Stability of dry liposomes in sugar glasses

Sugars, particularly trehalose and sucrose, are used to stabilize liposomes during hydration (freeze-drying and air-drying). As a result, dry liposomes are trapped in a sugar glass, a supersaturated and thermodynamically unstable solid solution. We investigated the effects of the glassy state on liposome fusion and solute retention in the dry state. Solute leakage from dry liposomes was extremely slow at temperatures below the glass transition temperature (Tg); however, it increased exponentially as temperature increased to near or above the Tg, indicating that the glassy state had to be maintained for dry liposomes to retain trapped solutes. The leakage of solutes from dry liposomes followed the law of first-order kinetics and was correlated linearly with liposome fusion. The kinetics of solute leakage showed an excellent fit with the Arrhenius equation at temperatures both above and below the Tg, with a transitional break near the Tg. The activation energy of solute leakage was 1320 kJ/mol at temperatures above the Tg, but increased to 1991 kJ/mol at temperatures below the Tg. The stabilization effect of sugar glass on dry liposomes may be associated with the elevated energy barrier for liposome fusion and the physical separation of dry liposomes in the glassy state. The half-life of solute retention in dry liposomes may be prolonged by storing dry liposomes at temperatures below the Tg and by increasing the Tg of the dry liposome preparation.

Protein inactivation in amorphous sucrose and trehalose matrices: effects of phase separation and crystallization

Trehalose is the most effective carbohydrate in preserving the structure and function of biological systems during dehydration and subsequent storage. We have studied the kinetics of protein inactivation in amorphous glucose/sucrose (1:10, w/w) and glucose/trehalose (1:10, w/w) systems, and examined the relationship between protein preservation, phase separation and crystallization during dry storage. The glucose/trehalose system preserved glucose-6-phosphate dehydrogenase better than did the glucose/sucrose system with the same glass transition temperature (Tg). The Williams-Landel-Ferry kinetic analysis indicated that the superiority of the glucose/trehalose system over the glucose/sucrose system was possibly associated with a low free volume and a low free volume expansion at temperatures above the Tg. Phase separation and crystallization during storage were studied using differential scanning calorimetry, and three separate domains were identified in stored samples (i.e., sugar crystals, glucose-rich and disaccharide-rich amorphous domains). Phase separation and crystallization were significantly retarded in the glucose/trehalose system. Our data suggest that the superior stability of the trehalose system is associated with several properties of the trehalose glass, including low free volume, restricted molecular mobility and the ability to resist phase separation and crystallization during storage.

Protein modification by Amadori and Maillard reactions during seed storage: roles of sugar hydrolysis and lipid peroxidation

The non-enzymatic modifications of proteins through Amadori and Maillard reactions play an important role in the loss of seed viability during storage. In the present study, the contribution of sugar hydrolysis and lipid peroxidation to Amadori and Maillard reactions, and to seed deterioration was investigated in mung-bean (Vigna radiata Wilczek). The contents of glucose and lipid peroxidation products in seed axes increased significantly during storage. The accumulation of Amadori products in seed axes was correlated to the lipid peroxidation, whereas the accumulation of Maillard products was closely correlated to sugar hydrolysis. The rate of accumulation of Maillard products was not well correlated to the content of Amadori products in both seed axes and protein/glucose model system, reflecting the complex nature of Amadori and Maillard reactions. The content of Amadori products in seed axes increased during the early stages of seed ageing, whereas the content of Maillard products increased steadily during the entire period of storage. The accumulation of Maillard products in seed axes was associated with the decline of seed vigour. These data suggest that, during seed ageing, sugar hydrolysis and lipid peroxidation are coupled with non-enzymatic protein modification through Amadori and Maillard reactions.

Protein stability in the amorphous carbohydrate matrix: relevance to anhydrobiosis

The formation of intracellular glass is proposed to be relevant to protein stabilization and survival of anhydrobiotic organisms in the dry state. The stability of proteins in the amorphous carbohydrate matrix and its relevance to seed survival have been investigated in the present study. Glucose-6-phosphate dehydrogenase (G6PDH) was preserved in the amorphous glucose/sucrose (1:10, w/w) matrix by freeze-drying. The stability of freeze-dried G6PDH was examined at temperatures above and below the glass transition temperature (Tg). The rate of G6PDH inactivation in the amorphous carbohydrate matrix deviated significantly from the Arrhenius kinetics, and conformed to the Williams-Landel-Ferry (WLF) relationship. The temperature dependence of G6PDH inactivation in two sets of samples with different Tg values was compared. Identical temperature dependence of G6PDH inactivation was observed after temperature normalization by (T-Tg). Seed survival of Vigna radiata Wilczek (mung bean) showed a similar WLF kinetics at storage temperatures T > or = Tg. In situ protein stability in mung bean embryonic axes was studied using differential scanning calorimetry (DSC). Thermal stability of seed proteins exhibited a strong dependence on the Tg of intracellular glass. These results indicate an important role of the glassy state in protein stabilization. Our data suggest an association between protein stability in intracellular glass and seed survival during storage.

Denitration of glycerol trinitrate by resting cells and cell extracts of Bacillus thuringiensis/cereus and Enterobacter agglomerans

A number of microorganisms were selected from soil and sediment samples which were known to have been previously exposed to nitrate ester contaminants. The two most effective bacteria for transforming glycerol trinitrate (GTN) were identified as Bacillus thuringiensis/cereus and Enterobacter agglomerans. For both isolates, denitration activities were expressed constitutively and GTN was not required for induction. Dialysis of cell extracts from both isolates did not affect denitration, which indicates that dissociable and depletable cofactors are not required for denitration. With thin-layer chromatography and high-performance liquid chromatography, the denitration pathway for both isolates was shown to be a sequential denitration of GTN to glycerol dinitrate isomers, glycerol mononitrate isomers, and ultimately to glycerol. GTN was observed to be completely converted to glycerol during a long-term incubation of cell extracts.

Effect of sucrose/raffinose mass ratios on the stability of co-lyophilized protein during storage above the Tg

PURPOSE

To examine the potential of raffinose as an excipient in stabilizing protein and to study the effect of sucrose/raffinose mass ratios on the stability of co-lyophilized protein and amorphous solids during storage at an elevated temperature.

METHODS

Glucose-6-phosphate dehydrogenase (G6PDH) was colyophilized with sucrose and raffinose mixed at different mass ratios. The activity of dried G6PDH was monitored during storage at 44 degrees C. Thermal properties of sucrose/raffinose matrices were determined by differential scanning calorimetry (DSC).

RESULTS

Mass ratios of sucrose to raffinose did not affect the recovery of G6PDH activity after freeze-drying, but significantly affected the stability of freeze-dried G6PDH during storage. The sucrose-alone formulation offered the best enzyme stabilization during storage. With increasing fraction of raffinose, the G6PDH stability decreased, sugar crystallization inhibited, and crystal-melting temperature increased.

CONCLUSIONS

Despite the higher Tg of the formulations with higher fraction of raffinose, they provided less protection for G6PDH than did sucrose alone during storage. Our data do not support the prediction from recent thermophysical studies that raffinose should be superior to sucrose and trehalose as a potential excipient or stabilizer.

Tyrosinase Reaction and Subsequent Chitosan Adsorption for Selective Removal of a Contaminant from a Fermentation Recycle Stream

In the industrial production of penicillin V, the phenoxyacetate precursor is added to the fermentor to direct biosynthesis. When used for producing semisynthetic penicillins, the penicillin V is often hydrolyzed to 6-aminopenicillanic acid with the regeneration of the phenoxyacetate precursor. To reduce raw-material as well as waste-disposal costs, it is desirable to recycle the phenoxyacetate precursor. Unfortunately, the recycle stream is generally contaminated by the p -hydroxylated derivative of this precursor. We examined a two-step approach to eliminate this contaminant. In the first step the tyrosinase enzyme was used to selectively convert the p -hydroxyphenoxyacetate contaminant to a reactive intermediate—presumably its quinone. In the second step, the tyrosinase-generated reactive intermediate was allowed to react with and strongly bind to chitosan. In contrast, the phenoxyacetate precursor was neither oxidized by tyrosinase nor bound to chitosan. When concentrated phenoxyacetate solutions were tested, the combination of tyrosinase and chitosan effectively converted low levels of the p -hydroxyphenoxyacetate contaminant and removed its products from solution, while the concentration of the phenoxyacetate precursor was unaffected.

Shear wave elastography and contrast-enhanced ultrasonography in the diagnosis of thyroid malignant nodules

The aim of the present study was to evaluate the value of shear wave elastography (SWE) and contrast-enhanced ultrasonography (CEUS) in the diagnosis of thyroid malignant nodules. A total of 253 patients with 319 thyroid nodules were subjected to two-dimensional ultrasound (2DUS) and CEUS examinations prior to thyroidectomy between March, 2014 and December, 2015. Young's modulus value for each nodule on 2DUS and CEUS images were recorded. The sensitivity, specificity and accuracy of 2DUS, SWE and CEUS in the diagnosis of thyroid malignant nodules were assessed. The results demonstrated that, of the 319 nodules that were pathologically confirmed, 183 were malignant and 136 were benign. The area under the receiver operating characteristic curve as a result of SWE diagnosis was 0.77. When the threshold of the Young's modulus value was ≥27.65 kPa in the diagnosis of malignant thyroid nodules, SWE exhibited a sensitivity of 84.55% (115/136), a specificity of 84.15% (154/183) and an accuracy of 84.32% (269/319). US contrast imaging of malignant thyroid nodules revealed a major tendency for early hypoenhancement and hypoenhancement. CEUS exhibited a sensitivity of 87.5% (119/136), a specificity of 86.33% (158/183) and an accuracy of 86.83% (277/319) in the diagnosis of malignant thyroid nodules. Compared with 2DUS, SWE, CEUS and their combined use exhibited statistically significant differences in the diagnosis of thyroid malignant nodules in terms of sensitivity, specificity and accuracy (χ²=9.220,15.310 and 40.296, respectively; P=0.000); SWE or CEUS did not differ significantly in the diagnosis of thyroid malignant nodules in terms of sensitivity, specificity or accuracy (χ²=0.737;P=0.542); Compared with the use of SWE or CEUS alone, their combination exhibited statistically significant differences in the diagnosis of malignant thyroid nodules in terms of sensitivity, specificity and accuracy (χ²=12.264 and 6.939, respectively; P=0.000,0.005). In conclusion, the high accuracy of the combined use of SWE and CEUS in the diagnosis of malignant thyroid nodules is of great clinical value.

State and phase transition behaviors of quercus rubra seed axes and cotyledonary tissues: relevance to the desiccation sensitivity and cryopreservation of recalcitrant seeds

Freezing and melting transitions of cellular water in embryonic axes and cotyledonary tissues of recalcitrant Quercus rubra (red oak) seeds were compared under slow and rapid cooling conditions. The relevance of desiccation sensitivity (critical water content) and state/phase transition behaviors to cryopreservation was examined. Under a slow to intermediate cooling condition (</=10 degrees C min(-1)), unfrozen water content in the tissues decreased to less than the critical water content, resulting in a dehydration damage. Under a rapid cooling condition (>100 degrees C min(-1)) using liquid nitrogen (LN(2)), freeze-induced dehydration damage could be avoided if the initial water content was >0.50 g g(-1) dry wt. However, at water content >0.50 g g(-1) dry wt, the vitrified cellular matrix was highly unstable upon warming at 10 degrees C min(-1). These results offered a theoretical explanation on the difficulty for successful cryopreservation of recalcitrant red oak embryonic axes. A complete state/phase transition diagram for red oak axes was constructed, and a vitrification-based cryopreservation protocol that employed predehydration and rapid cooling was examined. State/phase transition behaviors of cellular water are important parameters for cryopreservation; however, vitrification alone was not sufficient for seed tissues to survive the cryopreservation condition. Copyright 1999 Academic Press.

Dielectric relaxation of water and water-plasticized biomolecules in relation to cellular water organization, cytoplasmic viscosity, and desiccation tolerance in recalcitrant seed tissues

To understand the relationship between the organization of cellular water, molecular interactions, and desiccation tolerance, dielectric behaviors of water and water-plasticized biomolecules in red oak (Quercus rubra) seeds were studied during dehydration. The thermally stimulated current study showed three dielectric dispersions: (a) the relaxation of loosely-bound water and small polar groups, (b) the relaxation of tightly-bound water, carbohydrate chains, large polar groups of macromolecules, and (c) the "freezing in" of molecular mobility (glassy state). Seven discrete hydration levels (water contents of 1.40, 0.55, 0.41, 0.31, 0.21, 0.13, and 0.08 g/g dry weight, corresponding to -1.5, -8, -11, -14, -24, -74, and -195 MPa, respectively) were identified according to the changes in thermodynamic and dielectric properties of water and water-plasticized biomolecules during dehydration. The implications of intracellular water organization for desiccation tolerance were discussed. Cytoplasmic viscosity increased exponentially at water content < 0.40 g/g dry weight, which was correlated with the great relaxation slowdown of water-plasticized biomolecules, supporting a role for viscosity in metabolic shutdown during dehydration.

Associations between parent-reported sleep duration and adiposity in Chinese early adolescents

BACKGROUND

Short sleep duration has recently been found to be associated with obesity in children, but findings involving adolescents have been less consistent, and some have mentioned gender differences.

OBJECTIVES

To investigate the association between parent-reported sleep duration and adiposity in early adolescence (10-12 years old) and to explore gender differences within this population.

METHODS

Participants were 1309 fifth-grade students (685 boys) from 10 primary schools in Shanghai, China. Body mass index (BMI), waist-height ratio (WHeR) and body fat percentage (BF%) were assessed. Sleep and other potential contributors were recorded by parents or self-reported.

RESULTS

Compared with adolescents in the longest sleep group (greater than or equal to +1 SD, ≥10.05 h), those in the shortest sleep group (less than -1 SD, <8.89 h) had significantly higher BMI, WHeR and BF%. Sleep was found to be closely related to increased adiposity in girls who were in the shortest and shorter sleep group (<mean, <9.45 h). No association was found in boys.

CONCLUSIONS

Short sleep duration was associated with higher adiposity indices in early adolescents from China, especially in girls. Interventions focusing on modifying adolescents' sleep habits may potentially prevent obesity and overweight.

Biological denitration of propylene glycol dinitrate by Bacillus sp. ATCC 51912

In previous studies, bacterial cultures were isolated that had the ability to degrade the nitrate ester glyceryl trinitrate (i.e., nitroglycerin). The goal of the present study was to examine the ability of resting cells and cell-free extracts of the isolate Bacillus sp. ATCC 51912 to degrade the more recalcitrant nitrate ester propylene glycol dinitrate (PGDN). It was observed that the PGDN-denitrating activity was expressed during growth even when cells were cultured in the absence of nitrate esters. This indicates that nitrate esters are not required for expression of denitration activity. Using cell-free extracts, PGDN was observed to be sequentially denitrated to propylene glycol mononitrate (PGMN) and propylene glycol with the second denitration step proceeding more slowly than the first. Also it was observed that dialysis of the cell-free extracts did not affect denitration activity indicating that regenerable cofactors [e.g., NAD(P)H or ATP] are not required for denitration.

Desiccation tolerance of recalcitrant Theobroma cacao embryonic axes: the optimal drying rate and its physiological basis

Recalcitrant seed axes were reported to survive to lower water contents under fast-drying conditions. The present study was to examine the hypothesis that drying rate and dehydration duration could interact to determine desiccation tolerance through different physico-chemical mechanisms. The effect of drying rate on desiccation tolerance of Theobroma cacao seed axes at 16 degrees C was examined. Rapid-drying at low relative humidity (RH) and slow-drying at high RH were more harmful to cocoa axes, because electrolyte leakage began to increase and axis viability began to decrease at high water contents. Maximum desiccation tolerance was observed with intermediate drying rates at RH between 88% and 91%, indicating the existence of an optimal drying rate or optimal desiccation duration. This maximum level of desiccation tolerance for cocoa axes (corresponding to a critical water potential of -9 MPa) was also detected using the equilibration method, in which axes were dehydrated over a series of salt solutions or glycerol solutions until the equilibrium. These data confirmed that the physiological basis of the optimal drying rate is related to both mechanical stress during desiccation and the length of desiccation duration during which deleterious reactions may occur. The optimal drying rate represents a situation where combined damages from mechanical and metabolic stresses become minimal.

Protein modification by Amadori and Maillard reactions during seed storage: roles of sugar hydrolysis and lipid peroxidation

The non-enzymatic modifications of proteins through Amadori and Maillard reactions play an important role in the loss of seed viability during storage. In the present study, the contribution of sugar hydrolysis and lipid peroxidation to Amadori and Maillard reactions, and to seed deterioration was investigated in mung-bean (Vigna radiata Wilczek). The contents of glucose and lipid peroxidation products in seed axes increased significantly during storage. The accumulation of Amadori products in seed axes was correlated to the lipid peroxidation, whereas the accumulation of Maillard products was closely correlated to sugar hydrolysis. The rate of accumulation of Maillard products was not well correlated to the content of Amadori products in both seed axes and protein/glucose model system, reflecting the complex nature of Amadori and Maillard reactions. The content of Amadori products in seed axes increased during the early stages of seed ageing, whereas the content of Maillard products increased steadily during the entire period of storage. The accumulation of Maillard products in seed axes was associated with the decline of seed vigour. These data suggest that, during seed ageing, sugar hydrolysis and lipid peroxidation are coupled with non-enzymatic protein modification through Amadori and Maillard reactions.

Effect of antioxidant procyanidin b2 (pcb2) on ovine oocyte developmental potential in response to in vitro maturation (ivm) and vitrification stress

BACKGROUND

It was demonstrated that external stress, such as in vitro maturation (IVM) and vitrification process can induce significantly reduced development capacity in oocytes. Previous studies indicated that antioxidants play a pivotal part in the acquisition of adaptation in changed conditions. At present, the role of the natural potent antioxidant PCB2 in response to IVM and vitrification during ovine oocyte manipulation has not been explored.

OBJECTIVE

To investigate whether PCB2 treatment could improve the developmental potential of ovine oocytes under IVM and vitrification stimuli.

MATERIALS AND METHODS

The experiment was divided into two parts. Firstly, the effect of PCB2 on the development of oocytes during IVM was evaluated. Un-supplemented and 5 ug per mL PCB2-supplemented in the IVM solution were considered as control and experimental groups (C + 5 ug per mL PCB2). The polar body extrusion (PBE) rate, mitochondrial membrane potential (MMP), ATP, reactive oxygen species (ROS) levels and early apoptosis of oocytes were measured after IVM. Secondly, we further determine whether PCB2 could improve oocyte quality under vitrification stress. The survival rate, PBE rate and early apoptosis of oocytes were compared between fresh group, vitrified group and 5 ug per mL PCB2-supplemented in the IVM solution after vitrification (V + 5 ug per mL PCB2).

RESULTS

Compared to the control group, adding PCB2 significantly increased PBE rate (79.4% vs. 62.8%, P < 0.01) and MMP level (1.9 +/- 0.08 vs. 1.3 +/- 0.04, P < 0.01), and decreased ROS level (47.1 +/- 6.3 vs. 145.3 +/- 8.9, P < 0.01). However, there was no significant difference in ATP content and early apoptosis. Compared to the fresh group, vitrification significantly reduced oocytes viability (43.0% vs. 90.8%, P < 0.01) as well as PBE rate (24.2% vs. 60.6%, P < 0.05). However, 5 ug per mL PCB2-supplemention during maturation had no effect on survival, PBE or early apoptosis in vitrified oocytes.

CONCLUSION

PCB2 could effectively antagonise the oxidative stress during IVM and promote oocyte development. DOI: 10.54680/fr23210110412.

[Investigation of dose-dependent association between bedtime routines and sleep outcomes in infants and toddlers]

Objective: To investigate the current bedtime routine among Chinese children less than 3 years of age and explore its dose-dependent association with sleep duration and sleep quality. Method: Healthy full-term born children aged 0-35 months were selected by stratified cluster random sampling method from 8 provinces in China following the "Hospital of Province-City-County" sampling technical route during 2012-2013.Brief Infant Sleep Questionnaire(BISQ) was used to assess sleep conditions of these children.Children's personal and family information was obtained by Shanghai Children's Medical Center Socio-demographic Questionnaire.Both of these questionnaires were filled in by parents. The effects of bedtime routine on children's sleep duration and quality were analyzed by multivariate analysis of variance. Result: The children's average age was(12±10) months(n=1 304), of whom 689 were males (52.8%, 689/1 304). There were 48.5%(632/1 304)of the parents reported that their children had not established regular sleep routines. There was a consistent dose-dependent association between bedtime routine and sleep duration, as well as other indicators for sleep quality (all P<0.05). The more regular the sleep routines, the longer the sleep duration, the earlier the children went to sleep, the shorter the sleep onset latency, the fewer the nighttime wakeup and the shorter the nighttime waking.The nighttime sleep duration was significantly longer for those with a bedtime routine 'every night' than those who 'never' had a bedtime routine (9.5(95%CI: 9.4-9.6)vs. 8.9(95%CI: 8.6-9.3)h, t=3.345, P=0.001). Compared with children who never had bedtime routines, children with regular bedtime routines had fewer night wakeup (1.3(95%CI: 1.2-1.4) vs. 2.4( 95%CI: 2.0-2.9), t=3.182, P=0.001) and shorter night waking duration(16.6(95%CI: 14.6-18.8) vs. 59.2 (95%CI: 47.0-72.7)min, t=6.383, P<0.01). Conclusion: The percentage of children who have established regular bedtime routine is low in China. There is significant dose-dependent association between regular bedtime routine and sleep outcomes, especially sleep quality. The more regular the sleep routines, the better the sleep quality.

PERSPECTIVE: Cryopreservation of Human Oocytes and the 'Carryover' Effect on Early Embryo Development

Worldwide women are increasingly facing the issue of delayed child-bearing and fertility decline. Oocyte cryopreservation provides an option for fertility preservation, especially for women with diseases and other special needs to conceive babies later. In this review we examine the effect of oocyte cryopreservation on early development of human embryos. Databases (Medline, PubMed and Web of Science) were searched for relevant clinical studies published between 1999 and 2020. A total of 27 studies on oocyte cryopreservation and embryo development were identified, and data in those studies are retrieved for meta-analysis on the outcomes of oocyte survival, fertilization and early embryo development. In comparison to the slow freezing technique, vitrification yields significantly better oocyte survival (84.7% ± 0.6% vs 58.0% ± 0.5%), and subsequently higher rates of fertilization (65.5% ± 0.9% vs 40.0% ± 0.6%), cleavage (58.8% ± 0.9% vs 34.6% ± 0.8%), as well as embryo implantation (5.9% ± 0.3% vs 2.9% ± 0.2%). This analysis reveals a negative 'carryover' effect of oocyte cryopreservation on early development of embryos after oocyte fertilization (i.e., cleavage and implantation). This 'carryover' effect is greater for slowly-frozen oocytes than for vitrified oocytes, and may represent subtle functional or molecular alterations that are not severe enough to affect cell survival and fertilization, but sufficient to impair later development. The nature of the 'carryover' effect is unknown. Hypothermia, membrane ion channels, bioenergy metabolism and epigenetic modifications are likely involved. In conclusion, oocyte cryopreservation can negatively affect early development of human embryos. Future studies should go beyond oocyte survival and look further into the effects on epigenetic changes.

Pregnancy of cryopreserved ovine embryos at different developmental stages

BACKGROUND

Developmental stage and cryopreservation method have significant impact on the pregnancy rate after transfer of embryos produced in vivo.

OBJECTIVE

To determine the pregnancy outcomes from ovine embryos cryopreserved at different developmental stages.

MATERIALS AND METHODS

Embryos at different developmental stages were obtained from donor ewes through simultaneous estrus treatment and laparoscopic artificial insemination. Embryos, either cryopreserved via vitrification or slow freezing method, were implanted into recipient ewes. The pregnancy rate was determined 35 days after transfer.

RESULTS

The pregnancy rate of developing embryos increases after transfer from the morula stage, early blastocyst to expanded blastocyst stages (64.9%, 73.9% and 81.3%, respectively). However, cryopreservation significantly decreases the pregnancy rate of embryos at all three developmental stages, and there is no significant difference among developmental stages (43.9%, 43.7%, 52.9%, respectively). There is also no significant difference in the pregnancy rate between slowly-frozen embryos and vitrified embryos.

CONCLUSION

The pregnancy outcomes of embryo transfer is better at the expanded blastocyst stage than at earlier stages. However, no difference is observed in the pregnancy rate of embryos at different developmental stage after cryopreservation, either by slow freezing and vitrification. Cryopreservation methods for ovine embryos, both slow freezing and vitrification, need further improvement. doi.org/10.54680/fr22510110512.

Cryo-storage of porcine hides at the industrial scale for tissue engineering and regenerative medicine application

BACKGROUND

The industrial scale cryo-storage of raw tissue materials requires a robust, low-cost and easy-to-operate method that can facilitate the down-stream process.

OBJECTIVE

The study was aimed to develop the multifunctional protective solutions (MPS) for transportation at ambient conditions and also subsequent cryo-storage below -20 degree C of raw porcine hides for tissue engineering and regenerative medicine.

MATERIALS AND METHODS

Protective solutions with antimicrobial activity and proteinase-inhibiting activity were developed and tested for its efficacy in preserving the extracellular matrix of porcine dermis from microbial spoilage, proteolytic degradation, freeze damage and excessive dehydration during shipping and cryo-storage. The MPSs contained phosphate-buffered saline with ethylene diamine tetra acetic acid (EDTA) added as chelator and proteinase inhibitor, as well as glycerol or maltodextrin (M180) as cryoprotectants.

RESULTS

MPSs prepared with EDTA and glycerol or M180 had significant antimicrobial activity and proteinase-inhibiting activity during the period of shipping and handling. Glycerol and M180 prevented eutectic salt precipitation and excessive freeze dehydration upon cryo-storage of porcine hides. Without glycerol or M180, hides could be freeze-dehydrated to the low hydration at ~0.4 g/g dw, and formed irreversible plications after freezing. A critical hydration (0.8~0.9 g/g dw) was observed for the extracellular matrix of porcine dermis, and dehydration to a lower level could impose enormous stress and potential damage. The soaking of porcine hides in MPSs decreased water content as glycerol and M180 entered into dermis. Upon equilibration, the glycerol content in the tissue was about 94% of the incubating glycerol solution, but the M180 content in the tissue was only about 50% of the incubating M180 solution, indicating that M180 did not get into the entire aqueous domain within dermis. MPSs reduced ice formation and increased the unfrozen water content of porcine raw hides upon cryo-storage.

CONCLUSION

MPSs prepared with EDTA and glycerol or M180 have antimicrobial activity and proteinase-inhibiting activity, which can be used for transportation and cryo-storage of raw hides at the industrial scale. Glycerol at 7.5% w/v and M180 at 20% w/v were sufficient to prevent freeze damage and excessive freeze dehydration. Doi.org/10.54680/fr24310110312.

Effect of dextran molecular weight on protein stabilization during freeze-drying and storage

The effect of dextran molecular weight on structural stability of freeze-dried products and protein stability in amorphous matrices was investigated during storage at elevated temperatures. Glucose-6-phosphate dehydrogenase (G6PDH) was freeze-dried in 10% (w/v) dextrans of five molecular weights (12 kD, 42 kD, 71 kD, 512 kD and 2000 kD) to residual water content of 0.027 ( 0.004 g/g dry mass. The molecular weight of dextrans affected the glass transition temperature (Tg) of freeze-dried products and the recovery of enzyme activity after freeze-drying. As the molecular weight of dextrans increased from 12 kD to 2000 kD, the Tg increased from 100 degrees C to 120 degrees C, whereas the recovery of protein activity decreased from 85 +/- 4 % to 70 +/- 5%. The inactivation of freeze-dried protein during storage followed a bi-phasic first-order kinetics. The stability of amorphous matrices and protein increased significantly as the molecular weight increased from 12 kD to 512 kD. However, at a higher molecular weight (2000 kD), the stability was reduced. In a separate experiment, the stability of dried dextran/protein samples was studied during heating from 30 degrees C to 99 degrees C at 0.2 degrees C/min and subsequent incubation at 99 degrees C. Dextran with an average molecular weight of 512 kD was again found to provide the best protection. Mechanisms that cause the differences in protein stability among different molecular weight dextrans remain unclear.