Plant Fibers as Composite Reinforcements for Biomedical Applications.

Plant fibers possess high strength, high fracture toughness and elasticity, and have proven useful because of their diversity, versatility, renewability, and sustainability. For biomedical applications, these natural fibers have been used as reinforcement for biocomposites to infer these hybrid biomaterials mechanical characteristics, such as stiffness, strength, and durability. The reinforced hybrid composites have been tested in structural and semi-structural biodevices for potential applications in orthopedics, prosthesis, tissue engineering, and wound dressings. This review introduces plant fibers, their properties and factors impacting them, in addition to their applications. Then, it discusses different methodologies used to prepare hybrid composites based on these widespread, renewable fibers and the unique properties that the obtained biomaterials possess. It also examines several examples of hybrid composites and their biomedical applications. Finally, the findings are summed up and some thoughts for future developments are provided. Overall, the focus of the present review lies in analyzing the design, requirements, and performance, and future developments of hybrid composites based on plant fibers.

Antimicrobial Properties of Plant Fibers.

Healthcare-associated infections (HAI), or nosocomial infections, are a global health and economic problem in developed and developing countries, particularly for immunocompromised patients in their intensive care units (ICUs) and surgical site hospital areas. Recurrent pathogens in HAIs prevail over antibiotic-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. For this reason, natural antibacterial mechanisms are a viable alternative for HAI treatment. Natural fibers can inhibit bacterial growth, which can be considered a great advantage in these applications. Moreover, these fibers have been reported to be biocompatible and biodegradable, essential features for biomedical materials to avoid complications due to infections and significant immune responses. Consequently, tissue engineering, medical textiles, orthopedics, and dental implants, as well as cosmetics, are fields currently expanding the use of plant fibers. In this review, we will discuss the source of natural fibers with antimicrobial properties, antimicrobial mechanisms, and their biomedical applications.

Enhanced osteoblastic differentiation of mesenchymal stem cells seeded in RGD-functionalized PLLA scaffolds and cultured in a flow perfusion bioreactor.

The present study combines chemical and mechanical stimuli to modulate the osteogenic differentiation of mesenchymal stem cells (MSCs). Arg-Gly-Asp (RGD) peptides incorporated into biomaterials have been shown to upregulate MSC osteoblastic differentiation. However, these effects have been assessed under static culture conditions, while it has been reported that flow perfusion also has an enhancing effect on MSC osteoblastic differentiation. It is clear that there is a need to combine RGD modification of biomaterials with mechanical stimulation of MSCs via flow perfusion and evaluate its effects on MSC differentiation down the osteogenic lineage. In this study, the effect of different levels of RGD modification of poly(L-lactic acid) scaffolds on MSC osteogenesis was evaluated under conditions of flow perfusion. It was found that there is a synergistic enhancement of different osteogenic markers, due to the combination of flow perfusion and RGD surface modification when compared to their individual effects. Furthermore, under conditions of flow perfusion, there is an RGD surface concentration optimal for differentiation, and it is flow rate-dependent. This report underlines the significance of incorporating combined biomimesis via biochemical and mechanical microenvironments that modulate in vivo cell behaviour and tissue function for more efficient tissue-engineering strategies.

Histórico del proceso de creación de la Escuela de Odontología de la Universidad del Valle: primera acción investigativa de base: estudio de recursos Odontológicos en el Área sur-occidental de Colombia / Historical review of the process of creation of the Dental School of the Universidad del Valle: first base action of investigation: study of dentistry resources in the southwestern area of Colombia

Se presenta el resultado de la única Investigación Epidemiológica Cuantitativo–Cualitativa Regional e Interinstitucional que se ha realizado en América Latina como base para la fundación de una Facultad de Odontología. En 1.969, por acción integrada de la Sección de Odontología Sanitaria del Departamento de Medicina Preventiva y de Salud Publica de la Universidad del Valle y del Programa de Especialización en Odontología Sanitaria y de Salud Pública de la Escuela de Salud Pública de la Universidad de Antioquia, con la Asesoría de la Organización Panamericana de la Salud “OPS”, se llevó a cabo una investigación de campo en Odontología cuyos métodos y resultados generales, algunos de cuyos hallazgos se presentan en este manuscrito, se utilizaron como fundamento para la toma de decisiones curriculares por parte del Comité Universitario Pro Facultad de Odontología de la Universidad del Valle, “CUPFO” y por el Consejo Directivo de la Universidad para aprobar, en Junio de 1.970, la creación del Departamento de Estomatología de la División de Salud (por la Reforma Administrativa llevada a cabo en 1.968, las Facultades de disciplinas afines se agruparon en unos nuevos entes administrativos: las Divisiones. Dentro de estas, las antiguas y las nuevas Facultades pasaron a ser Departamentos) en la mencionada Alma Mater. La investigación incluyó algunos aspectos que no fueron tomados en cuenta en el Estudio de Recursos Humanos para la Salud que formó parte de la Encuesta Nacional de Morbilidad realizada en 1.965, aspectos que si se incluyeron en el Estudio de Recursos Odontológicos llevado a cabo por el Instituto Nacional para Programas Especiales de Salud, del cual el autor de la Reseña que aquí se presenta fue Asesor - Consultor y Odontólogo de trabajo de Campo en las Unidades de Cali, Santa Rosa de Cabal y Quibdó.

Results of the unique Epidemiological Quantitative - Qualitative Regional and Interinstitutional Research performed at Latin America as essential base to found a new Dental School are presented trough this paper. In 1969 by a cooperative work between the Universidad del Valle, Cali, Colombia and the Antioquia University Public Health and Sanitarian Dentistry Program, on the advice of the Pan American Health Dental Health (PAHO) it was carried out a field research to establish the dental health practice conditions and the data obtained were used as a baseline of curricular determination by the Pro Dental Scholl Committee at the Universidad del Valle “CUPFO”. The study took on accountsome aspects that have been neglected on the National Health Human Resources Research as part of the National Morbidity Research Study realized on 1965 but included in the Dental Health Resources Research performed by the National Special Health Resources Institute. It is necessary to clarify that the author of the present paper participated as a special member of the advisors committee and as field dentist of the Dental Health Resources Research realized by theNational Special Health Resources Institute in 1.965.

Preparation of a functionally flexible, three-dimensional, biomimetic poly(L-lactic acid) scaffold with improved cell adhesion.

Poly(L-lactic acid) (PLLA) is widely used in tissue-engineering applications because of its degradation characteristics and mechanical properties, but it possesses an inert nature, affecting cell-matrix interactions. It is desirable to modify the surface of PLLA to create biomimetic scaffolds that will enhance tissue regeneration. We prepared a functionally flexible, biomimetic scaffold by derivatizing the surface of PLLA foams into primary amines, activated pyridylthiols, or sulfhydryl groups, allowing a wide variety of modifications. Poly(L-lysine) (polyK) was physically entrapped uniformly throughout the scaffold surface and in a controllable fashion by soaking the foams in an acetone-water mixture and later in a polyK solution in dimethylsulfoxide. Arginine-glycine-aspartic acid-cysteine (RGDC) adhesion peptide was linked to the polyK via creating disulfide bonds introduced through the use of the linker N-succinimidyl-3-(2-pyridylthiol)-propionate. Presence of RGDC on the surface of PLLA 2-dimensional (2-D) disks and 3-D scaffolds increased cell surface area and the number of adherent mesenchymal stem cells. We have proposed a methodology for creating biomimetic scaffolds that is easy to execute, flexible, and nondestructive.

Improved mesenchymal stem cell seeding on RGD-modified poly(L-lactic acid) scaffolds using flow perfusion.

Arg-Gly-Asp (RGD) has been widely utilized to increase cell adhesion to three-dimensional scaffolds for tissue engineering. However, cell seeding on these scaffolds has only been carried out statically, which yields low cell seeding efficiencies. We have characterized, for the first time, the seeding of rat mesenchymal stem cells on RGD-modified poly(L-lactic acid) (PLLA) foams using oscillatory flow perfusion. The incorporation of RGD on the PLLA foams improves scaffold cellularity in a dose-dependent manner under oscillatory flow perfusion seeding. When compared to static seeding, oscillatory flow perfusion is the most efficient seeding technique. Cell detachment studies show that cell adhesion is dependent on the applied flow rate, and that cell attachment is strengthened at higher levels of RGD modification.

Flow perfusion improves seeding of tissue engineering scaffolds with different architectures.

Engineered bone grafts have been generated in static and dynamic systems by seeding and culturing osteoblastic cells on 3-D scaffolds. Seeding determines initial cellularity and cell spatial distribution throughout the scaffold, and affects cell-matrix interactions. Static seeding often yields low seeding efficiencies and poor cell distributions; thus creating a need for techniques that can improve these parameters. We have evaluated the effect of oscillating flow perfusion on seeding efficiency and spatial distribution of MC3T3-E1 pre-osteoblastic cells in fibrous polystyrene matrices (20, 35 and 50-microm fibers) and foams prepared by salt leaching, using as controls statically seeded scaffolds. An additional control was investigated where static seeding was followed by unidirectional perfusion. Oscillating perfusion resulted in the most efficient technique by yielding higher seeding efficiencies, more homogeneous distribution and stronger cell-matrix interactions. Cell surface density increased with inoculation cell number and then reached a maximum, but significant detachment occurred at greater flow rates. Oxygen plasma treatment of the fibers greatly improved seeding efficiency. Having similar porosity and dimensions, fibrous matrices yielded higher cell surface densities than foams. Fluorescence microscopy and histological analyses in polystyrene and PLLA scaffolds demonstrated that perfusion seeding produced more homogeneous cell distribution, with fibrous matrices presenting greater uniformity than the foams.

Extraction of nutraceuticals from milk thistle: I. Hot water extraction.

Milk thistle contains compounds that display hepatoxic protection properties. We examined the batch extraction of silymarin compounds from milk thistle seed meal in 50, 70, 85, and 100 degrees C water as a function of time. After 210 min of extraction at 100 degrees C, the yield of taxifolin was 1.2 mg/g of seed, a 6.2-fold increase over the results obtained in a Soxhlet extraction with ethanol on pretreated (defatted) seeds. Similarly, the yield of silychristin was 5.0 mg/g of seed, a 3.8-fold increase. The yields of silybinin A and silybinin B were 1.8 and 3.3 mg/g of seed, respectively, or roughly 30% of the Soxhlet yield. The ratios of the extracted compounds, and particularly the ratios at long extraction times, showed that the more polar compounds (taxifolin and silychristin) were preferentially extracted at 85 degrees C, while the less polar silybinin was favored at 100 degrees C.