A route toward fabrication of 3D printed bone scaffolds based on poly(vinyl alcohol)-chitosan/bioactive glass by sol-gel chemistry.

Among different methods for the fabrication of bone scaffolds, 3D printing has created great advances in tissue engineering and regenerative medicine owing to its ability to make objects mimicking native tissues. Thanks to its abundant availability, structural features, and favorable biological properties, chitosan (CS) hydrogel was selected to be used for preparation of the bone scaffolds. However, the 3D printing of CS-based hydrogels is still under early exploration. Knowing the fact that natural polymers are not so competent at holding large amounts of water, poly(vinyl alcohol) as the second polymer was employed. The novelty of the present research lies in the concept of employing sol-gel chemistry in order to attain proper viscosity and rheological behavior to give self-standing filaments of the polymer blends. Employing sol-gel reaction in the preparation of the hybrid hydrogels had the advantage of endowing shape fidelity to the polymer blend without any solidifying in the needle. The obtained organic-inorganic hybrids were directly printed and subsequently cross-linked. The best performance in terms of mechanical strength, cell viability, and bio-mineralization was observed for the 50:50 ratio. The in vitro cell culture and the bioactivity results showed that the printed scaffolds with this method have great potential in bone tissue engineering. Further, this method could be expandable to print other hydrogels with diverse applications such as implantable devices, soft robotics, etc.

Molecular dynamics investigation of the thermal behaviors of magnesium oxide ceramics at different pressures and temperatures.

Today, magnesia ceramics have attracted considerable attention due to their essential properties. Therefore, this paper investigates the impact of temperature (T) and pressure (P) on the thermal manner of magnesia ceramics using molecular dynamics simulations (MDS). As the T increases, the mobility of the structures increases. Therefore, the heat flux (HF) in the structures increments slightly due to the greater movement and the larger oscillation amplitude of the atomic samples. On the other hand, with increasing P, the oscillation amplitude and displacement of atomic samples are limited. Therefore, the thermal properties of the structure are expected to decrease. Studies show that increasing T from 250 to 350 K increases the average HF from 0.73 to 0.89 W/m2. Also, the average thermal conductivity (TC) increases from 30.58 to 38.27 W/mK. So, increasing the T means a certain amount of energy is fluxed in a shorter time. On the other hand, increasing the P from 0 to 5 bar decreases the average HF from 0.82 to 0.65 W/m2. Also, this issue leads to a decrease in the average TC from 33.49 to 30.96 W/mK.

Comparative evaluation of refractive surgery candidates with Placido topography, Orbscan II, Pentacam, and wavefront analysis.

PURPOSE: To study the role of the Pentacam (Oculus), Orbscan II (Bausch & Lomb), and WaveScan (Visx) in evaluating topographic features identified as risk factors for ectasia after laser in situ keratomileusis to identify parameters that may be important in interpreting elevation topography and wavefront data when screening refractive surgery candidates. SETTING: Private practice, New York, New York, USA. METHODS: One hundred forty-five eyes of 75 consecutive patients were evaluated for refractive surgery by ultrasound pachymetry (Humphrey Atlas), videokeratography, WaveScan, Orbscan II, and Pentacam. Eyes were classified as normal or suspect based on the Rabinowitz criteria for keratoconus suspect on Placido disk-based videokeratography. Forty-six parameters were evaluated in a comparison of topographically normal eyes and eyes that met the criteria for keratoconus suspect. RESULTS: The suspect group had thinner pachymetry, multiple distinguishing characteristics on the anterior and posterior corneal surfaces by elevation topography, and larger amounts of coma by wavefront analysis. Multivariable regression analysis identified the following as the strongest predictors of a suspect Placido topography: Pentacam, thinner pachymetry and larger differences between the highest and lowest points on the posterior elevation; Orbscan II, higher anterior maximum elevation, horizontal location of the thinnest point on the pachymetry map, and larger differences between the highest and lowest points on the posterior elevation. CONCLUSION: Several parameters provided by the Pentacam, Orbscan II, WaveScan, and pachymetry were statistically correlated with keratoconus suspect, defined by higher asymmetry and steeper curvature on Placido topography.

A case of fatal strongyloidiasis in a patient with chronic lymphocytic leukemia and molecular characterization of the isolate.

Strongyloides stercoralis is a human intestinal parasite which may lead to complicated strongyloidiasis in immunocompromised. Here, a case of complicated strongyloidiasis in a patient with chronic lymphocytic leukemia is reported. Presence of numerous S. stercoralis larvae in feces and sputum confirmed the diagnosis of hyperinfection syndrome in this patient. Following recovery of filariform larvae from agar plate culture of the stool, the isolate was characterized for the ITS1 region of ribosomal DNA gene by nested-PCR and sequencing. Albendazole therapy did not have cure effects; and just at the beginning of taking ivermectin, the patient died. The most important clue to prevent such fatal consequences is early diagnosis and proper treatment.

Transverse keratotomy followed by LASIK for the treatment of naturally occurring astigmatism.

PURPOSE: To evaluate the efficacy of transverse keratotomy followed by LASIK for patients with high amounts of naturally occurring astigmatism. METHODS: Thirteen eyes with naturally occurring astigmatism ranging from -3.75 to -6.50 diopters (D) underwent sequential transverse keratotomy (60 degrees at 6 mm) and LASIK procedures. The effect of these two procedures on the amount of astigmatism was studied. RESULTS: Transverse keratotomy led to a 46% reduction in refractive cylinder from -5.50 +/- 0.80 D to -3.00 +/- 1.00 D. After LASIK, the initial refractive astigmatism was reduced by 90% to -0.50 +/- 0.50 D with a minimum follow-up of 6 months. CONCLUSIONS: The combined technique of transverse keratotomy followed by LASIK is an effective and accurate way to treat high amounts of naturally occurring astigmatism, allowing the size of the optical zone of the excimer laser ablation to be maximized.

Effect of artificial tears on visual acuity.

PURPOSE: To study the effect of commonly used preservative free artificial tear, carboxymethylcellulose (CMC) 0.5% (Refresh Plus, Allergan, Irvine, California) on visual acuity in symptomatic dry eye (SDE) and asymptomatic dry eye (ADE) patients. DESIGN: Nonrandomized prospective clinical trial. METHODS: Prospective study involving 20 patients (40 eyes) with SDE and 20 patients (40 eyes) with ADE, all 40 years and older, were recruited from a clinic setting over a 1-month period. Distance visual acuity was measured by the Early Treatment of Diabetic Retinopathy Study (ETDRS) vision chart and near visual acuity was measured by the Lighthouse Near Vision chart before and 30 seconds after instillation of one drop of CMC. Distance and near visual acuity was measured both with and without correction. The duration of action of CMC was measured at 1-minute intervals until the patient's visual acuity returned to pretear level. RESULTS: In both SDE and ADE groups, uncorrected and corrected near and distance vision showed a statistically significant improvement after the use of CMC (P < .05). There was no statistically significant difference in improvement between the SDE and ADE groups in all categories (P values > .05). The mean duration of improvement of vision was 2.93 minutes in the SDE group and 3.70 minutes in the ADE group (P = .036). CONCLUSIONS: CMC 0.5% provides a temporary yet significant improvement in the visual acuity of SDE and ADE patients. The effect of artificial tears on visual acuity may be of diagnostic value in detecting ocular surface abnormality in symptomatic and asymptomatic patients.

Traumatic flap dislocation 4 years after laser in situ keratomileusis.

We present a case of late traumatic flap dislocation 47 months after laser in situ keratomileusis (LASIK). This is the latest reported case of traumatic LASIK flap dislocation to date. The patient was examined 5 days after being struck in the face and found to have a flap dislocation. The flap was repositioned surgically, and postoperatively the patient had 20/20 visual acuity and no visual complaints.