Single-step, acid-based fabrication of homogeneous gelatin-polycaprolactone fibrillar scaffolds intended for skin tissue engineering

Blends of natural and synthetic polymers have recently attracted great attention as scaffolds for tissue engineering applications due to their favorable biological and mechanical properties. Nevertheless, phase-separation of blend components is an important challenge facing the development of electrospun homogeneous fibrillar natural-synthetic polymers scaffolds; phase-separation can produce significant detrimental effects for scaffolds fabricated by electrospinning. In the present study, blends of gelatin (Gel; natural polymer) and polycaprolactone (PCL; synthetic polymer), containing 30 and 45 wt.% Gel, were prepared using acetic acid as a "green" sole solvent to straightforwardly produce appropriate single-step Gel-PCL solutions for electrospinning. Miscibility of Gel and PCL in the scaffolds was assessed and the morphology, chemical composition and structural and solid-state properties of the scaffolds were thoroughly investigated. Results showed that the two polymers proved miscible under the single-step solution process used and that the electrospun scaffolds presented suitable properties for potential skin tissue engineering applications. Viability, metabolic activity and protein expression of human fibroblasts cultured on the Gel-PCL scaffolds were evaluated using LIVE/DEAD (calcein/ethidium homodimer), MTT-Formazan and immunocytochemistry assays, respectively. In vitro results showed that the electrospun Gel-PCL scaffolds enhanced cell viability and proliferation in comparison to PCL scaffolds. Furthermore, scaffolds allowed fibroblasts expression of extracellular matrix proteins, tropoelastin and collagen Type I, in a similar way to positive controls. Results indicated the feasibility of the single-step solution process used herein to obtain homogeneous electrospun Gel-PCL scaffolds with Gel content ≥ 30 wt.% and potential properties to be used as scaffolds for skin tissue engineering applications for wound healing

Antibacterial composite membranes of polycaprolactone/gelatin loaded with zinc oxide nanoparticles for guided tissue regeneration

The bacterial colonization of absorbable membranes used for guided tissue regeneration (GTR), as well as their rapid degradation that can cause their rupture, are considered the major reasons for clinical failure. To address this, composite membranes of polycaprolactone (PCL) and gelatin (Gel) loaded with zinc oxide nanoparticles (ZnO-NPs; 1, 3 and 6 wt% relative to PCL content) were fabricated by electrospinning. To fabricate homogeneous fibrillar membranes, acetic acid was used as a sole common solvent to enhance the miscibility of PCL and Gel in the electrospinning solutions. The effects of ZnO-NPs in the physico-chemical, mechanical and in vitro biological properties of composite membranes were studied. The composite membranes showed adequate mechanical properties to offer a satisfactory clinical manipulation and an excellent conformability to the defect site while their degradation rate seemed to be appropriate to allow successful regeneration of periodontal defects. The presence of ZnO-NPs in the composite membranes significantly decreased the planktonic and the biofilm growth of the Staphylococcus aureus over time. Finally, the viability of human osteoblasts and human gingival fibroblasts exposed to the composite membranes with 1 and 3 wt% of ZnO-NPs indicated that those membranes are not expected to negatively influence the ability of periodontal cells to repopulate the defect site during GTR treatments. The results here obtained suggest that composite membranes of PCL and Gel loaded with ZnO-NPs have the potential to be used as structurally stable GTR membranes with local antibacterial properties intended for enhancing clinical treatments

Síntesis y estabilización de Dopamina insertada en una matriz de TiO2 por el método sol-gel

La dopamina (DA) es inestable químicamente ya que tiende a oxidarse con la luz y con el aire al ser una fuente mayoritaria de las especies de oxígeno reactivas. En este trabajo se describe la síntesis vía sol-gel de una matriz de TiO2 amorfo, que es muy estable químicamente y no tóxica; dentro de la cual se introdujo la DA formando el complejo TiO2/DA. Se logró estabilizar la DA retardando su proceso de oxidación y preservando su actividad biológica en forma prolongada. En una segunda muestra, se añadió el éter 15-Crown-5, con el que se retardó aún más el proceso de oxidación de la DA y formó nanocristales en la matriz. El monitoreo del proceso de oxidación de la DA de ambos complejos se realizó por absorción óptica y espectroscopia infrarroja. Al complejo TiO2/DA/15C5 se le realizaron estudios de TEM y DRX. *Agradecemos el apoyo a los proyectos CONACYT 79781, PUNTA, RedNyN, PAPIIT IN107510 y Proyecto SIP 20113905. Los autores agradecen al M. en C. Manuel Aguilar-Franco, Luis Rendón y a Diego Quiterio por la asistencia técnica

Photoconductivity behavior and Stabilization of DA embedded in amorphous TiO2 matrix synthesized by sol-gel method

Parkinson’s disease is a debilitating, often fatal, neurological disorder that affects about 1% of the population over 50 years of age. It is characterized by tremor in the extremities, difficulty initiating voluntary movements, and rigidity. It is well known that the Dopamine (DA) (Scheme 1) is an important neurotransmitter in mammalian central nervous system and low levels of DA have been found in patients with this disease 1. It seems to be that the lost of DArgetic neurons in the substantia nigra is the primary cause of the Parkinson’s disease 2. Literature reports that DA is one of the major sources of reactive oxygen species (ROS) 3. When exposed to the daylight, DA oxidizes very easy due to its chemical instability. DA contains an unstable catechol moiety with respect to its molecular structure; it can oxidize spontaneously in vitro, free radicals and quinones 4-6. In addition, in the human substantia nigra, the oxidation products of DA may polymerize to form neuromelanin which may also be a highly cytotoxic substance 7. Besides, a controlled release system to deliver the drug directly into the brain is of great interest for the treatment of the Parkinson’s disease. In this work, the synthesis of amorphous TiO2 matrix by sol-gel method at room temperature in air atmosphere is reported. DA was encapsulated in two kinds of TiO2 matrices to reduce its chemical instability. One sample is TiO2/DA and the second one was synthesized by adding 15C5 to protect the DA from oxidation process. The stabilization process to avoid the oxidation of the DA was followed by absorption spectra (Figure 1) and infrared spectroscopy. Oxidation processes of the DA can be identified by the presence of DA quinone and DA chrome whose infrared bands are reported in the literature (Figure 2). The TiO2/DA/15C5 shows more stability than the TiO2/DA. For TiO2/DA/15C5 sample, the oxidation process is retarded by one month approximately, while for TiO2/DA this process is retarded only seven days. Photoconductivity studies were performed on both kinds of films to analyze their charge transports. The experimental data were fitted with straight lines at darkness and under illumination at 320 nm, 400 nm, and 515 nm. This indicates an ohmic behavior. Transport parameters were calculated. The conductive effect is stronger under darkness than under illumination at 320 nm because the oxidation process in the darkness is less intense than under illumination. Besides, this effect is more intense in the TiO2/DA film (Figure 3). A photovoltaic effect is stronger on TiO2/DA/15C5 film than TiO2/DA film. References [1] S. Yuan, W. Chen, S. Hu, Mater.Sci. and Eng.C, 2005, 25, 479-485. [2] F. Trejo, P. Vergara, M. Brenne, J. Segovia, Life Sci., 1999, 65, 483-491. [3] C.-D. Kang, J.-H. Jang, K.-W. Kim, H.-J. Lee, C.-S. Jeong, C.-M. Kim, S.-H. Kim, B.-S. Chung, Neuroscience Lett., 1998, 256, 37-40. [4] G. Cohen, R.E. Heikkila, J. Biol. Chem., 1974, 249, 2447-2452. [5] D. G. Graham, S. M. Tiffany, W. R. Bell, Jr., W. F.Gutknecht, Mol. Pharmacol., 1978, 14, 644-653. [6] T. G. Hastings, J. Neurochem., 1995, 64, 919-924. * The authors acknowledge the financial supports of CONACYT 79781, Red NyN and PAPIIT IN107510. GVA is grateful for CONACYT postdoctoral fellowship. We thank to Jaqueline Cañetas-Ortega (SEM) and Diego Quiterio (preparation of samples for SEM) for technical assistance

Dopamine Released from TiO2 Semicrystalline Lattice Implants Attenuates Motor Symptoms in Rats Treated with 6‑Hydroxydopamine

The motor dysfunction featured by patients aggrieved by Parkinson’s disease (PD) results from the reduction of dopamine (DA) availability in the caudate nucleus (CN). Restituting CN DA levels is therefore essential to ameliorate PD motor deficits. In this regard, nanotechnology may offer solutions to restore CN DA availability. DA, however, can be rapidly oxidized into toxic compounds if made available in situ, unprotected. Then, we tested whether a semicrystalline TiO2 lattice, implanted into the CN of 6-hydroxydopamine (6-OHDA)-lesioned, hemiparkinsonian rats, was able to release DA during a time window sufficient to attenuate motor symptoms while protecting it from the ongoing oxidation. Accordingly, implanted semicrystalline TiO2 lattices released incremental amounts of DA into the CN of lesioned rats. Motor symptoms were already attenuated by the 1st month and significantly reduced 2 months after implantation. These effects were specific since TiO2 lattices alone did not modify motor symptoms in lesioned rats. DA-unloaded or -loaded TiO2 lattices did not produce obvious symptoms of systemic or neurological toxicity nor significantly increased CN lipid peroxidation in implanted, lesioned rats at the time of sacrifice. Our results thus support that loaded TiO2 lattices are capable of releasing DA while protecting it from the ongoing oxidation when implanted into the brain. Their implantation does not cause noticeable systemic or local toxicity. On the contrary, they attenuated motor symptoms in hemiparkinsonian rats

TiO2-dopamine complex implanted unilaterally in the caudate nucleus improves motor activity and behavior function of rats with induced hemiparkinsonism

Instituto Politécnico Nacional, CICATA-Legari

Dispositivos biocompatibles para La liberación de Dopamina en ratas

Instituto Politécnico Nacional, CICATA-Legari