Biopolymers for Tissue Engineering: Crosslinking, Printing Techniques, and Applications.

Currently, tissue engineering has been dedicated to the development of 3D structures through bioprinting techniques that aim to obtain personalized, dynamic, and complex hydrogel 3D structures. Among the different materials used for the fabrication of such structures, proteins and polysaccharides are the main biological compounds (biopolymers) selected for the bioink formulation. These biomaterials obtained from natural sources are commonly compatible with tissues and cells (biocompatibility), friendly with biological digestion processes (biodegradability), and provide specific macromolecular structural and mechanical properties (biomimicry). However, the rheological behaviors of these natural-based bioinks constitute the main challenge of the cell-laden printing process (bioprinting). For this reason, bioprinting usually requires chemical modifications and/or inter-macromolecular crosslinking. In this sense, a comprehensive analysis describing these biopolymers (natural proteins and polysaccharides)-based bioinks, their modifications, and their stimuli-responsive nature is performed. This manuscript is organized into three sections: (1) tissue engineering application, (2) crosslinking, and (3) bioprinting techniques, analyzing the current challenges and strengths of biopolymers in bioprinting. In conclusion, all hydrogels try to resemble extracellular matrix properties for bioprinted structures while maintaining good printability and stability during the printing process.

Three-Dimensionally Printed Hydrogel Cardiac Patch for Infarct Regeneration Based on Natural Polysaccharides.

Myocardial infarction is one of the more common cardiovascular diseases, and remains the leading cause of death, globally. Hydrogels (namely, those using natural polymers) provide a reliable tool for regenerative medicine and have become a promising option for cardiac tissue regeneration due to their hydrophilic character and their structural similarity to the extracellular matrix. Herein, a functional ink based on the natural polysaccharides Gellan gum and Konjac glucomannan has, for the first time, been applied in the production of a 3D printed hydrogel with therapeutic potential, with the goal of being locally implanted in the infarcted area of the heart. Overall, results revealed the excellent printability of the bioink for the development of a stable, porous, biocompatible, and bioactive 3D hydrogel, combining the specific advantages of Gellan gum and Konjac glucomannan with proper mechanical properties, which supports the simplification of the implantation process. In addition, the structure have positive effects on endothelial cells' proliferation and migration that can promote the repair of injured cardiac tissue. The results presented will pave the way for simple, low-cost, and efficient cardiac tissue regeneration using a 3D printed hydrogel cardiac patch with potential for clinical application for myocardial infarction treatment in the near future.

Development of a Mucoadhesive Vehicle Based on Lyophilized Liposomes for Drug Delivery through the Sublingual Mucosa.

A pharmaceutical vehicle based on lyophilized liposomes is proposed for the buccal administration of drugs aimed at systemic delivery through the sublingual mucosa. Liposomes made of egg phosphatidylcholine and cholesterol (7/3 molar ratio) were prepared and lyophilized in the presence of different additive mixtures with mucoadhesive and taste-masking properties. Palatability was assayed on healthy volunteers. The lyophilization cycle was optimized, and the lyophilized product was compressed to obtain round and capsule-shaped tables that were evaluated in healthy volunteers. Tablets were also assayed regarding weight and thickness uniformities, swelling index and liposome release. The results proved that lyophilized liposomes in unidirectional round tablets have palatability, small size, comfortability and buccal retention adequate for sublingual administration. In contact with water fluids, the tablets swelled, and rehydrated liposomes were released at a slower rate than permeation efficiency determined using a biomimetic membrane. Permeability efficiency values of 0.72 ± 0.34 µg/cm2/min and 4.18 ± 0.95 µg/cm2/min were obtained for the liposomes with and without additives, respectively. Altogether, the results point to the vehicle proposed as a liposomal formulation suitable for systemic drug delivery through the sublingual mucosa.

Single-Step Self-Assembly of Zein-Honey-Chitosan Nanoparticles for Hydrophilic Drug Incorporation by Flash Nanoprecipitation.

Zein- and chitosan-based nanoparticles have been described as promising carrier systems for food, biomedical and pharmaceutical applications. However, the manufacture of size-controlled zein and chitosan particles is challenging. In this study, an adapted anti-solvent nanoprecipitation method was developed. The effects of the concentration of zein and chitosan and the pH of the collection solution on the properties of the zein-honey-chitosan nanoparticles were investigated. Flash nanoprecipitation was demonstrated as a rapid, scalable, single-step method to achieve the self-assembly of zein-honey-chitosan nanoparticles. The nanoparticles size was tuned by varying certain formulation parameters, including the total concentration and ratio of the polymers. The zein-honey-chitosan nanoparticles' hydrodynamic diameter was below 200 nm and the particles were stable for 30 days. Vitamin C was used as a hydrophilic model substance and efficiently encapsulated into these nanoparticles. This study opens a promising pathway for one-step producing zein-honey-chitosan nanoparticles by flash nanoprecipitation for hydrophilic compounds' encapsulation.

Osmundea sp. macroalgal polysaccharide-based nanoparticles produced by flash nanocomplexation technique.

The macroalgae-derived polysaccharides' biological potential has been explored due to their attractive intrinsic properties such as biocompatibility, biodegradability, and their ability to conjugate with other compounds. In particular, in the drug delivery systems field, the anionic macroalgae polysaccharides have been combined with cationic compounds through ionotropic gelation and/or bulk mixing. However, these techniques did not assure reproducibility, and the stability of nanoparticles is undesired. To overcome these limitations, herein, the polysaccharide extracted from Osmundea sp. was used to produce nanoparticles through the flash nanocomplexation technique. This approach rapidly mixed the negative charge of macroalgae polysaccharide with a positive chitosan charge on a millisecond timescale. Further, diclofenac (an anti-inflammatory drug) was also incorporated into complex nanoparticles. Overall, the gathered data showed that hydrodynamic diameter nanoparticles values lower than 100 nm, presenting a narrow size distribution and stability. Also, the diclofenac exhibited a targeted and sustained release profile in simulating inflammatory conditions. Likewise, the nanoparticles showed excellent biological properties, evidencing their suitability to be used to treat inflammatory skin diseases.

Oromucosal Alginate Films with Zein Nanoparticles as a Novel Delivery System for Digoxin.

Digoxin is a hydrophobic drug used for the treatment of heart failure that possesses a narrow therapeutic index, which raises safety concerns for toxicity. This is of utmost relevance in specific populations, such as the elderly. This study aimed to demonstrate the potential of the sodium alginate films as buccal drug delivery system containing zein nanoparticles incorporated with digoxin to reduce the number of doses, facilitating the administration with a quick onset of action. The film was prepared using the solvent casting method, whereas nanoparticles by the nanoprecipitation method. The nanoparticles incorporated with digoxin (0.25 mg/mL) exhibited a mean size of 87.20 ± 0.88 nm, a polydispersity index of 0.23 ± 0.00, and a zeta potential of 21.23 ± 0.07 mV. Digoxin was successfully encapsulated into zein nanoparticles with an encapsulation efficiency of 91% (±0.00). Films with/without glycerol and with different concentrations of ethanol were produced. The sodium alginate (SA) films with 10% ethanol demonstrated good performance for swelling (maximum of 1474%) and mechanical properties, with a mean tensile strength of 0.40 ± 0.04 MPa and an elongation at break of 27.85% (±0.58), compatible with drug delivery application into the buccal mucosa. The current study suggests that SA films with digoxin-loaded zein nanoparticles can be an effective alternative to the dosage forms available on the market for digoxin administration.

Prevalence of vitamin D deficiency amongst soccer athletes and effects of 8 weeks supplementation.

BACKGROUND: High prevalence of vitamin D deficiency is well known around the world in risk populations. Although less is known about the athletic population, some studies report vitamin D deficiency amongst athletic population and adequate vitamin D levels are crucial for athletic population as they can prevent injuries such as stress fractures and might even have ergogenic effects for example on muscle function. The main objectives were to evaluate the basal serum levels of 25(OH)D and calcium in professional soccer athletes on the latitude 40°N, to evaluate the effects in 25(OH)D and calcium serum levels following supplementation of 1667 IU/day of cholecalciferol during a period of 8 weeks and evaluate eventual toxicity arising from it. METHODS: Twenty-eight professional athletes were evaluated according to the skin type. Basal serum levels of 25(OH)D and calcium were evaluated during winter months. Athletes were then supplemented with cholecalciferol 25.000 IU every two weeks. Serum levels of 25(OH)D and calcium were evaluated after supplementation. RESULTS: 25(OH)D initially ranged between 9.9 ng/mL and 32.9 ng/mL with a median of 19.2 IQR 7.24 ng/mL. A statistically significant inverse correlation exists between vitamin D deficiency and the Fitzpatrick Scale (ρ=-0.555 P=0.003). After 8 weeks, 25(OH)D ranged between 10.6 ng/mL and 43.4 ng/mL with a median of 33.2 ng/mL IQR 6.1 ng/mL. We verified a statistically significant increase of serum 25(OH) D levels (11.74±5.988; CI 95% [9,02; 14,47]; P<0.001. In addition, there was a statistically significant reduction of calcium: -0.36±0.457; CI 95% [- 0.57; -0.15]; P=0.002. CONCLUSIONS: Professional athletes have a high prevalence of vitamin D deficiency. Supplementation with cholecalciferol in winter months during 8 weeks is safe and effective in raising 25(OH)D serum levels. However, it may not be sufficient for athletes to reach adequate vitamin D levels.

Diagnóstico clínico y tratamiento quirúrgico de un meningocele occipital / Clinical diagnosis and surgical treatment of an occipital meningocele

El meningocele occipital es una malformación congénita producida por un defecto en el cierre del tubo neural. El curso natural de esta enfermedad es hacia la muerte por infección del sistema nervioso central o hacia un grado de incapacidad motora y sensitiva avanzada. Se han descrito diversas formas clínicas de esta malformación. Su diagnóstico se basa en el examen físico y estudios imagenológicos y neurofisiológicos, indispensables para conocer el contenido del saco herniario y determinar el tipo de cirugía a realizar. Se presentó el caso de un paciente que tuvo que ser intervenido quirúrgicamente, solamente por el examen físico y el estudio radiográfico simple de cráneo, debido a la imposibilidad económica de los padres de realizar el resto de los exámenes complementarios. Se realizó apertura del saco herniario, con drenaje del líquido cefalorraquídeo y reparación de los planos musculares y cutáneos. El paciente evolucionó favorablemente.

The occipital meningocele is a congenital malformation produced by a defect in the neural tube closure. This disease's natural course is toward death caused by the infection of the central nervous system or toward some level of advanced motor or sensitive disability. There have been described several forms of this malformation. Its diagnosis is based in the physical examination and in neurophysiologic and imaging studies, indispensable to know the content of the hernia sac and to determine the kind of surgery to carry out. We presented the case of a male patient that had to be surgically treated only for the results of the physical examination and simple radiographic study, due to the economical family impossibility of paying the rest of the complementary examination. We opened the hernia sac, drained the cerebrospinal fluid and repaired the skin and muscular planes. The patient had a favorable evolution.

Diagnóstico clínico y tratamiento quirúrgico de un meningocele occipital / Clinical diagnosis and surgical treatment of an occipital meningocele

El meningocele occipital es una malformación congénita producida por un defecto en el cierre del tubo neural. El curso natural de esta enfermedad es hacia la muerte por infección del sistema nervioso central o hacia un grado de incapacidad motora y sensitiva avanzada. Se han descrito diversas formas clínicas de esta malformación. Su diagnóstico se basa en el examen físico y estudios imagenológicos y neurofisiológicos, indispensables para conocer el contenido del saco herniario y determinar el tipo de cirugía a realizar. Se presentó el caso de un paciente que tuvo que ser intervenido quirúrgicamente, solamente por el examen físico y el estudio radiográfico simple de cráneo, debido a la imposibilidad económica de los padres de realizar el resto de los exámenes complementarios. Se realizó apertura del saco herniario, con drenaje del líquido cefalorraquídeo y reparación de los planos musculares y cutáneos. El paciente evolucionó favorablemente(AU)

The occipital meningocele is a congenital malformation produced by a defect in the neural tube closure. This disease's natural course is toward death caused by the infection of the central nervous system or toward some level of advanced motor or sensitive disability. There have been described several forms of this malformation. Its diagnosis is based in the physical examination and in neurophysiologic and imaging studies, indispensable to know the content of the hernia sac and to determine the kind of surgery to carry out. We presented the case of a male patient that had to be surgically treated only for the results of the physical examination and simple radiographic study, due to the economical family impossibility of paying the rest of the complementary examination. We opened the hernia sac, drained the cerebrospinal fluid and repaired the skin and muscular planes. The patient had a favorable evolution(AU)

Larga sobrevida en 5 pacientes con astrocitomas malignos / Long survival in 5 patients with malignant astrocytomas

Históricamente el tiempo de supervivencia promedio de los pacientes con glioblastoma multiforme y astrocitoma anaplásico ha sido de 6 a 12 meses y de 2 a 4 años respectivamente. Muy pocos pacientes alcanzan los 5 años de operados. El propósito fue identificar algún denominador común en los pacientes con larga sobrevida y diagnóstico histológico confirmado de astrocitoma anaplásico o glioblastoma multiforme. Se estableció comunicación con los familiares de 67 pacientes operados en el Instituto de Neurología y Neurocirugía entre los años 1983 a 1992. Se analizaron la edad de los pacientes al momento del diagnóstico, la localización del tumor, el estado neurológico en el comienzo de la enfermedad y el tiempo de evolución de esta, así como el tipo de tratamiento realizado. Se halló 5 pacientes con un tiempo de supervivencia mayor de 7 años. La edad menor de 35 años, la ubicación de la lesión en el lóbulo frontal derecho y el inicio clínico sin defecto neurológico focal, así como la exéresis quirúrgica total fue la norma en el 80 (por ciento) de estos casos. El Karnofsky inicial mayor de 70 puntos y el empleo de radioterapia y quimioterapia posquirúrgica fue común a todos. Los pacientes jóvenes con gliomas astrocíticos de alta malignidad ubicados en el lóbulo frontal derecho, que comienzan con un Karnofsky mayor de 70 puntos y son sometidos a exéresis quirúrgica total, radioterapia y quimioterapia posquirúrgica, tienen mayor probabilidad de prolongar su tiempo de sobrevivencia(AU)

Historically, the average time of survival of the patients with glioblastoma multiforme and anaplastic astrocytoma has ranged from 6 to 12 months and from 2 to 4 years, respectively. A few patients survive 5 years after surgery. The aim of this paper was to identify some common denominator in patients with long survival and confirmed histological diagnosis of anaplastic astrocytoma or multiform glioblastoma. Communication was established with the relatives of 67 patients operated on at the Institute of Neurology and Neurosurgery between 1983 and 1992. The age of the patients, the localization of the tumor, the neurological state at the onset of the disease, the time of evolution and the treatment used were analyzed. 5 patients had a time of survival over 7 years. The youngest patient was 35. The localization of the injury on the right frontal lobule, the clinical beginning without focal neurological defect, as well as the total exeresis was the norm in 80 percent of these cases. The initial scoring over 70 in Karnofsky scale (KS) and the use of radiotherapy and chemotherapy after surgery was common to all of them. Young patients with highly malignant astrocytic gliomas located in the right frontal lobule that begin with a KS over 70 points and undergo total exeresis, postsurgery radiotherapy and chemotherapy have greater probabilities of prolonging their time of survival(AU)

Larga sobrevida en 5 pacientes con astrocitomas malignos / Long survival in 5 patients with malignant astrocytomas

Históricamente el tiempo de supervivencia promedio de los pacientes con glioblastoma multiforme y astrocitoma anaplásico ha sido de 6 a 12 meses y de 2 a 4 años respectivamente. Muy pocos pacientes alcanzan los 5 años de operados. El propósito fue identificar algún denominador común en los pacientes con larga sobrevida y diagnóstico histológico confirmado de astrocitoma anaplásico o glioblastoma multiforme. Se estableció comunicación con los familiares de 67 pacientes operados en el Instituto de Neurología y Neurocirugía entre los años 1983 a 1992. Se analizaron la edad de los pacientes al momento del diagnóstico, la localización del tumor, el estado neurológico en el comienzo de la enfermedad y el tiempo de evolución de esta, así como el tipo de tratamiento realizado. Se halló 5 pacientes con un tiempo de supervivencia mayor de 7 años. La edad menor de 35 años, la ubicación de la lesión en el lóbulo frontal derecho y el inicio clínico sin defecto neurológico focal, así como la exéresis quirúrgica total fue la norma en el 80 (por ciento) de estos casos. El Karnofsky inicial mayor de 70 puntos y el empleo de radioterapia y quimioterapia posquirúrgica fue común a todos. Los pacientes jóvenes con gliomas astrocíticos de alta malignidad ubicados en el lóbulo frontal derecho, que comienzan con un Karnofsky mayor de 70 puntos y son sometidos a exéresis quirúrgica total, radioterapia y quimioterapia posquirúrgica, tienen mayor probabilidad de prolongar su tiempo de sobrevivencia(AU)