Nanosurfaces modulate the mechanism of peri-implant endosseous healing by regulating neovascular morphogenesis

Osseointegration of functionally graded Ti6Al4V porous implants: Histology of the pore network

The additive manufacturing of titanium into porous geometries offers a means to generate low-stiffness endosseous implants with a greater surface area available for osseointegration. In this work, selective laser melting was used to produce gyroid-based scaffolds with a uniform pore size of 300 μm or functionally graded pore size from 600 μm to 300 μm. Initial in vitro assessment with Saos-2 cells showed favourable cell proliferation at pore sizes of 300 and 600 μm. Following implantation into rabbit tibiae, early histological observations at four weeks indicated some residual inflammation alongside neovessel infiltration into the scaffold interior and some early apposition of mineralized bone tissue. At twelve weeks, both scaffolds were filled with a mixture of adipocyte-rich marrow, micro-capillaries, and mineralized bone tissue. X-ray microcomputed tomography showed a higher bone volume fraction (BV/TV) and percentage of bone-implant contact (BIC) in the implants with 300 μm pores than in the functionally graded specimens. In functionally graded specimens, localized BV/TV measurement was observed to be higher in the innermost region containing smaller pores (estimated at 300-400 μm) than in larger pores at the implant exterior. The unit cell topology of the porous implant was also observed to guide the direction of bone ingrowth by conducting along the implant struts. These results suggest that in vivo experimentation is necessary alongside parametric optimization of functionally graded porous implants to predict short-term and long-term bone apposition.

Multiscale morphological analysis of bone microarchitecture around Mg-10Gd implants

The utilization of biodegradable magnesium (Mg)-based implants for restoration of bone function following trauma represents a transformative approach in orthopaedic application. One such alloy, magnesium-10 weight percent gadolinium (Mg-10Gd), has been specifically developed to address the rapid degradation of Mg while enhancing its mechanical properties to promote bone healing. Previous studies have demonstrated that Mg-10Gd exhibits favorable osseointegration; however, it exhibits distinct ultrastructural adaptation in comparison to conventional implants like titanium (Ti). A crucial aspect that remains unexplored is the impact of Mg-10Gd degradation on the bone microarchitecture. To address this, we employed hierarchical three-dimensional imaging using synchrotron radiation in conjunction with image-based finite element modelling. By using the methods outlined, the vascular porosity, lacunar porosity and the lacunar-canaliculi network (LCN) morphology of bone around Mg-10Gd in comparison to Ti in a rat model from 4 weeks to 20 weeks post-implantation was investigated. Our investigation revealed that within our observation period, the degradation of Mg-10Gd implants was associated with significantly lower (p < 0.05) lacunar density in the surrounding bone, compared to Ti. Remarkably, the LCN morphology and the fluid flow analysis did not significantly differ for both implant types. In summary, a more pronounced lower lacunae distribution rather than their morphological changes was detected in the surrounding bone upon the degradation of Mg-10Gd implants. This implies potential disparities in bone remodelling rates when compared to Ti implants. Our findings shed light on the intricate relationship between Mg-10Gd degradation and bone microarchitecture, contributing to a deeper understanding of the implications for successful osseointegration.

3D printing metal implants in orthopedic surgery: Methods, applications and future prospects

Background

Currently, metal implants are widely used in orthopedic surgeries, including fracture fixation, spinal fusion, joint replacement, and bone tumor defect repair. However, conventional implants are difficult to be customized according to the recipient's skeletal anatomy and defect characteristics, leading to difficulties in meeting the individual needs of patients. Additive manufacturing (AM) or three-dimensional (3D) printing technology, an advanced digital fabrication technique capable of producing components with complex and precise structures, offers opportunities for personalization.

Methods

We systematically reviewed the literature on 3D printing orthopedic metal implants over the past 10 years. Relevant animal, cellular, and clinical studies were searched in PubMed and Web of Science. In this paper, we introduce the 3D printing method and the characteristics of biometals and summarize the properties of 3D printing metal implants and their clinical applications in orthopedic surgery. On this basis, we discuss potential possibilities for further generalization and improvement.

Results

3D printing technology has facilitated the use of metal implants in different orthopedic procedures. By combining medical images from techniques such as CT and MRI, 3D printing technology allows the precise fabrication of complex metal implants based on the anatomy of the injured tissue. Such patient-specific implants not only reduce excessive mechanical strength and eliminate stress-shielding effects, but also improve biocompatibility and functionality, increase cell and nutrient permeability, and promote angiogenesis and bone growth. In addition, 3D printing technology has the advantages of low cost, fast manufacturing cycles, and high reproducibility, which can shorten patients' surgery and hospitalization time. Many clinical trials have been conducted using customized implants. However, the use of modeling software, the operation of printing equipment, the high demand for metal implant materials, and the lack of guidance from relevant laws and regulations have limited its further application.

Conclusions

There are advantages of 3D printing metal implants in orthopedic applications such as personalization, promotion of osseointegration, short production cycle, and high material utilization. With the continuous learning of modeling software by surgeons, the improvement of 3D printing technology, the development of metal materials that better meet clinical needs, and the improvement of laws and regulations, 3D printing metal implants can be applied to more orthopedic surgeries.

The translational potential of this paper

Precision, intelligence, and personalization are the future direction of orthopedics. It is reasonable to believe that 3D printing technology will be more deeply integrated with artificial intelligence, 4D printing, and big data to play a greater role in orthopedic metal implants and eventually become an important part of the digital economy. We aim to summarize the latest developments in 3D printing metal implants for engineers and surgeons to design implants that more closely mimic the morphology and function of native bone.

Promotion of Wound Healing Using Nanoporous Silk Fibroin Sponges

Wound dressings are important for wound repair. The morphology of the biomaterials used in these dressings, and in particular, the pore structure affects tissue regeneration by facilitating attachment and proliferation of cells due to the hierarchical multiscale, water absorbance, and nutrient transport. In the present study, silk fibroin (SF) sponges with walls containing nanopores (SFNS) were prepared from SF nanoparticles generated during the autoclaving of SF solutions, followed by leaching the SF nanoparticles from the freeze-dried sponges of SF. The nano/microporous structure, biofluid absorbance, and porosity of the SF sponges with and without nanopores were characterized. In vitro cell proliferation, in vivo biocompatibility, and wound healing were evaluated with the sponges. The results demonstrated that SFNS had significantly increased porosity and water permeability, as well as cell attachment and proliferation when compared with SF sponges without the nanopores (SFS). Wound dressings were assessed in a rat skin wound model, and SFNS was superior to SFS in accelerating wound healing, supported by vascularization, deposition of collagen, and increased epidermal thickness over 21 days. Hence, such a dressing material with a hierarchical multiscale pore structure could promote cell migration, vascularization, and tissue regeneration independently without adding any growth factor, which would offer a new strategy to design and engineer better-performed wound dressing.

Topography-mediated immunomodulation in osseointegration; Ally or Enemy

Osteoimmunology is at full display during endosseous implant osseointegration. Bone formation, maintenance and resorption at the implant surface is a result of bidirectional and dynamic reciprocal communication between the bone and immune cells that extends beyond the well-defined osteoblast-osteoclast signaling. Implant surface topography informs adherent progenitor and immune cell function and their cross-talk to modulate the process of bone accrual. Integrating titanium surface engineering with the principles of immunology is utilized to harness the power of immune system to improve osseointegration in healthy and diseased microenvironments. This review summarizes current information regarding immune cell-titanium implant surface interactions and places these events in the context of surface-mediated immunomodulation and bone regeneration. A mechanistic approach is directed in demonstrating the central role of osteoimmunology in the process of osseointegration and exploring how regulation of immune cell function at the implant-bone interface may be used in future control of clinical therapies. The process of peri-implant bone loss is also informed by immunomodulation at the implant surface. How surface topography is exploited to prevent osteoclastogenesis is considered herein with respect to peri-implant inflammation, osteoclastic precursor-surface interactions, and the upstream/downstream effects of surface topography on immune and progenitor cell function.

Evolution of implants and advancements for osseointegration: A narrative review

Since ancient times, reduction and internal fixation has been applied to restore skeletal integrity. Despite advances in the understanding of fracture healing, the risk of complication such as implant loosening or implant-related infection still depicts a challenging complication. Nowadays, a great deal of research is devoted to unreveal the impact of implant surface modifications on osteogenic processes to enhance bone consolidation and osseointegration. This narrative review is aimed to (1) show the evolution and already achieved milestones of implant optimization, and (2) to outline the key factors that contribute to an enhanced osseointegration. Different physical and chemical roughening techniques are currently applied in various studies. Surface patterning on the nanoscale has been found to be an essential factor for the biological response, achievable by e.g. anodisation or laser texturing. Besides surface roughening, also different coating methods are vastly investigated. Next to metal or inorganic compounds as coating material, a variety of biomolecules is currently studied for their osteosupportive capacities. Osseointegration can be improved by surface modification on the micro and nanoscale. Bioactive agents can further improve the osseointegration potential. Used agents at the moment are e.g. inorganic compounds, growth factors (BMPs and non-BMPs) and antiresorptive drugs. The advancement in research on new implant generations therefore aims at actively supporting osseointegration processing.

State-of-the-art techniques for imaging the vascular microenvironment in craniofacial bone tissue engineering applications

Vascularization is a crucial step during musculoskeletal tissue regeneration via bioengineered constructs or grafts. Functional vasculature provides oxygen and nutrients to the graft microenvironment, facilitates wound healing, enhances graft integration with host tissue, and ensures the long-term survival of regenerating tissue. Therefore, imaging de novo vascularization (i.e., angiogenesis), changes in microvascular morphology, and the establishment and maintenance of perfusion within the graft site (i.e., vascular microenvironment or VME) can provide essential insights into engraftment, wound healing, as well as inform the design of tissue engineering (TE) constructs. In this review, we focus on state-of-the-art imaging approaches for monitoring the VME in craniofacial TE applications, as well as future advances in this field. We describe how cutting-edge in vivo and ex vivo imaging methods can yield invaluable information regarding VME parameters that can help characterize the effectiveness of different TE constructs and iteratively inform their design for enhanced craniofacial bone regeneration. Finally, we explicate how the integration of novel TE constructs, preclinical model systems, imaging techniques, and systems biology approaches could usher in an era of "image-based tissue engineering."

MOF-derived CuO@ZnO modified titanium implant for synergistic antibacterial ability, osteogenesis and angiogenesis

Surface modification of titanium implants with antibacterial, osteogenic and even angiogenic capabilities are essential to enhance their clinical applicability. Herein, metal-organic framework (MOF) derived CuO@ZnO composite was grafted onto the polydopamine (PDA) modified titanium alloy to achieve vascularized bone regeneration. The CuO@ZnO-coated titanium effectively inhibits the formation of bacterial biofilms and the sterilization rate of Staphylococcus aureus (S. aureus) reaches 99%. Benefitting from the intrinsic porous architecture of MOFs, the Zn2+ and Cu2+ could be controllably released to facilitate the production of excess intracellular reactive oxygen species (ROS) inside the bacteria, which ensures the excellent antibacterial performance of the composite coating. The CuO@ZnO-coated titanium also exhibits good cytocompatibility, effectively promotes the adhesion and proliferation of the human bone marrow mesenchymal stem cells (hBMSCs) and reduces the level of the cell apoptosis. The up-regulated expression of the osteogenesis-related genes and the superior extracellular matrix mineralization reveals that the CuO@ZnO coating possesses fantastic osteoinductive properties. In addition, the transwell and tube formation assays of the human umbilical vein endothelial cells (HUVECs) suggest the superior angiogenesis ability of the CuO@ZnO-coated titanium. The released Cu2+ stimulated the angiogenesis of the HUVECs in vitro by up-regulating the expression of the vascular endothelial growth factor (VEGF). These findings will provide new insight into the development of multifunctional titanium implants for clinical applications.

Fabrication of succinate-alginate xerogel films for in vitro coupling of osteogenesis and neovascularization

The osseointegration of metallic implants is reliant on a cascade of molecular interactions and the delivery of macromolecules to the implant environment that occurs before substantial bone formation. Early blood vessel formation is a requisite first step in the healing timeline for osteoid formation, where vascular development can be accelerated as a result of controlled hypoxic conditioning. In this study, alginate-derived xerogel films containing varied concentrations of disodium succinate salt which has been shown to induce pseudohypoxia (short-term hypoxic effects while maintaining an oxygenated environment) were developed. Xerogels were characterized for their morphology, succinate release over time and cellular response with osteoblast-mimicking Saos-2 and human umbilical vein endothelial cells (HUVEC). Scanning electron microscopy revealed a multiscale topography that may favour osseointegration and alamarBlue assays indicated no cytotoxic effects during in vitro proliferation of Saos-2 cells. pH measurements of eluted succinate reach 95 % of peak value after 7 h of immersion for all gels containing 10 mM of succinate or less, and 60 % within the first 40 min. In vitro exposure of HUVECs to succinate-conditioned media increased the net concentration of total proteins measured by bicinchoninic acid (BCA) assay and maintains stable vascular endothelial growth factor (VEGF) and extracellular platelet-derived growth factor (PDGF) for vessel formation through comparison of enzyme-linked immunosorbent assays (ELISAs) of the culture media and cell lysate. Tube formation assays also showed a sustained increase in tube diameter across the first 48 h of HUVEC culture when succinate concentrations of 1 and 10 μM in the xerogel. Overall, the succinate-alginate films serve as a prospective organic coating for bone-interfacing implant materials which may induce temporary pseudohypoxic conditions favourable for early angiogenesis and bone regeneration in vivo at succinate concentrations of 1 or 10 μM.

Mineralizing Coating on 3D Printed Scaffolds for the Promotion of Osseointegration

Design and fabrication of implants that can perform better than autologous bone grafts remain an unmet challenge for the hard tissue regeneration in craniomaxillofacial applications. Here, we report an integrated approach combining additive manufacturing with supramolecular chemistry to develop acellular mineralizing 3D printed scaffolds for hard tissue regeneration. Our approach relies on an elastin-like recombinamer (ELR) coating designed to trigger and guide the growth of ordered apatite on the surface of 3D printed nylon scaffolds. Three test samples including a) uncoated nylon scaffolds (referred to as "Uncoated"), b) ELR coated scaffolds (referred to as "ELR only"), and c) ELR coated and in vitro mineralized scaffolds (referred to as "Pre-mineralized") were prepared and tested for in vitro and in vivo performance. All test samples supported normal human immortalized mesenchymal stem cell adhesion, growth, and differentiation with enhanced cell proliferation observed in the "Pre-mineralized" samples. Using a rabbit calvarial in vivo model, 'Pre-mineralized' scaffolds also exhibited higher bone ingrowth into scaffold pores and cavities with higher tissue-implant integration. However, the coated scaffolds ("ELR only" and "Pre-mineralized") did not exhibit significantly more new bone formation compared to "Uncoated" scaffolds. Overall, the mineralizing coating offers an opportunity to enhance integration of 3D printed bone implants. However, there is a need to further decipher and tune their immunologic response to develop truly osteoinductive/conductive surfaces.

Maxillary sinus floor augmentation comparing bovine versus porcine bone xenografts mixed with autogenous bone graft. A split-mouth randomized controlled trial

Aim

To compare the effectiveness of two xenografts for maxillary sinus floor augmentation in terms of clinical, radiographical, histologic, and molecular outcomes.

Materials and methods

A split‐mouth randomized clinical trial was conducted at the University of Granada. Ten consecutive patients in need of bilateral two‐staged maxillary sinus floor augmentation were included. Each patient received both biomaterials (porcine bone mineral and anorganic bovine bone), which were randomly assigned for bilateral sinus augmentation. The maxillary autogenous bone scraped from the sinus access window was mixed with each xenograft at a 20:80 ratio. After a healing period of 6 months, bone biopsies were collected with a trephine during the implant placement in the regenerated area. Histologic, histomorphometrical, immunohistochemical, and molecular outcomes were analyzed. Clinical and radiographical data throughout the treatment phases were also evaluated.

Results

The resulting anatomic features were similar between both groups. After six months of graft consolidation, the graft resorption rates were similar between both biomaterials. The histologic, histomorphometrical, and immunohistochemical results showed no statistical differences between groups.

Conclusion

Anorganic bovine bone and porcine bone mineral combined with maxillary autogenous cortical bone show similar biologic and radiologic features in terms of biomaterial resorption, osteoconduction, and osteogenesis when used for maxillary sinus floor augmentation.

Implant-bone-interface: Reviewing the impact of titanium surface modifications on osteogenic processes in vitro and in vivo

Titanium is commonly and successfully used in dental and orthopedic implants. However, patients still have to face the risk of implant failure due to various reasons, such as implant loosening or infection. The risk of implant loosening can be countered by optimizing the osteointegration capacity of implant materials. Implant surface modifications for structuring, roughening and biological activation in favor for osteogenic differentiation have been vastly studied. A key factor for a successful stable long-term integration is the initial cellular response to the implant material. Hence, cell-material interactions, which are dependent on the surface parameters, need to be considered in the implant design. Therefore, this review starts with an introduction to the basics of cell-material interactions as well as common surface modification techniques. Afterwards, recent research on the impact of osteogenic processes in vitro and vivo provoked by various surface modifications is reviewed and discussed, in order to give an update on currently applied and developing implant modification techniques for enhancing osteointegration.

Assessing the Effects of VEGF Releasing Microspheres on the Angiogenic and Foreign Body Response to a 3D Printed Silicone-Based Macroencapsulation Device

Macroencapsulation systems have been developed to improve islet cell transplantation but can induce a foreign body response (FBR). The development of neovascularization adjacent to the device is vital for the survival of encapsulated islets and is a limitation for long-term device success. Previously we developed additive manufactured multi-scale porosity implants, which demonstrated a 2.5-fold increase in tissue vascularity and integration surrounding the implant when compared to a non-textured implant. In parallel to this, we have developed poly(ε-caprolactone-PEG-ε-caprolactone)-b-poly(L-lactide) multiblock copolymer microspheres containing VEGF, which exhibited continued release of bioactive VEGF for 4-weeks in vitro. In the present study, we describe the next step towards clinical implementation of an islet macroencapsulation device by combining a multi-scale porosity device with VEGF releasing microspheres in a rodent model to assess prevascularization over a 4-week period. An in vivo estimation of vascular volume showed a significant increase in vascularity (* p = 0.0132) surrounding the +VEGF vs. −VEGF devices, however, histological assessment of blood vessels per area revealed no significant difference. Further histological analysis revealed significant increases in blood vessel stability and maturity (** p = 0.0040) and vessel diameter size (*** p = 0.0002) surrounding the +VEGF devices. We also demonstrate that the addition of VEGF microspheres did not cause a heightened FBR. In conclusion, we demonstrate that the combination of VEGF microspheres with our multi-scale porous macroencapsulation device, can encourage the formation of significantly larger, stable, and mature blood vessels without exacerbating the FBR.

Design Considerations for Macroencapsulation Devices for Stem Cell Derived Islets for the Treatment of Type 1 Diabetes

Stem cell derived insulin producing cells or islets have shown promise in reversing Type 1 Diabetes (T1D), yet successful transplantation currently necessitates long-term modulation with immunosuppressant drugs. An alternative approach to avoiding this immune response is to utilize an islet macroencapsulation device, where islets are incorporated into a selectively permeable membrane that can protect the transplanted cells from acute host response, whilst enabling delivery of insulin. These macroencapsulation systems have to meet a number of stringent and challenging design criteria in order to achieve the ultimate goal of reversing T1D. In this progress report, the design considerations and functional requirements of macroencapsulation systems are reviewed, specifically for stem-cell derived islets (SC-islets), highlighting distinct design parameters. Additionally, a perspective on the future for macroencapsulation systems is given, and how incorporating continuous sensing and closed-loop feedback can be transformative in advancing toward an autonomous biohybrid artificial pancreas.

New insights into spatio-temporal dynamics of mesenchymal progenitor cell ingress during peri-implant wound healing: Provided by intravital imaging

Surface topography drives the success of orthopedic and dental implants placed in bone, by directing the biology occurring at the tissue-implant interface. Over the last few decades, striking advancements have been made in the development of novel implant surfaces that enhance bone anchorage to their surfaces through contact osteogenesis: the combination of the two phenomena of recruitment and migration of mesenchymal progenitor cells to the implant surface, and their differentiation into bone-forming cells. While the latter is generally understood, the mechanisms and dynamics underlying the migration and recruitment of such progenitor cells into the wound site have garnered little attention. To address this deficit, we surgically inserted metallic implants with two different surface topographies into the skulls of mice, and then employed real-time spatiotemporal microscopic monitoring of the peri-implant tissue healing to track the ingress of cells. Our results show that nano-topographically complex, in comparison to relatively smooth, implant surfaces profoundly affect recruitment of both endothelial cells, which are essential for angiogenesis, and the mesenchymal progenitor cells that give rise to the reparative tissue stroma. The latter appear concomitantly in the wound site with endothelial cells, from the vascularized areas of the periosteum, and demonstrate a proliferative "bloom" that diminishes with time, although some of these cells differentiate into important stromal cells, pericytes and osteocytes, of the reparative wound. In separate experiments we show, using trajectory plots, that the directionality of migration for both endothelial and perivascular cells can be explained by implant surface dependent release of local cytokine gradients from platelets that would become activated on the implant surfaces during initial blood contact. These findings provide new biological insights into the earliest stages of wound healing, and have broad implications in the application of putative nano-topographically complex biomaterials in many tissue types.

Microconvex Dot-Featured Silk Fibroin Films for Promoting Human Umbilical Vein Endothelial Cell Angiogenesis via Enhancing the Expression of bFGF and VEGF

Insufficient vascularization of grafts often leads to delayed tissue ingrowth and impaired tissue function in tissue engineering. The surface topography of grafts plays critical roles in angiogenesis. In the present study, we prepared silk fibroin (SF)-based microtopography films with the number of convex dots ranging from 37 to 4835/mm². The convex dot-featured topography surfaces were characterized by scanning electron microscopy, a Profilm3D optical profilometer, atomic force microscopy, and a contact angle goniometer. The effect of microtopographic films on the proliferation, adhesion, and expression of angiogenic factors of human umbilical vein endothelial cells (HUVECs) was investigated. Our results demonstrated that the SF film surface with 2899 convex dots/mm² significantly enhanced adhesion, viability, and levels of vascular endothelial growth factors and basic fibroblast growth factors of HUVECs and significantly downregulated the level of α-SMA in human aortic smooth muscle cells, indicating that the microtopographic films could promote angiogenesis. Furthermore, in vitro results showed that HUVEC proliferation was positively correlated with yes-associated protein (YAP) activation, suggesting that the enhanced angiogenesis was mediated via the YAP pathway. Finally, mice subcutaneous embedding model results indicated that the SF film surface with 2899 convex dots/mm² could significantly enhance angiogenesis in vivo. Altogether, our results showed that the SF film surface with 2899 convex dots/mm² promoted the angiogenesis of HUVECs and offered a novel angiogenesis-promoting strategy of implant surface design for tissue engineering.

The influence of implant design on the kinetics of osseointegration and bone anchorage homeostasis

Titanium implants have shown considerable success in terms of achieving quick and long-lasting stability in bone through the process of osseointegration. Further work aims to improve implant success rates by modifying implant design on the nano-, micro-, and macro- scales with the goal of achieving higher levels of bone anchorage more quickly. However, the most frequently used methods of analysis do not investigate bone anchorage as a whole but as a series of discrete points, potentially missing relevant insight which could inform the effects of topography on these 3 scale ranges. Herein we utilize an asymptotic curve fitting method to obtain a biologically relevant description of reverse torque data and compare the anchorage of 12 different implant groups. Implant surface topography had a significant effect on the rate and degree of anchorage achieved during the initial bone formation period of osseointegration but was not found to influence the relative change in anchorage during bony remodeling. Threaded implants significantly decreased the time required to reach peak anchorage compared to non-threaded implants and implants with micro-topographically complex surfaces required greater torque to be removed than implants without such features. Nanotopography increased overall anchorage and decreased the time required to reach peak anchorage but to a lesser degree than microtopography or macrogeometry respectively. The curve fitting method utilized in the present study allows for a more integrated analysis of bone anchorage and permits investigation of osseointegration with respect to time, which may lead to a more targeted approach to implant design.

pH-responsive silk fibroin-based CuO/Ag micro/nano coating endows polyetheretherketone with synergistic antibacterial ability, osteogenesis, and angiogenesis

Polyetheretherketone has been widely used for bone defect repair, whereas failures may happen due to implant loosening and infection. Thus, PEEK implant with multi-function (osteogenesis, angiogenesis, and bacteria-killing) is essential to solve this problem. Herein, copper oxide microspheres (µCuO) decorated with silver nanoparticles (nAg) were constructed on porous PEEK surface via silk fibroin. In vitro studies highlighted the pH controlled release ability of this coating. It liberated a high dose of Cu²⁺ and Ag⁺ at low pH environment (pH 5.0), leading to 99.99% killing of planktonic bacteria and complete eradication of sessile bacteria, avoiding biofilm formation. Under physiological environment (pH 7.4), a lower amount of leaked metal ions induced promoted ALP production, collagen secretion, and calcium deposition, as well as NO production, which indicated potentiated osteogenesis and angiogenesis. In vivo results displayed the highest new bone volume around, and the appearance of new bone inside porous structure of, PEEK implant with this coating in rabbit tibia, signified the abilities of this coating to promote bone regeneration and osseointegration. Our study established solid support for implants with this coating to be a successful bone defect repair solution. STATEMENT OF SIGNIFICANCE: In this study, CuO/Ag micro/nano particles were incorporated into the porous surface of PEEK through polydopamine and silk fibroin layers. The design of this coating conferred pH-controlled release behavior to Cu²⁺ and Ag⁺. High dose of metal ions were released at pH 5.0, which presented synergistic antibacterial ability and killed 99.99% of planktonic bacteria. Low concentration of metal ions were controlled by this coating at physiological environment, which potentiated osteodifferentiation of Ad-MSC in vitro and led to complete integration of implant with bone tissue in vivo.

Evolution of Nanotechnology in Delivering Drugs to Eyes, Skin and Wounds via Topical Route

The topical route is the most preferred one for administering drugs to eyes, skin and wounds for reaching enhanced efficacy and to improve patient compliance. Topical administration of drugs via conventional dosage forms such as solutions, creams and so forth to the eyes is associated with very low bioavailability (less than 5%) and hence, we cannot rely on these for delivering drugs to eyes more efficiently. An intravitreal injection is another popular drug delivery regime but is associated with complications like intravitreal hemorrhage, retinal detachment, endophthalmitis, and cataracts. The skin has a complex structure that serves as numerous physiological barriers to the entry of exogenous substances. Drug localization is an important aspect of some dermal diseases and requires directed delivery of the active substance to the diseased cells, which is challenging with current approaches. Existing therapies used for wound healing are costly, and they involve long-lasting treatments with 70% chance of recurrence of ulcers. Nanotechnology is a novel and highly potential technology for designing formulations that would improve the efficiency of delivering drugs via the topical route. This review involves a discussion about how nanotechnology-driven drug delivery systems have evolved, and their potential in overcoming the natural barriers for delivering drugs to eyes, skin and wounds.

Decoupling the effects of nanopore size and surface roughness on the attachment, spreading and differentiation of bone marrow-derived stem cells

The nanopore size and roughness of nanoporous surface are two critical variables in determining stem cell fate, but little is known about the contribution from each cue individually. To address this gap, we use two-dimensional nanoporous membranes with controlled nanopore size and roughness to culture bone marrow-derived mesenchymal stem cells (BMSCs), and study their behaviors such as attachment, spreading and differentiation. We find that increasing the roughness of nanoporous surface has no noticeable effect on cell attachment, and only slightly decreases cell spreading areas and inhibits osteogenic differentiation. However, BMSCs cultured on membranes with larger nanopores have significantly fewer attached cells and larger spreading areas. Moreover, these cells cultured on larger nanopores undergo enhanced osteogenic differentiation by expressing more alkaline phosphatase, osteocalcin, osteopontin, and secreting more collagen type I. These results suggest that although both nanopore size and roughness can affect BMSCs, nanopore size plays a more significant role than roughness in controlling BMSC behavior.

Comparative Study of Surface Modification Treatment for Porous Titanium

OBJECTIVES

This study was to investigate suitable surface treatment methods for porous titanium by ex vivo study of material properties and calcium phosphate deposition in simulated body fluid.

MATERIAL AND METHODS

Porous titanium with acid (H2SO4 and HCl mixed acid) or alkali (NaOH) treatment was prepared. The surfaces were observed, and the weight change ratio (after and before surface treatment) and compression strength were measured. To investigate the apatite formation ability, each sample was immersed in simulated body fluid (SBF). Surface observations were performed, and the weight change ratio (before/after immersing SBF) and calcification (by alizarin red staining) were measured.

RESULTS

The acid group showed a martensitic micro-scale rough structure and the weight and mechanical strength greatly decreased compared to the other groups. The alkali group exhibited a nano-scale roughness structure with similar weight and mechanical strength. Following immersion in SBF, an apatite-like crystal layer in the alkali group was observed. The weight of all samples increased. The change in weight of the samples in the alkali, acid, and control groups were significantly different, showing the following trend: alkali group (1.6%) > acid group (1.2%) > control group (0.8%). Calcium precipitation values were higher in the samples from alkali group than in those from the acid and control groups.

CONCLUSIONS

Alkali treatment was found to be a suitable surface modification method for porous titanium, resulting in good mechanical strength and apatite formation ability in simulated body fluid.

Ti-5Al-5Mo-5V-3Cr bone implants with dual-scale topography: a promising alternative to Ti-6Al-4V

Modifications to the compositional, topographical and morphological aspects of bone implants can lead to improved osseointegration, thus increasing the success of bone implant procedures. This study investigates the creation of dual-scale topography on Ti-5Al-5Mo-5V-3Cr (Ti5553), an alloy not presently used in the biomedical field, and compares it to Ti-6Al-4V (Ti64), the most used Ti alloy for bone implants. Dual-scale surface topography was obtained by combining selective laser melting (SLM) and electrochemical anodization, which resulted in micro- and nanoscale surface features, respectively. Ti5553 and Ti64 samples were manufactured by SLM and showed comparable surface topography. Subsequent electrochemical anodization succeeded in forming titania nanotubes (TNTs) on both alloys, with larger nanotubes obtained with Ti5553 at all investigated anodization voltages. At an anodization voltage of 40 V, a minimum time of 20 min was necessary to have nanotube formation on the surface of either alloy, while only nanopores were evident for shorter times. Seeded Saos-2 cells showed ideal interactions with surface-modified structures, with filopodia extending to both surface microparticles characteristic of SLM and to the interior of TNTs. Attractiveness of Ti5553 lies in its lower elastic modulus (E = 72 GPa) compared to Ti64, which should mitigate stress-shielding phenomena in vivo. This, combined with the analogous results obtained in terms of dual-scale surface topography and cell-substrate interaction, could indicate Ti5553 as a promising alternative to the widely-employed Ti64 for bone implant device manufacturing.

Hyperglycemia compromises Rat Cortical Bone by Increasing Osteocyte Lacunar Density and Decreasing Vascular Canal Volume

Uncontrolled diabetes is associated with increased risk of bony fractures. However, the mechanisms have yet to be understood. Using high-resolution synchrotron micro-CT, we calculated the changes in the microstructure of femoral cortices of streptozotocin-induced hyperglycemic (STZ) Wistar Albino rats and tested the mechanical properties of the mineralized matrix by nanoindentation. Total lacunar volume of femoral cortices increased in STZ group due to a 9% increase in lacunar density. However, total vascular canal volume decreased in STZ group due to a remarkable decrease in vascular canal diameter (7 ± 0.3 vs. 8.5 ± 0.4 µm). Osteocytic territorial matrix volume was less in the STZ group (14,908 ± 689 µm³) compared with healthy controls (16,367 ± 391 µm³). In conclusion, hyperglycemia increased cellularity and lacunar density, decreased osteocyte territorial matrix, and reduced vascular girth, in addition to decreasing matrix mechanical properties in the STZ group when compared with euglycemic controls.

Birol Ay et al. use high-resolution synchrotron radiation micro-CT to calculate the changes in the microstructure of femoral cortices in STZ-induced hyperglycemic rats. They show that hyperglycemia increases lacunar density due to a reduction in osteocytic territorial matrix volume but decreases total vascular canal volume due to a decrease in canal diameter.

Three-dimensional intravital imaging in bone research

Intravital imaging has emerged as a novel and efficient tool for visualization of in situ dynamics of cellular behaviors and cell-microenvironment interactions in live animals, based on desirable microscopy techniques featuring high resolutions, deep imaging and low phototoxicity. Intravital imaging, especially based on multi-photon microscopy, has been used in bone research for dynamics visualization of a variety of physiological and pathological events at the cellular level, such as bone remodeling, hematopoiesis, immune responses and cancer development, thus, providing guidance for elucidating novel cellular mechanisms in bone biology as well as guidance for new therapies. This review is aimed at interpreting development and advantages of intravital imaging in bone research, and related representative discoveries concerning bone matrices, vessels, and various cells types involved in bone physiologies and pathologies. Finally, current limitations, further refinement, and extended application of intravital imaging in bone research are concluded.

Engineering the vasculature for islet transplantation

The microvasculature in the pancreatic islet is highly specialized for glucose sensing and insulin secretion. Although pancreatic islet transplantation is a potentially life-changing treatment for patients with insulin-dependent diabetes, a lack of blood perfusion reduces viability and function of newly transplanted tissues. Functional vasculature around an implant is not only necessary for the supply of oxygen and nutrients but also required for rapid insulin release kinetics and removal of metabolic waste. Inadequate vascularization is particularly a challenge in islet encapsulation. Selectively permeable membranes increase the barrier to diffusion and often elicit a foreign body reaction including a fibrotic capsule that is not well vascularized. Therefore, approaches that aid in the rapid formation of a mature and robust vasculature in close proximity to the transplanted cells are crucial for successful islet transplantation or other cellular therapies. In this paper, we review various strategies to engineer vasculature for islet transplantation. We consider properties of materials (both synthetic and naturally derived), prevascularization, local release of proangiogenic factors, and co-transplantation of vascular cells that have all been harnessed to increase vasculature. We then discuss the various other challenges in engineering mature, long-term functional and clinically viable vasculature as well as some emerging technologies developed to address them. The benefits of physiological glucose control for patients and the healthcare system demand vigorous pursuit of solutions to cell transplant challenges. STATEMENT OF SIGNIFICANCE: Insulin-dependent diabetes affects more than 1.25 million people in the United States alone. Pancreatic islets secrete insulin and other endocrine hormones that control glucose to normal levels. During preparation for transplantation, the specialized islet blood vessel supply is lost. Furthermore, in the case of cell encapsulation, cells are protected within a device, further limiting delivery of nutrients and absorption of hormones. To overcome these issues, this review considers methods to rapidly vascularize sites and implants through material properties, pre-vascularization, delivery of growth factors, or co-transplantation of vessel supporting cells. Other challenges and emerging technologies are also discussed. Proper vascular growth is a significant component of successful islet transplantation, a treatment that can provide life-changing benefits to patients.

Longitudinal assessment of clinical and radiographic periimplant status around narrow and regular diameter implants placed in cigarette-smokers and nonsmokers

BACKGROUND

To date, no clinical investigation has assessed the clinical and radiographic indices around narrow diameter implants (NDIs) and regular diameter implants (RDIs) in individuals with cigarette smoking habit and nonsmokers.

OBJECTIVE

To estimate and compare the clinical and radiographic indices around NDIs (< 3.3 mm) and RDIs placed in cigarette smokers (CS) and nonsmokers (NS).

MATERIALS AND METHODS

Eighty-six patients requiring implant surgery in the anterior mandible were divided into two groups (39 CS and 43 NS). Patients were further categorized into two subgroups on the basis of implant diameter: (a) patients with NDIs (3.3 mm) and (b) patients with RDIs (4.1 mm). Clinical indices evaluating plaque index (PI), bleeding on probing (BOP), and probing depth (PD) were recorded at 18 and 36 months of follow-up. Digital periapical radiographs were studied to evaluate crestal bone levels (CBL) incorporating in a specialized software and examined on a calibrated computer display screen with the help of an image analyzer.

RESULTS

The mean age of patients in CS group and NS group was 44.6 and 42.5 years, respectively. There was no statistically significant difference in the overall mean scores of PI, PD, and CBL around NDIs and RDIs among CS and NS patients at 18 and 36 months of follow-up. However, there was a statistically significant difference only in the overall mean BOP around NDIs and RDIs among CS and NS patients at 18 and 36 months of follow-up.

CONCLUSION

The findings of the current study suggests that NDIs can show reliable clinical stability and radiographic bone levels as RDIs placed in CS and NS, with the support of strict oral hygiene protocols.

Intravital Imaging for Tracking of Angiogenesis and Cellular Events Around Surgical Bone Implants

IMPACT STATEMENT

These new experimental methods allow us to image, and quantify, angiogenesis and perivascular cell dynamics in the endosseous healing compartment. As such, the method is capable of providing a new perspective on, and unique information regarding, healing that occurs around orthopedic and dental implants.