Medicated hydrogels of hyaluronic acid derivatives for use in orthopedic field

The Intraoperative Use of Defensive Antibacterial Coating (DAC®) in the Form of a Gel to Prevent Peri-Implant Infections in Orthopaedic Surgery: A Clinical Narrative Review

Periprosthetic joint infections (PJIs) in arthroplasty and osteosynthesis-associated infections (OAIs) in reconstructive surgery still represent a challenging complication in orthopaedics and traumatology causing a burden worsening the patient's quality of life, for caregiver and treating physicians, and for healthcare systems. PJIs and OAIs are the result of bacterial adhesion over an implant surface with subsequent biofilm formation. Therefore, the clinical pathological outcome is a difficult-to-eradicate persistent infection. Strategies to treat PJIs and OAIs involve debridement, the replacement of internal fixators or articular prostheses, and intravenous antibiotics. However, long treatments and surgical revision cause discomfort for patients; hence, the prevention of PJIs and OAIs represents a higher priority than treatment. Local antibiotic treatments through coating-release systems are becoming a smart approach to prevent this complication. Hydrophilic coatings, loaded with antibiotics, simultaneously provide a barrier effect against bacterial adhesion and allow for the local delivery of an antibiotic. The intraoperative use of a hyaluronan (HY)-derivative coating in the form of a gel, loaded with antibiotics to prevent PJI, has recently raised interest in orthopaedics. Current evidence supports the use of this coating in the prophylaxis of PJI and IRIs in terms of clinical outcomes and infection reduction. Thus, the purpose of this narrative review is to assess the use of a commercially available HY derivative in the form of a gel, highlighting the characteristics of this biomaterial, which makes it attractive for the management of PJIs and IRIs in orthopaedics and traumatology.

Rheological Considerations of Pharmaceutical Formulations: Focus on Viscoelasticity

Controlling rheological properties offers the opportunity to gain insight into the physical characteristics, structure, stability and drug release rate of formulations. To better understand the physical properties of hydrogels, not only rotational but also oscillatory experiments should be performed. Viscoelastic properties, including elastic and viscous properties, are measured using oscillatory rheology. The gel strength and elasticity of hydrogels are of great importance for pharmaceutical development as the application of viscoelastic preparations has considerably expanded in recent decades. Viscosupplementation, ophthalmic surgery and tissue engineering are just a few examples from the wide range of possible applications of viscoelastic hydrogels. Hyaluronic acid, alginate, gellan gum, pectin and chitosan are remarkable representatives of gelling agents that attract great attention applied in biomedical fields. This review provides a brief summary of rheological properties, highlighting the viscoelasticity of hydrogels with great potential in biomedicine.

Antibacterial coatings on orthopedic implants

With the aging of population and the rapid improvement of public health and medical level in recent years, people have had an increasing demand for orthopedic implants. However, premature implant failure and postoperative complications frequently occur due to implant-related infections, which not only increase the social and economic burden, but also greatly affect the patient's quality of life, finally restraining the clinical use of orthopedic implants. Antibacterial coatings, as an effective strategy to solve the above problems, have been extensively studied and motivated the development of novel strategies to optimize the implant. In this paper, a variety of antibacterial coatings recently developed for orthopedic implants were briefly reviewed, with the focus on the synergistic multi-mechanism antibacterial coatings, multi-functional antibacterial coatings, and smart antibacterial coatings that are more potential for clinical use, thereby providing theoretical references for further fabrication of novel and high-performance coatings satisfying the complex clinical needs.

Translation of hyaluronic acid–based vitreous substitutes towards current regulations for medical devices

PURPOSE

Hydrogel-based vitreous substitutes have the potential to overcome the limitations of current clinically used endotamponades. With the goal of entering clinical trials, the present study aimed to (I) transfer the material synthesis of hyaluronic acid-based hydrogels into a routine, pharmaceutical-appropriate production and (II) evaluate the properties of the vitreous substitutes in terms of the current regulations for medical devices (MDR/ISO standards).

METHODS

The multistep manufacturing process of the vitreous substitutes, including the modification of hyaluronic acid with glycidyl methacrylate, photocopolymerization with N-vinylpyrrolidone, and successive hydrogel purification, was developed under laboratory conditions, characterized using ¹ H-NMR, FT-IR and UV/Vis spectroscopies and HPLC, and transferred towards a pharmaceutical production environment considering GMP standards. The optical and viscoelastic characteristics of the hyaluronic acid-based hydrogels were compared with those of extracted human vitreous and silicone oil. The effect of the hydrogels on the metabolic activity, proliferation and apoptosis of fibroblast (MRC-5, BJ, L929), retinal pigment epithelial (ARPE-19, hiPSC-derived RPE) and photoreceptor cells (661W) was studied as well as their mucosal tolerance via a HET-CAM assay.

RESULTS

Hyaluronic acid-based hydrogels having a suitable purity, sterility, high transparency (>90%), appropriate refractive index (1.3365) and viscoelasticity (G' > G″) were prepared in a standardized manner under controlled process conditions. The metabolic activity, proliferation and apoptosis of various cell types as well as egg choroid were unaffected by the hyaluronic acid-based vitreous substitutes, demonstrating their biocompatibility.

CONCLUSIONS

The present study demonstrates the successful transferability of the crucial synthesis steps of hyaluronic acid-based hydrogels into a routine, GMP-compliant production process while achieving the optical and viscoelastic properties, biocompatibility and purity required for their clinical use as vitreous substitutes.

Photothermal nanofibrillar membrane based on hyaluronic acid and graphene oxide to treat Staphylococcus aureus and Pseudomonas aeruginosa infected wounds

Here we reported the fabrication of an electrospun membrane based on a hyaluronic acid derivative (HA-EDA) to be used as a bandage for the potential treatment of chronic wounds. The membrane, loaded with graphene oxide (GO) and ciprofloxacin, showed photothermal properties and light-triggered drug release when irradiated with a near-infrared (NIR) laser beam. Free amino groups of HA-EDA derivative allowed autocrosslinking of the electrospun membrane; thus, a substantial enhancement in the hydrolytic resistance of the patch was obtained. In vitro antibacterial activity studies performed on Staphylococcus aureus and Pseudomonas aeruginosa revealed that such electrospun membranes, due to the synergistic effect of the antibiotic and NIR-mediated hyperthermia, reduced the viability of both pathogens. Specific in vitro experiment demonstrated also that is possible to disrupt, through laser irradiation, the biofilms formed onto the membrane.

WPI Hydrogels with a Prolonged Drug-Release Profile for Antimicrobial Therapy

Infectious sequelae caused by surgery are a significant problem in modern medicine due to their reduction of therapeutic effectiveness and the patients’ quality of life.Recently, new methods of local antimicrobial prophylaxis of postoperative sequelae have been actively developed. They allow high local concentrations of drugs to be achieved, increasing the antibiotic therapy’s effectiveness while reducing its side effects. We have developed and characterized antimicrobial hydrogels based on an inexpensive and biocompatible natural substance from the dairy industry—whey protein isolate—as matrices for drug delivery. The release of cefazolin from the pores of hydrogel structures directly depends on the amount of the loaded drug and occurs in a prolonged manner for three days. Simultaneously with the antibiotic release, hydrogel swelling and partial degradation occurs. The WPI hydrogels absorb solvent, doubling in size in three days and retaining cefazolin throughout the duration of the experiment. The antimicrobial activity of cefazolin-loaded WPI hydrogels against Staphylococcus aureus growth is prolonged in comparison to that of the free cefazolin. The overall cytotoxic effect of cefazolin-containing WPI hydrogels is lower than that of free antibiotics. Thus, our work shows that antimicrobial WPI hydrogels are suitable candidates for local antibiotic therapy of infectious surgical sequelae.

In-Vitro Antibacterial Activity of Curcumin-Loaded Nanofibers Based on Hyaluronic Acid against Multidrug-Resistant ESKAPE Pathogens

Bacterial infections have accompanied humanity throughout its history and became vitally important in the pandemic area. The most pathogenic bacteria are multidrug-resistant strains, which have become widespread due to their natural biological response to the use of antibiotics, including uncontrolled use. The current challenge is finding highly effective antibacterial agents of natural origin, which, however, have low solubility and consequently poor bioavailability. Curcumin, derived from Curcuma longa, is an example of a natural biologically active agent with a wide spectrum of biological effects, particularly against Gram-positive bacteria. However, curcumin exhibits extremely low antibacterial activity against Gram-negative bacteria. Curcumin’s hydrophobicity limits its use in medicine. As such, various polymeric systems have been used, especially biopolymer-based electrospun nanofibers. In the present study, the technological features of the fabrication of curcumin-loaded hyaluronic acid-based nanofibers are discussed in detail, their morphological characteristics, wettability, physico-chemical properties, and curcumin release profiles are demonstrated, and their antibacterial activity against multi-drug resistant ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) are evaluated. It is noteworthy that the fibers containing a stable HA–curcumin complex showed high antibacterial activity against both Gram-positive and Gram-negative bacteria, which is an undeniable advantage. It is expected that the results of this work will contribute to the development of antibacterial drugs for topical and internal use with high efficacy and considerably lower side effects.

Recent Advances in Multifunctional Hydrogels for the Treatment of Osteomyelitis

Osteomyelitis (OM), a devastating disease caused by microbial infection of bones, remains a major challenge for orthopedic surgeons. Conventional approaches for prevention and treatment of OM are unsatisfactory. Various alternative strategies have been proposed, among which, hydrogel-based strategies have demonstrated potential due to their unique properties, including loadable, implantable, injectable, printable, degradable, and responsive to stimuli. Several protocols, including different hydrogel designs, selection of antimicrobial agent, co-administration of bone morphogenetic protein 2 (BMP 2), and nanoparticles, have been shown to improve the biological properties, including antimicrobial effects, osteo-induction, and controlled drug delivery. In this review, we describe the current and future directions for designing hydrogels and their applications to improve the biological response to OM in vivo.

Development of Silver-Containing Hydroxyapatite-Coated Antimicrobial Implants for Orthopaedic and Spinal Surgery

The prevention of surgical site infections is directly related to the minimization of surgical invasiveness, and is in line with the concept of minimally invasive spine therapy (MIST). In recent years, the incidence of postoperative infections has been increasing due to the increased use of spinal implant surgery in patients at high risk of infection, including the elderly and easily infected hosts, the limitations of poor bone marrow transfer of antibiotics, and the potential for contamination of surgical gloves and instruments. Thus, the development of antimicrobial implants in orthopedic and spinal surgery is becoming more and more popular, and implants with proven antimicrobial, safety, and osteoconductive properties (i.e., silver, iodine, antibiotics) in vitro, in vivo, and in clinical trials have become available for clinical use. We have developed silver-containing hydroxyapatite (Ag-HA)-coated implants to prevent post-operative infection, and increase bone fusion capacity, and have successfully commercialized antibacterial implants for hip prostheses and spinal interbody cages. This narrative review overviews the present status of available surface coating technologies and materials; describes how the antimicrobial, safety, and biocompatibility (osteoconductivity) of Ag-HA-coated implants have been demonstrated for commercialization; and reviews the clinical use of antimicrobial implants in orthopedic and spinal surgery, including Ag-HA-coated implants that we have developed.

Classification and research progress of implant surface antimicrobial techniques

Due to the good biocompatibility and ideal mechanical property, titanium implants have been widely used in dental clinic and orthopedic surgery. However, bacteria induced infection can cause per-implant inflammation and decrease the success rate of implant surgery. Therefore, developing antimicrobial techniques is essential to successful application of titanium implants. Many surface antimicrobial techniques, including antimicrobial coating and surface modifications, have been explored and they always exert antimicrobial effect by reducing bacterial adhesion, inhibiting their metabolism, or destructing cell structure. In this paper, different surface antimicrobial techniques and their recent research progress are reviewed to provide a brief insight on this area.

Bioactive Coatings on Titanium: A Review on Hydroxylation, Self-Assembled Monolayers (SAMs) and Surface Modification Strategies

Titanium (Ti) and its alloys have been demonstrated over the last decades to play an important role as inert materials in the field of orthopedic and dental implants. Nevertheless, with the widespread use of Ti, implant-associated rejection issues have arisen. To overcome these problems, antibacterial properties, fast and adequate osseointegration and long-term stability are essential features. Indeed, surface modification is currently presented as a versatile strategy for developing Ti coatings with all these challenging requirements and achieve a successful performance of the implant. Numerous approaches have been investigated to obtain stable and well-organized Ti coatings that promote the tailoring of surface chemical functionalization regardless of the geometry and shape of the implant. However, among all the approaches available in the literature to functionalize the Ti surface, a promising strategy is the combination of surface pre-activation treatments typically followed by the development of intermediate anchoring layers (self-assembled monolayers, SAMs) that serve as the supporting linkage of a final active layer. Therefore, this paper aims to review the latest approaches in the biomedical area to obtain bioactive coatings onto Ti surfaces with a special focus on (i) the most employed methods for Ti surface hydroxylation, (ii) SAMs-mediated active coatings development, and (iii) the latest advances in active agent immobilization and polymeric coatings for controlled release on Ti surfaces.

Recent Strategies to Combat Infections from Biofilm-Forming Bacteria on Orthopaedic Implants

Biofilm-related implant infections (BRII) are a disastrous complication of both elective and trauma orthopaedic surgery and occur when an implant becomes colonised by bacteria. The definitive treatment to eradicate the infections once a biofilm has established is surgical excision of the implant and thorough local debridement, but this carries a significant socioeconomic cost, the outcomes for the patient are often poor, and there is a significant risk of recurrence. Due to the large volumes of surgical procedures performed annually involving medical device implantation, both in orthopaedic surgery and healthcare in general, and with the incidence of implant-related infection being as high as 5%, interventions to prevent and treat BRII are a major focus of research. As such, innovation is progressing at a very fast pace; the aim of this study is to review the latest interventions for the prevention and treatment of BRII, with a particular focus on implant-related approaches.

Clinical Application of Antibacterial Hydrogel and Coating in Orthopaedic and Traumatology Surgery

Implant related infection is one of the most frequent complications in orthopaedic and trauma surgery. Local antibiotic treatment strategies are becoming part of the prevention and treatment methodology for this fearful complication. To date, there are two coatings available on the market, both with a polylactic acid base. Current evidence supports the use of these types of coatings in the prophylaxis of periprosthetic infections and fracture-related infections. However, their therapeutic use has been less investigated. The purpose of this article is to summarise recent evidence relating to the clinical application of antibacterial hydrogels and coatings in orthopaedic and traumatology surgery and indicating which future applications may benefit from it.

Biofilm and its implications postfracture fixation: All I need to know

Biofilm represents an organized multicellular community of bacteria having a complex 3D structure, formed by bacterial cells and their self-produced extracellular matrix. It usually attaches to any foreign body or fixation implant. It acts as a physical protective barrier of the bacteria from the penetration of antibodies, bacteriophages, granulocytes and biocides, antiseptics, and antibiotics. Biofilm-related infections will increase in the near future. This group of surgical site infections is the most difficult to diagnose, to suppress, to eradicate, and in general to manage. Multispecialty teams involved in all stages of care are an effective way to improve results and save resources and time for the benefit of patients and the health system. Significant steps have occurred recently in the prevention and development of clever tools that we can employ in this everlasting fight with the bacteria. Herein, we attempt to describe the nature and role of the "biofilm" to the specific clinical setting of surgical site infections in the field of orthopaedic trauma surgery.

Hyaluronan alkyl derivatives-based electrospun membranes for potential guided bone regeneration: Fabrication, characterization and in vitro osteoinductive properties

The aim of the work was to determine the effects of the chemical functionalization of hyaluronic acid (HA) with pendant aliphatic tails at different lengths and free amino groups in terms of chemical reactivity, degradation rate, drug-eluting features, and surface properties when processed as electrospun membranes (EM) evaluating the osteoinductive potential for a possible application as guided bone regeneration (GBR). To this end, a series of HA derivatives with different aliphatic tails (DD-Cx mol% ≈ 12.0 mol%) and decreasing derivatization of free amino groups (DD_EDA mol% from 70.0 to 30.0 mol%) were first synthesized, namely Hn. Then dexamethasone-loaded Hn EM, i.e. HnX were prepared from aqueous polymeric solutions with polyvinyl alcohol (PVA), as a non-ionogenic linear flexible polymeric carrier, and the multifunctional 2-hydroxypropyl- cyclodextrin (HPCD) which acted as a rheological modifier, a stabilizer of Taylor's cone, and a solubilizing agent. A comprehensive characterization of the membranes was carried out through ATR-IR, XRD, and WCA measurements. According to the in vitro hydrolytic and enzymatic degradation and drug release in different aqueous media for two months, the insertion of alkyl pendant grafts and the crosslinking process provided tuneable additional resistance to the whole membrane suitably for the final application of the membranes. Cell culture showed the cytocompatibility and cell proliferation until 7 days. Osteogenic differentiation and mineralization of pre-osteoblastic MC3T3 cells occurred for most of membranes after 35 days as valued by measuring ALP activity (50 nmol 4-np/h/nf DNA) and the deposition of calcium (120-140 μg ml^-1).

Stability Evaluation and Degradation Studies of DAC® Hyaluronic-Polylactide Based Hydrogel by DOSY NMR Spectroscopy

The stability and the degradation of polymers in physiological conditions are very important issues in biomedical applications. The copolymer of hyaluronic acid and poly-D,L-lactic acid (made available in a product called DAC®) produces a hydrogel which retains the hydrophobic character of the poly-D,L-lactide sidechains and the hydrophilic character of a hyaluronic acid backbone. This hydrogel is a suitable device for the coating of orthopedic implants with structured surfaces. In fact, this gel creates a temporary barrier to bacterial adhesion by inhibiting colonization, thus preventing the formation of the biofilm and the onset of an infection. Reabsorbed in about 72 h after the implant, this hydrogel does not hinder bone growth processes. In the need to assess stability and degradation of both the hyaluronan backbone and of the polylactic chains along time and temperature, we identified NMR spectroscopy as a privileged technique for the characterization of the released species, and we applied diffusion-ordered NMR spectroscopy (DOSY-NMR) for the investigation of molecular weight dispersion. Our diffusion studies of DAC® in physiological conditions provided a full understanding of the product degradation by overcoming the limitations observed in applying classical chromatography approaches by gel permeation UV.

A scope at antifouling strategies to prevent catheter-associated infections

The use of invasive medical devices is becoming more common nowadays, with catheters representing one of the most used medical devices. However, there is a risk of infection associated with the use of these devices, since they are made of materials that are prone to bacterial adhesion with biofilm formation, often requiring catheter removal as the only therapeutic option. Catheter-related urinary tract infections (CAUTIs) and central line-associated bloodstream infections (CLABSIs) are among the most common causes of healthcare-associated infections (HAIs) worldwide while endotracheal intubation is responsible for ventilator-associated pneumonia (VAP). Therefore, to avoid the use of biocides due to the potential risk of bacterial resistance development, antifouling strategies aiming at the prevention of bacterial adherence and colonization of catheter surfaces represent important alternative measures. This review is focused on the main strategies that are able to modify the physical or chemical properties of biomaterials, leading to the creation of antiadhesive surfaces. The most promising approaches include coating the surfaces with hydrophilic polymers, such as poly(ethylene glycol) (PEG), poly(acrylamide) and poly(acrylates), betaine-based zwitterionic polymers and amphiphilic polymers or the use of bulk-modified poly(urethanes). Natural polysaccharides and its modifications with heparin, have also been used to improve hemocompatibility. Recently developed bioinspired techniques yielding very promising results in the prevention of bacterial adhesion and colonization of surfaces include slippery liquid-infused porous surfaces (SLIPS) based on the superhydrophilic rim of the pitcher plant and the Sharklet topography inspired by the shark skin, which are potential candidates as surface-modifying approaches for biomedical devices. Concerning the potential application of most of these strategies in catheters, more in vivo studies and clinical trials are needed to assure their efficacy and safety for possible future use.

Defensive antibacterial coating in revision total hip arthroplasty: new concept and early experience

BACKGROUND

Infections remains the most feared complication in total hip arthroplasty (THA). New strategies of PJI prevention includes coating of conventional implants. Defensive Antibacterial Coating (DAC), an antibacterial hydrogel coating made of hyaluronan, poly-D and L-lactide can protect biomaterials as an effective barrier at the time of implantation. In addition, it can be used with topical antibiotics to prevent early colonisation of the implant.

SCOPE

This manuscript describes the detailed function of the DAC in general as well as an analysis of its use in revision THA in a series of 28 patients in a short-term follow-up.Its use in patients undergoing cementless re-implantation after 2-staged procedures in THA is described in detail within the manuscript.

CONCLUSION

DAC found to be effective in terms of infection control and safety in our patient cohort and has been expanded for cementless 1-staged revisions in PJI of the hip in our institution.

New gellan gum-graft-poly(d,l-lactide-co-glycolide) copolymers as promising bioinks: Synthesis and characterization

This research focused on the aim of tackling the urgent demand of printable biomaterials, hence we synthetized and characterized three gellan gum-graft-poly(d,l-lactide-co-glycolide) copolymers (GGm-PLGA a, b and c) which differed in the graft substitution degree. We investigated the effect of the polyester chain grafted onto hydrophilic backbone of gellan gum in terms of physicochemical properties and the ability of the system to print 3D cell laden constructs. In particular, we evaluated thermo-rheological, ionotropic crosslinking, shear thinning, swelling and stability properties of these copolymers and their derived biomaterials and findings related to the degree of functionalization. Moreover, the optimization of the 3D process parameters and the effect of different water/DPBS mixtures was investigated, demonstrating the feasibility of the system to print 3D constructs. Finally, biological tests revealed that fibroblasts and chondrocytes remained viable after printing and over a culture period of seven days into scaffolds.

Hyaluronic Acid and Controlled Release: A Review

Hyaluronic acid (HA) also known as hyaluronan, is a natural polysaccharide—an anionic, non-sulfated glycosaminoglycan—commonly found in our bodies. It occurs in the highest concentrations in the eyes and joints. Today HA is used during certain eye surgeries and in the treatment of dry eye disease. It is a remarkable natural lubricant that can be injected into the knee for patients with knee osteoarthritis. HA has also excellent gelling properties due to its capability to bind water very quickly. As such, it is one the most attractive controlled drug release matrices and as such, it is frequently used in various biomedical applications. Due to its reactivity, HA can be cross-linked or conjugated with assorted bio-macromolecules and it can effectively encapsulate several different types of drugs, even at nanoscale. Moreover, the physiological significance of the interactions between HA and its main membrane receptor, CD44 (a cell-surface glycoprotein that modulates cell–cell interactions, cell adhesion and migration), in pathological processes, e.g., cancer, is well recognized and this has resulted in an extensive amount of studies on cancer drug delivery and tumor targeting. HA acts as a therapeutic but also as a tunable matrix for drug release. Thus, this review focuses on controlled or sustained drug release systems assembled from HA and its derivatives. More specifically, recent advances in controlled release of proteins, antiseptics, antibiotics and cancer targeting drugs from HA and its derivatives were reviewed. It was shown that controlled release from HA has many benefits such as optimum drug concentration maintenance, enhanced therapeutic effects, improved efficiency of treatment with less drug, very low or insignificant toxicity and prolonged in vivo release rates.

Polyanionic Hydrogels as Reservoirs for Polycationic Antibiotic Substitutes Providing Prolonged Antibacterial Activity

Implantation of biomedical devices is often followed by bacterial infections that may seriously affect implant functionalities and lead to their failure. In the context of bacterial resistance to antibiotics, which is a growing problem worldwide, new strategies that are able to overcome these problems are needed. In this work, we introduce a new formulation of hyaluronic acid (HA)-based antimicrobial material: HA hydrogels loaded with polyarginine (PAR), a polycationic antibiotic substitute. The loading is possible through electrostatic interactions between negatively charged HA and positively charged PAR. Such hydrogels absorb high quantities of PAR, which are then gradually released from the hydrogel. This original system provides a long-lasting antibacterial effect on an in vitro model of repetitive infection, thus demonstrating a strong potential to fight multiple rounds of infections that are resistant to antibiotic treatment. In addition, HA-PAR hydrogels could be deposited onto/into medical devices such as wound dressings and mesh prostheses used in clinical applications. Finally, we performed first in vivo tests of hydrogel-coated mesh materials to verify their biocompatibility in a rat model, which show no difference between control HA hydrogel and PAR-loaded hydrogel in terms of inflammation.

Antibiotic-Loaded Hydrogel Coating to Reduce Early Postsurgical Infections in Aseptic Hip Revision Surgery: A Retrospective, Matched Case-Control Study

Periprosthetic joint infections (PJIs) are a cause of frequent implant failure in revision hip replacement surgery. The purpose of this study is to evaluate the onset of early postoperative infections in patients who underwent hip surgery with cementless prostheses treated with an antibiotic loaded hydrogel on their surface, in addition to systemic prophylaxis, and compare them to a control group. The secondary objective was to evaluate the onset of any local and systemic adverse effects and interference with bone ingrowth processes and functional recovery. A retrospective observational study was conducted on patients who underwent revision hip surgery by performing a 1:1 match between patients treated with an antibiotic hydrogel (ALH) and the control patients. The incidence of PJIs was assessed with a minimum of six months follow-up. Seventeen patients treated with the ALH were compared with 17 patients from the control group. No PJIs were reported in the ALH group versus the six cases encountered in the control group (p < 0.0001). No significant differences were reported with regard to prosthetic osseointegration and functional results, nor were there side effects in the ALH group. Despite the low sample size, the use of on-site prophylaxis with ALH has proven effective and safe in reducing the risk of PJIs in patients with a high risk for infections. Further studies are needed to validate these results in other implant-related surgeries.

The application of hyaluronic acid in bone regeneration

Hyaluronic acid (HA) exists naturally as an important component of the extracellular matrix (ECM) in the human body. In recent decades, HA has been widely used in bone regeneration, and is currently a popular topic, particularly in the craniofacial and dental fields. From maxilla augmentation to craniofacial bone trauma, there is now a large demand for bone regenerative therapy. Serving as a cell-seeding scaffold or a carrier for bioactive components, hyaluronic acid-incorporated scaffolds and carriers in bone regeneration can be fabricated into either rigid or colloidal forms. Since the type of material used is a critical factor in the biological properties of a scaffold, HA derivatives or HA-incorporated composite scaffolds have shown excellent potential for improving osteogenesis and mineralization. Furthermore, in order to better enhance osteogenesis, local delivery carriers based on hyaluronic acid derivatives, rather than specifically serving as scaffolds, can be established by loading different osteoinductive or osteogenetic components and acquiring different release patterns. Such osteoinductive carriers immobilized on implant surfaces are also effective in improving osseointegration. Thus, as such a competent biomaterial, hyaluronic acid should be considered a promising tool in bone regeneration.

Implant materials and prosthetic joint infection: the battle with the biofilm

Prosthetic joint infection (PJI) is associated with poor clinical outcomes and is expensive to treat.Although uncommon overall (affecting between 0.5% and 2.2% of cases), PJI is one of the most commonly encountered complications of joint replacement and its incidence is increasing, putting a significant burden on healthcare systems.Once established, PJI is extremely difficult to eradicate as bacteria exist in biofilms which protect them from antibiotics and the host immune response.Improved understanding of the microbial pathology in PJI has generated potential new treatment strategies for prevention and eradication of biofilm associated infection including modification of implant surfaces to prevent adhesion of bacteria.Much research is currently ongoing looking at different implant surface coatings and modifications, and although most of this work has not translated into clinical medicine there has been some early clinical success. Cite this article: EFORT Open Rev 2019;4:633-639. DOI: 10.1302/2058-5241.4.180095.

Vancomycin-loaded oxidized hyaluronic acid and adipic acid dihydrazide hydrogel: Bio-compatibility, drug release, antimicrobial activity, and biofilm model

BACKGROUND

Prosthesis infection is a difficult-to-treat situation. Hydrogel is a novel biomaterial, which can be applied by simply spraying or by coating on implants before surgery and can be easily mixed with antibiotics.

METHODS

In order to evaluate the potential use of antibiotic-loaded hydrogel, we incorporated vancomycin into oxidized hyaluronic acid (HA) and adipic acid dihydrazide and evaluated the drug release and antimicrobial activity against methicillin-resistant Staphylococcus aureus (ATCC 29213).

RESULTS

The average release percentage of vancomycin on day 3 was about 86%. The antibiotic-loaded gel was biocompatible with mesenchymal stem cell, MC3T3, and L929 cell lines. The in vitro inhibition zones of vancomycin-loaded hydrogel [500X minimal inhibition concentration (MIC), 50X MIC, 10X MIC, and blank hydrogel] were 21, 13, 9, and 5 mm, respectively. In the Ti6Al4V implant biofilm model, 0.01-1% vancomycin-loaded gel exhibited significant anti-biofilm activity, measured by the MTT assay.

CONCLUSIONS

Vancomycin could be loaded onto oxidized HA and adipic acid dihydrazide, which exhibited excellent drug release and in vitro antimicrobial activity with minimal cell toxicity.

Two-stage cementless hip revision for peri-prosthetic infection with an antibacterial hydrogel coating: results of a comparative series

PURPOSE

The aim of this study was to investigate the hypothesis that a two-stage exchange procedure, performed with an antibiotic-loaded, fast-resorbable hydrogel coating, may provide better infection cure rate than a two-stage procedure without the coating, in patients affected by peri-prosthetic hip infection.

METHODS

In this case-control study, 27 patients, treated with a two-stage procedure, using cementless implants coated with an antibiotic-loaded hydrogel (DAC®, "Defensive Antibacterial Coating"), were compared with 27 matched controls, treated with a two-stage cementless revision procedure, without the coating.

RESULTS

At a mean follow-up of 2.7 (minimum 2.1-maximum 3.5) years, no evidence of infection, implant loosening, or adverse events were observed in the DAC-treated group, compared to four cases of infection recurrence in the control group.

CONCLUSIONS

Although in a relatively limited series of patients our data show that cementless two-stage hip revision, performed with an antibacterial hydrogel coating, may provide better infection control than two-stage without the coating, with reduced hospitalization time, these findings warrant further studies in the possible applications of antibacterial coating technologies to treat implant-related infections.

Engineering Adhesive and Antimicrobial Hyaluronic Acid/Elastin-like Polypeptide Hybrid Hydrogels for Tissue Engineering Applications

Hydrogel-based biomaterials have been widely used for tissue engineering applications because of their high water content, swellability, and permeability, which facilitate transport and diffusion of essential nutrients, oxygen, and waste across the scaffold. These characteristics make hydrogels suitable for encapsulating cells and creating a cell supportive environment that promotes tissue regeneration when implanted in vivo. This is particularly important in the context of tissues whose intrinsic regenerative capacity is limited, such as cartilage. However, the clinical translation of hydrogels has been limited by their poor mechanical performance, low adhesive strength, uncontrolled degradation rates, and their susceptibility to bacterial colonization. Here, we introduce an elastic, antimicrobial, and adhesive hydrogel comprised of methacrylated hyaluronic acid (MeHA) and an elastin-like polypeptide (ELP), which can be rapidly photo-cross-linked in situ for the regeneration and repair of different tissues. Hybrid hydrogels with a wide range of physical properties were engineered by varying the concentrations of MeHA and ELP. In addition, standard adhesion tests demonstrated that the MeHA/ELP hydrogels exhibited higher adhesive strength to the tissue than commercially available tissue adhesives. MeHA/ELP hydrogels were then rendered antimicrobial through the incorporation of zinc oxide (ZnO) nanoparticles, and were shown to significantly inhibit the growth of methicillin-resistant Staphylococcus aureus (MRSA), as compared to controls. Furthermore, the composite adhesive hydrogels supported in vitro mammalian cellular growth, spreading, and proliferation. In addition, in vivo subcutaneous implantation demonstrated that MeHA/ELP hydrogels did not elicit any significant inflammatory response, and could be efficiently biodegraded while promoting the integration of new autologous tissue. In summary, we demonstrated for the first time that MeHA/ELP-ZnO hydrogel can be used as an adhesive and antimicrobial biomaterial for tissue engineering applications, because of its highly tunable physical characteristics, as well as remarkable adhesive and antimicrobial properties.

Hydrogels based on poly(methyl vinyl ether-co-maleic acid) and Tween 85 for sustained delivery of hydrophobic drugs

Hydrogels based on poly(methyl vinyl ether-co-maleic acid) and Tween 85 were prepared for hydrophobic drug delivery. The hydrogels were synthesized following a simple procedure carried out in solid state. The process did not require the use of any solvent and, as it is based on an esterification reaction, no toxic by-products were obtained. The resulting hydrogels contained Tween 85 inside the structure and due to the amphiphilic nature of this compound, hydrophobic domains within the hydrogel structure were formed. The obtained hydrogels showed good swelling capacities ranging from 100% to 600%. The esterification reaction that took place between poly(methyl vinyl ether-co-maleic acid) and Tween 85 was confirmed by infrared spectroscopy. Hydrogels were loaded with a hydrophobic drug model, Curcumin (CUR), showing that the hydrogels were able to retain up to 36 mg of CUR per g of hydrogel. Additionally, the synthesized hydrogels provided in vitro sustained CUR release over periods of up to 30 days. Finally, and due to the mucoadhesive nature of the prepared materials, one of the hydrogels was tested in vitro as an oral drug delivery system. For this purpose, the selected material was milled into microparticles (45-90 µm diameter). The release of CUR from the microparticles was evaluated under simulated gastric and intestinal conditions. The microparticles were able to release their cargos in 7 h. However, further work is required to optimize this system for oral drug delivery applications.

Multifibrillar bundles of a self-assembling hyaluronic acid derivative obtained through a microfluidic technique for aortic smooth muscle cell orientation and differentiation

A hyaluronic acid derivative able to physically crosslink in a saline aqueous medium was employed for the production of fibers with a mean diameter of 50 μm using a microfluidic technique.

A mineral layer as an effective binder to achieve strong bonding between a hydrogel and a solid titanium substrate

This study has developed an effective strategy to bind a hydrogel with solid titanium by forming a CaCO₃ layer at their interface.

Sterilization of hydrogels for biomedical applications: A review

Despite the beneficial properties and outstanding potential of hydrogels for biomedical applications, several unmet challenges must be overcome, especially regarding to their known sensitivity to conventional sterilization methods. It is crucial for any biomaterial to withstand an efficient sterilization to obtain approval from regulatory organizations and to safely proceed to clinical trials. Sterility assurance minimizes the incidence of medical device-related infections, which still constitute a major concern in health care. In this review, we provide a detailed and comprehensive description of the published work from the past decade regarding the effects of sterilization on different types of hydrogels for biomedical applications. Advances in hydrogel production methods with simultaneous sterilization are also reported. Terminal sterilization methods can induce negative or positive effects on several material properties (e.g., aspect, size, color, chemical structure, mechanical integrity, and biocompatibility). Due to the complexity of factors involved (e.g., material properties, drug stability, sterilization conditions, and parameters), it is important to note the virtual impossibility of predicting the outcome of sterilization methods to determine a set of universal rules. Each system requires case-by-case testing to select the most suitable, effective method that allows for the main properties to remain unaltered. The impact of sterilization methods on the intrinsic properties of these systems is understudied, and further research is needed. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2472-2492, 2018.

Fast-resorbable antibiotic-loaded hydrogel coating to reduce post-surgical infection after internal osteosynthesis: a multicenter randomized controlled trial

BACKGROUND

Infection is one of the main reasons for failure of orthopedic implants. Antibacterial coatings may prevent bacterial adhesion and biofilm formation, according to various preclinical studies. The aim of the present study is to report the first clinical trial on an antibiotic-loaded fast-resorbable hydrogel coating (Defensive Antibacterial Coating, DAC®) to prevent surgical site infection, in patients undergoing internal osteosynthesis for closed fractures.

MATERIALS AND METHODS

In this multicenter randomized controlled prospective study, a total of 256 patients in five European orthopedic centers who were scheduled to receive osteosynthesis for a closed fracture, were randomly assigned to receive antibiotic-loaded DAC or to a control group (without coating). Pre- and postoperative assessment of laboratory tests, wound healing, clinical scores and X-rays were performed at fixed time intervals.

RESULTS

Overall, 253 patients were available with a mean follow-up of 18.1 ± 4.5 months (range 12-30). On average, wound healing, clinical scores, laboratory tests and radiographic findings did not show any significant difference between the two groups. Six surgical site infections (4.6%) were observed in the control group compared to none in the treated group (P < 0.03). No local or systemic side-effects related to the DAC hydrogel product were observed and no detectable interference with bone healing was noted.

CONCLUSIONS

The use of a fast-resorbable antibiotic-loaded hydrogel implant coating provides a reduced rate of post-surgical site infections after internal osteosynthesis for closed fractures, without any detectable adverse event or side-effects.

LEVEL OF EVIDENCE

2.

Hyaluronic Acid and Its Composites as a Local Antimicrobial/Antiadhesive Barrier

Living in biofilms is probably the most common condition for bacteria and fungi and biofilm-related infections account for the majority of bacterial infectious diseases worldwide. Among others biofilm-related infections, those associated with implanted biomaterials have an enormous and still largely underestimated impact in orthopaedics and trauma, cardio-surgery and several other surgical disciplines. Given the limited efficacy of existing antibiotics in the prevention and treatment of bacterial biofilms, new strategies are needed to protect implants and host tissues, overcoming the striking ability of the microorganisms to adhere on different surfaces and to immediately protect themselves by forming the biofilm matrix. Adhesion is a necessary first step in microbial colonization and pathogenesis and provides a potential target for new preventive and treatment approach. Among various polymers, tested as antibacterial coatings, hyaluronic acid and some of its composites do offer a well-established long-term safety profile and a proven ability to reduce bacterial adhesion and biofilm formation. Aim of the present review is to summarize the available evidence concerning the antiadhesion/antibiofilm activity of hyaluronic acid and some of its derivatives to reduce/prevent bacterial adhesion and biofilm formation in various experimental and clinical settings.

Hyaluronic acid and its derivatives in drug delivery and imaging: Recent advances and challenges

Hyaluronic acid (HA) is a biodegradable, biocompatible, nontoxic, and non-immunogenic glycosaminoglycan used for various biomedical applications. The interaction of HA with the CD44 receptor, whose expression is elevated on the surface of many types of tumor cells, makes this polymer a promising candidate for intracellular delivery of imaging and anticancer agents exploiting a receptor-mediated active targeting strategy. Therefore, HA and its derivatives have been most investigated for the development of several carrier systems intended for cancer diagnosis and therapy. Nonetheless, different and important delivery applications of the polysaccharide have also been described, including gene and peptide/protein drugs delivery. The aim of this review was to provide an overview of the existing recent literature on the use of HA and its derivatives for drug delivery and imaging. Notable attention is given to nanotheranostic systems obtained after conjugation of HA to nanocarriers as quantum dots, carbon nanotubes and graphene. Meanwhile, attention is also paid to some challenging aspects that need to be addressed in order to allow translation of preclinical models based on HA and its derivatives for drug delivery and imaging purposes to clinical testing and further their development.

Does an Antibiotic-Loaded Hydrogel Coating Reduce Early Post-Surgical Infection After Joint Arthroplasty?

Background: Infection remains among the main reasons for joint prosthesis failure. Preclinical reports have suggested that antibacterial coatings of implants may prevent bacterial adhesion and biofilm formation. This study presents the results of the first clinical trial on an antibiotic-loaded fast-resorbable hydrogel coating (Defensive Antibacterial Coating, DAC^®) in patients undergoing hip or knee prosthesis. Methods: In this multicenter, randomized prospective study, a total of 380 patients, scheduled to undergo primary (n=270) or revision (n=110) total hip (N=298) or knee (N=82) joint replacement with a cementless or a hybrid implant, were randomly assigned, in six European orthopedic centers, to receive an implant either with the antibiotic-loaded DAC coating (treatment group) or without coating (control group). Pre- and postoperative assessment of clinical scores, wound healing, laboratory tests, and x-ray exams were performed at fixed time intervals. Results: Overall, 373 patients were available at a mean follow-up of 14.5 ± 5.5 months (range 6 to 24). On average, wound healing, laboratory and radiographic findings showed no significant difference between the two groups. Eleven early surgical site infections were observed in the control group and only one in the treatment group (6% vs. 0.6%; p=0.003). No local or systemic side effects related to the DAC hydrogel coating were observed, and no detectable interference with implant osteointegration was noted. Conclusions: The use of a fast-resorbable, antibiotic-loaded hydrogel implant coating can reduce the rate of early surgical site infections, without any detectable adverse events or side effects after hip or knee joint replacement with a cementless or hybrid implant.

Polysaccharide-based antibiofilm surfaces

Surface treatment by natural or modified polysaccharide polymers is a promising means to fight against implant-associated biofilm infections. The present review focuses on polysaccharide-based coatings that have been proposed over the last ten years to impede biofilm formation on material surfaces exposed to bacterial contamination. Anti-adhesive and bactericidal coatings are considered. Besides classical hydrophilic coatings based on hyaluronic acid and heparin, the promising anti-adhesive properties of the algal polysaccharide ulvan are underlined. Surface functionalization by antimicrobial chitosan and derivatives is extensively surveyed, in particular chitosan association with other polysaccharides in layer-by-layer assemblies to form both anti-adhesive and bactericidal coatings.

STATEMENT OF SIGNIFICANCE

Bacterial contamination of surfaces, leading to biofilm formation, is a major problem in fields as diverse as medicine, first, but also food and cosmetics. Many prophylactic strategies have emerged to try to eliminate or reduce bacterial adhesion and biofilm formation on surfaces of materials exposed to bacterial contamination, in particular implant materials. Polysaccharides are widely distributed in nature. A number of these natural polymers display antibiofilm properties. Hence, surface treatment by natural or modified polysaccharides is a promising means to fight against implant-associated biofilm infections. The present manuscript is an in-depth look at polysaccharide-based antibiofilm surfaces that have been proposed over the last ten years. This review, which is a novelty compared to published literature, will bring well documented and updated information to readers of Acta Biomaterialia.

Antibacterial coating of implants in orthopaedics and trauma: a classification proposal in an evolving panorama

Implanted biomaterials play a key role in current success of orthopedic and trauma surgery. However, implant-related infections remain among the leading reasons for failure with high economical and social associated costs. According to the current knowledge, probably the most critical pathogenic event in the development of implant-related infection is biofilm formation, which starts immediately after bacterial adhesion on an implant and effectively protects the microorganisms from the immune system and systemic antibiotics. A rationale, modern prevention of biomaterial-associated infections should then specifically focus on inhibition of both bacterial adhesion and biofilm formation. Nonetheless, currently available prophylactic measures, although partially effective in reducing surgical site infections, are not based on the pathogenesis of biofilm-related infections and unacceptable high rates of septic complications, especially in high-risk patients and procedures, are still reported.In the last decade, several studies have investigated the ability of implant surface modifications to minimize bacterial adhesion, inhibit biofilm formation, and provide effective bacterial killing to protect implanted biomaterials, even if there still is a great discrepancy between proposed and clinically implemented strategies and a lack of a common language to evaluate them.To move a step forward towards a more systematic approach in this promising but complicated field, here we provide a detailed overview and an original classification of the various technologies under study or already in the market. We may distinguish the following: 1. Passive surface finishing/modification (PSM): passive coatings that do not release bactericidal agents to the surrounding tissues, but are aimed at preventing or reducing bacterial adhesion through surface chemistry and/or structure modifications; 2. Active surface finishing/modification (ASM): active coatings that feature pharmacologically active pre-incorporated bactericidal agents; and 3. Local carriers or coatings (LCC): local antibacterial carriers or coatings, biodegradable or not, applied at the time of the surgical procedure, immediately prior or at the same time of the implant and around it. Classifying different technologies may be useful in order to better compare different solutions, to improve the design of validation tests and, hopefully, to improve and speed up the regulatory process in this rapidly evolving field.

Does implant coating with antibacterial-loaded hydrogel reduce bacterial colonization and biofilm formation in vitro?

BACKGROUND

Implant-related infections represent one of the most severe complications in orthopaedics. A fast-resorbable, antibacterial-loaded hydrogel may reduce or prevent bacterial colonization and biofilm formation of implanted biomaterials.

QUESTIONS/PURPOSES

We asked: (1) Is a fast-resorbable hydrogel able to deliver antibacterial compounds in vitro? (2) Can a hydrogel (alone or antibacterial-loaded) coating on implants reduce bacterial colonization? And (3) is intraoperative coating feasible and resistant to press-fit implant insertion?

METHODS

We tested the ability of Disposable Antibacterial Coating (DAC) hydrogel (Novagenit Srl, Mezzolombardo, Italy) to deliver antibacterial agents using spectrophotometry and a microbiologic assay. Antibacterial and antibiofilm activity were determined by broth microdilution and a crystal violet assay, respectively. Coating resistance to press-fit insertion was tested in rabbit tibias and human femurs.

RESULTS

Complete release of all tested antibacterial compounds was observed in less than 96 hours. Bactericidal and antibiofilm effect of DAC hydrogel in combination with various antibacterials was shown in vitro. Approximately 80% of the hydrogel coating was retrieved on the implant after press-fit insertion.

CONCLUSIONS

Implant coating with an antibacterial-loaded hydrogel reduces bacterial colonization and biofilm formation in vitro.

CLINICAL RELEVANCE

A fast-resorbable, antibacterial-loaded hydrogel coating may help prevent implant-related infections in orthopaedics. However, further validation in animal models and properly controlled human studies is required.

Coatings and surface modifications imparting antimicrobial activity to orthopedic implants

Bacterial colonization and biofilm formation on an orthopedic implant surface is one of the worst possible outcomes of orthopedic intervention in terms of both patient prognosis and healthcare costs. Making the problem even more vexing is the fact that infections are often caused by events beyond the control of the operating surgeon and may manifest weeks to months after the initial surgery. Herein, we review the costs and consequences of implant infection as well as the methods of prevention and management. In particular, we focus on coatings and other forms of implant surface modification in a manner that imparts some antimicrobial benefit to the implant device. Such coatings can be classified generally based on their mode of action: surface adhesion prevention, bactericidal, antimicrobial-eluting, osseointegration promotion, and combinations of the above. Despite several advances in the efficacy of these antimicrobial methods, a remaining major challenge is ensuring retention of the antimicrobial activity over a period of months to years postoperation, an issue that has so far been inadequately addressed. Finally, we provide an overview of additional figures of merit that will determine whether a given antimicrobial surface modification warrants adoption for clinical use.

Grafting of cross-linked hydrogel networks to titanium surfaces

The performance of medical implants and devices is dependent on the biocompatibility of the interfacial region between tissue and the implant material. Polymeric hydrogels are attractive materials for use as biocompatible surface coatings for metal implants. In such systems, a factor that is critically important for the longevity of an implant is the formation of a robust bond between the hydrogel layer and the implant metal surface and the ability for this assembly to withstand physiological conditions. Here, we describe the grafting of cross-linked hydrogel networks to titanium surfaces using grit-blasting and subsequent chemical functionalization using a silane-based adhesion promoter. Metal surface characterization was carried out using profilometry, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) analysis. Hydrogel layers composed of poly(ethylene glycol)-dimethacrylate (PEG-DMA), poly(2-hydroxyethylmethacrylate) (PHEMA), or poly(ethylene glycol)/poly(acrylic acid) (PEG/PAA) semi-interpenetrating polymer networks (semi-IPNs) have been prepared. The mechanical properties of these hydrogel-metal assemblies have been characterized using lap-shear measurements, and the surface morphology was studied by SEM and EDX. We have shown that both high surface roughness and chemical functionalization are critical for adhesion of the hydrogel layer to the titanium substrate.

Beneficial effects of hyaluronic acid

Biomaterials are playing a vital role in our day-to-day life. Hyaluronan (hyaluronic acid), a biomaterial, receives special attention among them. Hyaluronic acid (HA) is a polyanionic natural polymer occurring as linear polysaccharide composed of glucuronic acid and N-acetylglucosamine repeats via a β-1,4 linkage. It is the most versatile macromolecule present in the connective tissues of all vertebrates. Hyaluronic acid has a wide range of applications with its excellent physicochemical properties such as biodegradability, biocompatibility, nontoxicity, and nonimmunogenicity and serves as an excellent tool in biomedical applications such as osteoarthritis surgery, ocular surgery, plastic surgery, tissue engineering, and drug delivery. It plays a key role in cushioning and lubricating the body and is abundant in the eyes, joints, and heart valves. A powerful antioxidant, hyaluronic acid is perhaps best known for its ability to bond water to tissue. Hyaluronan production increases in proliferating cells, and the polymer may play a role in mitosis. This chapter gives an overview of hyaluronic acid and its physicochemical properties and applications. This chapter gives a deep understanding on the special benefits of hyaluronic acid in the fields of pharmaceutical, medical, and environmental applications. Hyaluronic acid paves the way for beneficial research and applications to the welfare of life forms.