Orbital implants: State-of-the-art review with emphasis on biomaterials and recent advances

Update on surgical cosmetic solutions in equine ophthalmology

Following eye removal surgery, ocular cosmetic solutions exist for the equine patient. The objective of this review is to summarize the current best evidence on equine ophthalmic cosmetic solutions. A literature review of ophthalmic cosmetic solutions in horses was conducted. Four cosmetic solutions are described. Cosmetic outcome, return to work, owner satisfaction, complication rates, implant choice and future perspectives are discussed under the light of most recent publications. Seventeen peer-reviewed articles were selected: five retrospective studies, four case series, five case reports and three narrative reviews. Additionally, two congress proceedings were included. Recent publications identify intrascleral prosthesis and intraorbital implants adjoined to a corneoscleral shell as cosmetically superior. The orbital meshwork implant requires improvement to be cosmetically acceptable. Return to work is deemed feasible and standing sedation is an option for orbital implant placement beneath sutured eyelids. 3D printing creates new possibilities for implant development.

Clinical outcomes and complications of a new high-density polyethylene-based spherical integrated porous orbital implant

PURPOSE

To describe our experience over 6 years using a new high-density polyethylene-based spherical integrated porous orbital implants (Oculfit).

METHODS

This is an observational retrospective case series study analyzing all cases requiring Oculfit implants between February 2015 and September 2021. Clinical information regarding the population included, the characteristics of the implant, and the outcomes and complications during the follow-up were noted. The success of the implant was defined according to anatomical and functional parameters.

RESULTS

The study analyzed 90 cases of anophthalmic patients. The main causes for enucleation or evisceration were ocular decompensations (36.7%) and neoplasms (27.8% uveal melanoma and 7.8% retinoblastoma). Anatomical success was identified in 63 (70.0%) cases, functional success in 79 (87.8%) and complete success (anatomical + functional) in 61 (67.7%) cases. Factors associated with the functional success were age and exposure of the primary orbital implant. Complications appeared in 11 (12.2%) cases, which were completely resolved without sequelae in 4 (4.4%). Orbital explant was required in 5 (5.6%) cases.

CONCLUSION

In our experience, Oculfit can be considered a useful alternative among the currently available options for orbital implants and has a good efficacy/safety profile.

Design Characteristics of a Neoteric, Superhydrophilic, Mechanically Robust Hydrogel Engineered To Limit Fouling in the Ocular Environment

Current challenges with ocular drug delivery and the chronic nature of many ocular ailments render the use of traditional ocular devices for additional drug delivery purposes very attractive. To achieve this feat, there is the need to develop biomaterials that are biocompatible, mechanically robust for ocular applications, highly transparent (depending on the targeted ocular device), and with ultralow protein adhesion potential (the primary step in processes that lead to fouling and potential device failure). Herein is reported the facile synthesis of a novel, highly transparent, mechanically robust, nontoxic, bulk functionalized hydrogel with characteristics suited to scalable fabrication of ocular implantable and nonimplantable devices. Synergistic superhydrophilicity between methacrylated poly(vinyl alcohol) (PVAGMA) and zwitterionic sulfobetaine methacrylate was exploited to obtain a superhydrophilic polymer conjugate through facile photoinitiated cross-linking polymerization. Proton nuclear magnetic resonance (1H NMR), attenuated total reflectance-Fourier transform infrared spectroscopy (ATF-FTIR), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) were used to confirm the synthesis and establish the physicochemical parameters for both the starting materials, the conjugated polymer, and the hydrogels. Cytotoxicity and cell adhesion potential evaluated in primary human retinal epithelial cells showed no toxicity or adhesion of the ocular cells. Biofilm adhesion studies in Escherichia coli and Staphylococcus aureus showed over 85% reduction in biofilm adhesion for the best-modified polymer compared to the unconjugated PVAGMA, highlighting its antifouling potential.

Long-Term Outcomes of Enucleation and Secondary Orbital Implantation Surgeries Using Polyester Mesh-Wrapped Acrylic Orbital Implants

OBJECTIVE

To reveal the long-term outcomes of enucleation and secondary orbital implantation surgeries employing nonabsorbable surgical mesh-wrapped acrylic orbital implants for various reasons.

METHODS

A retrospective interventional study of 48 eyes that underwent primary or late primary enucleation and secondary orbital implantation using polyester mesh-wrapped acrylic orbital implants, between 2012 and 2021. Patient demographics, diagnosis, prior ophthalmic surgery, implant size, follow-up periods, and implant-associated complications were evaluated.

RESULTS

The records of 36 patients who underwent primary or late primary enucleation and 12 who underwent secondary orbital implantation due to sphere extrusion were evaluated. Patients' mean age was 38.7 (range: 2-75) and the mean follow-up period was 48.3 months (range: 24-72 mo). Major causes for surgeries were trauma and malignancies (54.1% and 33.3%, respectively). No complications, such as conjunctival dehiscence, implant exposure or extrusion, contracted socket, or fornix insufficiency were observed in any patient during the long-term follow-up period postsurgeries.

CONCLUSION

Using polyester mesh-wrapped acrylic orbital implants in enucleation and secondary orbital implantation surgeries proves to be a successful, safe, and cost-effective option.

Clinical application of biomaterials in orbital implants: a systematic review

PURPOSE

Various materials have been proposed for reconstructing orbital fractures. The materials used must meet certain criteria to ensure their suitability for restoring the structure and function of the organ. These criteria include biocompatibility, ease of application, non-toxicity, hypo-allergenicity, and non-carcinogenicity. In this study, we systematically reviewed the studies regarding the biomaterials in orbital implants and their clinical application.

METHODS

A comprehensive search across various databases, including PubMed, Scopus, EMBASE, Cochrane Library, and Web of Science, was conducted until April 10th, 2023. After retrieving the search results and eliminating duplicates, final studies were included after screening through defined criteria. Human and animal studies assessing the clinical application of biomaterials in orbital implants were included. The quality of the case series and controlled intervention studies were evaluated using the NIH tool, and for animal studies, the risk of bias was assessed using SYRCLE's tool.

RESULTS

Seventeen studies were included according to defined criteria. These studies aimed to explore the clinical application of biomaterials and examine the associated complications in orbital implants.

CONCLUSION

We found that using biomaterials did not result in elevated intraocular pressure (IOP). However, we did observe certain complications, with infection, residual diplopia, and enophthalmos being the most frequently reported issues.

Tuning zinc content in wollastonite bioceramic endowing outstanding angiogenic and antibacterial functions beneficial for orbital reconstruction

Prosthetic eye is indispensable as filler after enucleation in patients with anophthalmia, whereas there are still many complications including postoperative infection and eye socket depression or extrusion during the conventional artificial eye material applications. Some Ca-silicate biomaterials showed superior bioactivity but their biological stability in vivo limit the biomedical application as long-term or permanent implants. Herein we aimed to understand the physicochemical and potential biological responses of zinc doping in wollastonite bioceramic used for orbital implants. The wollastonite powders with different zinc dopant contents (CSi-Znx) could be fabricated as porous implants with strut or curve surface pore geometries (cubic, IWP) via ceramic stereolithography. The experimental results indicated that, by increasing zinc-substituting-Ca ratio (up to 9%), the sintering and mechanical properties could be significantly enhanced, and meanwhile the bio-dissolution in vitro and biodegradability in vivo were thoroughly inhibited. In particular, an appreciable angiogenic activity and expected antibacterial efficacy (over 90 %) were synergistically achieved at 9 mol% Zn dopant. In the back-embedding and enucleation and implantation model experiments in rabbits, the superior continuous angiogenesis was corroborated from the 2D/3D fibrovascular reconstruction in the IWP-pore CSi-Zn9 and CSi-Zn13.5 groups within very short time stages. Totally, the present silicate-based bioceramic via selective Zn doping could produce outstanding structural stability and bifunctional biological responses which is especially valuable for developing the next-generation implants with vascular insertion and fixation in orbital reconstruction prothesis.

Research progress of photo-crosslink hydrogels in ophthalmology: A comprehensive review focus on the applications

Hydrogel presents a three-dimensional polymer network with high water content. Over the past decade, hydrogel has developed from static material to intelligent material with controllable response. Various stimuli are involved in the formation of hydrogel network, among which photo-stimulation has attracted wide attention due to the advantages of controllable conditions, which has a good application prospect in the treatment of ophthalmic diseases. This paper reviews the application of photo-crosslink hydrogels in ophthalmology, focusing on the types of photo-crosslink hydrogels and their applications in ophthalmology, including drug delivery, tissue engineering and 3D printing. In addition, the limitations and future prospects of photo-crosslink hydrogels are also provided.

Synthetic Calcium-Phosphate Materials for Bone Grafting

Synthetic bone grafting materials play a significant role in various medical applications involving bone regeneration and repair. Their ability to mimic the properties of natural bone and promote the healing process has contributed to their growing relevance. While calcium-phosphates and their composites with various polymers and biopolymers are widely used in clinical and experimental research, the diverse range of available polymer-based materials poses challenges in selecting the most suitable grafts for successful bone repair. This review aims to address the fundamental issues of bone biology and regeneration while providing a clear perspective on the principles guiding the development of synthetic materials. In this study, we delve into the basic principles underlying the creation of synthetic bone composites and explore the mechanisms of formation for biologically important complexes and structures associated with the various constituent parts of these materials. Additionally, we offer comprehensive information on the application of biologically active substances to enhance the properties and bioactivity of synthetic bone grafting materials. By presenting these insights, our review enables a deeper understanding of the regeneration processes facilitated by the application of synthetic bone composites.

Radiopaque Crystalline, Non-Crystalline and Nanostructured Bioceramics

Radiopacity is sometimes an essential characteristic of biomaterials that can help clinicians perform follow-ups during pre- and post-interventional radiological imaging. Due to their chemical composition and structure, most bioceramics are inherently radiopaque but can still be doped/mixed with radiopacifiers to increase their visualization during or after medical procedures. The radiopacifiers are frequently heavy elements of the periodic table, such as Bi, Zr, Sr, Ba, Ta, Zn, Y, etc., or their relevant compounds that can confer enhanced radiopacity. Radiopaque bioceramics are also intriguing additives for biopolymers and hybrids, which are extensively researched and developed nowadays for various biomedical setups. The present work aims to provide an overview of radiopaque bioceramics, specifically crystalline, non-crystalline (glassy), and nanostructured bioceramics designed for applications in orthopedics, dentistry, and cancer therapy. Furthermore, the modification of the chemical, physical, and biological properties of parent ceramics/biopolymers due to the addition of radiopacifiers is critically discussed. We also point out future research lacunas in this exciting field that bioceramists can explore further.

Next-generation finely controlled graded porous antibacterial bioceramics for high-efficiency vascularization in orbital reconstruction

Eyeball loss due to severe ocular trauma, intraocular malignancy or infection often requires surgical treatment called orbital implant reconstruction to rehabilitate the orbital volume and restore the aesthetic appearance. However, it remains a challenge to minimize the postoperative exposure and infection complications due to the inert nature of conventional orbital implants. Herein, we developed a novel Ca-Zn-silicate bioceramic implant with multi-functions to achieve the expected outcomes. The porous hardystonite (Ca2ZnSi2O7) scaffolds with triply periodic minimal surfaces (TPMS)-based pore architecture and graded pore size distribution from center to periphery (from 500 to 800 μm or vice versa) were fabricated through the digital light processing (DLP) technique, and the scaffolds with homogeneous pores (500 or 800 μm) were fabricated as control. The graded porous scaffolds exhibited a controlled bio-dissolving behavior and intermediate mechanical strength in comparison with the homogeneous counterparts, although all of porous implants presented significant antibacterial potential against S. aureus and E. coli. Meanwhile, the pore size-increasing scaffolds indicated more substantial cell adhesion, cell viability and angiogenesis-related gene expression in vitro. Furthermore, the gradually increasing pore feature exhibited a stronger blood vessel infiltrating potential in the dorsal muscle embedding model, and the spherical implants with such pore structure could achieve complete vascularization within 4 weeks in the eyeball enucleation rabbit models. Overall, our results suggested that the novel antibacterial hardystonite bioceramic with graded pore design has excellent potential as a next-generation orbital implant, and the pore topological features offer an opportunity for the improvement of biological performances in orbital reconstruction.

Influence of Magnesium Content on the Physico-Chemical Properties of Hydroxyapatite Electrochemically Deposited on a Nanostructured Titanium Surface

The aim of this research was to obtain hydroxyapatite (HAp)-based coatings doped with different concentrations of Mg on a Ti nanostructured surface through electrochemical techniques and to evaluate the influence of Mg content on the properties of HAp. The undoped and doped HAp-based coatings were electrochemically deposited in galvanostatic pulsed mode on titania nanotubes with a diameter of ~72 nm, being designed to enhance the adhesion of the HAp coatings to the Ti substrate. The obtained materials were investigated by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), and Fourier-Transform Infra-Red spectroscopy (FTIR). The adhesion of the coatings to the substrate was also evaluated with the help of the “tape-test” and the micro-scratch test. The morphology (SEM) of all the coatings is made of very thin and narrow ribbon-like crystals, with some alterations with respect to the Mg amount in the coatings. Thus, a concentration of 1 mM of Mg in the electrolyte leads to wider and thicker ribbon-like crystals, while a concentration of 1.5 mM in the electrolyte generated a morphology that resembles the undoped HAp. Both phase composition (XRD) and chemical bonds (FTIR) analysis proved the formation of HAp in all coatings. Moreover, according to XRD, all coatings have a strong orientation toward the (002) plane. Irrespective of the Mg content, all coatings registered an average roughness between approx. 500 and 600 nm, while the coating thickness increased after addition of Mg, from a value of 9.6 μm, for the undoped HAp, to 11.3 μm and ~13.7 μm for H/Mg1 and H/Mg2, respectively. In terms of adhesion, it was shown that the coatings a H/Mg2 had a poorer adhesion when compared to H/Mg1 and the undoped HAp (H), which registered similar adhesion, indicating that a concentration of 1.5 mM of Mg in the electrolyte reduces the adhesion of the Hap-based coatings to the nanostructured surface. The obtained results indicated that Mg concentrations up to 1 mM in the electrolyte can enhance the properties of HAp-based coatings electrochemically deposited on a nanostructured surface, while even a slightly higher concentration of 1.5 mM can negatively impact the characteristics of HAp coatings.

Copper-Doped Bioactive Glass/Poly (Ether-Ether-Ketone) Composite as an Orbital Enucleation Implant in a Rabbit Model: An In Vivo Study

An orbital enucleation implant is used to compensate for the orbital volume deficits in the absence of the globe. In this work, copper-doped bioactive glass in poly(ether-ether-ketone) (CuBG/PEEK) composite scaffolds as an orbital enucleation implant were designed and fabricated by cool-pressed sintering and particle-leaching techniques, the incorporation of copper-doped bioactive glass in poly(ether-ether-ketone) (CuBG/PEEK) was expected to significantly improve the biocompatibility of the PEEK implant. The consequences after implantation of the CuBG/PEEK composite scaffolds in experimental, eviscerated rabbits was observed and assayed in term of histopathological examination. In detail, 24 rabbits were randomly divided into three groups: Group A, PEEK scaffolds; Group B, 20% CuBG/PEEK composite scaffolds; Group C, 40% CuBG/PEEK composite scaffolds; the rabbits were sacrificed at week 4 and week 12, followed by histochemical staining and observation. As a result, the PEEK group exhibited poor material exposure and tissue healing, while the CuBG/PEEK scaffolds showed good biocompatibility, and the 40% CuBG/PEEK composite scaffold exhibited the best performance in angiogenesis and tissue repair. Therefore, this study demonstrates the potential of CuBG/PEEK composite scaffolds as an orbital enucleation implant.

The Evolution of Orbital Implants and Current Breakthroughs in Material Design, Selection, Characterization, and Clinical Use

It is occasionally essential to surgically remove the damaged eye of the patient in the case of serious oculoorbital injuries, intraocular cancers, and other life-threatening diseases. An orbital implant is placed into the anophthalmic socket after the eye is removed to provide adequate volume reinstatement and revamp the cosmetic look of a normal eye. In the previous few decades, implant design and material selection criteria have progressed from basic nonporous polymeric spheres to devices with more complicated shapes and functions to ensure improved long-term clinical results. Because of their highly interconnected porous design, ceramic and polymeric porous implants have found popularity as a passive framework for fibrovascular ingrowth, with lower obstacle rates and the option of setting to improve prosthetic eye mobility. These materials, however, are not without flaws. The danger of migration and extrusion, infections after surgery, and poor motility transferred to the cosmetic ocular prosthesis are important elements of orbital implants of today. As a result, the development of novel biomaterials with improved functionalities (i.e., antibacterial effect, angiogenesis, and in situ moldability) that allow better eye replacement is more desirable than ever, highlighting one of the most challenging aspects of research topics in the field of ocular implants. This study highlights the history of orbital implants. It gives an outline of current advancements in the area, over and above some essential observations for materials design, selection, characterization, and transformation to clinical applications.

Integrating pore architectures to evaluate vascularization efficacy in silicate-based bioceramic scaffolds

Pore architecture in bioceramic scaffolds plays an important role in facilitating vascularization efficiency during bone repair or orbital reconstruction. Many investigations have explored this relationship but lack integrating pore architectural features in a scaffold, hindering optimization of architectural parameters (geometry, size and curvature) to improve vascularization and consequently clinical outcomes. To address this challenge, we have developed an integrating design strategy to fabricate different pore architectures (cube, gyroid and hexagon) with different pore dimensions (∼350, 500 and 650 μm) in the silicate-based bioceramic scaffolds via digital light processing technique. The sintered scaffolds maintained high-fidelity pore architectures similar to the printing model. The hexagon- and gyroid-pore scaffolds exhibited the highest and lowest compressive strength (from 15 to 55 MPa), respectively, but the cube-pore scaffolds showed appreciable elastic modulus. Moreover, the gyroid-pore architecture contributed on a faster ion dissolution and mass decay in vitro. It is interesting that both μCT and histological analyses indicate vascularization efficiency was challenged even in the 650-μm pore region of hexagon-pore scaffolds within 2 weeks in rabbit models, but the gyroid-pore constructs indicated appreciable blood vessel networks even in the 350-μm pore region at 2 weeks and high-density blood vessels were uniformly invaded in the 500- and 650-μm pore at 4 weeks. Angiogenesis was facilitated in the cube-pore scaffolds in comparison with the hexagon-pore ones within 4 weeks. These studies demonstrate that the continuous pore wall curvature feature in gyroid-pore architecture is an important implication for biodegradation, vascular cell migration and vessel ingrowth in porous bioceramic scaffolds.

Anophthalmic Socket Syndrome: Prevalence, Impact and Management Strategies

Anophthalmic socket syndrome determines functional deficits and facial deformities, and may lead to poor psychological outcomes. This review aims to comprehensively evaluate the features of the syndrome, based on literature review and authors’ clinical and surgical experience. An electronic database (PubMed,MEDLINE and Google Scholar) search of all articles written in English and non-English language with abstract translated to English on anophthalmic socket syndrome was performed. Data reviewed included demographics, presentations, investigations, management, complications and outcomes. Different types of orbital implants were evaluated; the management of implant exposure was examined; different orbital volume enhancement procedures such as secondary implantation, subperiosteal implants and the use of fillers in anophthalmic patients were described; the problems related to socket contraction were outlined; the treatment options for chronic anophthalmic socket pain and phantom eye syndrome were assessed; the most recent advances in the management of congenital anophthalmia were described. Current clinical evidence does not support a specific orbital implant; late exposure of porous implants may be due to pegging, which currently is seldom used; filler absorption in the orbit appears to be faster than in the dermis, and repeated treatments could be a potential source of inflammation; socket contraction results in significant functional and psychological disability, and management is challenging. Patients affected by anophthalmic socket pain and phantom eye syndrome need specific counseling. It is auspicable to use a standardized protocol to treat children affected by clinical congenital anophthalmia; dermis fat graft is a suitable option in these patients as it helps continued socket expansion. Dermis fat graft can also address the volume deficit in case of explantation of exposed implants and in contracted sockets in both children and adults. Appropriate clinical care is essential, as adequate prosthesis wearing improves the quality of life of anophthalmic patients.

Fouling in ocular devices: implications for drug delivery, bioactive surface immobilization, and biomaterial design

The last 30 years has seen a proliferation of research on protein-resistant biomaterials targeted at designing bio-inert surfaces, which are prerequisite for optimal performance of implantable devices that contact biological fluids and tissues. These efforts have only been able to yield minimal results, and hence, the ideal anti-fouling biomaterial has remained elusive. Some studies have yielded biomaterials with a reduced fouling index among which high molecular weight polyethylene glycols have remained dominant. Interestingly, the field of implantable ocular devices has not experienced an outflow of research in this area, possibly due to the assumption that biomaterials tested in other body fluids can be translated for application in the ocular space. Unfortunately, progression in the molecular understanding of many ocular conditions has brought to the fore the need for treatment options that necessitates the use of anti-fouling biomaterials. From the earliest implanted horsehair and silk seton for glaucoma drainage to the recent mini telescopes for sight recovery, this review provides a concise incursion into the gradual evolution of biomaterials for the design of implantable ocular devices as well as approaches used to overcome the challenges with fouling. The implication of fouling for drug delivery, the design of immune-responsive biomaterials, as well as advanced surface immobilization approaches to support the overall performance of implantable ocular devices are also reviewed.

Outcomes of secondary autologus dermo-fat orbital implants in anophthalmic sockets

Objectives:

To evaluate the outcomes of secondary autologous dermis-fat graft as an orbital implant in anophthalmic sockets.

Methods:

In this prospective study, which was conducted at Jinnah Post Graduate Medical Centre, Karachi, between January 2015 and January 2020, we evaluated 12 patients between the ages of four and 60 years. Most of the adults were victims of trauma, whereas children were known cases of retinoblastoma or trauma and all underwent enucleation. All of them were primarily treated elsewhere and not offered primary orbital implants. We performed autologous dermis-fat graft as an orbital implant in these patients harvesting graft from gluteal region and followed them up to look for complications.

Results:

Out of 12 patients two went into failure, while rest of the patients showed successful outcome. All patients underwent successful surgery. Initially, a silicon conformer was placed, which was later on replaced with artificial prosthetic eye.

Conclusion:

Regardless of the small sample size, this procedure proved to be a safe and effective method for augmenting orbital volume in anophthalmic sockets in children and adults.

Copper-containing bioactive glasses and glass-ceramics: From tissue regeneration to cancer therapeutic strategies

Copper is one of the most used therapeutic metallic elements in biomedicine, ranging from antibacterial approaches to cancer theranostics. This element could be easily incorporated into different types of biomaterials; specifically, copper-doped bioactive glasses (BGs) provide great opportunities for biomedical engineers and clinicians as regards their excellent biocompatibility and regenerative potential. Although copper-incorporated BGs are mostly used in bone tissue engineering, accelerated soft tissue healing is achievable, too, with interesting potentials in wound treatment and skin repair. Copper can modulate the physico-chemical properties of BGs (e.g., reactivity with bio-fluids) and improve their therapeutic potential. Improving cell proliferation, promoting angiogenesis, reducing or even prohibiting bacterial growth are counted as prominent biological features of copper-doped BGs. Recent studies have also suggested the suitability of copper-doped BGs in cancer photothermal therapy (PTT). However, more research is needed to determine the extent to which copper-doped BGs are actually applicable for tissue engineering and regenerative medicine strategies in the clinic. Moreover, copper-doped BGs in combination with polymers may be considered in the future to produce relatively soft, pliable composites and printable inks for use in biofabrication.

Facile fabrication of elastic, macro-porous, and fast vascularized silicone orbital implant

Orbital implants with interconnected porous architecture had gained prominence, as they were capable of being colonized by fibrovascular tissue and minimizing complications. However, mechanical properties of orbital implant had received little attention among existing design philosophy. Herein, a compliant porous silicone scaffold was developed by gelatin porogen-leaching method and used as the orbital implant in this study. The silicone scaffolds exhibited desired microstructure and simulated mechanical properties, including high porosity of ~90%, suitable pore size of 280-450 μm, reduced modulus of 50.1 ± 11.7 KPa, and excellent elasticity. in vitro results showed that the porous silicone scaffolds did not exhibit noticeable cytotoxicity and were favorable for both adhesion and proliferation of human vascular ECs. The porous silicone scaffold was easy to be manipulated when implanted into the anophthalmic sockets of rabbits. The implanted scaffolds provided satisfactory volume replacement and induced extensive fibro-vascularization, showing desirable orbital reconstruction effects. Therefore, our novel porous silicone scaffolds may be promising substitutes for current orbital implants.

"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.

Autologous pericranium grafts for large orbital implants

INTRODUCTION

Insufficient orbital volume in an anophthalmic socket is a major problem for the placement of an ocular prosthesis. This study reports the outcomes of the use of autologous pericranium graft in association with a large primary or secondary orbital implant in patients with a contracted socket and large orbital volume deficit.

METHODS

This was a retrospective single-institution study. Participants were 13 patients with contracted socket, volume deficit, and insufficient conjunctiva to cover the new implant divided into two groups, A (n = 3) and B (n = 10), according to the baseline condition of the socket. Surgery was primary evisceration (group A only) and placement of a large orbital implant followed by an autologous pericranium graft over the implant (groups A and B).

RESULTS

Mean follow-up duration for the patient series was 9.5 months (range 9-24). Complete epithelialization of the pericranium graft was recorded at 47.3 days of follow-up (range 33-67). No cases of implant exposure or shrinkage were noted during follow-up. Main postoperative complications were conjunctival granuloma (five patients, 38.5%), conjunctival seroma (one patient, 7.7%). All patients were satisfied with the aesthetic outcome.

CONCLUSION

Autologous pericranial graft was effective in reconstructing the contracted socket so that the anophthalmic socket could accommodate a larger or secondary orbital implant. The efficacy of this procedure needs to be confirmed in a larger patient series.

Regulation of the Ocular Cell/Tissue Response by Implantable Biomaterials and Drug Delivery Systems

Therapeutic advancements in the treatment of various ocular diseases is often linked to the development of efficient drug delivery systems (DDSs), which would allow a sustained release while maintaining therapeutic drug levels in the target tissues. In this way, ocular tissue/cell response can be properly modulated and designed in order to produce a therapeutic effect. An ideal ocular DDS should encapsulate and release the appropriate drug concentration to the target tissue (therapeutic but non-toxic level) while preserving drug functionality. Furthermore, a constant release is usually preferred, keeping the initial burst to a minimum. Different materials are used, modified, and combined in order to achieve a sustained drug release in both the anterior and posterior segments of the eye. After giving a picture of the different strategies adopted for ocular drug release, this review article provides an overview of the biomaterials that are used as drug carriers in the eye, including micro- and nanospheres, liposomes, hydrogels, and multi-material implants; the advantages and limitations of these DDSs are discussed in reference to the major ocular applications.

Use of semisynthetic dura mater substitute as a patch graft for prosthesis extrusion in anophthalmic socket

We present a case report of a three-year old patient diagnosed with retinoblastoma in her left eye. The course of the disease made enucleation of the latter eye and a prosthesis implant necessary. Two years after surgery, partial prosthesis extrusion occurred and a semisynthetic dura mater substitute was used as a patch graft to cover the defect. To our knowledge, semisynthetic dura mater substitutes' use in this scenario has not been previously reported.

Simultaneous enhancement of vascularization and contact-active antibacterial activity in diopside-based ceramic orbital implants

Rapid vascularization and long-term antibacterial property are desirable characteristics of the next-generation implants in orbital reconstruction. In this study, the new diopside-based orbital implants were developed by direct ink writing of diopside (CaMgSi₂O₆; DIO) and low-melt bioactive glass (BG)-assisted sintering approaches. The mechanical tests showed that the addition 5% or 10% BG could readily enhance the compressive strength of the DIO porous bioceramics after sintering at 1150 °C. The Tris buffer immersion test in vitro indicated that the porous bioceramics exhibited appreciable mechanical stability and very limited mass loss (<3.5%) after 8 weeks. The DIO/10BG porous bioceramic sintered at 1150 °C or 1250 °C could promote appreciable angiogenesis response at the early stage (2-6 weeks) of implantation in the rabbit panniculus carnosus muscle models in vivo. It is interesting that the steam autoclaved bioceramics exhibited outstanding contact-active inhibition against Staphylococcus aureus and Pseudomonas aeruginosa, but as-sintered bioceramics showed no antibacterial effect. It is reasonable to consider that our strategy paves the way toward a simple and effective approach to fabricate the multifunctional tailormade implants for orbital implantation, thus accelerating the clinical translation of biomaterials research.

Production and Physicochemical Characterization of Cu-Doped Silicate Bioceramic Scaffolds

Development of ion-releasing implantable biomaterials is a valuable approach for advanced medical therapies. In the effort of tackling this challenge, we explored the feasibility of porous bioceramic scaffolds releasing copper ions, which are potentially able to elicit angiogenetic and antibacterial effects. First, small amounts of CuO were incorporated in the base silicate glass during melting and the obtained powders were further processed to fabricate glass–ceramic scaffolds by sponge replica method followed by sinter crystallization. As the release of copper ions from these foams in simulated body fluid (SBF) was very limited, a second processing strategy was developed. Silicate glass–ceramic scaffolds were coated with a layer of Cu-doped mesoporous glass, which exhibited favorable textural properties (ultrahigh specific surface area >200 m²/g, mesopore size about 5 nm) for modulating the release of copper. All the produced scaffolds, containing biocompatible crystals of wollastonite (CaSiO₃), revealed high stability in a biological environment. Furthermore, the materials had adequate compressive strength (>10 MPa) for allowing safe manipulation during surgery. Overall, the results achieved in the present work suggest that these Cu-doped glass-derived scaffolds show promise for biomedical application and motivate further investigation of their suitability from a biological viewpoint.

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.

Injectable silicone rubber for ocular implantation after evisceration

OBJECTIVE

To investigate the usefulness of addition type liquid silicone rubber (ATLSR) as injectable implant after evisceration to maintain the eyeball volume in an animal experiment.

METHODS

Twelve adult New Zealand white rabbits were included. One eye of each rabbit was randomly selected for evisceration with the fellow eye as control. ATLSR was injected to fill the eyeball socket after evisceration. In vivo observation and photographs were performed up to 24 weeks post-op. Two rabbits were sacrificed respectively at post-operative week 1, 2, 4, 8, 12 and 24. After enucleation, the vertical, horizontal and sagittal diameters of the experimental eyeballs were measured and compared with the control eyes. Histopathological studies were performed to evaluate signs of inflammation.

RESULTS

Cornea remained clear throughout the observation period despite mild epithelial edema and neovascularization. Compared to the control eyes, the experimental eyes were significantly smaller in vertical diameter (17.00±1.17 vs. 17.54±1.11 mm, P<0.001), but larger in sagittal diameter (16.85±1.48 vs. 16.40±1.38 mm, P = 0.008), and had no significant difference in horizontal diameter (17.49±1.53 vs. 17.64±1.21 mm, P = 0.34). Postoperative inflammation was observed at one week after surgery, which peaked at 2-3 weeks, then regressed gradually. At week 12 and week 24, most of the inflammatory cells disappeared with some residual plasma cells and eosinophils.

CONCLUSION

Injectable addition type silicon rubber may be a good choice for ocular implantation after evisceration, maintaining eyeball volume and cosmetically satisfactory when compared to the fellow eye. Spontaneous regression of inflammation implied good biocompatibility for at least 24 weeks.

Prosthetics in Facial Reconstruction

Reconstruction of the head and neck can be a challenging undertaking owing to numerous considerations for successful rehabilitation. Although head and neck defects were once considered irretrievably morbid and associated with a poor quality of life, advances in surgical technique has immensely contributed to the well-being of these patients. However, all patients are not suitable surgical candidates and many have sought nonsurgical options for functional and cosmetic restoration. As such, the advent of prostheses has ameliorated those concerns and provided a viable alternative for select patient populations. Prosthetic reconstruction has evolved significantly over the past decade. Advances in biocompatible materials and imaging adjuncts have spurred further discovery and forward progress. A multidisciplinary approach to head and neck reconstruction focused on appropriate expectations and patient-centered goals is most successfully coordinated by a team of head and neck surgeons, maxillofacial surgeons, and prosthetic specialists. The aim of this article is to provide a comprehensive review of the current trends for prosthetic rehabilitation of head and neck defects, and further elaborate on the limitations and advancements in the field.