49 research outputs found
Alkaline treatments to render starch-based biodegradable polymers self-mineralizable
The present research aims to develop a new route for surface functionalization of biodegradable polymers. The method is based on a wet chemistry modification, resulting in etching and/or hydrolysis in order to increase the amount of polar groups, such as hydroxyl (--OH) and carboxylic (--COOH) groups on the surface of the polymer. The polymer used as substrate was a corn starch-ethylene vinyl alcohol biodegradable blend (SEVA-C). For that purpose it was used in two different types of activation: (a) calcium hydroxide solution [Ca(OH)(2)] and (b) sodium hydroxide solution (NaOH). These treatments lead to the formation carboxylic acid-rich SEVA-C surfaces. Then, the samples were soaked in simulated body fluid (SBF) for different time periods of time until 7 days. After 1 day in SBF, the surface of SEVA-C was fully covered with spherulite particles. As the soaking time increased, the particles increased and coalesced, leading to the formation of a dense and uniform layer. Furthermore, thin-film X-ray diffraction confirms that the layer formed on the surface of the polymer was an apatite-like layer. These results suggest that this rather simple treatment is a good method for surface functionalization and subsequent mineral nucleation and growth on biodegradable polymeric surfaces to be used for bone-related applications
Development of a bioactive glass fiber reinforced starch-polycaprolactone composite
For bone regeneration and repair, combinations of different materials are often
needed. Biodegradable polymers are often combined with osteoconductive materials, such as
bioactive glass (BaG), which can also improve the mechanical properties of the composite. The
aim of this work was to develop and characterize BaG fiber reinforced starch–poly-ecaprolactone
(SPCL) composite. Sheets of SPCL (30/70 wt %) were produced using singlescrew
extrusion. They were then cut and compression-molded in layers with BaG fibers to
form composite structures with different combinations. Mechanical and degradation properties
of the composites were studied. The actual amount of BaG in the composites was
determined using combustion tests. Initial mechanical properties of the reinforced composites
were at least 50% better than the properties of the nonreinforced specimens. However, the
mechanical properties of the composites after 2 weeks of hydrolysis were comparable to those
of the nonreinforced samples. During the 6 weeks hydrolysis the mass of the composites had
decreased only by about 5%. The amount of glass in the composites remained as initial for the
6-week period of hydrolysis. In conclusion, it is possible to enhance initial mechanical
properties of SPCL by reinforcing it with BaG fibers. However, mechanical properties of the
composites are typical for bone fillers and strength properties need to be further improved for
allowing more demanding bone applications.Technology Development Center in Finland (TEKES); contract grant number: 90220.European Commission (European Union Project EXPER-TISSUES); contract grant number: NMP3-CT-2004-500328.Academy of Finland; contract grant number: 37726.The Ministry of Italian University (MIUR)-Rome, through the PRIN'06 prot. n. 2006038548 project; InterUniversity Consortium of Materials Science and Technology (INSTM), Florence, through the PRISMA'04 project
Study of the influence of Beta-radiation on the properties and mineralization of different starch-based biomaterials
In this work, the effects of beta-radiation are assessed, for the first time, on starch-based biodegradable polymers, with the aim of using it as an alternative sterilization process to the previously studied sterilization methods. Different doses of radiation were used in order to investigate the possibility of using this sterilization technique as a treatment to tailor the surface and bulk properties (namely mechanical) of these polymers. The as-treated substrates were characterized by water-uptake measurements and contact angle (theta) measurements. The mechanical properties of the materials were characterized by tensile tests by means of ultimate tensile strength (UTS) and strain at break (epsilon). The fracture of the surfaces was observed by scanning electron microscopy (SEM). Dynamic mechanical analysis (DMA) was also used to characterize the viscolelastic behavior of the irradiated materials. The main effect of sterilization with beta-radiation over the starch-based polymers seems to be a surface modification by an increase of the hydrophilicity. Nevertheless, because beta-radiation did not significantly affect the mechanical properties, it can be regarded as an effective way of modifying the surface for applications were more hydrophilic surfaces are desirable
Changes on surface morphology of corn starch blend films
This study aims at evaluating the influence of enzymatic degradation solution on the surface morphology and thermal properties of a poly(ethylene-vinyl alcohol) copolymer-corn starch thermoplastic blend (SEVA-C), as a function of immersion time. To perform this study, three different batches were assessed using SEVA-C samples of different thicknesses and a fixed weight of 1.6 g, immersed in alpha-amylase (50 u/L) up to 90 days at 37 degrees C. TGA, contact angle measurements, scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques were used. Three degradation mechanisms are considered in these systems: namely, mass loss due to plasticizer leaching (glycerol), starch enzymatic cleavage, and synthetic polymer fractions degradation. Enzymatic hydrolysis of the starch fraction and subsequent leaching from the internal bulk structure led to an increase in surface porosity, pore size, roughness, and to the development of small pits throughout the surface, as observed by SEM and AFM
Entrapment ability and release profile of corticosteroids from starch-based microparticles
We previously described the synthesis of starchbased microparticles that were shown to be bioactive (when combined with Bioactive Glass 45S5) and noncytotoxic. To
further assess their potential for biomedical applications such as controlled release, three corticosteroids with a similar basic structure—dexamethasone (DEX), 16-methylprednisonole
(MP), and 16-methylprednisolone acetate
(MPA) - were used as models for the entrapment and release of bioactive agents. DEX, MP, and MPA were entrapped
into starch-based microparticles at 10% wt/wt of the starch-based polymer and the loading efficiencies, as well as the release profiles, were evaluated. Differences were
found for the loading efficiencies of the three corticosteroids, with DEX and MPA being the most successfully loaded (82 and 84%, respectively), followed by MP (51%). These differences might be explained based on the differential distribution of the molecules within the matrix of the microparticles.
Furthermore, a differential burst release was observed in the first 24 h for all corticosteroids with DEX and MP being
more pronounced (around 25%), whereas only 12% of MPA was released during the same time period. Whereas the water uptake profile can account for this first stage burst
release, the subsequent slower release stage was mainly attributed to degradation of the microparticle network. Differences
in the release profiles can be explained based on the structure of the molecule, because MPA, a more bulky and hydrophobic molecule, is released at a slower rate compared
with DEX and MP. In this work, it is shown that these carriers were able to sustain a controlled release of the entrapped corticosteroids over 30 days, which confirms the potential of these systems to be used as carriers for the delivery of bioactive agents
Nucleation and growth of biomimetic apatite layers on 3D plotted biodegradable polymeric scaffolds : effect of static and dynamic coating conditions
Apatite layers were grown on the surface of newly developed starch/polycaprolactone (SPCL)-based scaffolds by a 3D plotting technology.
To produce the biomimetic coatings, a sodium silicate gel was used as nucleating agent, followed by immersion in a simulated
body fluid (SBF) solution. After growing a stable apatite layer for 7 days, the scaffolds were placed in SBF under static, agitated (80 strokes
min!1) and circulating flow perfusion (Q = 4 ml min!1; tR = 15 s) for up to 14 days. The materials were characterized by scanning
electron microscopy/energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and thin-film X-ray diffraction.
Cross-sections were obtained and the coating thickness was measured. The elemental composition of solution and coatings was monitored
by inductively coupled plasma spectroscopy. After only 6 h of immersion in SBF it was possible to observe the formation of small
nuclei of an amorphous calcium phosphate (ACP) layer. After subsequent SBF immersion from 7 to 14 days under static, agitated and
circulating flow perfusion conditions, these layers grew into bone-like nanocrystalline carbonated apatites covering each scaffold fiber
without compromising its initial morphology. No differences in the apatite composition/chemical structure were detectable between
the coating conditions. In case of flow perfusion, the coating thickness was significantly higher. This condition, besides mimicking better
the biological milieu, allowed for the coating of complex architectures at higher rates, which can greatly reduce the coating step.The authors acknowledge the Portuguese Foundation for Science and Technology (PhD grant to A.L.O., SFRH/BD/10956/2002 and post-doctoral Grant to R.A.S., SFRH/BPD/17151/2004, under the POCTI Program). This work was partially supported by FCT through POCTI and/or FEDER programmes and also partially supported by the EU Project HIPPOCRATES (NMP3-CT-2003-505758) and EXPERTISSUES (NMP-CT-2004-500283)
Does the white coat influence satisfaction, trust and empathy in the doctor-patient relationship in the General and Family Medicine consultation? Interventional study
Objectives To understand the influence of the white coat on
patient satisfaction, opinions about medical clothing, perception
about confidence, empathy and medical knowledge and the
satisfaction and comfort level of physicians in consultation.
Setting An interventional study was conducted with a
representative sample of the population attending primary care
in central Portugal.
Participants The sample was composed by 286 patients
divided into two groups exposed or not to a doctor wearing a
white coat. The first and last patients in consultation every day
for 10 consecutive days were included.
Interventions Every other day the volunteer physicians
consulted with or without the use of a white coat. At the end
of the consultation, a questionnaire was distributed to the
patient with simple questions with a Likert scale response, the
Portuguese version of the ‘Trust in physician’ scale and the
Jefferson Scale of Patient Perceptions of Physician Empathy
- Portuguese Version (JSPPPE-VP
scale). A questionnaire was
also distributed to the physician.
Outcomes Planned and measured primary outcomes were
patient satisfaction, trust and perception about empathy and
secondary outcomes were opinion about medical clothing,
satisfaction and comfort level of physicians in consultation.
Results The sample was homogeneous in terms of
sociodemographic variables. There were no statistically
significant differences between the groups in terms of
satisfaction, trust, empathy and knowledge perceived by the
patients. There were differences in the opinion of the patients
about the white coat, and when the physician was wearing
the white coat this group of patients tended to think that this
was the only acceptable attire for the physician (p<0.001).
But when the family physician was in consultation without
the white coat, this group of patients tended to agree that
communication was easier (p=0.001).
Conclusions There was no significant impact of the white
coat in patient satisfaction, empathy and confidence in the
family physician.
Trial registration number ClinicalTrials. gov ID number:
NCT0396541
Nature-inspired calcium phosphate coatings : present status and novel advances in the science of mimicry
There has been a growing awareness in materials science that the adaptation of nature biological processes can lead to significant progresses in the controlled fabrication of advanced materials for an all range of applications. To learn from, understand and apply these natural processes for producing calcium phosphate coatings that are biologically similar to bone apatite, mimicking its properties, has driven the attention of many researchers in recent years. This article reviews the most relevant advances in this emerging research field, pointing out several approaches being introduced and explored by distinct laboratories