Garima Bhardwaj

Decreased Staphylococcus aureus and increased osteoblast density on nanostructured electrophoretic-deposited hydroxyapatite on titanium without the use of pharmaceuticals.

Background Plasma-spray deposition of hydroxyapatite on titanium (Ti) has proven to be a suboptimal solution to improve orthopedic-implant success rates, as demonstrated by the increasing number of orthopedic revision surgeries due to infection, implant loosening, and a myriad of other reasons. This could be in part due to the high heat involved during plasma-spray deposition, which significantly increases hydroxyapatite crystal growth into the nonbiologically inspired micron regime. There has been a push to create nanotopographies on implant surfaces to mimic the physiological nanostructure of native bone and, thus, improve osteoblast (bone-forming cell) functions and inhibit bacteria functions. Among the several techniques that have been adopted to develop nanocoatings, electrophoretic deposition (EPD) is an attractive, versatile, and effective material-processing technique. Objective The in vitro study reported here aimed to determine for the first time bacteria responses to hydroxyapatite coated on Ti via EPD. Results There were six and three times more osteoblasts on the electrophoretic-deposited hydroxyapatite on Ti compared with Ti (control) and plasma-spray-deposited hydroxyapatite on Ti after 5 days of culture, respectively. Impressively, there were 2.9 and 31.7 times less Staphylococcus aureus on electrophoretic-deposited hydroxyapatite on Ti compared with Ti (control) and plasma-spray-deposited hydroxyapatite on Ti after 18 hours of culture, respectively. Conclusion Compared with uncoated Ti and plasma-sprayed hydroxyapatite coated on Ti, the results provided significant promise for the use of EPD to improve bone-cell density and be used as an antibacterial coating without resorting to the use of antibiotics.

Reduced bacterial growth and increased osteoblast proliferation on titanium with a nanophase TiO 2 surface treatment

Background The attachment and initial growth of bacteria on an implant surface dictates the progression of infection. Treatment often requires aggressive antibiotic use, which does not always work. To overcome the difficulties faced in systemic and local antibiotic delivery, scientists have forayed into using alternative techniques, which includes implant surface modifications that prevent initial bacterial adhesion, foreign body formation, and may offer a controlled inflammatory response. Objective The current study focused on using electrophoretic deposition to treat titanium with a nanophase titanium dioxide surface texture to reduce bacterial adhesion and growth. Two distinct nanotopographies were analyzed, Ti-160, an antimicrobial surface designed to greatly reduce bacterial colonization, and Ti-120, an antimicrobial surface with a topography that upregulates osteoblast activity while reducing bacterial colonization; the number following Ti in the nomenclature represents the atomic force microscopy root-mean-square roughness value in nanometers. Results There was a 95.6% reduction in Staphylococcus aureus (gram-positive bacteria) for the Ti-160-treated surfaces compared to the untreated titanium alloy controls. There was a 90.2% reduction in Pseudomonas aeruginosa (gram-negative bacteria) on Ti-160-treated surfaces compared to controls. For ampicillin-resistant Escherichia coli, there was an 81.1% reduction on the Ti-160-treated surfaces compared to controls. Similarly for surfaces treated with Ti-120, there was an 86.8% reduction in S. aureus, an 82.1% reduction in P. aeruginosa, and a 48.6% reduction in ampicillin-resistant E. coli. The Ti-120 also displayed a 120.7% increase at day 3 and a 168.7% increase at day 5 of osteoblast proliferation over standard titanium alloy control surfaces. Conclusion Compared to untreated surfaces, Ti-160-treated titanium surfaces demonstrated a statistically significant 1 log reduction in S. aureus and P. aeruginosa, whereas Ti-120 provided an additional increase in osteoblast proliferation for up to 5 days, criteria, which should be further studied for a wide range of orthopedic applications.

Enhanced chondrocyte culture and growth on biologically inspired nanofibrous cell culture dishes.

Chondral and osteochondral defects affect a large number of people in which treatment options are currently limited. Due to its ability to mimic the natural nanofibrous structure of cartilage, this current in vitro study aimed at introducing a new scaffold, called XanoMatrix™, for cartilage regeneration. In addition, this same scaffold is introduced here as a new substrate onto which to study chondrocyte functions. Current studies on chondrocyte functions are limited due to nonbiologically inspired cell culture substrates. With its polyethylene terephthalate and cellulose acetate composition, good mechanical properties and nanofibrous structure resembling an extracellular matrix, XanoMatrix offers an ideal surface for chondrocyte growth and proliferation. This current study demonstrated that the XanoMatrix scaffolds promote chondrocyte growth and proliferation as compared with the Corning and Falcon surfaces normally used for chondrocyte cell culture. The XanoMatrix scaffolds also have greater hydrophobicity, three-dimensional surface area, and greater tensile strength, making them ideal candidates for alternative treatment options for chondral and osteochondral defects as well as cell culture substrates to study chondrocyte functions.

Antibacterial properties of PEKK for orthopedic applications

Orthopedic implant infections have been steadily increasing while, at the same time, antibiotics developed to kill such bacteria have proven less and less effective with every passing day. It is clear that new approaches that do not rely on the use of antibiotics are needed to decrease medical device infections. Inspired by cicada wing surface topographical features, nanostructured surfaces represent a new approach for imposing antibacterial properties to biomaterials without using drugs. Moreover, new chemistries with altered surface energetics may decrease bacterial attachment and growth. In this study, a nanostructured surface was fabricated on poly-ether-ketone-ketone (PEKK), a new orthopedic implant chemistry, comprised of nanopillars with random interpillar spacing. Specifically, after 5 days, when compared to the orthopedic industry standard poly-ether-ether-ketone (PEEK), more than 37% less Staphylococcus epidermidis were found on the PEKK surface. Pseudomonas aeruginosa attachment and growth also decreased 28% after one day of culture, with around a 50% decrease after 5 days of culture when compared to PEEK. Such decreases in bacteria function were achieved without using antibiotics. In this manner, this study demonstrated for the first time, the promise that nanostructured PEKK has for numerous anti-infection orthopedic implant applications.

XanoMatrix surfaces as scaffolds for mesenchymal stem cell culture and growth

Stem cells are being widely investigated for a wide variety of applications in tissue engineering due to their ability to differentiate into a number of cells such as neurons, osteoblasts, and fibroblasts. This ability of stem cells to differentiate into different types of cells is greatly based on mechanical and chemical cues received from their three-dimensional environments. All organs are formed by a number of cells linked together via an extracellular matrix (ECM). The ECM is a complex network of proteins and carbohydrates, which occupies intercellular spaces and regulates cellular activity by controlling cell adhesion, migration, proliferation, and differentiation. The ECM is composed of two main types of macromolecules, namely, polysaccharide glycosaminoglycans, which are covalently attached to proteins in the form of proteoglycans and fibrous proteins belonging to two functional groups, structural (collagen and elastin) and adhesive (fibronectin, laminin, vitronectin, etc). Tissue engineering is a multidisciplinary field that aims to develop biomimetic scaffolds that emulate properties of the ECM to help repair or regenerate diseased or damaged tissue. This study introduces one of these matrices, XanoMatrix, as an optimal scaffold for tissue engineering applications, in particular, for stem cell research, based on its composition, nanofibrous structure, and porosity. Results of this study suggest that XanoMatrix scaffolds are promising for stem cell tissue engineering applications and as improved cell culture inserts for studying stem cell functions (compared to traditional Corning and Falcon cell culture plates) and, thus, should be further studied.

Functionalized nanophase hydroxyapatite (HA) for orthopedic applications

Orthopedic implants fail due to various reasons such as extensive bacterial colonization, poor osseointegration, extensive inflammation and osteolysis due to wear debris. In order to reduce orthopedic implant failures, the main objective of this study was to create a biomimetic bone tissue engineering material based on the osteoconductive properties of nanophase hydroxyapatite (HA), the bacterial inhibition properties of the MAM7 peptide1, the quorum sensing inhibitor RNAIII peptide2, and the anticancer properties of the PCK3145 peptide3 as well as curcumin4. Results showed promise for these materials to combat common failure modes of orthopedic implants.

Reduced Bacterial Growth on Titanium Screws With Nanophase TiO2 Surface Treatment

Category: Other Introduction/Purpose: An important strategy in the reduction of orthopedic infections is to develop implant materials that prevent initial bacteria adhesion and growth onto implant surfaces. Bacterial localization and biofilm formation may lead to acute and chronic infections[1]. Biofilm formation on implant surfaces protects bacteria from the immune system and antibiotic therapy, thus, requiring an aggressive treatment of antibiotics that frequently do not work post biofilm formation[2]. Thus, to prevent implant infections, various strategies have been developed aside from conventional systemic and local antibiotic treatment. Recently, there has been increasing interest for coating implants with other materials to improve osseointegration and prevent infection, chronic inflammation, and unwanted foreign body responses[3]. The current study focuses on modifying the surface of titanium implants by treating them with nanophase titanium dioxide using electrophoretic deposition. Methods: Nanophase titanium dioxide was synthesized using a wet chemical synthesis and was deposited on Ti-6Al-4 V titanium screws using a cathodic arc deposition plasma system. Bacterial assays were conducted using Staphylococcus aureus (ATCC® 29740™), Pseudomonas aeruginosa (ATCC® 39324™) and an ampicillin resistant strain of E. coli (BIO-RAD Strain HB101 K-12 #166-0408 and pGLO Plasmid #166-0405). 0.03% tryptic soy broth (TSB) (Sigma Aldrich, Cat # 22092) and agar (Sigma-Aldrich, Cat # A1296) were used as the media and colony forming assays were performed to determine bacterial adhesion. Results: Nanophase titanium dioxide was successfully synthesized and applied onto the desired surface. A statistically significant decrease in bacterial adhesion was observed across all 3 strains of bacteria; an example of confocal images for S. Aureus is given in figure 1. In addition, decreased macrophage functions and increase osteoblast functions were also observed in the nano TiO2 treated Ti6Al4 V screws. Importantly, this was all achieved without the use of drugs and/or antibiotics decreasing the chance for the spread of antibiotic resistant bacteria and drug side effects. Conclusion: The screws were successfully coated using EPD and reduced bacterial adhesion on the coated surface was observed.

Increased NIH 3T3 fibroblast functions on cell culture dishes which mimic the nanometer fibers of natural tissues

Traditional flat tissue cell culture dishes have consisted of polystyrene treated with plasma gases for growing, subculturing, and studying cell behavior in vitro. However, increasingly it has been observed that mimicking natural tissue properties (such as chemistry, three-dimensional structure, mechanical properties, etc) in vitro can lead to a better correlation of in vitro to in vivo cellular functions. The following studies compared traditional NIH 3T3 fibroblasts’ functions on XanoMatrix scaffolds to standard tissue culture polystyrene. Results found significantly greater fibroblast adhesion and proliferation on XanoMatrix cell culture dishes which mimic the nanoscale geometry of natural tissue fibers with true, tortuous fiber beds creating a robust, consistent, and versatile growth platform. In this manner, this study supports that cell culture dishes which mimic features of natural tissues should be continually studied for a wide range of applications in which mimicking natural cellular functions are important.