Bone Reconstruction: Au Nanocomposite Bioglasses with Antibacterial Properties

The unexplored role of alkali and alkaline earth elements (ALAEs) on the structure, processing, and biological effects of bioactive glasses

Bioactive glass has been employed in several medical applications since its inception in 1969. The compositions of these materials have been investigated extensively with emphasis on glass network formers, therapeutic transition metals, and glass network modifiers. Through these experiments, several commercial and experimental compositions have been developed with varying chemical durability, induced physiological responses, and hydroxyapatite forming abilities. In many of these studies, the concentrations of each alkali and alkaline earth element have been altered to monitor changes in structure and biological response. This review aims to discuss the impact of each alkali and alkaline earth element on the structure, processing, and biological effects of bioactive glass. We explore critical questions regarding these elements from both a glass science and biological perspective. Should elements with little biological impact be included? Are alkali free bioactive glasses more promising for greater biological responses? Does this mixed alkali effect show increased degradation rates and should it be employed for optimized dissolution? Each of these questions along with others are evaluated comprehensively and discussed in the final section where guidance for compositional design is provided.

Bone implant substitutes from synthetic polymer and reduced graphene oxide: Current perspective

In the present work, bone implant materials (BIM) were produced, in sheet form which comprises epoxy resin (synthetic polymer) (ER), calcium carbonate (CaCO3), and reduced graphene oxide (R-GO), by open mold method, for the possibility uses in bone tissue engineering. The developed BIM was analyzed for its physico-chemical, mechanical, bioactivity test, antimicrobial study, and biocompatibility. The BIM had excellent mechanical properties such as tensile strength (194.44 + 0.21 MPa), flexural strength (278.76 + 0.41 MPa), and water absorption (02.61 + 0.24%). A pore size distribution study using the HR-SEM has proved the 180 and 255 μm average pore was observed in the BIM structure. The Bioactivity test of BIM was examined after being immersed in a simulated body fluids (SBF) solution. The result of BIM formed an excellent deposition of bone tube apatite crystals. High-resolution scanning electron microscopy (HR-SEM) morphology of the bone tube apatite crystals revealed the diameter size in the range from 100 ± 159 to 210 ± 188 nm. BIM has excellent antimicrobial characteristics against E. coli (8.75 + 0.06 mm) and S. aureus (9.82 + 0.08 mm). The biocompatibility of the study MTT (3-(4, 5-dimethyl) thiazol-2-yl-2, 5-dimethyl tetrazolium bromide) assay using the MG-63 (human osteoblast cell line) has proven to be the 78% viable cell presence in BIM. After receiving the necessary approval, the scaffold with the required strength and biocompatibility could be tested as a bone implant material in large animals.

Human Ovarian Follicular Fluid Mesenchymal Stem Cells Express Osteogenic Markers When Cultured on Bioglass 58S-Coated Titanium Scaffolds

Recent studies have reported that stem cells (human follicular fluid mesenchymal stem cells or hFF-MSCs) are present in ovarian follicular fluid (hFF) and that they have a proliferative and differentiative potential which is similar to that of MSCs derived from other adult tissue. These mesenchymal stem cells, isolated from human follicular fluid waste matter discarded after retrieval of oocytes during the IVF process, constitute another, as yet unutilized, source of stem cell materials. There has been little work on the compatibility of these hFF-MSCs with scaffolds useful for bone tissue engineering applications and the aim of this study was to evaluate the osteogenic capacity of hFF-MSCs seeded on bioglass 58S-coated titanium and to provide an assessment of their suitability for bone tissue engineering purposes. Following a chemical and morphological characterization with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), cell viability, morphology and expression of specific osteogenic markers were examined after 7 and 21 days of culture. The hFF-MSCs seeded on bioglass and cultured with osteogenic factors, when compared with those seeded on tissue culture plate or on uncoated titanium, exhibited enhanced cell viability and osteogenic differentiation, as reflected by increased calcium deposition and increased ALP activity with expression and production of bone-related proteins. Taken together, these results demonstrate that MSCs from human follicular fluid waste materials can be easily cultured in titanium scaffolds coated with bioglass, having osteoinductive properties. This process has significant potential for regenerative medicine applications and indicates that hFF-MSCs may be a valid alternative to hBM-MSC cells in experimental models in bone tissue engineering.

Antibacterial Properties of Gold Nanoparticles in the Modification of Medical Implants: A Systematic Review

The widespread occurrence of bacterial infections and their increased resistance to antibiotics has led to the development of antimicrobial coatings for multiple medical implants. Owing to their desirable properties, gold nanoparticles (AuNPs) have been developed as antibacterial agents. This systematic investigation sought to analyze the antibacterial effects of implant material surfaces modified with AuNPs. The data from 27 relevant studies were summed up. The included articles were collected from September 2011 to September 2021. According to the retrieved literature, we found that medical implants modified by AuNPs have good antibacterial effects against gram-positive and gram-negative bacteria, and the antibacterial effects would be improved by near-infrared (NIR) radiation.

Bioactive glasses incorporating less-common ions to improve biological and physical properties

Bioactive glasses (BGs) have been a focus of research for over five decades for several biomedical applications. Although their use in bone substitution and bone tissue regeneration has gained important attention, recent developments have also seen the expansion of BG applications to the field of soft tissue engineering. Hard and soft tissue repair therapies can benefit from the biological activity of metallic ions released from BGs. These metallic ions are incorporated in the BG network not only for their biological therapeutic effects but also in many cases for influencing the structure and processability of the glass and to impart extra functional properties. The "classical" elements in silicate BG compositions are silicon (Si), phosphorous (P), calcium (Ca), sodium (Na), and potassium (K). In addition, other well-recognized biologically active ions have been incorporated in BGs to provide osteogenic, angiogenic, anti-inflammatory, and antibacterial effects such as zinc (Zn), magnesium (Mg), silver (Ag), strontium (Sr), gallium (Ga), fluorine (F), iron (Fe), cobalt (Co), boron (B), lithium (Li), titanium (Ti), and copper (Cu). More recently, rare earth and other elements considered less common or, some of them, even "exotic" for biomedical applications, have found room as doping elements in BGs to enhance their biological and physical properties. For example, barium (Ba), bismuth (Bi), chlorine (Cl), chromium (Cr), dysprosium (Dy), europium (Eu), gadolinium (Gd), ytterbium (Yb), thulium (Tm), germanium (Ge), gold (Au), holmium (Ho), iodine (I), lanthanum (La), manganese (Mn), molybdenum (Mo), nickel (Ni), niobium (Nb), nitrogen (N), palladium (Pd), rubidium (Rb), samarium (Sm), selenium (Se), tantalum (Ta), tellurium (Te), terbium (Tb), erbium (Er), tin (Sn), tungsten (W), vanadium (V), yttrium (Y) as well as zirconium (Zr) have been included in BGs. These ions have been found to be particularly interesting for enhancing the biological performance of doped BGs in novel compositions for tissue repair (both hard and soft tissue) and for providing, in some cases, extra functionalities to the BG, for example fluorescence, luminescence, radiation shielding, anti-inflammatory, and antibacterial properties. This review summarizes the influence of incorporating such less-common elements in BGs with focus on tissue engineering applications, usually exploiting the bioactivity of the BG in combination with other functional properties imparted by the presence of the added elements.

Bioactive glass doped with noble metal nanoparticles for bone regeneration: in vitro kinetics and proliferative impact on human bone cell line

This work investigates the bioactivity of novel silver-doped (BG-Ag) and gold-doped (BG-Au) quaternary 46S6 bioactive glasses synthesized via a semi-solid-state technique. A pseudo-second-order kinetic model successfully predicted the in vitro uptake kinetic profiles of the initial ion-exchange release of Ca in simulated body fluid, the subsequent Si release, and finally, the adsorption of Ca and P onto the bioactive glasses. Doping with silver nanoparticles enhanced the rate of P uptake by up to approximately 90%; whereas doping with gold nanoparticles improved Ca and P uptake rates by up to about 7 and 2 times, respectively; as well as Ca uptake capacity by up to about 19%. The results revealed that the combined effect of Ca and Si release, and possibly the release of silver and gold ions into solution, influenced apatite formation due to their effect on Ca and P uptake rate and capacity. In general, gold-doped bioactive glasses are favoured for enhancing Ca and P uptake rates in addition to Ca uptake capacity. However, silver-doped bioactive glasses being less expensive can be utilized for applications targeting rapid healing. In vitro studies showed that BG, BG-Ag and BG-Au had no cytotoxic effects on osteosarcoma MG-63 cells, while they exhibited a remarkable cell proliferation even at low concentration. The prepared bioactive glass doped with noble metal nanoparticles could be potentially used in bone regeneration applications.

Nano-Modified Titanium Implant Materials: A Way Toward Improved Antibacterial Properties

Titanium and its alloys have superb biocompatibility, low elastic modulus, and favorable corrosion resistance. These exceptional properties lead to its wide use as a medical implant material. Titanium itself does not have antibacterial properties, so bacteria can gather and adhere to its surface resulting in infection issues. The infection is among the main reasons for implant failure in orthopedic surgeries. Nano-modification, as one of the good options, has the potential to induce different degrees of antibacterial effect on the surface of implant materials. At the same time, the nano-modification procedure and the produced nanostructures should not adversely affect the osteogenic activity, and it should simultaneously lead to favorable antibacterial properties on the surface of the implant. This article scrutinizes and deals with the surface nano-modification of titanium implant materials from three aspects: nanostructures formation procedures, nanomaterials loading, and nano-morphology. In this regard, the research progress on the antibacterial properties of various surface nano-modification of titanium implant materials and the related procedures are introduced, and the new trends will be discussed in order to improve the related materials and methods.

Biological behavior of bioactive glasses and their composites

This review summarizes current developments in improving the biological behavior of bioactive glasse and their composites.

Biofilm-based implant infections in orthopaedics

The demand for joint replacement surgery is continuously increasing with rising costs for hospitals and healthcare systems. Staphylococci are the most prevalent etiological agents of orthopedic infections. After an initial adhesin-mediated implant colonization, Staphylococcus aureus and Staphylococcus epidermidis produce biofilm. Biofilm formation proceeds as a four-step process: (1) initial attachment of bacterial cells; (2) cell aggregation and accumulation in multiple cell layers; (3) biofilm maturation and (4) detachment of cells from the biofilm into a planktonic state to initiate a new cycle of biofilm formation elsewhere. The encasing of bacteria in biofilms gives rise to insuperable difficulties not only in the treatment of the infection, but also in assessing the state and the nature of the infection using traditional cultural methods. Therefore, DNA-based molecular methods have been developed to provide rapid identification of all microbial pathogens. To combat biofilm-centered implant infections, new strategies are being developed, among which anti-infective or infective-resistant materials are at the forefront. Infection-resistant materials can be based on different approaches: (i) modifying the biomaterial surface to give anti-adhesive properties, (ii) doping the material with antimicrobial substances, (iii) combining anti-adhesive and antimicrobial effects in the same coating, (iv) designing materials able to oppose biofilm formation and support bone repair.

The expanding horizon of prosthetic joint infections

Prosthetic joint infection (PJI) is a serious and potentially devastating complication of arthroplasty. Prior arthroplasty, immunosuppression, severe comorbid conditions, and prolonged surgical duration are important risk factors for PJI. More than half of the cases of PJI are caused by Staphylococcus aureus and coagulase-negative staphylococci. The biofilm plays a central role in its pathogenesis. The diagnosis of PJI requires the presence of purulence, sinus tract, evidence of inflammation on histopathology, or positive microbiologic cultures. The use of diagnostic imaging techniques is generally limited but may be helpful in selected cases. The most effective way to prevent PJI is to optimize the health of patients, using antibiotic prophylaxis in a proper and timely fashion. Management of PJI frequently requires removal of all hardware and administration of intravenous antibiotics. This review summarizes and analyzes the results of previous reports of PJI and assesses the prevention and management of this important entity.

From Koch's postulates to biofilm theory. The lesson of Bill Costerton

The clinical diagnoses of implant infections pose insurmountable difficulties for cultural methods because of their frequent failure when bacteria are growing in biofilms. In 1978 Bill Costerton warned that chronic infections in patients with indwelling medical devices were caused by bacteria growing in well-developed glycocalyx-enclosed biofilms and that bacteria within biofilms resist antibiotic therapies and immune host defenses. Costerton's "biofilm theory" opened two lines of scientific endeavor: the study of the biochemistry and genetics of biofilm formation and function; and, on the other side, the search for new methods for medical diagnosis and treatment of biofilm-centered implant infections. This Editorial and the entire 2012 issue "Focus on Implant Infections" are dedicated to the memory of Bill Costerton, recognized worldwide as the Father of Biofilms for his innovation and body of work on infections caused by sessile bacteria. Bill Costerton was a great scientist, heedful both to the biological aspects of biofilms and to the medical challenges of new diagnostic methods and modern therapeutic approaches to implant infections. But, most of all, he was a charming Maestro for the large number of colleagues and students whose enthusiasm for the science he was able to nourish. Bill passed away on May 12th, 2012 and the entire science community mourns the death of a friend and a leader.

A review of the biomaterials technologies for infection-resistant surfaces

Anti-infective biomaterials need to be tailored according to the specific clinical application. All their properties have to be tuned to achieve the best anti-infective performance together with safe biocompatibility and appropriate tissue interactions. Innovative technologies are developing new biomaterials and surfaces endowed with anti-infective properties, relying either on antifouling, or bactericidal, or antibiofilm activities. This review aims at thoroughly surveying the numerous classes of antibacterial biomaterials and the underlying strategies behind them. Bacteria repelling and antiadhesive surfaces, materials with intrinsic antibacterial properties, antibacterial coatings, nanostructured materials, and molecules interfering with bacterial biofilm are considered. Among the new strategies, the use of phages or of antisense peptide nucleic acids are discussed, as well as the possibility to modulate the local immune response by active cytokines. Overall, there is a wealth of technical solutions to contrast the establishment of an implant infection. Many of them exhibit a great potential in preclinical models. The lack of well-structured prospective multicenter clinical trials hinders the achievement of conclusive data on the efficacy and comparative performance of anti-infective biomaterials.

Biofilm formation in Staphylococcus implant infections. A review of molecular mechanisms and implications for biofilm-resistant materials

Implant infections in orthopaedics, as well as in many other medical fields, are chiefly caused by staphylococci. The ability of growing within a biofilm enhances the chances of staphylococci to protect themselves from host defences, antibiotic therapies, and biocides. Advances in scientific knowledge on structural molecules (exopolysaccharide, proteins, teichoic acids, and the most recently described extracellular DNA), on the synthesis and genetics of staphylococcal biofilms, and on the complex network of signal factors that intervene in their control are here presented, also reporting on the emerging strategies to disrupt or inhibit them. The attitude of polymorphonuclear neutrophils and macrophages to infiltrate and phagocytise biofilms, as well as the ambiguous behaviour exhibited by these innate immune cells in biofilm-related implant infections, are here discussed. Research on anti-biofilm biomaterials is focused, reviewing materials loaded with antibacterial substances, or coated with anti-adhesive/anti-bacterial immobilized agents, or surfaced with nanostructures. Latter approaches appear promising, since they avoid the spread of antibacterial substances in the neighbouring tissues with the consequent risk of inducing bacterial resistance.

New Trends in Diagnosis and Control Strategies for Implant Infections

In implant infections, a quick and reliable identification of the etiological agent is crucial to realizing efficacious therapies. Among molecular methods, automated ribotyping has proven to be an accurate and rapid technique. More recently, MALDI-TOF/MS and PCR-electrospray ionization (ESI)/ MS have been applied successfully to microbiological diagnosis. In implant infections, biofilm is still the major problem for bacterial persistence and recalcitrance to antibiotic therapy. Among biofilm-disrupting agents, enzymes promise the greatest therapeutic possibilities. DNase I degrades biofilm extracellular DNA and has been shown to sensitize biofilm to various biocides and anionic detergents, while dispersin B acts on biofilm exopolysaccharide and, combined with antiseptic, gives a broad-spectrum antibiofilm and antimicrobial activity. The novel antimicrobial approach based on photodynamic treatment (PDT) applies, in combination with antibiotics, to the implant or medical devices reachable by optical fibers. Better progress could be gained by the development of infection-resistant biomaterials able to both inhibit bacterial adhesion and promote tissue integration. New knowledge regarding the fibronectin-mediated internalization of Staphylococcus aureus by osteoblasts, and on its role in the pathogenesis of implant-related osteomyelitis, paves the way for the development of vaccines against staphylococcal adhesins, to prevent both adhesion on biomaterials and bacterial invasion of bone cells.