Optically Clear Silk Fibroin Films with Tunable Properties for Potential Corneal Tissue Engineering Applications: A Process-Property-Function Relationship Study

Biomaterial-based strategies for primary human corneal endothelial cells for therapeutic applications: from cell expansion to transplantable carrier

The treatment of corneal blindness due to corneal diseases and injuries often requires the transplantation of healthy cadaveric corneal endothelial graft tissue to restore corneal clarity and visual function. However, the limited availability of donor corneas poses a significant challenge in meeting the demand for corneal transplantation. As a result, there is a growing interest in developing strategies alleviate this unmet need, and one of the postulated approaches is to isolate and expand primary human corneal endothelial cells (HCECs) in vitro for use in cell therapy. This review summarizes the recent advancements in the expansion of HCECs using biomaterials. Two principal biomaterial-based approaches, including extracellular matrix (ECM) coating and functionalized synthetic polymers, have been investigated to create an optimal microenvironment for the expansion and maintenance of corneal endothelial cells (CECs). This review highlights the challenges and opportunities in expanding primary HCECs using biomaterials. It emphasizes the importance of optimizing biomaterial properties, cell culture conditions, and the roles of biophysical cues to achieve efficient expansion and functional maintenance of CECs. Biomaterial-based strategies hold significant promise for expanding primary HCECs and improving the outcomes of CEC transplantation. The integration of biomaterials as cell culture substrates and transplantable carriers offers a comprehensive approach to address the limitations associated with current corneal tissue engineering techniques.

Silk biomaterials for corneal tissue engineering: From research approaches to therapeutic potentials; A review

The corneal complications can result in opacity and eventual blindness. Furthermore, a shortage of available donors constrains the existing therapeutic options. Therefore, one of the most promising strategies involves the application of biomaterials, particularly silk. Silk has garnered significant attention among these biomaterials due to its natural origin and diverse features derived from different sources. One of the most critical factors of silk is its transparency, which is crucial for the cornea, and there are no concerns about infection. This material also possesses several advantages, including cost-effectiveness in production, biocompatibility in vivo and in vitro, biodegradation, and desirable mechanical characteristics. Modifications in the topographical structure, porosity, and crystallinity of silk enhance its properties and optimize its suitability for wound dressing, efficient drug delivery systems, and various cornea-related treatments. In each layer, silk was examined as a single biomaterial or blended with the others, so, this review aims to explore silk as a potential material for corneal regenerative medicine from a novel viewpoint. By considering a range of studies, a classification system has been developed that categorizes the utilization of silk in the various layers of the cornea and sub-categorizes the different modifications and applications of silk.

A dual responsive bis-thiophene affixed thiosemicarbazide based chemosensor for colorimetrically Hg2+ and fluorometrically Cu2+ ions and their applications in live cell imaging

In this work, we developed a fast and straightforward colorimetric and photoluminescent chemosensor probe (P1), featuring bis-thiophene-thiosemicarbazide moieties as its signaling and binding unit. This probe exhibited rapid sensitivity to Hg2+ and Cu2+ ions in a semi-aqueous medium, resulting in distinct colorimetric and photoluminescent changes. In the presence of Cu2+, P1 displayed an impressive 50-fold increase in photoluminescence (PL) at 450 nm (with excitation at 365 nm). The probe P1 formed a 1:1 complex with Hg2+ and Cu2+ ions, featuring association constant values of 4.04 × 104 M-1 and 1.25 × 103 M-1, respectively. P1 has demonstrated its efficacy in the analysis of real samples, yielding promising results. Additionally, the probe successfully visualized copper ions on a mouse fibroblast cell line (NIH3T3), highlighting its potential as an intracellular probe for copper ion detection.

Ciprofloxacin hydrochloride-loaded ocular silk fibroin liposomes: Formulation, characterisation, in vitro cytotoxicity, and antimicrobial activity

Ocular drugs have low absorption because of the unique environment in the eye, making ocular drugs one of the most challenging pharmaceutical initiatives. Liposomes have shown to be a promising ocular drug delivery system over the years because of enhanced drug absorption, biocompatibility, and biodegradability. Utilising a mucoadhesive material alongside liposomes could be a promising strategy to increase the therapeutic efficacy of ocular drugs. The present study aimed to develop a silk fibroin (SF)-coated liposomal formulation as an ocular drug delivery system. Regenerated silk fibroin (a novel biopolymer) was coated on ciprofloxacin hydrochloride-loaded liposomes (CPH-SFLs). Studies were carried out on the morphology, drug encapsulation efficiency, and in vitro drug release. Human corneal epithelial cells (HCEC) were used to examine the cellular adherence and cytotoxicity of CPH-SFLs. CPH-SFLs had an average particle size of 183 ± 3 nm as opposed to 169 ± 4 of blank SFLs. CPH-loaded SFLs lacked the endothermic peak of CPH at 150 °C, indicating that the CPH molecules were trapped in the SF polymeric grid. In the case of the formulations, 25 %-45 % of the medicine was released at a relatively fast pace over the course of the first 4 h and then at a slower rate over the course of the next 12-24 h. CPH-SFLs demonstrated sustained drug release and high in vitro ocular penetration of CPH. The MTT test was conducted to gauge the viability of HCECs, cell viability was higher than 85 %, demonstrating that CPH-SFLs had no adverse effects on HCEC. The observed CPH-SFL adhesions to HCECs were swift and persistent, like the cellular uptake of CPH-SFLs by HCECs. When compared to CPH-solution, the produced formulation CPH-SFLs demonstrated significantly (P < 0.0001) greater susceptibility. The studies concluded that SF-coated liposomes could be the most viable ocular drug delivery in comparison to conventional eye drops.

Silk fibroin/vitreous humor hydrogel scaffold modified by a carbodiimide crosslinker for wound healing

Natural-derived biomaterials can be used as substrates for the growth, proliferation, and differentiation of cells. In this study, bovine vitreous humor as a biological material was cross-linked to silk fibroin with different concentration ratios to design a suitable substrate for corneal tissue regeneration. The cross-linked samples were evaluated with different analyses such as structural, physical (optical, swelling, and degradation), mechanical, and biological (viability, cell adhesion) assays. The results showed that all samples had excellent transparency, especially those with higher silk fibroin content. Increasing the ratio of vitreous humor to silk fibroin decreased mechanical strength and increased swelling and degradation, respectively. There was no significant difference in the toxicity of the samples, and with the increase in vitreous humor ratio, adhesion and cell proliferation increased. Generally, silk fibroin with vitreous humor can provide desirable characteristics as a transparent film for corneal wound healing.

A review on the use of composites of a natural protein, silk fibroin with Mxene/carbonaceous materials in biomedical science

Silk fibroin (SF), a natural biodegradable and biocompatible protein, has garnered significant attention in biomedical applications due to its impressive properties, including excellent biocompatibility, biodegradability, and mechanical resilience. Nevertheless, its broader usage faces obstacles by its insufficient mechanical strength and electrical conductivity. In order to address these constraints, recent studies have concentrated on combining SF with cutting-edge nanomaterials like MXene and carbon-based materials. This review comprehensively examines the applications and potential of silk fibroin-MXene/carbon-based nanocomposites in biomedical fields. The unique properties of SF, MXene, and carbon-based materials are explored, emphasizing how their combination enhances mechanical strength, conductivity, and biocompatibility. These composites show substantial enhancements in performance for several biomedical applications by utilising the excellent conductivity and mechanical capabilities of MXene and carbonaceous elements. The innovative potential of these nanocomposites is highlighted by critically discussing key applications such as tissue engineering, drug delivery, and biosensing. In addition, the work discusses the latest research progress, difficulties, and future prospects in the sector, providing valuable insights into possible breakthroughs and uses. This review seeks to comprehensively analyse the existing information on silk fibroin-MXene/carbon based nanocomposites in healthcare.

Comparative Analysis of Silk Fibroin Membranes across Cross-Linking Methods: Processing and Characterization

Silk fibroin (SF) extracted from silkworm silk can be transformed into transparent membranes with well-suited physical properties for ophthalmic applications. There is ample literature on the fabrication and characterization of SF-based membranes; however, the use of diverse SF extraction protocols and characterization methods or their settings makes it difficult to compare different silk membrane properties across studies. In this work, we fabricated 10 families of SF-based membranes by physical cross-linking and one non-cross-linked as a control. We evaluated transparency (ranging from 84.5 to 95.3% in the visible spectrum), enzyme stability (from 24 h to 200 days in protease XIV), decomposition temperature (280-290 °C), water uptake (40-60%), Young's modulus (8-30 MPa), roughness (1.6-22.7 nm), and FTIR spectra for the secondary structure. We found correlation between water uptake and the Young's modulus (the lower the water uptake, the higher the Young's modulus) and a relationship between membrane stability in protease XIV and the secondary structure of the proteins. Higher surface roughness and faster degradation were found in membranes cross-linked with polyethylene glycol, and conversely, lower roughness and lower degradation were found in methanol, ethanol, or isopropanol crossed-link membranes. This ample compilation of materials and their characterization will aid in the selection of a SF-based material according to the needs of the application.

A thiazole-based colorimetric and photoluminescent chemosensors for As3+ ions detection: Density functional theory, test strips, real samples, and bioimaging applications

A Schiff-base Ethyl (E)-2-(3-((2-carbamothioylhydrazono)methyl)-4-hydroxyphenyl)-4-methylthiazole-5-carboxylate (TZTS) dual functional colorimetric and photoluminescent chemosensor which includes thiazole and thiosemicarbazide has been synthesized to detect arsenic (As3+) ions selectively in DMSO: H2O (7:3, v/v) solvent system. The molecular structure of the probe was characterized via FT-IR, 1H, and 13C NMR & HRMS analysis. Interestingly, the probe exhibits a remarkable and specific colorimetric and photoluminescence response to As3+ ions when exposed to various metal cations. The absorption spectral changes of TZTS were observed upon the addition of As3+ ions, with a naked eye detectable color change from colorless to yellow color. Additionally, the chemosensor (TZTS) exhibited a new absorption band at 412 nm and emission enhancements in photoluminescence at 528 nm after adding As3+ ions. The limit of detection (LOD) for As3+ ions was calculated to be 16.5 and 7.19 × 10-9 M by the UV-visible and photoluminescent titration methods, respectively. The underlying mechanism and experimental observations have been comprehensively elucidated through techniques such as Job's plot, Benesi-Hildebrand studies, and density functional theory (DFT) calculations. For practical application, the efficient determination of As3+ ions were accomplished using a spike and recovery approach applied to real water samples. In addition, the developed probe was successfully employed in test strip applications, allowing for the naked-eye detection of arsenic ions. Moreover, fluorescence imaging experiments of As3+ ions in the breast cancer cell line (MCF-7) demonstrated their practical applications in biological systems. Consequently, these findings highlight the significant potential of the TZTS sensor for detecting As3+ ions in environmental analysis systems.

Bridging the gap: The promise of corneal bioengineering and regeneration

In recent years, significant advances in tissue engineering and regenerative medicine have led to innovative approaches in addressing the various challenges associated with corneal transplants using bioengineered corneas. This mini-review aims to introduce the general ophthalmologist to the concept and technique of bioengineered cornea and provide an overview of the developments so far and an insight into the future direction. By summarizing the latest research and current limitations, we aim to highlight their potential for the future in ultimately contributing to vision restoration.

Sustainable Bombyx mori's silk fibroin for biomedical applications as a molecular biotechnology challenge: A review

Silk is a natural engineering material with a unique set of properties. The major constituent of silk is fibroin, a protein widely used in the biomedical field because of its mechanical strength, toughness and elasticity, as well as its biocompatibility and biodegradability. The domestication of silkworms allows large amounts of fibroin to be extracted inexpensively from silk cocoons. However, the industrial extraction process has drawbacks in terms of sustainability and the quality of the final medical product. The heterologous production of fibroin using recombinant DNA technology is a promising approach to address these issues, but the production of such recombinant proteins is challenging and further optimization is required due to the large size and repetitive structure of fibroin's DNA and amino acid sequence. In this review, we describe the structure-function relationship of fibroin, the current extraction process, and some insights into the sustainability of silk production for biomedical applications. We focus on recent advances in molecular biotechnology underpinning the production of recombinant fibroin, working toward a standardized, successful and sustainable process.

In Vitro Profiling of the Extracellular Matrix and Integrins Expressed by Human Corneal Endothelial Cells Cultured on Silk Fibroin-Based Matrices

Developing a scaffold for culturing human corneal endothelial (HCE) cells is crucial as an alternative cell therapeutic approach to bridge the growing gap between the demand and availability of healthy donor corneas for transplantation. Silk films are promising substrates for the culture of these cells; however, their tensile strength is several-fold greater than the native basement membrane which can possibly influence the dynamics of cell-matrix interaction and the extracellular matrix (ECM) secreted by the cells in long-term culture. In our current study, we assessed the secretion of ECM and the expression of integrins by the HCE cells on Philosamia ricini (PR) and Antheraea assamensis (AA) silk films and fibronectin-collagen (FNC)-coated plastic dishes to understand the cell-ECM interaction in long-term culture. The expression of ECM proteins (collagens 1, 4, 8, and 12, laminin, and fibronectin) on silk was comparable to that on the native tissue. The thicknesses of collagen 8 and laminin at 30 days on both PR (4.78 ± 0.55 and 5.53 ± 0.51 μm, respectively) and AA (4.66 ± 0.72 and 5.71 ± 0.61 μm, respectively) were comparable with those of the native tissue (4.4 ± 0.63 and 5.28 ± 0.72 μm, respectively). The integrin expression by the cells on the silk films was also comparable to that on the native tissue, except for α3 whose fluorescence intensity was significantly higher on PR (p ≤ 0.01) and AA (p ≤ 0.001), compared to that on the native tissue. This study shows that the higher tensile strength of the silk films does not alter the ECM secretion or cell phenotype in long-term culture, confirming the suitability of using this material for engineering the HCE cells for transplantation.