Browsing by Author "Ambrose, Catherine G."
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Item Adjustable-volume liquid dispensing pump(2012-09-11) Oden, Maria; Schutze, Gordon E.; Bennett, Kimberly A.; Schwab, Brian D.; Ginnings, Charles A.; Jeans, Megan E.; Ambrose, Catherine G.; Rice University; Baylor College of Medicine; Board of Regents of the University of Texas System; United States Patent and Trademark OfficeAn adjustable-volume liquid dispenser is disclosed. In one embodiment, an adjustable-volume liquid dispenser includes a spout and a plunger secured to the spout. The dispenser further includes a plunger lock moveable lengthwise along the plunger. The plunger lock is securable to the plunger at a plurality of positions on the plunger to adjust a volume of liquid to be dispensed. The dispenser also includes a spring in contact with the plunger. In addition, the dispenser includes a chamber comprising an interior for containing liquid. The plunger is slidably arranged with the chamber. A portion of the plunger is disposed within the chamber. Moreover, the dispenser includes a chamber cap secured to the chamber, and a valve disposed within the chamber. The dispenser also includes a shaft secured to the chamber.Item Antibiotic microspheres for treatment and prevention of osteomyelitis and enhancement of bone regrowth(2015-03-24) Ambrose, Catherine G.; Clyburn, Terry A.; Mikos, Antonio G.; Rice University; United States Patent and Trademark OfficeA method of treating or preventing infection at a surgical site comprising a bony defect and an implanted metal device is disclosed. Biodegradable microspheres are placed at the site and are capable of near-linear controlled release of an antibiotic agent for a predetermined period of time. The microspheres are configured to be large enough to avoid being phagocytosed and removed from the body, and small enough in diameter to not physically inhibit bone growth at said bony defect site. The microspheres are formed of polylactic-co-glycolic acid (PLGA), with or without polyethylene glycol (PEG), and sufficient antibiotic agent to produce bactericidal levels in body tissues. The microspheres exhibit near-linear delivery of the antibiotic agent for at least 4 weeks at levels exceeding the minimum inhibitory concentration (MIC) for organisms commonly found to be the cause of infections, and facilitate bone ingrowth or regrowth at the site.Item Development of a biodegradable interbody fusion device(2004) Timmer, Mark Davis; Mikos, Antonios G.; Ambrose, Catherine G.Novel polymer networks based on poly(propylene fumarate) (PPF) and the crosslinking agent poly(propylene fumarate)-diacrylate (PPF-DA) were investigated as a material for a biodegradable interbody fusion cage. The aim of this work was to establish the effect of the macromolecular network structure on the physical properties in order to tailor the material to demonstrate high strength, controllable degradation, and suitable biocompatibility for this implant. The PPF/PPF-DA network structure was characterized with a newly developed technique in which the networks were degraded into simpler linear constituents that provided insight to the macromolecular structure. The double bond conversion and crosslinking density of the polymer networks was controlled by the concentrations of PPF and PPF-DA in the network, as dictated by the double bond ratio of fumarate groups in the PPF backbone to acrylate groups in the PPF-DA crosslinker. Lower double bond ratios yielded higher conversions and a more densely crosslinked network. The network structure was further influenced by the free radical initiator system. The mechanical properties of the PPF/PPF-DA networks increased with decreasing double bond ratios as a result of higher crosslinking densities. Photo-crosslinking produced a stronger material and also facilitated processing of PPF/PPF-DA networks because there is greater control over the crosslinking reaction. Examination of the in vitro degradation behavior of PPF/PPF-DA networks in simulated body fluids showed that the degradation rate was faster for networks with lower crosslinking densities. The biocompatibility of the material was also controlled by the macromolecular structure as PPF/PPF-DA networks with higher double bond conversions and crosslinking densities exhibited no adverse cytotoxicity and enabled fibroblast attachment. A prototype PPF/PPF-DA interbody fusion cage was fabricated by photo-crosslinking the polymers in transparent silicone molds. The PPF/PPF-DA implant demonstrated similar mechanical properties as a clinical approved allograft spacer and suggested that the device can provide sufficient support for interbody fusion. This work demonstrated that PPF/PPF-DA networks are a suitable material for a biodegradable interbody fusion device as well as other load bearing orthopaedic implants.Item Type-I collagen produced by distinct fibroblast lineages reveals specific function during embryogenesis and Osteogenesis Imperfecta(Springer Nature, 2021) Chen, Yang; Yang, Sujuan; Lovisa, Sara; Ambrose, Catherine G.; McAndrews, Kathleen M.; Sugimoto, Hikaru; Kalluri, RaghuType I collagen (Col1) is the most abundant protein in mammals. Col1 contributes to 90% of the total organic component of bone matrix. However, the precise cellular origin and functional contribution of Col1 in embryogenesis and bone formation remain unknown. Single-cell RNA-sequencing analysis identifies Fap+ cells and Fsp1+ cells as the major contributors of Col1 in the bone. We generate transgenic mouse models to genetically delete Col1 in various cell lineages. Complete, whole-body Col1 deletion leads to failed gastrulation and early embryonic lethality. Specific Col1 deletion in Fap+ cells causes severe skeletal defects, with hemorrhage, edema, and prenatal lethality. Specific Col1 deletion in Fsp1+ cells results in Osteogenesis Imperfecta-like phenotypes in adult mice, with spontaneous fractures and compromised bone healing. This study demonstrates specific contributions of mesenchymal cell lineages to Col1 production in organogenesis, skeletal development, and bone formation/repair, with potential insights into cell-based therapy for patients with Osteogenesis Imperfecta.