Mechanisms of ingested polystyrene micro-nanoplastics (MNPs) uptake and translocation in an in vitro tri-culture small intestinal epithelium.

Micro and nanoplastics (MNPs) are now ubiquitous contaminants of food and water. Many cellular and animal studies have shown that ingested MNPs can breach the intestinal barrier to reach the circulation. To date however, the cellular mechanisms involved in intestinal absorption of MNPs have not been investigated with physiologically relevant models, and thus remain unknown. We employed in vitro simulated digestion, a tri-culture small intestinal epithelium model, and a panel of inhibitors to assess the contributions of the possible mechanisms to absorption of 26 nm carboxylated polystyrene (PS26C) MNPs. Inhibition of ATP synthesis reduced translocation by only 35 %, suggesting uptake by both active endocytic pathways and passive diffusion. Translocation was also decreased by inhibition of dynamin and clathrin, suggesting involvement of clathrin mediated endocytosis (CME) and fast endophilin-mediated endocytosis (FEME). Inhibition of actin polymerization also significantly reduced translocation, suggesting involvement of macropinocytosis or phagocytosis. However, inhibition of the Na+-H+ exchanger had no effect on translocation, thus ruling out macropinocytosis. Together these results suggest uptake by passive diffusion as well as by active phagocytosis, CME, and FEME pathways. Further studies are needed to assess uptake mechanisms for other environmentally relevant MNPs as a function of polymer, surface chemistry, and size.

Extracellular histones promote calcium phosphate-dependent calcification in mouse vascular smooth muscle cells.

Vascular calcification, a major risk factor for cardiovascular events, is associated with a poor prognosis in chronic kidney disease (CKD) patients. This process is often associated with the transformation of vascular smooth muscle cells (VSMCs) into cells with osteoblast-like characteristics. Damage-associated molecular patterns (DAMPs), such as extracellular histones released from damaged or dying cells, are suspected to accumulate at calcification sites. To investigate the potential involvement of DAMPs in vascular calcification, we assessed the impact of externally added histones (extracellular histones) on calcium and inorganic phosphate-induced calcification in mouse VSMCs. Our study found that extracellular histones intensified calcification. We also observed that the histones decreased the expression of VSMC marker genes while simultaneously increasing the expression of osteoblast marker genes. Additionally, histones treated with DNase I, which degrades dsDNA, attenuated this calcification, compared with the non-treated histones, suggesting a potential involvement of dsDNA in this process. Elevated levels of dsDNA were also detected in the serum of CKD model mice, underlining its potential role in vascular calcification in CKD. Our findings suggest that extracellular histones could play a pivotal role in the vascular calcification observed in CKD.

The Effect of Polymeric Nanofibers Used for 3D-Printed Scaffolds on Cellular Activity in Tissue Engineering: A Review.

Promising scaffolds for developing advanced tissue engineering architectures have emerged in recent years through the use of nanofibers and 3D printing technologies. Despite this, structural integrity and cell proliferation are highlighted as fundamental challenges for design scaffolds and future prospects. As a biomimetic scaffold, the nanofiber-reinforced hydrogels demonstrated a better compressive modulus and cell growth. Our review focuses on recent promising advances in the development of 3D-printed hydrogels containing polymeric nanofibers that can improve cell-material interaction in biomedical applications. Moreover, an effort has been made to induce studies with diverse types of scaffolds for various cells. Additionally, we discuss the challenges and future prospects of 3D-bioprinted reinforced hydrogels with nanofibers in the medical field, as well as high-performance bioinks.

Lignin-facilitated growth of Ag/CuNPs on surface-activated polyacryloamidoxime nanofibers for superior antibacterial activity with improved biocompatibility.

INTRODUCTION: Nanofibers are one of the role-playing innovations of nanotechnology. Their high surface-to-volume ratio allows them to be actively functionalized with a wide range of materials for a variety of applications. The functionalization of nanofibers with different metal nanoparticles (NPs) has been studied widely to fabricate antibacterial substrates to battle antibiotic-resistant bacteria. However, metal NPs show cytotoxicity to living cells, thereby restricting their application in biomedicine. OBJECTIVES: To minimize the cytotoxicity of NPs, biomacromolecule lignin was employed as both a reducing and capping agent to green synthesize silver (Ag) and copper (Cu) NPs on the surface of highly activated polyacryloamidoxime nanofibers. The activation of polyacrylonitrile (PAN) nanofibers via amidoximation was employed for enhanced loading of NPs to achieve superior antibacterial activity. METHODOLOGY: At first, electrospun PAN nanofibers (PANNM) were activated to produce polyacryloamidoxime nanofibers (AO-PANNM) by immersing PANNM in a solution of Hydroxylamine hydrochloride (HH) and Na2CO3 under controlled conditions. Later, Ag and Cu ions were loaded by immersing AO-PANNM in different molar concentrations of AgNO3 and CuSO4 solutions in a stepwise manner. The reduction of Ag and Cu ions into NPs to fabricate bimetal-coated PANNM (BM-PANNM) was carried out via alkali lignin at 37 °C for 3 h in a shaking incubator with ultrasonication every 1 h. RESULTS: AO-APNNM and BM-PANNM hold their nano-morphology except for some changes in fiber orientation. XRD analysis demonstrated the formation of Ag and CuNPs as evident from their respective spectral band. Maximum 8.46 ± 0.14 wt% and 0.98 ± 0.04 wt% Ag and Cu species were loaded on AO-PANNM, respectively as revealed by ICP spectrometric analysis. The hydrophobic PANNM turned into super hydrophilic, having WCA of 14 ± 3.32° after amidoximation which further reduced to 0° for BM-PANNM. However, the swelling ratio of PANNM reduced from 13.19 ± 0.18 g/g to 3.72 ± 0.20 g/g for AO-PANNM. Even at the third cycle test against S. aureus strains, 0.1Ag/Cu-PANNM, 0.3Ag/Cu-PANNM, and 0.5Ag/Cu-PANNM displayed bacterial reduction of 71.3 ± 1.64 %, 75.2 ± 1.91 %, and 77.24 ± 1.25 %, respectively. On 3rd cycle test against E. coli, above 82 % bacterial reduction was noticed for all BM-PANNM. Amidoximation increased COS-7 cell viability up to 82 %. The cell viability of 0.1Ag/Cu-PANNM, 0.3Ag/Cu-PANNM, and 0.5Ag/Cu-PANNM was found to be ∼68 %, ∼62, and 54 %, respectively. In LDH assay, almost no release of LDH was detected, suggesting the compatibility of the cell membrane in contact with BM-PANNM. The improved biocompatibility of BM-PANNM even at higher loading (%) of NPs must be ascribed to the controlled release of metal species in the early stage, antioxidant, and biocompatible lignin capping of NPs. CONCLUSIONS: BM-PANNM displayed superior antibacterial activity against E. coli and S. aureus bacterial strains and acceptable biocompatibility of COS-7 cells even at higher loading (%) of Ag/CuNPs. Our findings suggest that BM-PANNM can be used as a potential antibacterial wound dressing and other antibacterial applications where sustained antibacterial activity is needed.

Synthesized bioactive lignin nanoparticles/polycaprolactone nanofibers: A novel nanobiocomposite for bone tissue engineering.

The use of artificial biomaterial with enhanced bioactivity for osteostimulation is a major research concern at present days. In this research, antibacterial and osteostimulative core-shell lignin nanoparticles (LgNP) were synthesized from alkali lignin using tetrahydrofuran (THF) as solvent via a simultaneous pH and solvent shifting technology. Later, LgNP-loaded polycaprolactone (PCL) composite nanofibers were fabricated via the electrospinning technique. The addition of LgNP significantly increased the diameter of the nanofibers, ranging from 400 to 2200 nm. The addition of LgNP reduced the mechanical performance, crystallinity, and porosity of the nanofibers while improving surface wetting and swelling properties of the inherently hydrophobic PCL polymer. The prepared nanofibers showed excellent bactericidal efficacy against major bone infectious Gram-positive Staphylococcus aureus bacterial strains. The incorporation of LgNP imparted superior antioxidant activity and boosted the biodegradation process of the nanofibers. The deposition of biomineral apatite with platelet-like clustered protrusions having a Ca/P ratio of 1.67 was observed while incubating the scaffold in simulated body fluid. Based on the results of the LDH and WST-1 assay, it was demonstrated that the composite nanofibers are non-toxic to pre-osteoblastic cell line (MC3T3-E1) when they are placed in direct contact with the LgNP/PCL scaffold nanofibers. The MC3T3-E1 cells exhibited excellent proliferation and attachment on the prepared composite scaffold via filopodial and lamellipodial expansion with cell-secreted Ca deposition. According to the alkaline phosphatase activity test, LgNP/PCL nanofiber scaffolds significantly improved osteogenic differentiation of MC3T3-E1 cells compared to neat PCL nanofibers. Overall, our findings suggest that LgNP/PCL nanofiber scaffold could be a promising functional biomaterial for bone tissue engineering.

Development of PVA-Psyllium Husk Meshes via Emulsion Electrospinning: Preparation, Characterization, and Antibacterial Activity.

In this study, polyvinyl alcohol (PVA) and psyllium husk (PSH)/D-limonene electrospun meshes were produced by emulsion electrospinning for use as substrates to prevent the growth of bacteria. D-limonene and modified microcrystalline cellulose (mMCC) were preferred as antibacterial agents. SEM micrographs showed that PVA-PSH electrospun mesh with a 4% amount of D-limonene has the best average fiber distribution with 298.38 ± 62.8 nm. Moreover, the fiber morphology disrupts with the addition of 6% D-limonene. FT-IR spectroscopy was used to analyze the chemical structure between matrix-antibacterial agents (mMCC and D-limonene). Although there were some partial physical interactions in the FT-IR spectrum, no chemical reactions were seen between the matrixes and the antibacterial agents. The thermal properties of the meshes were determined using thermal gravimetric analysis (TGA). The thermal stability of the samples increased with the addition of mMCC. Further, the PVA-PSH-mMCC mesh had the highest value of contact angle (81° ± 4.05). The antibacterial activity of functional meshes against Gram (-) (Escherichia coli, Pseudomonas aeruginosa) and Gram (+) bacteria (Staphylococcus aureus) was specified based on a zone inhibition test. PPMD6 meshes had the highest antibacterial results with 21 mm, 16 mm, and 15 mm against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa, respectively. While increasing the amount of D-limonene enhanced the antibacterial activity, it significantly decreased the amount of release in cases of excess D-limonene amount. Due to good fiber morphology, the highest D-limonene release value (83.1%) was observed in PPMD4 functional meshes. The developed functional meshes can be utilized as wound dressing material based on our data.

MiRNA-Nanofiber, the Next Generation of Bioactive Scaffolds for Bone Regeneration: A Review.

Scaffold-based bone tissue engineering has been introduced as an alternative treatment option for bone grafting due to limitations in the allograft. Not only physical conditions but also biological conditions such as gene expression significantly impact bone regeneration. Scaffolds in composition with bioactive molecules such as miRNA mimics provide a platform to enhance migration, proliferation, and differentiation of osteoprogenitor cells for bone regeneration. Among scaffolds, fibrous structures showed significant advantages in promoting osteogenic differentiation and bone regeneration via delivering bioactive molecules over the past decade. Here, we reviewed the bone and bone fracture healing considerations for the impact of miRNAs on bone regeneration. We also examined the methods used to improve miRNA mimics uptake by cells, the fabrication of fibrous scaffolds, and the effective delivery of miRNA mimics using fibrous scaffold and their processes for bone development. Finally, we offer our view on the principal challenges of miRNA mimics delivery by nanofibers for bone tissue engineering.

Fabrication of Poly(Ethylene-glycol 1,4-Cyclohexane Dimethylene-Isosorbide-Terephthalate) Electrospun Nanofiber Mats for Potential Infiltration of Fibroblast Cells.

Recently, bio-based electrospun nanofiber mats (ENMs) have gained substantial attention for preparing polymer-based biomaterials intended for use in cell culture. Herein, we prepared poly(ethylene-glycol 1,4-Cyclohexane dimethylene-isosorbide-terephthalate) (PEICT) ENMs using the electrospinning technique. Cell adhesion and cell viability of PEICT ENMs were checked by fibroblast cell culture. Field emission electron microscope (FE-SEM) image showed a randomly interconnected fiber network, smooth morphology, and cell adhesion on PEICT ENM. Fibroblasts were cultured in an adopted cell culturing environment on the surface of PEICT ENMs to confirm their biocompatibility and cell viability. Additionally, the chemical structure of PEICT ENM was checked under Fourier-transform infrared (FTIR) spectroscopy and the results were supported by -ray photoelectron (XPS) spectroscopy. The water contact angle (WCA) test showed the hydrophobic behavior of PEICT ENMs in parallel to good fibroblast cell adhesion. Hence, the results confirmed that PEICT ENMs can be potentially utilized as a biomaterial.

Wet-spun bi-component alginate based hydrogel fibers: Development and in-vitro evaluation as a potential moist wound care dressing.

In this study, bi-component alginate-hyaluronic acid (AHA) fibers were developed by using two different routes. In the first method, sodium alginate dope solution was extruded into a coagulation bath containing CaCl2 and subsequently dip-coated with hyaluronic acid (HA) whereas, in the second method, hyaluronic acid-containing sodium alginate dope solution was directly extruded into CaCl2 bath. The resulting AHA fibers were then dehydrated in 25-100% v/v acetone solutions and dried in air. The fibers were characterized by surface morphology, physicochemical analysis, mechanical performance, swelling percentage, and total liquid absorption (g/g), cell viability, and release behavior. The results showed that AHA fibers produced by the second method have better mechanical performance, high liquid absorption, and swelling percentage with a more controlled release of hyaluronic acid. The AHA fibers showed high biocompatibility toward nHDF cell line in in-vitro testing, and the MVTR values (650-800 g/m2/day) are in a suitable range for maintaining a moist wound surface proving to be appropriate for promoting wound healing.

Bioactive Sambong oil-loaded electrospun cellulose acetate nanofibers: Preparation, characterization, and in-vitro biocompatibility.

Blumea balsamifera oil loaded cellulose acetate nanofiber mats were prepared by electrospinning. The inclusion of blumea oil increased the nanofiber diameter. FTIR spectra confirm the addition of blumea oil in the nanofiber mats. The XRD pattern suggests that the inclusion of blumea oil has caused a misalignment in the polymer chains of the cellulose acetate. Thus, a decrease in the tensile strength was observed for the blumea oil loaded nanofibers. The increase in fiber diameter causes a reduction in the porosity of the nanofiber mats. The blumea oil loaded nanofiber mats showed antibacterial efficacy against Escherichia coli and Staphylococcus aureus. The blumea oil showed antioxidant abilities against the DPPH solution. MVTR of the neat and blumea oil loaded nanofiber mats was in the range of 2450-1750 g/m2/day, which is adequate for the transport of air and moisture from the wound surface. Blumea oil loaded mats showed good cell viability ~92% for NIH 3T3 cells in more extended periods of incubation. A biphasic release profile was obtained, and the release followed the first-order kinetics depending upon the highest value of the coefficient of correlation R 2 (88.6%).

Design and characterization of dual drug delivery based on in-situ assembled PVA/PAN core-shell nanofibers for wound dressing application.

Core-shell nanofibers with the ability to carry multiple drugs are attracting the attention to develop appropriate drug delivery systems for wounds dressing applications. In this study, biocompatible core-shell nanofibers have been designed as a promising dual-drug carrier with the capability of delivering both water-soluble and organic solvent-soluble drugs simultaneously. With the aim of fabricating the core-shell nanofibers, the dipping method has been employed. For this propose, core nanofibers made from polyvinyl alcohol (PVA) were immersed in various concentrations of polyacrylonitrile (PAN) and cross-linked by dipping into ethanol. Diclofenac sodium salt (DSs) and gentamicin sulfate (GENs) have been loaded into the core and shell nanofibers as models of the drug, respectively. The morphology study of core-shell nanofibers showed that the concentrations between 1% w/w up to 2% w/w PAN/GENs, with deep penetration into the internal layers of PAV/DSs nanofibers could lead to the core-shell structure. The cytotoxicity results showed the competency of designed core-shell nanofibers for wound dressing application. Also, the release profile exhibits the controllable behavior of drug release.

Antibacterial properties of in situ and surface functionalized impregnation of silver sulfadiazine in polyacrylonitrile nanofiber mats.

BACKGROUND: Silver, incorporation with natural or synthetic polymers, has been used as an effective antibacterial agent since decades. Silver has potential applications in healthcare especially in nanoparticles form but silver sulfadiazine (AgSD) is the most efficient antibacterial agent especially for burn wound dressings. METHOD: In this report, mechanical, structural, and antibacterial properties of PAN nanofibers incorporation with silver sulfadiazine are mainly focused. AgSD was loaded for the first time on electrospinning as well as self-synthesized AgSD on PAN nanofibers by solution immersion method and then compared the results of both. RESULTS: Occurrence of chemical reaction among the functional groups of AgSD and PAN were analyzed using FTIR, for both types of specimen. Morphological and surface properties of prepared nanofiber mats were characterized by scanning electron microscope, and it resulted in uniform nanofibers without bead formation. Diameter of nanofibers was slightly increased with addition of AgSD by in situ and immersion methods respectively. Nanoparticles distribution was analyzed by transmission electron microscopy. Thermal properties were analyzed by thermo-gravimetric analyzer and it was observed that AgSD decreased thermal stability of PAN which is better from biomedical perspective. X-ray diffraction declared crystalline structure of nanofiber mats. Presence of Ag and S contents in nanofiber mats was analyzed by X-ray photo spectroscopy. Antibacterial properties of nanofiber mats were investigated by disc diffusion method was carried out. E. coli and Bacillus bacteria strain were used as gram-negative and gram-positive respectively. Zone inhibition of the bacteria was used as a tool to determine effectiveness of AgSD released from PAN nanofiber mats. The antibacterial properties of PAN nanofibers impregnated with AgSD were determined with both types of bacteria strains to compare with control one. CONCLUSION: On the basis of characterization results it is concluded that PAN/AgSD (immersion) nanofiber mats have better structural and antibacterial properties than that of PAN/AgSD (in situ) nanofiber mats. So, from our point of view, self-synthesized AgSD is recommended for further production of nanofiber mats for antibacterial applications.

Self-Cleaning Properties of Electrospun PVA/TiO2 and PVA/ZnO Nanofibers Composites.

In this report, polyvinyl alcohol/zinoxide (PVA/ZnO) & polyvinyl alcohol/titanium dioxide (PVA/TiO2) nanofibers were manufactured in three different concentrations of ZnO and TiO2 NPs for the application of self-cleaning properties because metallic oxides, specifically ZnO & TiO2, have the properties to remove the contaminants by hydroxyl radical (OH-1), which degrades the contaminants into small molecules and finally into CO2 and H2O. Therefore, these composites were manufactured by electrospinning. The resultant nanofibers were characterized for morphology by scan electron microscopy (SEM) & transmission electron microscopy (TEM), chemical interactions by Fourier-transform infrared (FT-IR) spectra, crystalline structure by X-ray diffraction (XRD) spectra water absorbency was evaluated by water contact angle, self-cleaning by solar simulator, and thermal degradation was done by thermogravimetric analysis (TGA) for the sake of nanoparticles the content. On the base of the characterization results it was concluded that these PVA/ZnO & PVA/TiO2 nanofibers have self cleaning properties, but PVA/ZnO nanofibers have higher self-cleaning properties than PVA/TiO2 nanofibers because PVA/ZnO nanofibers have 95% self-cleaning properties, which is higher than PVA/TiO2 nanofibers.

Preparation and In-Vitro Assessment of Hierarchal Organized Antibacterial Breath Mask Based on Polyacrylonitrile/Silver (PAN/AgNPs) Nanofiber.

In this report, we designed and synthesized polyacrylonitrile/silver (PAN/AgNPs) nanofibers via an in-situ method to obtain a washable with high-dispersed silver nanoparticles membrane to form the hierarchically organized antibacterial mask to prevent the two-way effect of bacteria from person to environment and environment to person. For this objective, the electrospun PAN nanofibers were stabilized via the heating method. Different amounts of AgNPs were loaded into the PAN nanofibers by using silver nitrate and sodium hydroxide solutions. The basic results showed that AgNPs was homogenously loaded in PAN nanofiber matrixes. Furthermore, the release profile based on two-stage release theory showed that when the negligible amount of AgNPs was loaded into the nanofibers, the release significantly decreased, whereas antibacterial activity increased. The greatest potential antibacterial activity of the lowest amount of AgNPs showed controllable AgNPs release from PAN nanofibers that has a direct relationship with the washability and could promote the application of the produced product.

Silver sulfadiazine loaded zein nanofiber mats as a novel wound dressing.

In this report a novel antibacterial wound dressing was prepared and then characterized for required testing. We loaded silver sulfadiazine (AgSD) for the first time by electrospinning. AgSD was added in zein (0.3%, 0.4%, 0.5%, and 0.6% by weight) and was electrospun to fabricate nanofiber mats for wound dressings. Nanofiber mats were characterized by Fourier transform infrared spectroscopy (FTIR) to check if there was any chemical reaction between AgSD and zein. Morphological properties were analyzed by Scanning Electron Microscopy (SEM), which showed uniform nanofibers without any bead formation. The diameter of the nanofibers gradually decreased with an increase in the amount of AgSD, which can be associated with strong physical bonding between zein and AgSD. Thermal properties of nanofiber mats were analyzed by Thermogravimetric Analysis (TGA). X-Ray Diffraction (XRD) further demonstrated the crystalline structure of the nanofiber mats, and X-ray Photoelectron spectroscopy (XPS) was performed to confirm Ag and S contents in the prepared wound dressings. In order to investigate antibacterial properties, a disc diffusion method was employed. Bacillus and E. coli bacteria strains were used as Gram-positive and Gram-negative strains respectively. The antibacterial effectiveness of AgSD released from zein nanofibers was determined from the zone inhibition of the bacteria. The antibacterial activity of zein nanofibers loaded with drug was observed with both strains of bacteria in comparison to a control. Excellent antibacterial efficacy was attributed to the sample with 0.6% AgSD. Excellent release properties were also associated with the sample with 0.6% AgSD in zein nanofibers. Keeping in mind the abovementioned characteristics, prepared nanofiber mats would be effective for application in wound dressings.

Fabrication and characterization of nanofibers of honey/poly(1,4-cyclohexane dimethylene isosorbide trephthalate) by electrospinning.

We report the fabrication of novel nanofibers using naturally occurring antimicrobial honey incorporated in poly(1,4-cyclohexane dimethylene isosorbide trephthalate) (PICT) for the potential wound dressing applications. We fabricated PICT/honey using three blend ratios 90:10, 85:15 and 80:20 respectively. Morphology of PICT nanofibers and PICT/honey nanofibers was observed under Scanning Electron Microscope and it showed bead-free nanofibers. Fourier Transform Infrared Spectroscope was used to confirm the presence of honey in PICT electrospun nanofibers. Tensile strength of PICT/honey nanofibers was slightly reduced with variation in effect of elongation. Water contact angle measurements were done with the static contact angle by a contact angle meter, which showed that hydrophobicity was decreased by adding the honey. The XPS spectra showed that honey was present in the PICT/honey nanofibers. The release behavior of honey was investigated by UV-visible Spectrophotometer. The release was complete in 15min and the maximum release of honey was 72mg/L in 10min. Therefore, PICT/honey nanofibers having 15% concentration of honey are suitable for good elastic behavior and tensile strength as compared to other concentrations of honey.

Electrospun tri-layered zein/PVP-GO/zein nanofiber mats for providing biphasic drug release profiles.

Simple sequential electrospinning was utilized to create a functional tri-layered nanofiber mesh that achieves time-regulated biphasic drug release behavior. A tri-layered nanofiber mesh -composed of zein and poly(vinylpyrrolidone) (PVP) as the top/bottom and middle layers, respectively - was constructed through sequential electrospinning with ketoprofen (KET) as the model drug. PVP was blended with graphene oxide (GO) to improve the drug release functionality of PVP nanofiber as well as its mechanical properties. Scanning electron microscopy confirmed that the resultant nanofibers had a linear morphology, smooth surface, and tri-layered structure. In addition, X-ray diffraction patterns, differential scanning calorimetric analyses, and Fourier transform infrared spectra verified that the drugs were uniformly dispersed throughout the nanofiber due to good compatibility between the polymer and KET induced by hydrogen interaction. In vitro release test of the tri-layered structure, each component of which had distinct release features, successfully demonstrated time-regulated biphasic drug release. Also, it was confirmed that the drug release rate and duration can be controlled by designing a morphological feature - namely, mesh thickness - which was achieved by simply regulating the spinning time of the first and third layer. This multilayered electrospun nanofiber mesh fabricated by sequential electrospinning could provide a useful method of controlling drug release behavior over time, which will open new routes for practical applications and stimulate further research in the development of effective drug release carriers.

Corrosion casts of big bubbles formed during deep anterior lamellar keratoplasty.

PURPOSE: To characterize the walls of big bubbles formed during deep anterior lamellar keratoplasty (DALK) using the corrosion casting technique. METHODS: Fresh corneoscleral buttons with normal transparency and without any known eye diseases (n = 11) were obtained from 11 human donors. A 20-gauge needle was used to inject a solution of 20 % polyvinyl alcohol (PVA) immediately beneath the corneal endothelium to form big bubbles in eight corneoscleral buttons. In the second experiment on three corneoscleral buttons, a big bubble was first formed by air injection beneath the endothelium. Thereafter, 20 % PVA was injected into the bubble space. Scanning electron microscopy was used to characterize the surfaces of the casts, which replicated the walls of the big bubbles. RESULTS: A type-1 bubble was formed in all corneas. In one cornea, one type-1 bubble was initially formed centrally, and while it was enlarged, an eccentric type-2 bubble appeared. Scanning electron microscopy showed that the casts of type-1 bubbles had two distinct surfaces. The anterior surface demonstrated several holes or pits, depending on the material used for the bubble formation, whereas the posterior surface exhibited an uneven surface. The anterior and posterior surfaces of the type-2 cast were more or less similar. A communication measuring 531.9 µm in length and 171.4 µm in diameter was found between the two bubbles. CONCLUSIONS: The corrosion casting technique provides a permanent three-dimensional record of the potential spaces and barriers in the posterior corneal stroma, which explains several features associated with big-bubble DALK.