releasing degraded or inactive therapeutics can induce immunogenic effects. While controlling protein release from PEG hydrogels has been extensively investigated, few studies have detailed protein stability long-term or under stress conditions. Here, lysozyme and alcohol dehydrogenase (ADH) stability were explored upon encapsulation in PEG hydrogels formed through Michael-type addition.The stability and structure of the two model proteins were monitored by measuring the free energy of unfolding and fluoresce quenching when confined in a hydrogel and compared to PEG solution and buffer. Hydrogels destabilized lysozyme structure at low denaturant concentrations but prevented complete unfolding at high concentrations. ADH was stabilized as the confining mesh size approached the protein radius of gyration. Both proteins retained enzymatic activity within the hydrogels under stress conditions, including denaturant, high temperature, and agitation. Conjugation between lysozyme and PEG-acrylate was identified at long reaction times but no conjugation was observed in the time required for complete gelation. Studies of protein stability in PEG hydrogels, as the one detailed here, can lead to designer technologies for the improved formulation, storage, and delivery of protein therapeutics.

The present study evaluates the crosslinking of electrospun gelatin nanofibers by physical and chemical methods to further elucidate the importance of the application of gelatin scaffold platforms for cell-based assays. The dehydrothermally cross-linked electrospun gelatin scaffolds were unable to retained their structure morphology and integrity upon exposure to 1X PBS or cell-culture media. The DHT and EDC/Sulfo-NHS cross-linked gelatin scaffolds exhibited fiber diameter on average in the nanometer range. Subsequently, we utilized 1X PBS and cell culture media to evaluate the stability of the nanofibers in solution. The immersion evaluation indicated that the chemically cross-linked gelatin nanofibers maintained their random nanofiber distribution and morphology. However, a high degree of swelling was observed in the presence of cell culture media. Overall, the gelatin scaffold demonstrated good performance in PBS and cell culture media. Hence, EDC/Sulfo-NHS cross-linked electrospun gelatin nanofibrous scaffolds have good biocompatibility and are promising bio-scaffolds for cell-based assays.

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Introduction: Previous studies on the quality of life of strabismus patients have not examined the existence of censoring to express the relation between the response variable and its predictors. Methods & Materials: The information used in this study is a conducted cross-sectional study in 2012. The sample size is 90 children in the age range (4-18) years and with congenital strabismus. We used the RAND Health Insurance Study questionnaire with ten subscales to evaluate the quality of life, which was increased to 11 dimensions by adding some items related to eye alignment concerns introduced by Archer et al. The demographic profile is also recorded by 13 other questions. We have expressed the relationship between the independent and response variables in each of the 11 dimensions of the questionnaire and the overall quality of life score by fitting the multiple linear regression model. Then we fitted the two models of classic Tobit and CLAD, which are for censoring, to all dimensions of the questionnaire. Results: We showed that in fitting the models to the overall quality of life scale variable, the best model is the multiple linear regression. Because the response variable was normal, and there was no censoring (ceiling and floor effect). However, in the depression subscale, due to the high censoring (28.89% of the ceiling effect) and the almost normal distribution of the response variable (p-value of skewness< 0.05), the appropriate model according to the criteria is the classic Tobit (AIC = 546.33). That is, the classic Tobit model is the best alternative to the multiple linear regression model in the presence of censoring. But these conditions did not exist in all variables. In the subscale, there was a severe censoring performance constraint (67.78% of the ceiling effect). When censoring is high, the distribution of the response variable becomes very skewed, and the distribution of response variables deviates drastically from normal. The distribution of the performance constraint variable was very skewed (p-value <0.001). Here the RMSE standard scale for the classic Tobit model was 28.74, which is much higher than the standard scale for the multiple linear regression model (14.23). The best model for the high censoring was CLAD. Conclusion: To use the appropriate statistical method in the analysis, one must look at how the response variable is distributed. The multiple linear regression model is very widely used, but in the presence of censoring, the use of this model gives skewed results. In this case, the classic Tobit model and its derived model, CLAD, are replaced. The nonparametric CLAD model calculates accurate estimates with minimum defaults and censoring.