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1.
Macromol Biosci ; 23(1): e2200333, 2023 01.
Article in English | MEDLINE | ID: mdl-36287084

ABSTRACT

Shear-thinning biomaterials (STBs) based on gelatin-silicate nanoplatelets (SNs) are emerging as an alternative to conventional coiling and clipping techniques in the treatment of vascular anomalies. Improvements in the cohesion of STB hydrogels pave the way toward their translational application in minimally invasive therapies such as endovascular embolization repair. In the present study, sodium phytate (Phyt) additives are used to tune the electrostatic network of SNs-gelatin STBs, thereby promoting their mechanical integrity and facilitating injectability through standard catheters. We show that an optimized amount of Phyt enhances storage modulus by approximately one order of magnitude and reduces injection force by ≈58% without compromising biocompatibility and hydrogel wet stability. The Phyt additives are found to decrease the immune responses induced by SNs. In vitro embolization experiments suggest a significantly lower rate of failure in Phyt-incorporated STBs than in control groups. Furthermore, the addition of Phyt leads to accelerated blood coagulation (reduces clotting time by ≈45% compared to controls) due to the contributions of negatively charged phosphate groups, which aid in the prolonged durability of STB in coagulopathic patients. Therefore, the proposed approach is an effective method for the design of robust and injectable STBs for minimally invasive treatment of vascular malformations.


Subject(s)
Biocompatible Materials , Hemostatics , Humans , Biocompatible Materials/pharmacology , Gelatin/pharmacology , Phytic Acid , Silicates/pharmacology , Hydrogels/pharmacology
2.
Regen Biomater ; 9: rbac063, 2022.
Article in English | MEDLINE | ID: mdl-36196294

ABSTRACT

Hemorrhage is the leading cause of trauma-related deaths, in hospital and prehospital settings. Hemostasis is a complex mechanism that involves a cascade of clotting factors and proteins that result in the formation of a strong clot. In certain surgical and emergency situations, hemostatic agents are needed to achieve faster blood coagulation to prevent the patient from experiencing a severe hemorrhagic shock. Therefore, it is critical to consider appropriate materials and designs for hemostatic agents. Many materials have been fabricated as hemostatic agents, including synthetic and naturally derived polymers. Compared to synthetic polymers, natural polymers or biopolymers, which include polysaccharides and polypeptides, have greater biocompatibility, biodegradability and processibility. Thus, in this review, we focus on biopolymer-based hemostatic agents of different forms, such as powder, particles, sponges and hydrogels. Finally, we discuss biopolymer-based hemostatic materials currently in clinical trials and offer insight into next-generation hemostats for clinical translation.

3.
Int J Neuropsychopharmacol ; 17(10): 1591-8, 2014 Oct.
Article in English | MEDLINE | ID: mdl-24825251

ABSTRACT

Transcranial direct current stimulation (tDCS) has been shown to modulate subjective craving ratings in drug dependents by modification of cortical excitability in dorsolateral prefrontal cortex (DLPFC). Given the mechanism of craving in methamphetamine (meth) users, we aimed to test whether tDCS of DLPFC could also alter self-reported craving in abstinent meth users while being exposed to meth cues. In this double-blinded, crossover, sham-controlled study, thirty two right-handed abstinent male meth users were recruited. We applied 20 min 'anodal' tDCS (2 mA) or 'sham' tDCS over right DLPFC in a random sequence while subjects performed a computerized cue-induced craving task (CICT) starting after 10 min of stimulation. Immediate craving was assessed before the stimulation, after 10 min of tDCS, and after tDCS termination by visual analog scale (VAS) of 0 to 100. Anodal tDCS of rDLPFC altered craving ratings significantly. We found a significant reduction of craving at rest in real tDCS relative to the sham condition (p = 0.016) after 10 min of stimulation. On the other hand, cue-induced VAS craving was rated significantly higher in the real condition in comparison with sham stimulation (p = 0.012). Our findings showed a state dependent effect of tDCS: while active prefrontal tDCS acutely reduced craving at rest in the abstinent meth users, it increased craving during meth-related cue exposure. These findings reflect the important role of the prefrontal cortex in both cue saliency evaluation and urge to meth consumption.


Subject(s)
Amphetamine-Related Disorders/psychology , Amphetamine-Related Disorders/therapy , Craving , Prefrontal Cortex/physiology , Transcranial Direct Current Stimulation/methods , Adult , Cross-Over Studies , Cues , Diagnosis, Computer-Assisted , Double-Blind Method , Humans , Male , Photic Stimulation , Psychiatric Status Rating Scales , Treatment Outcome , Visual Analog Scale
4.
Adv Healthc Mater ; 3(6): 929-39, 2014 Jun.
Article in English | MEDLINE | ID: mdl-24453182

ABSTRACT

Tissue engineered heart valves (TEHV) can be useful in the repair of congenital or acquired valvular diseases due to their potential for growth and remodeling. The development of biomimetic scaffolds is a major challenge in heart valve tissue engineering. One of the most important structural characteristics of mature heart valve leaflets is their intrinsic anisotropy, which is derived from the microstructure of aligned collagen fibers in the extracellular matrix (ECM). In the present study, a directional electrospinning technique is used to fabricate fibrous poly(glycerol sebacate):poly(caprolactone) (PGS:PCL) scaffolds containing aligned fibers, which resemble native heart valve leaflet ECM networks. In addition, the anisotropic mechanical characteristics of fabricated scaffolds are tuned by changing the ratio of PGS:PCL to mimic the native heart valve's mechanical properties. Primary human valvular interstitial cells (VICs) attach and align along the anisotropic axes of all PGS:PCL scaffolds with various mechanical properties. The cells are also biochemically active in producing heart-valve-associated collagen, vimentin, and smooth muscle actin as determined by gene expression. The fibrous PGS:PCL scaffolds seeded with human VICs mimick the structure and mechanical properties of native valve leaflet tissues and would potentially be suitable for the replacement of heart valves in diverse patient populations.


Subject(s)
Decanoates/chemistry , Glycerol/analogs & derivatives , Heart Valves/cytology , Polyesters/chemistry , Polymers/chemistry , Actins/metabolism , Animals , Biomimetic Materials/chemistry , Biomimetic Materials/pharmacology , Cell Survival/drug effects , Cells, Cultured , Collagen/metabolism , Elastic Modulus , Extracellular Matrix/chemistry , Extracellular Matrix/metabolism , Glycerol/chemistry , Heart Valves/metabolism , Humans , Swine , Tensile Strength , Tissue Engineering , Tissue Scaffolds , Vimentin/metabolism
5.
J Tissue Eng Regen Med ; 8(1): 1-14, 2014 Jan.
Article in English | MEDLINE | ID: mdl-22711442

ABSTRACT

Micro- and nanotechnologies have emerged as potentially effective fabrication tools for addressing the challenges faced in tissue engineering and drug delivery. The ability to control and manipulate polymeric biomaterials at the micron and nanometre scale with these fabrication techniques has allowed for the creation of controlled cellular environments, engineering of functional tissues and development of better drug delivery systems. In tissue engineering, micro- and nanotechnologies have enabled the recapitulation of the micro- and nanoscale detail of the cell's environment through controlling the surface chemistry and topography of materials, generating 3D cellular scaffolds and regulating cell-cell interactions. Furthermore, these technologies have led to advances in high-throughput screening (HTS), enabling rapid and efficient discovery of a library of materials and screening of drugs that induce cell-specific responses. In drug delivery, controlling the size and geometry of drug carriers with micro- and nanotechnologies have allowed for the modulation of parametres such as bioavailability, pharmacodynamics and cell-specific targeting. In this review, we introduce recent developments in micro- and nanoscale engineering of polymeric biomaterials, with an emphasis on lithographic techniques, and present an overview of their applications in tissue engineering, HTS and drug delivery.


Subject(s)
Biocompatible Materials , Drug Delivery Systems , Tissue Engineering , High-Throughput Screening Assays , Tissue Scaffolds
6.
Arch Iran Med ; 16(10): 599-601, 2013 Oct.
Article in English | MEDLINE | ID: mdl-24093142

ABSTRACT

Methadone detoxification is among the widely used treatment programs for opioid dependence. The aims of this study were to identify which patient baseline factors and treatment regimen features are predictors of the treatment outcome in an outpatient flexible dose-duration methadone detoxification program.  We studied 126 opioid dependents in a naturalistic nonexperimental clinical setting. The patients were assessed for baseline demographic characteristics, and drug abuse characteristics. Treatment regimen features were recorded during the program. Successful treatment completion was defined as the last daily dose of methadone being less than 15 mg, negative urine analysis in the last two weeks of treatment, and based on the final clinician-client's decision.  Out of 126 patients, 60 patients completed detoxification successfully. Younger age, longer duration of the opioid abuse, and higher subjective opiate intoxication severity before treatment entry were all significantly associated with negative treatment outcome. Among treatment regimen features, higher maximum methadone dose had a marginally significant independent effect on treatment failure. Patients with maximum methadone dose of more than 75 mg per day had around ten times worse success rate when compared to those who received lesser doses. The study findings could be used to predict treatment outcome and prognosis in a more individualized and patient-tailored approach in the real clinical setting. Guideline development for treatment selection and outcome monitoring in addiction medicine based on similar studies could enhance treatment outcome in clinical services.


Subject(s)
Methadone/therapeutic use , Opioid-Related Disorders/drug therapy , Adolescent , Adult , Female , Humans , Male , Prospective Studies , Time Factors , Treatment Outcome
7.
Basic Clin Neurosci ; 4(1): 64-75, 2013.
Article in English | MEDLINE | ID: mdl-25337330

ABSTRACT

Many diseases are related to cerebrospinal fluid (CSF) hydrodynamics. Therefore, understanding the hydrodynamics of CSF flow and intracranial pressure is helpful for obtaining deeper knowledge of pathological processes and providing better treatments. Furthermore, engineering a reliable computational method is promising approach for fabricating in vitro models which is essential for inventing generic medicines. A Fluid-Solid Interaction (FSI)model was constructed to simulate CSF flow. An important problem in modeling the CSF flow is the diastolic back flow. In this article, using both rigid and flexible conditions for ventricular system allowed us to evaluate the effect of surrounding brain tissue. Our model assumed an elastic wall for the ventricles and a pulsatile CSF input as its boundary conditions. A comparison of the results and the experimental data was done. The flexible model gave better results because it could reproduce the diastolic back flow mentioned in clinical research studies. The previous rigid models have ignored the brain parenchyma interaction with CSF and so had not reported the back flow during the diastolic time. In this computational fluid dynamic (CFD) analysis, the CSF pressure and flow velocity in different areas were concordant with the experimental data.

8.
Biofabrication ; 2(3): 035003, 2010 Sep.
Article in English | MEDLINE | ID: mdl-20823504

ABSTRACT

For tissue engineering applications, scaffolds should be porous to enable rapid nutrient and oxygen transfer while providing a three-dimensional (3D) microenvironment for the encapsulated cells. This dual characteristic can be achieved by fabrication of porous hydrogels that contain encapsulated cells. In this work, we developed a simple method that allows cell encapsulation and pore generation inside alginate hydrogels simultaneously. Gelatin beads of 150-300 microm diameter were used as a sacrificial porogen for generating pores within cell-laden hydrogels. Gelation of gelatin at low temperature (4 degrees C) was used to form beads without chemical crosslinking and their subsequent dissolution after cell encapsulation led to generation of pores within cell-laden hydrogels. The pore size and porosity of the scaffolds were controlled by the gelatin bead size and their volume ratio, respectively. Fabricated hydrogels were characterized for their internal microarchitecture, mechanical properties and permeability. Hydrogels exhibited a high degree of porosity with increasing gelatin bead content in contrast to nonporous alginate hydrogel. Furthermore, permeability increased by two to three orders while compressive modulus decreased with increasing porosity of the scaffolds. Application of these scaffolds for tissue engineering was tested by encapsulation of hepatocarcinoma cell line (HepG2). All the scaffolds showed similar cell viability; however, cell proliferation was enhanced under porous conditions. Furthermore, porous alginate hydrogels resulted in formation of larger spheroids and higher albumin secretion compared to nonporous conditions. These data suggest that porous alginate hydrogels may have provided a better environment for cell proliferation and albumin production. This may be due to the enhanced mass transfer of nutrients, oxygen and waste removal, which is potentially beneficial for tissue engineering and regenerative medicine applications.


Subject(s)
Cell Culture Techniques/methods , Hydrogel, Polyethylene Glycol Dimethacrylate/chemistry , Tissue Engineering/methods , Tissue Scaffolds/chemistry , Albumins , Alginates/chemistry , Analysis of Variance , Cell Membrane Permeability , Cell Proliferation , Cell Survival , Compressive Strength , Gelatin/chemistry , Hep G2 Cells , Humans , Microscopy, Electron, Scanning , Microscopy, Fluorescence , Porosity , Spheroids, Cellular , Temperature
9.
Small ; 6(8): 937-44, 2010 Apr 23.
Article in English | MEDLINE | ID: mdl-20358531

ABSTRACT

Cell-laden hydrogels show great promise for creating engineered tissues. However, a major shortcoming with these systems has been the inability to fabricate structures with controlled micrometer-scale features on a biologically relevant length scale. In this Full Paper, a rapid method is demonstrated for creating centimeter-scale, cell-laden hydrogels through the assembly of shape-controlled microgels or a liquid-air interface. Cell-laden microgels of specific shapes are randomly placed on the surface of a high-density, hydrophobic solution, induced to aggregate and then crosslinked into macroscale tissue-like structures. The resulting assemblies are cell-laden hydrogel sheets consisting of tightly packed, ordered microgel units. In addition, a hierarchical approach creates complex multigel building blocks, which are then assembled into tissues with precise spatial control over the cell distribution. The results demonstrate that forces at an air-liquid interface can be used to self-assemble spatially controllable, cocultured tissue-like structures.


Subject(s)
Fibroblasts/cytology , Hydrogels/chemical synthesis , Tissue Engineering/methods , Animals , Cell Aggregation , Cell Survival , Mice , NIH 3T3 Cells , Tissue Scaffolds
10.
Organogenesis ; 6(4): 234-44, 2010.
Article in English | MEDLINE | ID: mdl-21220962

ABSTRACT

Tissue engineering aims to develop functionalized tissues for organ replacement or restoration. Biodegradable scaffolds have been used in tissue engineering to support cell growth and maintain mechanical and biological properties of tissue constructs. Ideally cells on these scaffolds adhere, proliferate, and deposit matrix at a rate that is consistent with scaffold degradation. However, the cellular rearrangement within these scaffolds often does not recapitulate the architecture of the native tissues. Directed assembly of tissue-like structures is an attractive alternative to scaffold-based approach for tissue engineering which potentially can build tissue constructs with biomimetic architecture and function. In directed assembly, shape-controlled microstructures are fabricated in which organized structures of different cell types can be used as tissue building blocks. To fabricate tissue building blocks, hydrogels are commonly used as biomaterials for cell encapsulation to mimic the matrix in vivo. The hydrogel-based tissue building blocks can be arranged in pre-defined architectures by various directed tissue assembly techniques. In this paper, recent advances in directed assembly-based tissue engineering are summarized as an emerging alternative to meet challenges associated with scaffold-based tissue engineering and future directions are addressed.


Subject(s)
Biocompatible Materials/chemistry , Hydrogels/chemistry , Tissue Engineering , Tissue Scaffolds/chemistry , Emulsions , Humans , Hydrogels/chemical synthesis , Microfluidics
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