Amnion and collagen-based blended hydrogel improves burn healing efficacy on a rat skin wound model in the presence of wound dressing biomembrane

BACKGROUND

A burn wound is one of the most frequent and devastating injuries for patients which requires extensive care. Early treatment of burn wounds improves healing significantly.

OBJECTIVE

This study was designed to investigate the efficacy of amnion and collagen-based hydrogels on cutaneous burn wound healing in rats with covering membrane.

METHODS

We prepared a novel cell free hydrogel comprising human amnion, rabbit collagen, carboxymethyl cellulose sodium salt, citric acid, methyl paraben, propyl paraben, glycerin and triethanol amine. The wound covering membrane was developed from rabbit collagen and prawn shell chitosan. Beside swelling ratio, water absorption, equilibrium water content, gel fraction and spreadability analysis, in vitro cytotoxicity and biocompatibility tests were performed for the formulated hydrogels. Following the skin irritation study, second-degree burns were created on the dorsal region of the rats and the gels were applied with/without covering membrane to study the wound contraction and re-epithelialization period.

RESULTS

The formulated hydrogels were observed non-cytotoxic and compatible with human blood cells. No erythema and edema were found in skin irritation assay confirming the safety and applicability. Hydrogel consisting in a combination of amnion and collagen demonstrated significantly rapid wound healing, driven by complete re-epithelialization (16.75 ± 0.96 days) and closure by wound contraction (72 ± 3.27%, P < 0.0000009) when wound dressing membrane was used, whereas this gel alone healed about 62.5 ± 4.43% (P < 0.00001) and required 18.75 ± 0.50 days to complete re-epithelialization. Additionally, the gel with covering membrane treated group had maximum average body weight, food and water intake.

CONCLUSION

The amnion and collagen-based blended gel offers alternative possibilities to treat skin wounds when covered with film, which could overcome the limitations associated with modern therapeutic products such as high costs, long manufacturing times, complexities, storing, and presence of living biomaterials.

Human bone and amniotic membrane banking in Bangladesh for grafting: the impact of the international atomic energy agency (IAEA) programme

The idea of establishing a human tissue bank in Bangladesh was started in 1985. However, in 2003, with the active cooperation of international atomic energy agency (IAEA) and Bangladesh Atomic Energy Commission, a tissue bank laboratory was upgraded as a unit for tissue banking and research. Due to increasing demand of allograft, this unit was transformed as an independent institute "Institute of Tissue Banking and Biomaterial Research (ITBBR)" in 2016. This is the only human tissue bank in Bangladesh, which processes human bone and amniotic membrane to provide safe and cost-effective allografts for transplantation. Importantly, banking of human cranial bone as autograft has also started at ITBBR. These processed grafts are sterilized using gamma radiation according to the IAEA Code of Practice for the radiation sterilization of tissues allografts. The amount of grafts produced by the ITBBR from 2007 to 2018 were 120,800 cc of bone chips, 45,420 cm² of amniotic membranes, 277 vials of de-mineralized bone granules (DMB), 95 pieces of massive bones, and 134 pieces of cranial bones. Overall, 112,748 cc of bone chips, 40,339 cm² of amniotic membranes, 174 vials of DMB, 44 pieces of massive bones, and 64 pieces of cranial bones were transplanted successfully. Nevertheless, to cope up with the modern advanced concepts of cell and tissue banking for therapeutic purpose, ITBBR is working to set up facilities for skin banking, stem cells banking including amniotic and cord blood derived stem cells and scaffold designing. To ensure the quality, safety, ethical and regulatory issues are sustainable in cell and tissue banking practices, ITBBR always works with the Government of Bangladesh for enhancing the national tissue transplantation programme within the contemporary facilities.

Fabrication of biocompatible porous scaffolds based on hydroxyapatite/collagen/chitosan composite for restoration of defected maxillofacial mandible bone

Fabrication of scaffolds from biomaterials for restoration of defected mandible bone has attained increased attention due to limited accessibility of natural bone for grafting. Hydroxyapatite (Ha), collagen type 1 (Col1) and chitosan (Cs) are widely used biomaterials which could be fabricated as a scaffold to overcome the paucity of bone substitutes. Here, rabbit Col1, shrimp Cs and bovine Ha were extracted and characterized with respect to physicochemical properties. Following the biocompatibility, degradability and cytotoxicity tests for Ha, Col1 and Cs a hydroxyapatite/collagen/chitosan (Ha·Col1·Cs) scaffold was fabricated using thermally induced phase separation technique. This scaffold was cross-linked with (1) either glutaraldehyde (GTA), (2) de-hydrothermal treatment (DTH), (3) irradiation (IR) and (4) 2-hydroxyethyl methacrylate (HEMA), resulting in four independent types (Ha·Col1·Cs-GTA, Ha·Col1·Cs-IR, Ha·Col1·Cs-DTH and Ha·Col1·Cs-HEMA). The developed composite scaffolds were porous with 3D interconnected fiber microstructure. However, Ha·Col1·Cs-IR and Ha·Col1·Cs-GTA showed better hydrophilicity and biodegradability. All four scaffolds showed desirable blood biocompatibility without cytotoxicity for brine shrimp. In vitro studies in the presence of human amniotic fluid-derived mesenchymal stem cells revealed that Ha·Col1·Cs-IR and Ha·Col1·Cs-DHT scaffolds were non-cytotoxic and compatible for cell attachment, growth and mineralization. Further, grafting of Ha·Col1·Cs-IR and Ha·Col1·Cs-DHT was performed in a surgically created non-load-bearing rabbit maxillofacial mandible defect model. Histological and radiological observations indicated the restoration of defected bone. Ha·Col1·Cs-IR and Ha·Col1·Cs-DHT could be used as an alternative treatment in bone defects and may contribute to further development of scaffolds for bone tissue engineering.

Human tissue banking in Bangladesh: hope for the patients of massive burns, surgical wound and bone associated complications

Each year throughout Bangladesh, thousands of people suffering from massive burns and surgical wounds require amniotic grafts for transplantation. Additionally, the stricken persons of the country have to embrace bone associated disability for the whole life due to traumatic complications need bone graft to treat. As a result, these two problems are the largest financial burden as this situation not only affect the family of patients but also cripple down national economy. However, institute of tissue banking in Bangladesh has undertaken the service program on the processing, preservation and clinical applications of amnion membrane and bone graft for rehabilitative surgery. Importantly, in recent years, this institute has started cranial bone autograft processing and transplantation. In accidental cases such as head injury, it is difficult to provide suitable cranial bone allograft according to demand. In this situation, injured cranial bone of the patient is being transported to the lab of the institute, where the scientist, tissue banker and medic work together immediately to process the cranial bone and sterilize by gamma radiation; and after quality assurance, the processed cranial bone autograft is being supplied for replacement surgery. The use of irradiated amnion and bone allografts and cranial bone autograft in reconstructive surgery restore normalcy to lives of many patients from disabilities. This tissue bank is based on finding and obtaining qualified donors from the community and a demand for tissue grafts from the hospitals. Although growing needs for tissue transplantation but raw and processed tissue grafts preservation and banking braces enormous logistical limitations. The only human tissue bank in Bangladesh, however, ensures the availability of tissue allografts of high quality and acceptability to the recipients for rehabilitative surgery for a decade, regardless patients' socio-economic status.

Variations of Weight of Thyroid Gland in Different Age and Sex Groups of Bangladeshi Cadavers

A cross sectional descriptive study was designed to find out the difference in weight of the thyroid gland of Bangladeshi people in relation to age and sex. The present study was performed on 70 post mortem human thyroid gland (35 of male and 35 of female) collected from the morgue in the Department of Forensic Medicine, Mymensingh Medical College, Mymensingh by purposive sampling technique. The specimens were collected from Bangladeshi cadavers of age ranging from 10 years to 85 years. All the specimens were grouped into three categories Group A (upto 20 years), Group B (21 to 50 years) and Group C (>50 years) according to age. Dissection was performed according to standard autopsy techniques. The weight of the thyroid glands were measured and recorded. The mean weight of the thyroid gland was 6.94 ± 5.20 gm in Group A, 7.91 ± 5.89 gm in Group B and 10.42 ± 6.27 gm in Group C. The mean weight of the thyroid gland in male was 7.0 ± 5.77 gm in Group A, 9.94 ± 7.63 gm in Group B and 11.89 ± 5.73 gm in Group C and in female was 6.88 ± 4.88 gm in Group A, 5.88 ± 2.15 gm in Group B and 9.10 ± 6.74 gm in Group C. Variance analysis shows that there was no significant difference in mean weight between the Age Group A & B, B & C and C & A. There was significant difference of weight of thyroid gland between sex in age Group B but in Group A and Group C were statistically insignificant. The weight of the thyroid gland was found to increases with age. In statistical analysis, differences between age groups were analyzed by using one way ANOVA test. The present study will help to increase the information pool on the weight of thyroid gland of Bangladeshi people.

TGF-β/BMP signaling and other molecular events: regulation of osteoblastogenesis and bone formation

Transforming growth factor-beta (TGF-β)/bone morphogenetic protein (BMP) plays a fundamental role in the regulation of bone organogenesis through the activation of receptor serine/threonine kinases. Perturbations of TGF-β/BMP activity are almost invariably linked to a wide variety of clinical outcomes, i.e., skeletal, extra skeletal anomalies, autoimmune, cancer, and cardiovascular diseases. Phosphorylation of TGF-β (I/II) or BMP receptors activates intracellular downstream Smads, the transducer of TGF-β/BMP signals. This signaling is modulated by various factors and pathways, including transcription factor Runx2. The signaling network in skeletal development and bone formation is overwhelmingly complex and highly time and space specific. Additive, positive, negative, or synergistic effects are observed when TGF-β/BMP interacts with the pathways of MAPK, Wnt, Hedgehog (Hh), Notch, Akt/mTOR, and miRNA to regulate the effects of BMP-induced signaling in bone dynamics. Accumulating evidence indicates that Runx2 is the key integrator, whereas Hh is a possible modulator, miRNAs are regulators, and β-catenin is a mediator/regulator within the extensive intracellular network. This review focuses on the activation of BMP signaling and interaction with other regulatory components and pathways highlighting the molecular mechanisms regarding TGF-β/BMP function and regulation that could allow understanding the complexity of bone tissue dynamics.

Mapping and identification of the region and secondary structure required for the maturation of the nukacin ISK-1 prepeptide

The prepeptide NukA of the lantibiotic nukacin ISK-1 consists of an N-terminal leader peptide followed by a propeptide moiety that undergoes post-translational modifications, that is, formation of unusual amino acids by NukM, cleavage of the leader peptide and transport by NukT to yield a mature peptide. To identify the region and conformation required for the maturation of prepeptide, we expressed a series of NukA mutants, mutants with the N-terminus-truncated leader peptide and site-directed mutants with conserved residues in the leader peptide of type A(II) lantibiotics, which were evaluated on the basis of the production of nukacin ISK-1. In addition, the secondary structure data of NukA mutants or fragments were obtained by circular dichroism spectra. The results indicated the importance of the alpha-helical leader peptide with hydrophobic and hydrophilic orientation consisting of the conserved residues in type A(II) lantibiotics. The expression data from various combinations of the chimeric prepeptides consisting of NukA and LctA (the prepeptide of lacticin 481, which shows high identity with NukA) further revealed that the amino acid difference at the C-terminus of the propeptide moiety between NukA and LctA, especially His at position 15 and Phe at position 19, was important for the maturation processes by the nukacin ISK-1 biosynthetic enzymes. Our findings suggest that the determinants in NukA were critically involved in the biosynthesis of nukacin ISK-1 and would thus be important for recognition by the nukacin ISK-1 biosynthetic enzymes.

Lantibiotics: insight and foresight for new paradigm

Lantibiotics are a unique type of antimicrobial peptide produced by a large number of gram-positive bacteria that contain unusual amino acids, such as lanthionine and dehydrated amino acids. Ribosomally synthesized lantibiotic prepeptide consists of an N-terminal leader peptide followed by a C-terminal propeptide moiety that undergoes several post-translational modification events to yield a biologically active lantibiotic. Research on lantibiotics has drawn much attention in recent years and has undergone extensive progress as a step forward to the next paradigm. Unusual amino acids in lantibiotics solely contribute to their biological activity and also enhance their structural stability. Thus, enzymes involved in lantibiotic biosynthesis would have a high potential for peptide engineering by introducing unusual amino acids into desired peptides, which may establish a universal approach to advance the structural design of novel peptides, termed lantibiotic engineering. In this review, we focus on recent development with contemporary innovations and perspective of lantibiotic research.

Lysine-oriented charges trigger the membrane binding and activity of nukacin ISK-1

The antibacterial activities and membrane binding of nukacin ISK-1 and its fragments and mutants were evaluated to delineate the determinants governing structure-function relationships. The tail region (nukacin(1-7)) and ring region (nukacin(7-27)) were shown to have no antibacterial activity and also had no synergistic effect on each other or even on nukacin ISK-1. Both a fragment with three lysines in the N terminus deleted (nukacin(4-27)) and a mutant with three lysines in the N terminus replaced with alanine (K1-3A nukacin ISK-1) imparted very low activity (32-fold lower than nukacin ISK-1) and also exhibited a similar antagonistic effect on nukacin ISK-1. Addition of two lysine residues at the N terminus (+2K nukacin ISK-1) provided no further increased antibacterial activity. Surface plasmon resonance sensorgrams and kinetic rate constants determined by a BIAcore biosensor revealed that nukacin ISK-1 has remarkably higher binding affinity to anionic model membrane than to zwitterionic model membrane. Similar trends of strong binding responses and kinetics were indicated by the high affinities of nukacin ISK-1 and +2K nukacin ISK-1, but there was no binding of tail region, ring region, nukacin(4-27), and K1-3A nukacin ISK-1 to the anionic model membrane. Our findings therefore suggest that the complete structure of nukacin ISK-1 is necessary for its full activity, in which the N-terminus three lysine residues play a crucial role in electrostatic binding to the target membrane and therefore nukacin ISK-1's ability to exert its potent antibacterial activity.

Lantibiotics: A Candidate for Future Generation of Antibiotics

Emergence of multi-resistant pathogens has urged the exploration of antibiotic repertoires. The long reliability on the glycopeptide antibiotic vancomycin against fatal diseases caused by Gram-positive bacteria is also in wrecked to insist on finding more promising alternative antibiotics. The peptide antibiotic nisin is effective against vancomycin resistant bacteria. Nisin is the first lantibiotic that was discovered before penicillin and has been widely used as a safe alternative for chemical reagents in food preservation in around 50 countries for over 40 years without natural resistance development. Therefore, lantibiotics are one of the most promising alternative candidate for future antibiotics that maintain their antibacterial efficacy by many modes of action. Till now, more than 60 lantibiotics have been isolated, identified and characterized. We explained various aspects of biosynthesis, grouping, mutagenesis, activities and modes of action of lantibiotics in this review. DOI: http://dx.doi.org/10.3329/sjm.v1i1.9096 Stamford Journal of Microbiology, Vol.1(1), July 2011, p.1-12