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A novel approach to evaluate the mechanical responses of elastin-like bioresorbable poly(glycolide-co-caprolactone) (PGCL) suture

Low YJ, Kittur MI, Andriyana A, Ang BC, Zainal Abidin NI

J Mech Behav Biomed Mater, 2023 Apr;140:105723.
PMID: 36821908 DOI: 10.1016/j.jmbbm.2023.105723

Poly(glycolide-co-caprolactone) (PGCL) has become a novice to the bioresorbable suture owing to the synergistic properties taken from the homo-polyglycolide (PGA) and polycaprolactone (PCL) such as excellent bioresorption and flexibility. In addition to under conventional monotonic loading, the understanding of mechanical responses of PGCL copolymers under complex loading conditions such as cyclic and stress relaxation is crucial for its application as a surgical suture. Consequently, the present work focuses on evaluating the mechanical responses of PGCL sutures under monotonic, cyclic, and stress relaxation loading conditions. Under monotonic loading, the stress-strain behavior of the PGCL suture was found to be non-linear with noticeable strain-rate dependence. Under cyclic loading, inelastic responses including stress-softening, hysteresis and permanent set were observed. During cyclic loading, both stress-softening and hysteresis were found to increase with the maximum strain. In multi-step stress relaxation, the PGCL sutures were observed to exhibit a strong viscoelastic response. In an attempt to describe the relationship between the stress-relaxation and strain-induced crystallization (SIC) occurring during the loading and relaxation processes, a schematic illustration of the conformational change of polymer chains in PGCL sutures was proposed in this work. Results showed that SIC was dependent on the strain level as well as the loading and relaxation durations. The inelastic phenomena observed in PGCL sutures can be thus correlated to the combined effect of stress relaxation and SIC.

Matched MeSH terms: Elastin*
Biodegradable and antithrombogenic chitosan/elastin blended polyurethane electrospun membrane for vascular tissue integration

Selvaras T, Alshamrani SA, Gopal R, Jaganathan SK, Sivalingam S, Kadiman S, et al.

J Biomed Mater Res B Appl Biomater, 2023 Jun;111(6):1171-1181.
PMID: 36625453 DOI: 10.1002/jbm.b.35223

Current commercialized vascular membranes to treat coronary heart disease (CHD) such as Dacron and expanded polytetrafluoroethylene (ePTFE) have been associated with biodegradable and thrombogenic issues that limit tissue integration. In this study, biodegradable vascular membranes were fabricated in a structure of electrospun nanofibers composed of polyurethane (PU), chitosan (CS) and elastin (0.5%, 1.0%, and 1.5%). The physicochemical properties of the membranes were analyzed, followed by the conduction of several test analyses. The blending of CS and elastin has increased the fiber diameter, pore size and porosity percentage with the appearance of identical chemical groups. The wettability of PU membranes was enhanced up to 39.6%, demonstrating higher degradation following the incorporation of both natural polymers. The PU/CS/elastin electrospun membranes exhibited a controlled release of CS (Higuchi and first-order mechanisms) and elastin (Higuchi and Korsmeyer-Peppas mechanisms). Delayed blood clotting time was observed through both activated partial thromboplastin time (APTT) and partial thromboplastin time (PT) analyses where significantly delay of 26.8% APTT was recorded on the PU membranes blended with CS and elastin, in comparison with the PU membranes, supporting the membrane's antithrombogenic properties. Besides, these membranes produced a minimum of 2.6 ± 0.1 low hemolytic percentage, projecting its hemocompatibility to be used as vascular membrane.

Matched MeSH terms: Elastin
Fulltext Molecular Mechanisms of Stress-Responsive Changes in Collagen and Elastin Networks in Skin

Aziz J, Shezali H, Radzi Z, Yahya NA, Abu Kassim NH, Czernuszka J, et al.

Skin Pharmacol Physiol, 2016;29(4):190-203.
PMID: 27434176 DOI: 10.1159/000447017

Collagen and elastin networks make up the majority of the extracellular matrix in many organs, such as the skin. The mechanisms which are involved in the maintenance of homeostatic equilibrium of these networks are numerous, involving the regulation of genetic expression, growth factor secretion, signalling pathways, secondary messaging systems, and ion channel activity. However, many factors are capable of disrupting these pathways, which leads to an imbalance of homeostatic equilibrium. Ultimately, this leads to changes in the physical nature of skin, both functionally and cosmetically. Although various factors have been identified, including carcinogenesis, ultraviolet exposure, and mechanical stretching of skin, it was discovered that many of them affect similar components of regulatory pathways, such as fibroblasts, lysyl oxidase, and fibronectin. Additionally, it was discovered that the various regulatory pathways intersect with each other at various stages instead of working independently of each other. This review paper proposes a model which elucidates how these molecular pathways intersect with one another, and how various internal and external factors can disrupt these pathways, ultimately leading to a disruption in collagen and elastin networks.

Matched MeSH terms: Elastin/metabolism*; Elastin/radiation effects; Elastin/ultrastructure*
Formation of tissue-engineered human auricular cartilage via tissue engineering technique for future use in ear surgery

Saim L, Aminuddin BS, Munirah S, Chua KH, Izuddin Fahmy A, Fuzina NH, et al.

Med J Malaysia, 2004 May;59 Suppl B:192-3.
PMID: 15468883

To date there is no optimal approach to reconstruct an external ear. However, advances in tissue engineering technologies have indicated that in vitro autologous elastic cartilage might be of great importance in the future treatment of these patients. The aim of this study was to observe monolayer expansion of auricular cartilage and to evaluate engineered cartilage using standard histochemical study.

Matched MeSH terms: Elastin/metabolism
Fulltext Characterization and in vivo study of decellularized aortic scaffolds using closed sonication system

Hazwani A, Sha'Ban M, Azhim A

Organogenesis, 2019;15(4):120-136.
PMID: 31495272 DOI: 10.1080/15476278.2019.1656997

Extracellular matrix (ECM) based bioscaffolds prepared by decellularization has increasingly emerged in tissue engineering application because it has structural, biochemical, and biomechanical cues that have dramatic effects upon cell behaviors. Therefore, we developed a closed sonication decellularization system to prepare ideal bioscaffolds with minimal adverse effects on the ECM. The decellularization was achieved at 170 kHz of ultrasound frequency in 0.1% and 2% Sodium Dodecyl Sulphate (SDS) solution for 10 hours. The immersion treatment as control was performed to compare the decellularization efficiency with our system. Cell removal and ECM structure were determined by histological staining and biochemical assay. Biomechanical properties were investigated by the indentation testing to test the stiffness, a residual force and compression of bioscaffolds. Additionally, in vivo implantation was performed in rat to investigate host tissue response. Compared to native tissues, histological staining and biochemical assay confirm the absence of cellularity with preservation of ECM structure. Moreover, sonication treatment has not affected the stiffness [N/mm] and a residual force [N] of the aortic scaffolds except for compression [%] which 2% SDS significantly decreased compared to native tissues showing higher SDS has a detrimental effect on ECM structure. Finally, minimal inflammatory response was observed after 1 and 5 weeks of implantation. This study reported that the novelty of our developed closed sonication system to prepare ideal bioscaffolds for tissue engineering applications.

Matched MeSH terms: Elastin/metabolism
Characterization of human adipose-derived stem cells and expression of chondrogenic genes during induction of cartilage differentiation

Hamid AA, Idrus RB, Saim AB, Sathappan S, Chua KH

Clinics (Sao Paulo), 2012;67(2):99-106.
PMID: 22358233

OBJECTIVES: Understanding the changes in chondrogenic gene expression that are involved in the differentiation of human adipose-derived stem cells to chondrogenic cells is important prior to using this approach for cartilage repair. The aims of the study were to characterize human adipose-derived stem cells and to examine chondrogenic gene expression after one, two, and three weeks of induction.
MATERIALS AND METHODS: Human adipose-derived stem cells at passage 4 were evaluated by flow cytometry to examine the expression of surface markers. These adipose-derived stem cells were tested for adipogenic and osteogenic differentiation capacity. Ribonucleic acid was extracted from the cells for quantitative polymerase chain reaction analysis to determine the expression levels of chondrogenic genes after chondrogenic induction.
RESULTS: Human adipose-derived stem cells were strongly positive for the mesenchymal markers CD90, CD73, CD44, CD9, and histocompatibility antigen and successfully differentiated into adipogenic and osteogenic lineages. The human adipose-derived stem cells aggregated and formed a dense matrix after chondrogenic induction. The expression of chondrogenic genes (collagen type II, aggrecan core protein, collagen type XI, COMP, and ELASTIN) was significantly higher after the first week of induction. However, a significantly elevated expression of collagen type X was observed after three weeks of chondrogenic induction.
CONCLUSION: Human adipose-derived stem cells retain stem cell characteristics after expansion in culture to passage 4 and serve as a feasible source of cells for cartilage regeneration. Chondrogenesis in human adipose-derived stem cells was most prominent after one week of chondrogenic induction.

Matched MeSH terms: Elastin/genetics; Elastin/metabolism
Co-localization of LTBP-2 with FGF-2 in fibrotic human keloid and hypertrophic scar

Sideek MA, Teia A, Kopecki Z, Cowin AJ, Gibson MA

J Mol Histol, 2016 Feb;47(1):35-45.
PMID: 26644005 DOI: 10.1007/s10735-015-9645-0

We have recently shown that Latent transforming growth factor-beta-1 binding protein-2 (LTBP-2) has a single high-affinity binding site for fibroblast growth factor-2 (FGF-2) and that LTBP-2 blocks FGF-2 induced cell proliferation. Both proteins showed strong co-localisation within keloid skin from a single patient. In the current study, using confocal microscopy, we have investigated the distribution of the two proteins in normal and fibrotic skin samples including normal scar tissue, hypertrophic scars and keloids from multiple patients. Consistently, little staining for either protein was detected in normal adult skin and normal scar samples but extensive co-localisation of the two proteins was observed in multiple examples of hypertrophic scars and keloids. LTBP-2 and FGF-2 were co-localised to fine fibrous elements within the extracellular matrix identified as elastic fibres by immunostaining with anti-fibrillin-1 and anti-elastin antibodies. Furthermore, qPCR analysis of RNA samples from multiple patients confirmed dramatically increased expression of LTBP-2 and FGF-2, similar TGF-beta 1, in hypertrophic scar compared to normal skin and scar tissue. Overall the results suggest that elevated LTBP-2 may bind and sequester FGF-2 on elastic fibres in fibrotic tissues and modulate FGF-2's influence on the repair and healing processes.

Matched MeSH terms: Elastin/genetics; Elastin/metabolism
Fulltext Multimeric disintegrin protein polymer fusions that target tumor vasculature

Janib SM, Gustafson JA, Minea RO, Swenson SD, Liu S, Pastuszka MK, et al.

Biomacromolecules, 2014 Jul 14;15(7):2347-58.
PMID: 24871936 DOI: 10.1021/bm401622y

Recombinant protein therapeutics have increased in number and frequency since the introduction of human insulin, 25 years ago. Presently, proteins and peptides are commonly used in the clinic. However, the incorporation of peptides into clinically approved nanomedicines has been limited. Reasons for this include the challenges of decorating pharmaceutical-grade nanoparticles with proteins by a process that is robust, scalable, and cost-effective. As an alternative to covalent bioconjugation between a protein and nanoparticle, we report that biologically active proteins may themselves mediate the formation of small multimers through steric stabilization by large protein polymers. Unlike multistep purification and bioconjugation, this approach is completed during biosynthesis. As proof-of-principle, the disintegrin protein called vicrostatin (VCN) was fused to an elastin-like polypeptide (A192). A significant fraction of fusion proteins self-assembled into multimers with a hydrodynamic radius of 15.9 nm. The A192-VCN fusion proteins compete specifically for cell-surface integrins on human umbilical vein endothelial cells (HUVECs) and two breast cancer cell lines, MDA-MB-231 and MDA-MB-435. Confocal microscopy revealed that, unlike linear RGD-containing protein polymers, the disintegrin fusion protein undergoes rapid cellular internalization. To explore their potential clinical applications, fusion proteins were characterized using small animal positron emission tomography (microPET). Passive tumor accumulation was observed for control protein polymers; however, the tumor accumulation of A192-VCN was saturable, which is consistent with integrin-mediated binding. The fusion of a protein polymer and disintegrin results in a higher intratumoral contrast compared to free VCN or A192 alone. Given the diversity of disintegrin proteins with specificity for various cell-surface integrins, disintegrin fusions are a new source of biomaterials with potential diagnostic and therapeutic applications.

Matched MeSH terms: Elastin/chemistry
Fulltext Role of α-helical structure in organic solvent-activated homodimer of elastase strain K

Rahman RN, Salleh AB, Basri M, Wong CF

Int J Mol Sci, 2011;12(9):5797-814.
PMID: 22016627 DOI: 10.3390/ijms12095797

Recombinant elastase strain K overexpressed from E. coli KRX/pCon2(3) was purified to homogeneity by a combination of hydrophobic interaction chromatography and ion exchange chromatography, with a final yield of 48% and a 25-fold increase in specific activity. The purified protein had exhibited a first ever reported homodimer size of 65 kDa by SDS-PAGE and MALDI-TOF, a size which is totally distinct from that of typically reported 33 kDa monomer from P. aeruginosa. The organic solvent stability experiment had demonstrated a stability pattern which completely opposed the rules laid out in previous reports in which activity stability and enhancement were observed in hydrophilic organic solvents such as DMSO, methanol, ethanol and 1-propanol. The high stability and enhancement of the enzyme in hydrophilic solvents were explained from the view of alteration in secondary structures. Elastinolytic activation and stability were observed in 25 and 50% of methanol, respectively, despite slight reduction in α-helical structure caused upon the addition of the solvent. Further characterization experiments had postulated great stability and enhancement of elastase strain K in broad range of temperatures, pHs, metal ions, surfactants, denaturing agents and substrate specificity, indicating its potential application in detergent formulation.

Matched MeSH terms: Elastin/metabolism