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Mastitis, an inflammatory reaction frequently develops in response to intra-mammary bacterial infection‌‌, may induce the generation of peroxynitrite (PON)‌ which is a highly potent reactive oxygen and nitrogen species. Caseins as the intrinsically unfolded proteins seem feasible substrates to react with PON. Therefore, in the current study, structural and functional aspects of both β-casein (β-CN) and whole casein fraction (WCF) were evaluated after PON modification, using a variety of techniques. Modification of the bovine caseins with PON results in an important enhancement in the carbonyl, nitrotryptophan, nitrotyrosine and dityrosine content of these proteins‌. The results of fluorescence and far UV-CD assessments suggested significant structural alteration of caseins upon PON-modification. The chaperone-like activity of β-casein was significantly altered after PON modification. The results of scanning electron microscopy suggest that bovine caseins display unique morphological features after treatment with PON. Also, the PON-modified caseins preserved their allergenicity profile and displayed partial resistance against digestion by the pancreatic proteases. Ascorbic acid, an important antioxidant component of milk, was also capable to significantly prevent the PON-induced structural damages in bovine milk caseins. In conclusion, our results suggest that PON may have significant role in the structural and functional alteration of milk caseins. Also, the PON-induced structural damaging effects of caseins might be effectively prevented by a sufficient level of milk antioxidant components particularly by ascorbic acid.

Chitosan (CS) is a carbohydrate biopolymer, which has been known as a biological material in promoting the healing process of soft and hard connective tissues. It is biocompatible, biodegradable, bioactive, non-toxic, non-expensive and non-immunogenic, with antibacterial capability. Additionally, the capacity of forming complexes with other anionic biomaterials and molecules offers CS the characteristics to be used in biomedical applications. Therefore, this natural polysaccharide has widely been used as a wound dressing and in bone and cartilage regeneration because of these considerable properties. However, some studies have showed limited value in application of CS in tissue regeneration. It has been used alone or in combination with other biopolymers, bioceramics, or promotive growth factors to enhance regeneration of the soft and hard connective tissues. This study has reviewed various forms of CS including hydrogels, sponges, films, and nanofiber membranes. The role of CS alone or in combined form with other materials has also been reviewed in healing and regeneration of the cutaneous, cartilage and bone wounds. In addition, the present study has attempted to clarify the controversies and conflicts regarding effectiveness of CS in the healing process.

Peroxynitrite (PON) and methylglyoxal (MGO), two diabetes-associated compounds, are believed to be important causative players in development of diabetic cataracts. In the current study, different spectroscopic methods, gel electrophoresis, lens culture and microscopic assessments were applied to examine the impact of individual, subsequent or simultaneous modification of lens crystallins with MGO and PON on their structure, oligomerization and aggregation. The protein modifications were confirmed with detection of the significantly increased quantity of carbonyl groups and decreased levels of sulfhydryl, tyrosine and tryptophan. Also, lens proteins modification with these chemical agents was accompanied with important structural alteration, oligomerization, disulfide/chromophore mediated protein crosslinking and important proteolytic instability. All these structural damages were more pronounced when the lens proteins were modified in the presence of both mentioned chemical agents, either in sequential or simultaneous manner. Ascorbic acid and glutathione, as the main components of lens antioxidant defense mechanism, were also capable to markedly prevent the damaging effects of PON and MGO on lens crystallins, as indicated by gel electrophoresis. The results of this study may highlight the importance of lens antioxidant defense system in protection of crystallins against the structural insults induced by PON and MGO during chronic hyperglycemia in the diabetic patients.

This study compared the regeneration potentials of the hydroxyapatite (HA) and beta-tricalcium phosphate (β-TCP) alone or in combination with a HA:TCP ratio of 30:70 in the critical-sized radial bone defects of rats. Bilateral 60 radial bone defects created were randomly divided into six equal groups (n=10 defects/group) including autograft, untreated or defect, chitosan-gelatin-platelet gel (CGP), CGP-HA, CGP-TCP and CGP-HA/TCP. The defects were evaluated by radiography, morphology, histopathology, histomorphometry, CT scan, scanning electron microscopy and biomechanical testing after eight weeks. Compared with the untreated and CGP-HA groups, the CGP and CGP-HA/TCP groups showed significantly higher new bone formation, bone volume, and mechanical properties. The CGP-HA and CGP-TCP scaffolds showed low biodegradability, whereas the CGP scaffolds were completely degraded. Osteoconductivity and osteoinductivity of the CGP and CGP-HA/TCP scaffolds were superior to the CGP-HA ones. The untreated and CGP-HA groups repaired mostly through fibrosis, while there were evidence of higher bone formation in the autograft, CGP and CGP-HA/TCP groups. In conclusion, addition of HA or β-TCP alone into the CGP scaffolds impaired bone regeneration, while bone regeneration with the CGP and CGP-HA/TCP scaffolds was comparable with the autograft. Therefore, the CGP-HA/TCP scaffold can be a possible option to substitute the autologous bone grafting.

Bone tissue scaffolds made from either natural or synthetic polymers are employed to promote bone healing. However, lack of sufficient or poor mechanical properties such as low integrity and stability reduces their medical applications. Crosslinking, defined as induction of chemical or physical links among polymer chains, is a simple method generally used to modify mechanical, biological and degradation properties of hydrogels. Although crosslinking through chemical reactions improves the mechanical properties of bone substitutes, most of the reagents used for this aim demonstrate undesirable effects and may exert toxic reactions. Glutaraldehyde is a widely-used chemical crosslinker with unique ability to crosslink a wide variety of biomaterials; however, many contradictory views have been recently raised on its cytotoxic effects. By keeping this limit in mind, green chemicals or natural crosslinking agents have been shown to provide desired improvements in mechanical properties of bone scaffolds. Therefore, developing more efficient crosslinking materials and methods are desirable to obtain crosslinked scaffolds with perfect properties in bone tissue engineering from different biopolymers such as collagen, gelatin, cellulose, chitosan, alginate, etc. In this review, we focused on developed or developing modalities used to improve mechanical properties of various bone scaffolds and matrices based on common crosslinking reagents.

Polysaccharides are the main macromolecules of Aloe vera gel but no data about their effect on extracellular matrix (ECM) elements are available. Here, mannose rich Aloe vera polysaccharides (AVP) with molecular weight between 50 and 250 kDa were isolated and characterized. Open cutaneous wounds on the back of 45 rats (control and treated) were daily treated with 25 mg ( n = 15) and 50 mg ( n = 15) AVP for 30 days. The levels of MMP-3 and TIMP-2 gene expression were analyzed using real time PCR. The levels of n-acetyl glucosamine (NAGA), n-acetyl galactosamine (NAGLA) and collagen contents were also measured using standard biochemical methods. Faster wound closure was observed at day 15 post wounding in AVP treated animals in comparison with untreated group. At day 10 post wounding, AVP inhibited MMP-3 gene expression, while afterwards MMP-3 gene expression was upregulated. AVP enhanced TIMP-2 gene expression, collagen, NAGLA and NAGA synthesis in relation to untreated wounds. Our results suggest that AVP has positive effects on the regulation of ECM factor synthesis, which open up new perspectives for the wound repair activity of Aloe vera polysaccharide at molecular level.

Total soluble lens proteins (TSPs) and α-crystallin (α-Cry) were individually subjected to the long-term glycation in the presence of d-glucose. The glycated and non-glycated protein counterparts were incubated under different stress conditions and compared according to their structure, stability and aggregation propensity by various spectroscopic techniques and gel mobility shift analyses. Extensive glycation of the lens proteins was accompanied with structural alteration, reduction in their surface hydrophobicity and increment of their surface tension. Our results suggest that glycation causes lens crystallins to partially resist against structural alteration and aggregation/fibrillation under both thermal and thermochemical systems. The conformational stability of lens crystallins was increased upon glycation, showing the reason behind resistance of glycated proteins against stress-induced structural alteration and aggregation. Due to the resistance of glycated lens crystallins against aggregation, the role of this modification in development of senile cataract can be explained with the associated damaging consequences highlighted in this article.