Andrea Paola Rodriguez

Drug delivery vehicles on a nano-engineering perspective.

Nanoengineered drug delivery systems (nDDS) have been successfully used as clinical tools for not only modulation of pharmacological drug release profile but also specific targeting of diseased tissues. Until now, encapsulation of anti-cancer molecules such as paclitaxel, vincristin and doxorubicin has been the main target of nDDS, whereby liposomes and polymer-drug conjugates remained as the most popular group of nDDS used for this purpose. The success reached by these nanocarriers can be imitated by careful selection and optimization of the different factors that affect drug release profile (i.e. type of biomaterial, size, system architecture, and biodegradability mechanisms) along with the selection of an appropriate manufacture technique that does not compromise the desired release profile, while it also offers possibilities to scale up for future industrialization. This review focuses from an engineering perspective on the different parameters that should be considered before and during the design of new nDDS, and the different manufacturing techniques available, in such a way to ensure success in clinical application.

Secreted frizzled related protein (sFRP)-2 inhibits bone formation and promotes cell proliferation in ameloblastoma

Secreted frizzled related protein (sFRP)-2, a Wnt antagonist, was strongly expressed by both stromal and tumor cells of ameloblastoma. The aim of this study is to evaluate whether sFRP-2 secreted from tumor cells have any direct role in suppressed bone formation or not. A pre-osteoblastic cell line, KUSA/A1 cells, cultured in conditioned medium of an ameloblastoma-derived cell line (AM-1CM) was used in the study. Alkaline phosphatase (ALP) activity, alizarin red staining, mineral quantification and MTS assay was performed. Wnt-canonical pathway is a major pathway for osteoblasts. Antagonists of this pathway, sFRP-1, 2 and 3, were detected by immunohistochemistry and western blot analysis. KUSA/A1 cells cultured in AM-1CM showed high cell proliferation, low ALP activity without mineralized matrix deposition. sFRP-2 was strongly expressed in ameloblastoma tissue and AM-1 cells. After sFRP-2 depletion, the cells showed diffuse mineralization. In this study, it was confirmed that ameloblastoma cells have a major role in decreased bone formation by secreting sFRP-2 in cell culture model. Though, sFRP-2 has great effect on tumor progression, inhibition of sFRP-2s anti-bone formation activity and cell proliferative activity may reduce the invasive property of ameloblastoma and possibility of recurrence rate.

Allelic loss of the ING gene family loci is a frequent event in ameloblastoma

Ameloblastoma is the most frequently encountered odontogenic tumor, characterized by a locally invasive behavior, frequent recurrences, and, although rare, metastatic capacity. Loss or inactivation of tumor suppressor genes (TSGs) allows cells to acquire neoplastic growth. The ING family proteins are tumor suppressors that physically and functionally interact with p53 to perform important roles in apoptosis, DNA repair, cell cycle regulation, and senescence. TP53 genetic alterations were reported to infrequently occur in ameloblastoma. Considering that other TSGs related to TP53 could be altered in this tumor, we focused our study on the ING family genes. We analyzed the loss of heterozygosity (LOH) status of the ING family (ING1-ING5) chromosomal loci in a group of ameloblastomas by microsatellite analysis, and correlated the ING LOH status with clinicopathological characteristics. By using specific microsatellite markers, high frequency of LOH was found at the loci of each ING gene family member (33.3-72.2%). A significant relationship was shown between LOH of D2S 140 (ING5 locus) and solid tumor type (p = 0.02). LOH of ING3MS (ING3 locus) was also high in solid type tumors, showing a near significant association. In addition, a notable tendency toward higher LOH for half of the markers was observed in recurrent cases. LOH of ING family genes appears as a common genetic alteration in solid ameloblastoma. The current study provides interesting novel information regarding the potential prognostic significance of the allelic loss of the ING gene family loci in ameloblastoma tumorigenesis.

Effect of a New Titanium Coating Material (CaTiO3-aC) Prepared by Thermal Decomposition Method on Osteoblastic Cell Response

Titanium and hydroxyapatite (HA) are widely used as biomaterials for dental and medical applications. HA-coated titanium implants have excellent biocompatibility and mechanical properties. However, the adherence of HA film formed on titanium substrate is weak because of the lack of chemical interaction between HA and titanium. A solution to this problem is to form an intermediate film on titanium substrate, which provide excellent adherence to both titanium substrate and HA. We developed a novel biomaterial called calcium titanate-amorphous carbon (CaTiO3-aC) coating prepared by modified thermal decomposition method. The purpose of this study was to evaluate the effect of CaTiO 3-aC and HA coating (positive control), and Ti (negative control) on osteoblastic (MT3T3-E1) cell responses. An increased cellular proliferation was observed in CaTiO3-aC coating compared to HA coating. The maximum expressions of ALP activity, Col I and ALP mRNA were higher and achieved in shorter period of time in CaTiO3-aC coating compared to others. These results demonstrated that CaTiO3-aC promoted better cell attachment, cellular proliferation, and osteoblastic differentiation compared with HA. In conclusion, we suggested that CaTiO3-aC could be considered as an important candidate as a coating material.

Effect of fluoride-substituted apatite on in vivo bone formation.

Biological apatites are characterized by the presence of minor constituents such as magnesium (Mg), chloride (Cl), or fluoride (F) ions. These ions affect cell proliferation and osteoblastic differentiation during bone tissue formation. F-substituted apatites are being explored as potential bonegraft materials. The aim of the present study is to investigate the mechanism of bone formation induced by fluoride-substituted apatite (FAp) by analyzing the effect of FAp on the process of in vivo bone formation. FAps containing different F concentrations (l-FAp: 0.48wt%, m-FAp: 0.91wt%, h-FAp: 2.23wt%) and calcium-deficient apatite (CDA), as positive control, were implanted in rat tibia and bone formation was evaluated by histological examination, immuhistochemistry, in situ hybridization and tartrate-resistant acid phosphatase examinations. The results showed that l-FAp, m-FAp, h-FAp, and CDA biomaterials allowed migration of macrophages, attachment, proliferation, and phenotypic expression of bone cells leading to new bone formation in direct apposition to the particles. However, the l-FAp preparation allowed faster bone conduction compared to the other experimental materials. These results suggest that FAp with low F concentration may be an efficient bonegraft material for dental and medical application.

Recombinant human bone morphogenetic protein-2/atelocollagen composite as a new material for ossicular reconstruction

Ossicular reconstruction is the rebuilding of the damaged middle ear. There are many different prosthesis and techniques used to reconstruct the middle ear ossicles. However, precision in the surgical procedures and prostheses used for ossiculoplasty are still imperfect. The objective of this study was to evaluate the potential of recombinant human bone morphogenetic protein-2 (rhBMP-2)/ atelocollagen composite for ossicular reconstruction implanted in the tympanic cavity of rat. The ossicles were extirpated by perforating the tympanic membranes of rats. rhBMP-2/atelocollagen composite was implanted as substitute of ossicles in intimate contact with the tympanic membrane. Composites were subjected to histological, immunohistochemical, and radiological examination. To evaluate the auditory function, auditory brainstem response (ABR) was measured. rhBMP-2/atelocollagen composites showed good stability and durability without any inflammatory reaction within the tympanic cavity. The process of new bone formation was similar to intramembranous ossification. They also demonstrated that the hearing ability was re-established by ABR threshold shifts. rhBMP-2/atelocollagen composite exhibited excellent potential for ossicular reconstruction, maintaining their vibratory function. This ossicular tissue engineering may be considered as a future therapeutic strategy for ossiculoplasty.

Controlled degradability of PCL-ZnO nanofibrous scaffolds for bone tissue engineering and their antibacterial activity

Up to date, tissue regeneration of large bone defects is a clinical challenge under exhaustive study. Nowadays, the most common clinical solutions concerning bone regeneration involve systems based on human or bovine tissues, which suffer from drawbacks like antigenicity, complex processing, low osteoinductivity, rapid resorption and minimal acceleration of tissue regeneration. This work thus addresses the development of nanofibrous synthetic scaffolds of polycaprolactone (PCL) - a long-term degradation polyester - compounded with hydroxyapatite (HA) and variable concentrations of ZnO as alternative solutions for accelerated bone tissue regeneration in applications requiring mid- and long-term resorption. In vitro cell response of human fetal osteoblasts as well as antibacterial activity against Staphylococcus aureus of PCL:HA:ZnO and PCL:ZnO scaffolds were here evaluated. Furthermore, the effect of ZnO nanostructures at different concentrations on in vitro degradation of PCL electrospun scaffolds was analyzed. The results proved that higher concentrations ZnO may induce early mineralization, as indicated by high alkaline phosphatase activity levels, cell proliferation assays and positive Alizarin-Red-S-stained calcium deposits. Moreover, all PCL:ZnO scaffolds particularly showed antibacterial activity against S. aureus which may be attributed to release of Zn2+ ions. Additionally, results here obtained showed a variable PCL degradation rate as a function of ZnO concentration. Therefore, this work suggests that our PCL:ZnO scaffolds may be promising and competitive short-, mid- and long-term resorption systems against current clinical solutions for bone tissue regeneration.

In Vivo evaluation of adipogenic induction in fibrous and honeycomb-structured atelocollagen scaffolds.

Nowadays, soft tissue restoration techniques are mainly focused on volume regeneration instead of function recovering. So far, autologous fat transplant has been the most popular method although its multiple reported problems like volume and function loss. Adipose tissue engineering therefore emerges as a solution for development of biological substitutes for soft tissue which promotes not only volume regeneration but also function restoration with minimal consequences. Here we tested fibrous-structured atelocollagen (FSA) scaffolds and honeycomb atelocollagen (HCA) scaffolds for their ability to induce adipogenesis in vivo. Implants were subjected to histological and immunohistochemical assessment after 1, 2, and 4 weeks of implantation. Our studies showed that FSA scaffolds induced in vivo a markedly adipogenic response, whereas an acute inflammatory process was observed at HCA scaffolds without tissue regeneration detected within them. Our histological findings concerning FSA scaffolds clearly showed the presence of adipose-like tissue surprisingly composed by a mixture of brown-like and white-like adipocytes at week 2 whereas only white-like adipocytes at week 4. Subsequent positive Pax7 immunostaining at weeks 1 and 2 suggested the existence of a common myogenic progenitor shared by brown-like and white-like adipocytes observed. Then, in this work we present FSA scaffolds as a promising structure for brown and white adipose tissue engineering.