Ultrastructural investigation of intact orbital implant surfaces using atomic force microscopy

"Hard" ceramics for "Soft" tissue engineering: Paradox or opportunity?

Tissue engineering provides great possibilities to manage tissue damages and injuries in modern medicine. The involvement of hard biocompatible materials in tissue engineering-based therapies for the healing of soft tissue defects has impressively increased over the last few years: in this regard, different types of bioceramics were developed, examined and applied either alone or in combination with polymers to produce composites. Bioactive glasses, carbon nanostructures, and hydroxyapatite nanoparticles are among the most widely-proposed hard materials for treating a broad range of soft tissue damages, from acute and chronic skin wounds to complex injuries of nervous and cardiopulmonary systems. Although being originally developed for use in contact with bone, these substances were also shown to offer excellent key features for repair and regeneration of wounds and "delicate" structures of the body, including improved cell proliferation and differentiation, enhanced angiogenesis, and antibacterial/anti-inflammatory activities. Furthermore, when embedded in a soft matrix, these hard materials can improve the mechanical properties of the implant. They could be applied in various forms and formulations such as fine powders, granules, and micro- or nanofibers. There are some pre-clinical trials in which bioceramics are being utilized for skin wounds; however, some crucial questions should still be addressed before the extensive and safe use of bioceramics in soft tissue healing. For example, defining optimal formulations, dosages, and administration routes remain to be fixed and summarized as standard guidelines in the clinic. This review paper aims at providing a comprehensive picture of the use and potential of bioceramics in treatment, reconstruction, and preservation of soft tissues (skin, cardiovascular and pulmonary systems, peripheral nervous system, gastrointestinal tract, skeletal muscles, and ophthalmic tissues) and critically discusses their pros and cons (e.g., the risk of calcification and ectopic bone formation as well as the local and systemic toxicity) in this regard. STATEMENT OF SIGNIFICANCE: Soft tissues form a big part of the human body and play vital roles in maintaining both structure and function of various organs; however, optimal repair and regeneration of injured soft tissues (e.g., skin, peripheral nerve) still remain a grand challenge in biomedicine. Although polymers were extensively applied to restore the lost or injured soft tissues, the use of bioceramics has the potential to provides new opportunities which are still partially unexplored or at the very beginning. This reviews summarizes the state of the art of bioceramics in this field, highlighting the latest evolutions and the new horizons that can be opened by their use in the context of soft tissue engineering. Existing results and future challenges are discussed in order to provide an up-to-date contribution that is useful to both experienced scientists and early-stage researchers of the biomaterials community.

Nanoscale Topographical Characterization of Orbital Implant Materials

The search for an ideal orbital implant is still ongoing in the field of ocular biomaterials. Major limitations of currently-available porous implants include the high cost along with a non-negligible risk of exposure and postoperative infection due to conjunctival abrasion. In the effort to develop better alternatives to the existing devices, two types of new glass-ceramic porous implants were fabricated by sponge replication, which is a relatively inexpensive method. Then, they were characterized by direct three-dimensional (3D) contact probe mapping in real space by means of atomic force microscopy in order to assess their surface micro- and nano-features, which were quantitatively compared to those of the most commonly-used orbital implants. These silicate glass-ceramic materials exhibit a surface roughness in the range of a few hundred nanometers (S_q within 500–700 nm) and topographical features comparable to those of clinically-used “gold-standard” alumina and polyethylene porous orbital implants. However, it was noted that both experimental and commercial non-porous implants were significantly smoother than all the porous ones. The results achieved in this work reveal that these porous glass-ceramic materials show promise for the intended application and encourage further investigation of their clinical suitability.

Complications of orbital endoimplantation in the Eye Clinic of the Lithuanian University of Health Sciences

The aim of the study was to analyse the rate of complications of orbital endoimplantation in patients operated from 2002 to 2014 at the Eye Clinic of the Lithuanian University of Health Sciences and to compare it with the results in the literature. Enucleation must be performed very carefully in order to prevent any additional trauma, infection, deformation, and to create an optimal conjunctival socket. However, complications occur despite efforts and qualified surgeons. The most common complications described in the literature are thinning and cysts of the conjunctiva, a foreign body reaction, secretion, symblepharons, fornix deficiency, ptosis, permanent pain, dislocation, migration and protrusion of the implant, a primary or secondary infection, and implant extrusion. From 2002 to 2014, 128 patients underwent orbital endoimplantation surgery at the Eye Clinic. The most common complications were conjunctival erosion (five patients, or 2.9%), cysts (nine patients, or 7%), and implant extrusion (five patients, or 2.9%). The type and rate of complications were very similar to the data in the literature.

Bioceramics in ophthalmology

The benefits of ceramics in biomedical applications have been universally appreciated as they exhibit an extraordinarily broad set of physico-chemical, mechanical and biological properties which can be properly tailored by acting on their composition, porosity and surface texture to increase their versatility and suitability for targeted healthcare applications. Bioceramics have traditionally been used for the repair of hard tissues, such as bone and teeth, mainly due to their suitable strength for load-bearing applications, wear resistance (especially alumina, zirconia and composites thereof) and, in some cases, bone-bonding ability (calcium orthophosphates and bioactive glasses). Bioceramics have been also applied in other medical areas, like ophthalmic surgery; although their use in such a context has been scientifically documented since the late 1700s, the potential and importance of ceramic ocular implants still seem to be underestimated and an exhaustive, critical assessment is currently lacking in the relevant literature. The present review aims to fill this gap by giving a comprehensive picture of the ceramic-based materials and implants that are currently used in ophthalmology and pointing out the strengths and weaknesses of the existing devices. A prospect for future research is also provided, highlighting the potential of new, smart bioceramics able to carry specific added values which could have a significant impact on the treatment of ocular diseases.

Biomaterials for orbital implants and ocular prostheses: overview and future prospects

The removal of an eye is one of the most difficult and dramatic decisions that a surgeon must consider in case of severe trauma or life-threatening diseases to the patient. The philosophy behind the design of orbital implants has evolved significantly over the last 60 years, and the use of ever more appropriate biomaterials has successfully reduced the complication rate and improved the patient's clinical outcomes and satisfaction. This review provides a comprehensive picture of the main advances that have been made in the development of innovative biomaterials for orbital implants and ocular prostheses. Specifically, the advantages, limitations and performance of the existing devices are examined and critically compared, and the potential of new, smart and suitable biomaterials are described and discussed in detail to outline a forecast for future research directions.

Structural and biomechanical effects of photooxidative collagen cross-linking with photosensitizer riboflavin and 370 nm UVA light on human corneoscleral tissues

This study quantitatively investigated the immediate effects of a photooxidative collagen cross-linking treatment with photosensitizer riboflavin (RF) and 370 nm UVA light in in vitro human corneoscleral collagen fibrils using histology, thickness, scanning electron microscopy, and atomic force microscopy analyses. Twenty 8 x 2 mm corneoscleral strips were dissected sagittally from donor tissue using a scalpel. Four parameters were investigated, including the density, thickness, adhesion force, and stiffness of corneoscleral tissues before and after the collagen cross-linking treatment. The RFUVA-catalyzed collagen cross-linking treatment led to an increase in the density of both corneal (8%) and scleral (23%) stromal collagens. However, there was no difference in corneoscleral thickness. Furthermore, RFUVA-catalyzed collagen cross-linking treatment led to an increased biomechanical response of corneosclera: 25 and 8% increases in corneoscleral stiffness, and 24 and 22% increases in corneoscleral adhesion force. The collagen cross-linking treatment through RF-sensitized photoreaction may cause structural and biomechanical changes in the collagen fibril network of the cornea and the sclera. This is due to narrowing of the interfibrillar spacing and the stromal edema.

Short-term response of mitomycin C on the human rectus muscle following strabismus surgery: histological, ultrastructural, and biomechanical evaluation

This study investigated the inflammatory effect of intraoperative mitomycin C (MMC) on adhesion reformation in human rectus muscles. Ten consecutive patients who underwent medial rectus resection had their postoperative rectus muscles divided into two groups: control group (n = 10) and MMC group (n = 10). In the MMC group, the muscle was soaked for 2 min with MMC, prepared as a 0.2 mg/mL (0.02%) solution. The 0.02% MMC reactions were examined using histological analysis with hematoxylin-eosin (inflammatory response) and Masson's trichrome (collagen fibrils), immunoreactivities of cyclooxygenase-II (inflammatory response), and collagen type I and III, scanning electron microscopy analysis to quantify the diameter and D-periodicity of collagen fibrils, and atomic force microscopy analysis to quantify the diameter, D-periodicity, and adhesion force of collagen fibrils. The rectus muscles treated with 0.02% MMC showed a significantly increased inflammatory response (p < 0.05), increased collagen density (p < 0.0001), increased fibril diameter (p < 0.001 or p < 0.05), and decreased fibril adhesion force (p < 0.005) compared to the rectus muscles in the control group. MMC simultaneously caused an inflammatory response as well as nanostructural and biomechanical property changes in the collagen fibril network.

AFM study for morphological characteristics and biomechanical properties of human cataract anterior lens capsules

The aim of this study was to quantitatively investigate the morphologies (surface roughness) and biomechanical properties (Young's modulus) of human anterior lens capsules (ALCs) for noncataract and cataract groups using atomic force microscopy. Eight human ALCs obtained during phacoemulsification from patients with senile cataracts (72 ± 13 years) were investigated in both the hydrated and dehydrated conditions. The cataract group showed clearly the proliferated lens epithelial cells (LECs) with a monomorphic cell structure, a diameter of 12.54 ± 4.31 μm, and a height of 0.23 ± 0.04 μm, whereas the control group showed no LECs. A substantial amount of false-positive calcification was observed caused by the deposition of remnants of dried salt solution. Cataract group showed significantly higher surface roughness (382.06 nm, p ≤ 0.001) than control group in the anterior side of ALCs, whereas cataract group showed significantly lower surface roughness (353.79 nm, p ≤ 0.001) than control group in their posterior side. Cataract group showed significantly higher Young's modulus (69.52 kPa, p ≤ 0.001) compared to the control group, regardless of the ALC side. Therefore, it is significant that this study provides a new method to examine the nanostructural characteristic and biomechanical property of human ALCs through a nanometer-scale resolution microscopy technique.

Effects of extracorporeal shockwave therapy on nanostructural and biomechanical responses in the collagenase-induced Achilles tendinitis animal model

The aim of this study was to quantitatively investigate the effects of extracorporeal shockwave therapy (ESWT) on the nanostructure and adhesion force of collagen fibrils in a rat model of collagenase-induced Achilles tendinitis (CIAT) using histology and atomic force microscopy. A total of 45 rats were divided into experimental groups of three rats each: a control group, 27 CIAT rats with nine time points, and 15 ESWT rats with five time points. Progressive changes in nanostructure including the fibrillary diameter and D-periodicity, and biomechanical properties including the fibrillary adhesion forces in each healing phase were investigated over a 5-week period after collagenase injection. On postoperative day 3, CIAT rats showed granulomatous tissue associated with subacute inflammation, and a deterioration in nanostructure and mechanical properties compared to controls. On postoperative day 12, the ESWT group showed increased vascularity, fibroblastic activity, lymphocyte and plasma cell infiltration, dense histocytes, and disorganization of the fibers compared to the CIAT group. The ESWT group showed and improvement in nanostructure and mechanical properties compared to controls, while the CIAT group showed a deterioration in nanostructure and mechanical properties compared to controls. On postoperative day 26, the ESWT group showed 30% inflamed tissue and 70% fibrotic tissue, while the CIAT group showed chronic inflammation. By the end of the experiments, in both groups the changes had reversed and the tissues were similar in appearance to those in the control group. Following ESWT the deformed and irregular collagen network returned to a well-aligned normal collagen network nanostructure. These results suggest that ESWT may promote the healing response in Achilles tendinitis.

Short-term nanostructural effects of high radiofrequency treatment on the skin tissues of rabbits

The aim of this study is to quantitatively investigate the short-term effects of RF tissue-tightening treatment in in vivo rabbit dermal collagen fibrils. These effects were measured at different energy levels and at varying pass procedures on the nanostructural response level using histology and AFM analysis. Each rabbit was divided into one of seven experimental groups, which included the following: control group, and six RF group according to RF energy (20 W and 40 W) and three RF pass procedures. The progressive changes in the diameter and D-periodicity of rabbit dermal collagen fibrils were investigated in detail over a 7-day post-treatment period. The dermal tissues treated with the RF tissue-tightening device showed more prominent inflammatory responses with inflammatory cell ingrowth compared to the control. This effect showed more prominent with the passage of day after treatment. Although an increase in the diameter and D-periodicity of dermal collagen fibrils was identified immediately after the RF treatment, a decrease in the morphology of dermal collagen fibrils continued until post-operative day 7. Furthermore, RF treatment led to the loss of distinct borders. Increases in RF energy with the same pass procedure, as well as an increase in the number of RF passes, increased the occurrence of irreversible collagen fibril injury. A multiple-pass treatment at low energy rather than a single-pass treatment at high energy showed a large amount of collagen fibrils contraction at the nanostructural level.