Days In Phosphate-buffered Saline Research Articles

Sustained release of dipyridamole from collagen membranes

Commercial collagen membranes that are used as bioresorbable barrier membranes in guided bone regeneration do not contain active ingredients to promote bone regeneration. The emerging efforts to repurpose old drugs produced mounting scientific evidence that dipyridamole (DIPY), which inhibits platelet aggregation and serves as a coronary artery vasodilator, also exhibits therapeutic effects to promote bone healing/regeneration. The therapeutic effect of DIPY on bone healing/regeneration occurs via G-protein coupled adenosine (P1) receptors of the purinergic family. In this study, we investigated the feasibility of synthesizing collagen membranes for sustained release of DIPY, with the ultimate purpose of using them as tools to promote bone regeneration. The synthesized membranes were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and a universal mechanical testing machine. We conducted an in vitro release experiment to evaluate the release kinetics of DIPY from these membranes. The chemical and physical characterization confirmed the successful synthesis of DIPY-containing collagen membranes, namely DCM-1 and DCM-2. Both membranes had weaker tensile strength than other commercial collagen membranes, although both supported continuous release of DIPY. The in vitro release of DIPY from DCM-1 continued for at least 30 days in phosphate buffer saline (pH 7.4) at 37 °C, while DCM-2 achieved sustained release of DIPY for more than 10 weeks. These results warrant the further evaluation of DIPY-containing collagen membranes for their potential applications in guided bone regeneration after optimization of their mechanical strength.

Development of photoreactive demineralized bone matrix 3D printing colloidal inks for bone tissue engineering.

Demineralized bone matrix (DBM) has been widely used clinically for dental, craniofacial and skeletal bone repair, as an osteoinductive and osteoconductive material. 3D printing (3DP) enables the creation of bone tissue engineering scaffolds with complex geometries and porosity. Photoreactive methacryloylated gelatin nanoparticles (GNP-MAs) 3DP inks have been developed, which display gel-like behavior for high print fidelity and are capable of post-printing photocrosslinking for control of scaffold swelling and degradation. Here, novel DBM nanoparticles (DBM-NPs, ∼400 nm) were fabricated and characterized prior to incorporation in 3DP inks. The objectives of this study were to determine how these DBM-NPs would influence the printability of composite colloidal 3DP inks, assess the impact of ultraviolet (UV) crosslinking on 3DP scaffold swelling and degradation and evaluate the osteogenic potential of DBM-NP-containing composite colloidal scaffolds. The addition of methacryloylated DBM-NPs (DBM-NP-MAs) to composite colloidal inks (100:0, 95:5 and 75:25 GNP-MA:DBM-NP-MA) did not significantly impact the rheological properties associated with printability, such as viscosity and shear recovery or photocrosslinking. UV crosslinking with a UV dosage of 3 J/cm2 directly impacted the rate of 3DP scaffold swelling for all GNP-MA:DBM-NP-MA ratios with an ∼40% greater increase in scaffold area and pore area in uncrosslinked versus photocrosslinked scaffolds over 21 days in phosphate-buffered saline (PBS). Likewise, degradation (hydrolytic and enzymatic) over 21 days for all DBM-NP-MA content groups was significantly decreased, ∼45% less in PBS and collagenase-containing PBS, in UV-crosslinked versus uncrosslinked groups. The incorporation of DBM-NP-MAs into scaffolds decreased mass loss compared to GNP-MA-only scaffolds during collagenase degradation. An in vitro osteogenic study with bone marrow-derived mesenchymal stem cells demonstrated osteoconductive properties of 3DP scaffolds for the DBM-NP-MA contents examined. The creation of photoreactive DBM-NP-MAs and their application in 3DP provide a platform for the development of ECM-derived colloidal materials and tailored control of biochemical cue presentation with broad tissue engineering applications.

Phosphoric Acid Triester Micelles: Characterization and Self-Assembly.

In this study, we analyzed the properties of amphiphilic alkyldi(methoxy poly(ethylene glycol) (MePEG)350-lactate) phosphates based on ethyl lactate, the monomethyl ether of poly(ethylene glycol)350, and alkyldichloro phosphates. Interestingly, these triesters combine two biodegradable bonds, -P(O)-O-C and -C(O)-O-C-, and include hydrophilic (MePEG350-lactate) and hydrophobic (R-aliphatic chain of alcohols) moieties. The properties of these esters resemble those of phospholipids. After being placed in an aqueous solution, they self-assembled. We also determined the effects of ester composition on micelle formation, stability, and size using dynamic light scattering. Solubilization tests using Sudan III or doxorubicin hydrochloride (Dox·HCl) revealed that they could be incorporated into the hydrophobic cores of dodecyl di(MePEG350-lactate) phosphate and hexadecyl di(MePEG350-lactate) phosphate. Notably, dodecyl di(MePEG350-lactate) phosphate was stable for five days, whereas hexadecyl di(MePEG350- lactate) phosphate was stable for seven days in phosphate-buffered saline. Moreover, Dox·HCl release rates from the micelles were approximately 30-40, 70-80, and 90-100% after 1, 5, and 28 d, respectively.

Influence of Acidic Environmental Conditions on Push-Out Bonding Strength of Four Calcium Silicate-Based Materials to Root Dentin.

Introduction Calcium silicate-based cements (CSCs) are frequently used in various endodontic procedures such as perforation repair, vital pulp therapy, regenerative treatments, or apexification. One of their areas of use, treatment of perforations, can be challenging in clinical practice. Selection of stable, durable, and compatible material with structural and biological alterations is a must in such situations. Aim This study aimed to compare the dislocation resistance of various calcium-silicate-containing materials used in endodontic treatment exposed to various environmental conditions in a push-out study model. Methods Selected ninety-six human mandibular premolars with single root canals were cut from the middle portion to obtain dentin slices of 2 mm thickness (n = 192). Then, the canal lumen was enlarged by using #4Gates-Glidden drills. Specimens for each repair material (MTA, Angelus, Endosequence RRM (ERRM), Biodentine, BioMTA) were placed in shaped lumens, wrapped in pieces of gauze, and randomly divided into four groups (n = 48) according to the storage time and media: group A: 4 days in phosphate-buffered saline (PBS), group B: 4 days in acetic acid (pH = 4.4), group C: 34 days in PBS, and group D: 4 days in acetic acid (pH = 4.4) followed by exposure to PBS for 30 days. A universal testing machine measured the dislodgement resistance followed by scanning electron microscopy imaging to evaluate the material-dentin interface. Results ERRM showed the highest dislocation resistance in all test groups (p < 0.05). The greatest bonding strength was observed (13,54 ± 5,56 MPa) after exposure to 34 days in PBS (pH = 7.2). The values for ERRM decreased in contact with acetic acid (pH = 4.4) and increased when placed in PBS (p > 0.05). Conclusion All repair materials showed a higher dislocation resistance when stored in PBS regardless of storage time. However, the improved pH of the surrounding media was not successful in reversing the deteriorating effect caused by lower pH in relation to dislocation resistance in all tested materials except for ERRM.

Autonomous Chemistry Enabling Environment-Adaptive Electrochemical Energy Storage Devices

Autonomous Chemistry Enabling Environment-Adaptive Electrochemical Energy Storage Devices

Sustained and Long-Term Release of Doxorubicin from PLGA Nanoparticles for Eliciting Anti-Tumor Immune Responses.

Immunogenic cell death (ICD) is a powerful trigger eliciting strong immune responses against tumors. However, traditional chemoimmunotherapy (CIT) does not last long enough to induce sufficient ICD, and also does not guarantee the safety of chemotherapeutics. To overcome the disadvantages of the conventional approach, we used doxorubicin (DOX) as an ICD inducer, and poly(lactic-co-glycolic acid) (PLGA)-based nanomedicine platform for controlled release of DOX. The diameter of 138.7 nm of DOX-loaded PLGA nanoparticles (DP-NPs) were stable for 14 days in phosphate-buffered saline (PBS, pH 7.4) at 37 °C. Furthermore, DOX was continuously released for 14 days, successfully inducing ICD and reducing cell viability in vitro. Directly injected DP-NPs enabled the remaining of DOX in the tumor site for 14 days. In addition, repeated local treatment of DP-NPs actually lasted long enough to maintain the enhanced antitumor immunity, leading to increased tumor growth inhibition with minimal toxicities. Notably, DP-NPs treated tumor tissues showed significantly increased maturated dendritic cells (DCs) and cytotoxic T lymphocytes (CTLs) population, showing enhanced antitumor immune responses. Finally, the therapeutic efficacy of DP-NPs was maximized in combination with an anti-programmed death-ligand 1 (PD-L1) antibody (Ab). Therefore, we expect therapeutic efficacies of cancer CIT can be maximized by the combination of DP-NPs with immune checkpoint blockade (ICB) by achieving proper therapeutic window and continuously inducing ICD, with minimal toxicities.

Application of nondestructive mechanical characterization testing for creating in vitro vessel models with material properties similar to human neurovasculature.

Vessel models are a first step in developing endovascular medical devices. However, these models, often made from glass or silicone, do not accurately represent the mechanical properties of human vascular tissue, limiting their use to basic training and proof-of-concept testing. This study outlines methods to quantify human vascular tissue mechanical properties and synthetic biomaterials for creating representative vessel models. Human vascular tissue was assessed and compared to silicone and new UV-cured polymers (VC-A30) using the following eight mechanical tests: compressive, shear, tensile dynamic elastic modulus, Poisson's ratio, hardness, radial force, compliance, and lubricity. Half of these testing methods were nondestructive, allowing for multiple mechanical and histological characterizations of the same human tissue sample. Histological evaluation of the cellular and extracellular matrix of the human vessels verified that the dynamic moduli and Poison's ratio tests were nondestructive. Fluid absorption by VC-A30 showed statistically significant softening of mechanical properties, stabilizing after 4 days in phosphate-buffered saline (PBS). Human vasculature exhibited notably similar results to VC-A30 in five of eight mechanical tests (≤30% difference) versus two of eight for standard silicone (≤38% difference). Results show that VC-A30 provides a new option for 3D-printing translucent in vitro vascular models with anatomically relevant mechanical properties. These new vessel analogs may simulate patient-specific vessel disease states, improve surgical training models, accelerate new endovascular device developments, and ultimately reduce the need for animal models.

Development of Metronidazole-loaded In situ Thermosensitive Hydrogel for Periodontitis Treatment

Periodontal treatment focuses on the thorough removal of specific periodontal pathogens, mainly anaerobic Gram-negative bacteria, by mechanical scaling and root planning. In case the periodontal abscess is detected after treatment, a high dose of antimicrobial agents is commonly applied via oral administration. However, this approach increases the risk of antibiotic resistance and systemic side effects and decreases efficacy. To overcome the aforementioned issues, this study focused on the development of thermosensitive hydrogel to deliver the antibiotic drug metronidazole (MTZ) directly and locally to the oral infection site. The thermosensitive hydrogels were prepared by blending 28% w/v Pluronic F127 with various concentrations of methylcellulose (MC) and silk fibroin (SF). The gel properties, such as sol-gel transition time, viscosity, and gel strength, were investigated. The drug dissolution profiles, together with their theoretical models and gel dissolution characteristics, were also determined. All hydrogel formulations exhibited sol-gel transitions at 37°C within 1 min. An increase in MC content proportionally increased the viscosity but decreased the gel strength of the hydrogel. By contrast, the SF content did not significantly affect the viscosity but increased the gel strength of the hydrogel. The thermosensitive hydrogels also showed prolonged MTZ release characteristics for 10 days in phosphate-buffered saline (PBS) at pH 6.6, which followed the Higuchi diffusion model. Moreover, MTZ-thermosensitive hydrogel exhibited delayed dissolution in PBS at 37°C for more than 9 days. MTZ-thermosensitive hydrogels could be considered a prospective local oral drug delivery system to achieve efficient sustained release and improve the drug pharmacological properties in periodontitis treatment.

Corrosion Behaviour and J774A.1 Macrophage Response to Hyaluronic Acid Functionalization of Electrochemically Reduced Graphene Oxide on Biomedical Grade CoCr

Improvements in the lubrication of metal–metal joint prostheses are of great clinical interest in order to minimize the particles released during wear–corrosion processes. In this work, electrochemically reduced graphene oxide (ErGO) on CoCr was functionalized with hyaluronic acid (ErGOHA). Functionalization was carried out by soaking for 24 h in phosphate buffer saline (PBS) solution containing 3 g/L hyaluronic acid (HA). The corrosion performance of CoCrErGO and CoCrErGOHA surfaces was studied by electrochemical impedance spectroscopy (EIS) for 7 days in PBS. Biocompatibility and cytotoxicity were studied in mouse macrophages J774A.1 cell line by the measurement of mitochondrial activity (WST-1 assay) and plasma membrane damage (LDH assay). The inflammatory response was examined through TNF-α and IL-10 cytokines in macrophages culture supernatants, used as indicators of pro-inflammatory and anti-inflammatory responses, respectively. EIS diagrams of CoCrErGOHA revealed two time constants: the first one, attributed to the hydration and diffusion processes of the HA layer adsorbed on ErGO, and the second one, the corrosion resistance of ErGOHA/CoCr interface. Macrophage assays showed better behavior on CoCrErGOHA than CoCr and CoCrErGO surfaces based on their biocompatible, cytotoxic, and inflammatory responses. Comparative analysis of IL-10 showed that functionalization with HA induces higher values of anti-inflammatory cytokine, suggesting an improvement in inflammatory behavior.

3D printable and injectable lactoferrin-loaded carboxymethyl cellulose-glycol chitosan hydrogels for tissue engineering applications.

In this study, carboxymethyl cellulose (CMC)-glycol chitosan (GC) hydrogel, a potential three-dimensional (3D) printing biomaterial ink for tissue engineering applications was synthesized using simple, biocompatible in situ-gelling Schiff's base reaction and ionic interactions. Different grades of hydrogels (C70G30, C50G50 and C30G70) were synthesized at physiological conditions. The oxidation of CMC and imine bond formation in the hydrogel were confirmed spectroscopically. Scanning electron microscopic images revealed the crosslinked interconnected pores in the cross-sectioned hydrogels (dried). Swelling (equilibrium: 1 h), porosity (~75%), in vitro degradation (>30 days) and thermal gravimetric analyses of the dried gels were studied. Initially, cytotoxicity assay was evaluated using mouse osteoblastic cells (MC3T3). These experiments revealed that CMC-GC gels formed stable hydrogel networks and were biocompatible. Particularly, C50G50 gels showed high printability (continuous extrusion) and post-printing stability (without secondary crosslinking). Gel 3D printing was optimized by varying the air pressure, temperature, needle size and nozzle speed, to obtain stable lattice structures (2 to 16 layers). The printed (2 and 5 layers) hydrogels showed high stability in phosphate buffer saline (PBS) solution (1 h), under UV light (1 h) and after autoclaving. The strut dimensions and porosity of the printed gels before and after the stability tests were analyzed. The hydrogel stability may be attributed to both the imine bond and ionic interaction between the cationic and anionic polymer side chains. Lactoferrin (glycoprotein) incorporated C50G50 gels showed sustained release up to 21 days in PBS (pH 7.4) solution and demonstrated increased biocompatibility (>80%) during in vitro cytotoxicity assays (MC3T3 cells and bone marrow mesenchymal stem cells) and Live/Dead assay (MC3T3 cells). A higher number of live osteoblast cells on the C50G50 hydrogels with increasing lactoferrin concentration was observed. These results show that the CMC-GC gels are promising bio-ink candidates for 3D printing and loading proteins or drugs for tissue engineering applications.

Quality by design-enabled development and characterisation of nanocarrier of azithromycin

Background: Azithromycin is an antibiotic, which is preferentially used in the treatment of Mycobacterium Avium Complex (MAC). However, it suffers from drawbacks such as poor solubility, poor bioavailability and adverse effects such as gastrointestinal intolerance, resulting into poor patient compliance. Aim: To develop and optimize lipid based nanocarriers of Azithromycin using QbD approach. Methods: Nanostructured lipid carrier (NLC) were developed by using the solvent diffusion evaporation method with view to release drug in a sustained release manner. The initial factors screening and risk assessment done through Taguchi design and afterwards the optimization of independent factors along with final outcome i.e. critical quality attributes (CQAs) were done by Box Behnken Design (BBD). Results: The results of Physicochemical analysis revealed that a size of optimized Azithromycin Nanocarrier is 346.18 ± 12.90 nm and Polydispersity Index (PDI) of 0.21 ± 0.08; the entrapment efficiency (% EE) of 68.45 ± 4.42% w/w and drug loading of 47.16 ± 0.80 % w/w. The in vitro release study of the Azithromycin Nanocarrier showed a biphasic drug release pattern in simulated intestinal fluid (SIF) nanocarrier shown sustained release kinetics up to 02 days and similar pattern shown in Phosphate buffer saline (PBS) pH 7.4, release kinetics shows initial burst release upto 12 hr followed by sustained release upto 04 days in PBS, pH7.4. The sustained release pattern of the formulation is beneficial to improve the oral bioavailability of the drug. Conclusion: Thus, present research leads to development of formulations which may reduce dose of drug, dosing frequency and enhanced efficaciously of drug. Ultimately it reducing the patient avoidance in treatment.

Long-Lived, Transferred Crystalline Silicon Carbide Nanomembranes for Implantable Flexible Electronics.

Implantable electronics are of great interest owing to their capability for real-time and continuous recording of cellular-electrical activity. Nevertheless, as such systems involve direct interfaces with surrounding biofluidic environments, maintaining their long-term sustainable operation, without leakage currents or corrosion, is a daunting challenge. Herein, we present a thin, flexible semiconducting material system that offers attractive attributes in this context. The material consists of crystalline cubic silicon carbide nanomembranes grown on silicon wafers, released and then physically transferred to a final device substrate (e.g., polyimide). The experimental results demonstrate that SiC nanomembranes with thicknesses of 230 nm do not experience the hydrolysis process (i.e., the etching rate is 0 nm/day at 96 °C in phosphate-buffered saline (PBS)). There is no observable water permeability for at least 60 days in PBS at 96 °C and non-Na+ ion diffusion detected at a thickness of 50 nm after being soaked in 1× PBS for 12 days. These properties enable Faradaic interfaces between active electronics and biological tissues, as well as multimodal sensing of temperature, strain, and other properties without the need for additional encapsulating layers. These findings create important opportunities for use of flexible, wide band gap materials as essential components of long-lived neurological and cardiac electrophysiological device interfaces.

Crosslinked poly(Lactose) microgels and nanogels for biomedical applications

HypothesisLactose (LAC) is a primary carbohydrate and energy source of milk has received intensive attention due to its’ unique functional and nutritional properties. Many biological beneficences of LAC make it an appealing molecule to seek for designing functional interfaces. Therefore, crosslinked poly(lactose) (p(LAC)) microgel from lactose disaccharides for potential biomedical applications was pursued as biocolloids for the first time. Experimentp(LAC) microgels prepared by chemical crosslinking with DiVinyl Sulfone (DVS) were chemically modified with ethylenediamine (EDA) to obtain amine-modified p(LAC) (p(LAC)-EDA) microgels to induce new functionalities and properties. Blood compatibilities of bare p(LAC)-EDA microgels were tested through hemolysis and blood clotting tests. Rosmarinic acid (RA) used as a model drug was loaded into p(LAC) and p(LAC)-EDA microgels to demonstrate their applicability to be used in drug loading and release applications. FindingsA facile preparation of p(LAC) microgels with high yield, 90 ± 5% and 0.5–50 µm size range was accomplished via water-in-oil (w/o) microemulsion crosslinking method. Upon chemical modification, the isoelectric point (IEP) from pH 1.8 for p(LAC) microgels changed to pH 7.7 for p(LAC)-EDA microgels, and the blood compatibility studies revealed that both microgels can be considered as blood compatible up to 2 mg/mL concentration, and only slight decrease in blood clotting index (BCI) of p(LAC)-EDA microgels was observed. Rosmarinic Acid (RA) was demonstrated to be released up to 4 days in phosphate buffer saline (PBS) with a linear release profile for p(LAC)-EDA microgels.

Release of Transforming Growth Factor Beta 1 from Human Tooth Dentin after Application of Either ProRoot MTA or Biodentine as a Coronal Barrier

IntroductionVarious factors may influence intracanal calcification in teeth treated with regenerative endodontic procedures. Bioactive materials, including ProRoot MTA (MTA; Dentsply Tulsa Dental Specialties, Memphis, TN) and Biodentine (BD; Septodont, Saint-Maur-des-Fossés, France), have been widely used as a coronal barrier in the final step of regenerative endodontic procedures. The purposes of this study were to evaluate the effect of either MTA or BD after application as a coronal barrier on transforming growth factor beta 1 (TGF-β1) release from root canal dentin and to observe the impact of these materials on human apical papilla cell (APC) mineralization. MethodsEither MTA or BD was applied in enlarged root canals of human root segments. After storing for 14 days in phosphate-buffered saline, TGF-β1 release was evaluated using an enzyme-linked immunosorbent assay. To investigate the effect of the materials on APC mineralization, APCs were grown in the presence of either the materials alone or material-filled root segments. Cell mineralization was quantified after 14 and 21 days using alizarin red S staining. Calcium deposits were quantitatively analyzed. Statistical analysis was performed using the Kruskal-Wallis and Mann-Whitney U tests with the significance level at .05. ResultsThe greatest amount of TGF-β1 release was observed in the root segments treated with BD. BD, used either alone or as a coronal barrier, promoted greater APC mineralization than did MTA on both days 14 and 21. Interestingly, when BD was applied as a coronal barrier, the mineralization effect was significantly reduced compared with the use of the materials alone (P < .05). ConclusionsWhen used as a coronal barrier, BD promoted the release of TGF-β1 from the root canal dentin. A higher mineralization effect was observed with BD than with MTA.

Invitro Biodegradability of Silk Fibroin/Xanthan Biopolymeric Composite Scaffolds

Silk fibroin/xanthan scaffolds were prepared by blending silk fibroin and xanthan in the ratios 80SF:20Xa (SFX82), 60SF:40Xa (SFX64), and 50SF:50Xa (SFX55) using freeze drying method. In-vitro degradation behavior of the prepared scaffolds was studied for 37 days in phosphate buffer saline. The degradation rate was the function of silk fibroin, xanthan and β-crystallite contents in the silk fibroin/ xanthan composites. SFX82 degraded extremely slowly whereas SFX55 showed faster degradation rate. Hydrophilic xanthan was the main contributor of weight loss. SFX82 and SFX64 exhibited surface degradation whereas SFX55 showed bulk degradation which indicated that higher silk fibroin ratios favor surface degradation. Due to bulk degradation, SFX55 showed maximum surface roughness among the composite scaffolds. The FTIR spectrum revealed total loss of xanthan from the composites after degradation. The broad and low-intensity peaks in the FTIR spectrum of composite scaffolds confirmed reduction in β-sheet crystallite content during degradation. XRD analysis also confirmed reduction in β-sheet crystals and revealed that degraded composite scaffold had predominantly amorphous structure. The degraded scaffold showed higher porous structure than the non-degraded scaffold. The in vitro degradability testing gives a good approximation of degradation of scaffold in vivo and helps in designing a robust biopolymeric composite scaffold for tissue engineering.

Synthesis, electrospinning and in vitro test of a new biodegradable gelatin-based poly(ester urethane urea) for soft tissue engineering

Biodegradable polyurethanes have been studied as scaffolds for tissue engineering due to their adjustable physico-chemical properties. In this work, we synthesized a biodegradable gelatin-based poly(urethane urea) using polycaprolactone-diol, as soft segment, and isophorone diisocyanate and gelatin from cold water fish skin as hard segment. The synthesis was confirmed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance and the influence of the amount of gelatin introduced in the polymer backbone was analyzed by thermal analysis. Gelatin-based poly(urethane urea) electrospun fibrous mats and solvent cast films were then produced and their physico-chemical and biological properties studied. They present an amorphous structure, elastomeric behavior and water contact angles typical of hydrophobic surfaces. Hydrolytic degradation was analyzed in phosphate buffer saline (PBS), lipase and trypsin solutions. No mass changes were detected during 37 days in PBS and trypsin while significant degradation by lipase was observed. Human foetal foreskin fibroblasts were seeded on the fibrous mats and films. Populations were evaluated by colorimetric cell viability assays and morphology by fluorescence imaging. The substrates supported cell adhesion and proliferation. The novel gelatin-based poly(urethane urea) fibrous mats offer attractive physico-chemical and biological properties for soft tissue engineering applications.

Dicationic Imidazolium-Based Ionic Liquid Coatings on Zirconia Surfaces: Physico-Chemical and Biological Characterization.

In the present work, dicationic imidazolium-based ionic liquids (ILs) were investigated as multi-functional coatings on a zirconia (ZrO2) surface to prevent biofilm formation and enhance the wear performance of zirconia while maintaining the material’s compatibility with host cells. ILs containing phenylalanine and methionine were synthesized and deposited on zirconia. Intermolecular interactions driving IL deposition on zirconia were studied using X-ray photoelectron spectroscopy (XPS). Anti-biofilm activity and cell compatibility were evaluated in vitro after one and seven days, and wear performance was tested using a pin-on-disk apparatus. ILs were observed to form strong hydrogen bonds with zirconia. IL containing phenylalanine formed a stable film on the surface after one and seven days in phosphate-buffered saline (PBS) and artificial saliva and showed excellent anti-biofilm properties against Streptococcus salivarius and Streptococcus sanguinis. Compatibility with gingival fibroblasts and pre-osteoblasts was maintained, and conditions for growth and differentiation were preserved. A significantly lower coefficient of friction and wear volume loss were observed for IL-coated surfaces as compared to non-coated substrates. Overall, zirconia is an emerging alternative to titanium in dental implants systems, and this study provides additional evidence of the materials’ behavior and IL coatings as a potential surface treatment technology for improvement of its properties.

Drug Release as a function of bioactivity, incubation regime, liquid, and initial load: Release of bortezomib from calcium phosphate-containing silica/collagen xerogels.

The ability of silica-/collagen-based composite xerogels to act as drug delivery systems was evaluated by taking into account the initial drug concentration, bioactivity of the xerogels, liquid, and incubation regime. The proteasome inhibitor bortezomib was chosen as a model drug, used for the systemic treatment of multiple myeloma. Incubation during 14 days in phosphate-buffered saline (PBS) or simulated body fluid (SBF) showed a weak initial burst and was identified to be of first order with subsequent release being independent from the initial load of 0.1 or 0.2 mg bortezomib per 60 mg monolithic sample. Faster drug release occurred during incubation in SBF compared to PBS, and during static incubation without changing the liquid, compared to dynamic incubation with daily liquid changes. Drug-loaded xerogels with hydroxyapatite as a third component exhibited enhanced bioactivity retarding drug release, explained by formation of a surface calcium phosphate layer. The fastest release of 50% of the total drug load was observed for biphasic xerogels after 7 days during dynamic incubation in SBF. As a result, the presented concept is suitable for the intended combination of the advantageous bone substitution properties of xerogels and local application of drugs exemplified by bortezomib. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1165-1173, 2018.

Phosphatidylcholine Coatings Deliver Local Antimicrobials and Reduce Infection in a Murine Model: A Preliminary Study.

Phosphatidylcholine coatings have been shown to elute antibiotics for several days. A recently developed biofilm inhibitor, cis-2-decenoic acid (C2DA), has been shown to exhibit synergistic activity with several common antibiotics. This study aims to evaluate the effectiveness of C2DA and amikacin dual drug delivery from a phosphatidylcholine coating. (1) What are the in vitro elution profiles of amikacin and C2DA from phosphatidylcholine-coated coupons in incubated phosphate-buffered saline? (2) Does the presence of C2DA in eluate samples lower the amount of amikacin needed for bacterial inhibition in overnight bacterial turbidity assays? (3) Does addition of amikacin and C2DA result in decreased colony-forming units (CFUs) on wire implants and bone when compared with phosphatidylcholine coatings alone in a mouse model of periprosthetic joint infection? Effects of loading concentrations were assessed during 7-day in vitro elution studies for coatings containing all mixtures of 0%, 5%, 15%, and 25% wt of amikacin and C2DA (n = 4) through quantitative high-performance liquid chromatography concentration determination and plotting concentration eluted over time. Antimicrobial activity was assessed by overnight turbidity testing of elution study samples against Staphylococcus aureus or Pseudomonas aeruginosa. In vivo efficacy was assessed using phosphatidylcholine-coated wire implants in a murine (mouse) model of infection (n = 3). Wire implants were coated with phosphatidylcholine containing no antimicrobials, amikacin alone, C2DA alone, or amikacin and C2DA and then inserted into the intramedullary femur of each mouse and inoculated with S aureus. The number of viable bacterial colonies on the implant surface and in the surrounding bone was determined after 1 week with the goal of achieving complete bacterial clearance. Total viable CFU count and proportion of samples achieving complete clearance were compared between groups. Elution samples showed a burst response of amikacin and C2DA for 1 to 2 days with C2DA release continuing at low levels through Day 4. All tested eluate samples inhibited P aeruginosa. Samples from coatings containing 25% amikacin or 15% amikacin and any amount of C2DA were able to inhibit S aureus formation, but all coatings with 5% amikacin or 15% amikacin but no C2DA were not inhibitory. All in vivo treatment groups achieved complete bacterial clearance on the wire implant, and the C2DA alone and amikacin alone coatings cleared all CFUs in bone (pin: phosphatidylcholine only one of three; amikacin three of three, C2DA three of three, amikacin + C2DA three of three, p = 0.04 [Fisher's exact test]; bone: coating only: zero of three; amikacin: three of three; C2DA; three of three; C2DA + amikacin: one of three; p = 0.03 [Fisher's exact test]). Phosphatidylcholine coatings elute antimicrobials in vitro under infinite sink conditions for up to 4 days in phosphate-buffered saline and were able to reduce bacterial colonies in a preliminary in vivo model. Turbidity testing with eluate samples containing varying amounts of C2DA and amikacin agrees with previous studies showing synergy between them. Used as an adjunctive to systemic therapy, C2DA-loaded phosphatidylcholine coatings have potential value as a prophylactic infection prevention measure. Future studies may include different antibiotics, animal studies with larger sample sizes and more controls, and advanced coating delivery methods.

Stabilization of Natural Antioxidants by Silk Biomaterials.

The stabilities of three natural antioxidants, vitamin C (VC), (-)-epigallocatechin gallate (EGCG), and curcumin, in silk films were examined and mechanisms of stabilization were elucidated. The antioxidants were physically incorporated into three types of silk films: as-cast, dried from hydrogels, and methanol-treated. Films were stored at 4, 37, and 45 °C for 30 days in phosphate-buffered saline, pH 7.4, along with controls consisting of free antioxidants. Incorporation of antioxidants did not significantly change film morphology or secondary structure. When stored at 4 °C, all samples showed similar antioxidant activities (percent scavenging) at different time points, determined by the colorimetric 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. At higher temperatures, VC in the as-cast film, EGCG in the as-cast and dried hydrogel films, and curcumin in the methanol-treated films retained more than 50% scavenging activity after 14 days of storage, significantly higher than the other samples. Interaction between antioxidants and silk, as well as degradation of the antioxidants, was investigated by fast-performance liquid chromatography (FPLC) and high-pressure liquid chromatography (HPLC), with an aim of understanding the mechanisms of silk-based stabilization. Binding of antioxidant molecules to hydrophobic or to hydrophilic/hydrophilic boundary regions of silk, depending on the chemical properties of the antioxidant, may account for the observed stabilization effects. The data can help guide further engineering of antioxidant-functionalized silk biomaterials.