| 1. |
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| 2. |
- Gustafsson, Olof, et al.
(författare)
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Scalable and Sustainable Total Pathogen Removal Filter Paper for Point-of-Use Drinking Water Purification in Bangladesh
- 2019
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Ingår i: ACS Sustainable Chemistry and Engineering. - : AMER CHEMICAL SOC. - 2168-0485. ; 7:17, s. 14373-14383
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Tidskriftsartikel (refereegranskat)abstract
- This article describes for the first time the full cycle of development from raw material cultivation to real-life application of a truly sustainable and scalable filter paper material intended for point-of-use drinking water purification in Bangladesh. The filter paper, featuring tailored pathogen removal properties, is produced from nanocellulose extracted from Pithophora green macroalgae, growing locally in Bangladesh, a new unexploited resource that can address a global problem. We demonstrate that the Pithophora cellulose filter paper can be used as a total pathogen barrier to remove all types of infectious viruses and bacteria from water. The performance of the filter is validated using surrogate latex nanobeads, in vitro model viruses, and real-life water samples collected from the Turag River and Dhanmondi Lake in Dhaka, Bangladesh. Access to clean drinking water is a persistent problem in Bangladesh, affecting tens of millions of people every day. The mortality rate due to water-borne diarreal infections, including viral infections, among susceptible population groups, especially among children under age of 5, is still very high. The proposed solution can dramatically improve the quality of lives for millions of people in the entire Southeast Asian region including and beyond the borders of Bangladesh.
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| 3. |
- Tummala, Gopi Krishna, 1986-, et al.
(författare)
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Biocompatibility of nanocellulose-reinforced PVA hydrogel with human corneal epithelial cells for Ophthalmic applications
- 2019
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Ingår i: Journal of Functional Biomaterials. - : MDPI AG. - 2079-4983. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Transparent composite hydrogel in the form of a contact lens made from poly(vinyl alcohol) (PVA) and cellulose nanocrystals (CNCs) was subjected to in vitro biocompatibility evaluation with human corneal epithelial cells (HCE-2 cells). The cell response to direct contact with the hydrogels was investigated by placing the samples on top of confluent cell layers and evaluating cell viability, morphology, and cell layer integrity subsequent to 24 h culture and removal of the hydrogels. To further characterize the lens-cell interactions, HCE-2 cells were seeded on the hydrogels, with and without simulated tear fluid (STF) pre-conditioning, and cell viability and morphology were evaluated. Furthermore, protein adsorption on the hydrogel surface was investigated by incubating the materials with STF, followed by protein elution and quantification. The hydrogel material was found to have affinity towards protein adsorption, most probably due to the interactions between the positively charged lysozyme and the negatively charged CNCs embedded in the PVA matrix. The direct contact experiment demonstrated that the physical presence of the lenses did not affect corneal epithelial cell monolayers in terms of integrity nor cell metabolic activity. Moreover, it was found that viable corneal cells adhered to the hydrogel, showing the typical morphology of epithelial cells and that such response was not influenced by the STF pre-conditioning of the hydrogel surface. The results of the study confirm that PVA-CNC hydrogel is a promising ophthalmic biomaterial, motivating future in vitro and in vivo biocompatibility studies.
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| 4. |
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| 5. |
- Tummala, Gopi Krishna, 1986-
(författare)
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Contact lenses reinforced with nanocellulose
- 2016
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Konferensbidrag (refereegranskat)abstract
- Data from World Health Organization (WHO) states that there are 246 million people worldwide who are visually impaired, out of which 43% are due to uncorrected refractive errors. Vision corrective lenses include prescription eyeglasses and contact lenses. Compared to eyeglasses contact lenses are lightweight and virtually invisible. Furthermore there are certain non-standard visual impairments, i.e. non-myopia, hyperopia, astigmatism, which cannot be corrected by normal glasses Contact lenses remain an important part of the modern eye care and culture, and more than 85 million people worldwide wear contact lenses for corrective, cosmetic and therapeutic purposes.Contact lenses can be broadly classified into two types: hard and soft contact lenses. The hard contact lenses had low oxygen permeability which led to unwanted clinical events such as corneal hypoxia and various types of edema. The quest for oxygen permeability led to the development of soft contact lenses. The main advantages of soft contact lenses are the increased oxygen permeability, lens wettability, and overall comfort.Although contemporary commercially available thin soft contact lenses have good oxygen permeability and good comfort level, they are encountered with the problem of proteinaceous deposits onto the polymer matrix. Further increasing the water content to reduce the extent of protein deposition has so far been not feasible considering that hydrogels are in general mechanically weak and this would compromise their mechanical strength properties.We here present a novel nanocellulose reinforced hydrogel material featured with a set of optical and mechanical properties that are highly suitable for ophthalmic applications.
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| 6. |
- Tummala, Gopi Krishna, 1986-
(författare)
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Hydrogels of Poly(vinyl alcohol) and Nanocellulose for Ophthalmic Applications : Synthesis, Characterization, Biocompatibility and Drug Delivery Studies
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hydrogels are commonly used materials in ophthalmic care as contact lenses, bandage lenses, corneal implants, and cornea regeneration scaffolds. Hydrogels can be produced by physical, chemical, or radiation crosslinking of hydrophilic polymers. Poly(vinyl alcohol) (PVA) is a hydrophilic polymer that has been long known to the scientific community and is used in ophthalmic formulations.In this thesis, PVA was reinforced with nanocellulose to obtain self-standing hydrogels. Cryo-gelation technique was used to obtain transparent hydrogels from PVA dissolved in DMSO-water mixed solvent. The properties of these hydrogels were analyzed to explore the possibility of their application for ophthalmic use as a drug delivery vehicle and as cornea regeneration implant.The results indicate that oxidized nanocellulose can be combined with PVA to produce transparent, elastic, macroporous and high-water content hydrogel lenses. The water-filled macroporous structure of these hydrogels aids with oxygen transport and can enhance comfort while worn. The developed hydrogel also features moderate UV-light blocking properties in addition to high transparency. Furthermore, it was observed that the light scattering due to surface roughness of the hydrogel increases with measurement time, due to the rapid evaporation of the water layer from the surface of the hydrogel film.Mechanical analysis results revealed that the hydrogels exhibited a strain-induced stiffening behavior, which is usually noticed in hyper-elastic materials and collagenous soft tissues. The results of this study suggest that in order to mimic collagenous behavior, the material should possess high water content and a specific structural architecture combining soft and rigid elements as building blocks.Furthermore, PVA-CNC composite hydrogel showed no toxic effects on the corneal cells in both direct and indirect contact studies. It was found that the hydrogel promoted cell attachment and was stable when sutured ex vivo to a porcine excised cornea.To study enzyme-triggered drug release, hydrogel lenses loaded with chitosan-poly(acrylic acid) nanoparticles were exposed to lysozyme, an enzyme present in the eye. Nanoparticles were shown to disintegrate due to the hydrolysis of chitosan chains by lysozyme. Overall, with these distinctive properties, PVA-CNC hydrogel has great potential as an ophthalmic biomaterial for therapeutic and cornea regeneration applications.
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| 7. |
- Tummala, Gopi Krishna, 1986-, et al.
(författare)
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Hyperelastic Nanocellulose-Reinforced Hydrogel of High Water Content for Ophthalmic Applications
- 2016
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Ingår i: ACS Biomaterials Science & Engineering. - : American Chemical Society (ACS). - 2373-9878. ; 2:11, s. 2072-2079
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Tidskriftsartikel (refereegranskat)abstract
- A nanocellulose-reinforced poly(vinyl alcohol) hydrogel material of exceptionally high water content for ophthalmic applications is presented (>90 wt %), which also features a hitherto unprecedented combination of optical, mechanical, viscoelastic, oxygen permeability, and biocompatibility properties. The hydrogel combines the desired softness with remarkable strain-dependent mechanical strength and thereby demonstrates hyperelastic, rubber-like mechanical properties. The observed unusual mechanical behavior is due to both high water content and the combination of relatively stiff cellulose nanowhiskers entangled in a soft polymer matrix of poly(vinyl alcohol) (PVA), thus mimicking the structural characteristics of the cornea's main constituents, i.e., water and collagen.
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| 8. |
- Tummala, Gopi Krishna, 1986-, et al.
(författare)
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Light scattering in poly (vinyl alcohol) hydrogels reinforced with nanocellulose for ophthalmic use
- 2017
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Ingår i: Optical Materials Express. - : Optical Society of America. - 2159-3930 .- 2159-3930. ; 7:8, s. 2824-2837
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Tidskriftsartikel (refereegranskat)abstract
- Scattering of ophthalmic devices is a complex phenomenon involving both surface and bulk light-material interactions. In this work, light scattering of nanocellulose reinforced PVA hydrogels contact lenses for ophthalmic applications was investigated. Optical microscopy, fluorescence microscopy and atomic force microscopy (AFM) techniques were used for ultrastructure characterization. Further, 3D angle resolved light scattering measurements in the visible spectral range were performed using a BTDF (bidirectional transmittance distribution function) sensor to quantify the scattered light. Surface and bulk scattering properties were discerned using white light interferometry. Total scatter levels ranging from 3% to 40% were observed depending on the hydrogel composition. The most critical factor affecting the light scattering properties in nanocellulose-reinforced PVA hydrogels was related to the state of hydration of the hydrogels, which is critical to maintain visual acuity of ophthalmic devices.
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| 9. |
- Tummala, Gopi Krishna, 1986-, et al.
(författare)
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Poly(vinyl alcohol) Hydrogels Reinforced with Nanocellulose for Ophthalmic Applications : General Characteristics and Optical Properties
- 2016
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 120:51, s. 13094-13101
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Tidskriftsartikel (refereegranskat)abstract
- Globally, uncorrected refractive errors are one of the main causes of visual impairment, and contact lenses form an important part of modern day eye care and culture. Several hydrogels with varying physicochemical properties are in use to manufacture soft contact lenses. Hydrogels are generally too soft and reinforcement with appropriate materials is desirable to achieve high water content without compromising mechanical properties. In this study, we have developed a highly transparent macroporous hydrogel with water content >90%, by combining poly(vinyl alcohol) with nanocellulose. Furthermore, the results show that the composite hydrogel has refractive index close to that of water and very good UV-blocking properties.
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| 10. |
- Tummala, Gopi Krishna, 1986-, et al.
(författare)
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Role of Solvent on Structure, Viscoelasticity and Mechanical Compressibility in Nanocellulose-Reinforced Poly(vinyl alcohol) Hydrogels
- 2019
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 136:6
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanocrystals (CNCs) reinforced polyvinyl alcohol (PVA)‐based hydrogels with high water content and tunable mechanical properties that can be molded in to any desired shape are presented in this work. Freeze thawing of PVA‐CNC solutions in a mixed solvent system of dimethyl sulfoxide and water enabled to produce a set of physically crosslinked hydrogels with tunable mechanical properties. It was observed that the composition of the solvent altered the mechanical properties and network structure in the hydrogel systems. Differential scanning calorimetry was used to understand the thermal events behind solvent effect on the properties of the hydrogel. Optical microscopy results suggest that these hydrogels possess a macroporous structure. Furthermore, dynamic viscoelastic analysis and axial compression tests have shown that the viscoelastic and mechanical compression properties of the hydrogels improved upon reinforcement with CNC. Overall, the hydrogel enjoys appealing properties as a synthetic biomaterial for soft tissue applications.
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| 11. |
- Tummala, Gopi Krishna, 1986-, et al.
(författare)
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Strain-induced stiffening of nanocellulose-reinforced poly(vinyl alcohol) hydrogels mimicking collagenous soft tissues
- 2017
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 13:21, s. 3936-3945
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Tidskriftsartikel (refereegranskat)abstract
- Soft tissues possess remarkable mechanical strength for their high water content, which is hard to mimic in synthetic materials. Here, we demonstrate how strain-induced stiffening in hydrogels plays a major role in mimicking the mechanical properties of collagenous soft tissues. In particular, nanocellulose reinforced polyvinyl alcohol (PVA) hydrogels of exceptionally high water content (90-93 wt%) are shown to exhibit collagen-like mechanical behavior typical for soft tissues. High water content and co-existence of both soft and rigid domains in the gel network are the main factors responsible for strain-induced stiffening. This observed effect due to the alignment of rigid components of the hydrogel is simulated through modeling and visualized through strain-induced birefringence experiments. Design parameters such as nanocellulose aspect ratio and solvent composition are also shown to be important to control the mechanical properties. In addition, owing to their transparency (90-95% at 550 nm) and hyperelastic properties (250-350% strain), the described hydrogels are promising materials for biomedical applications, especially in ophthalmology.
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| 12. |
- Åhlén, Michelle, et al.
(författare)
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Nanoparticle-loaded Hydrogels as a Pathway for Enzyme-triggered Drug Release in Ophthalmic Applications
- 2018
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Ingår i: International Journal of Pharmaceutics. - : Elsevier. - 0378-5173 .- 1873-3476. ; 536:1, s. 73-81
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to develop nanoparticle loaded hydrogel based contact lenses that could be used for ocular drug delivery. Two potential contact lens platforms for controlled ophthalmic drug delivery were developed by incorporating chitosan-poly(acrylic acid) nanoparticles into polyvinyl alcohol (PVA) hydrogels and in-situ gelled nanoparticles and cellulose nanocrystals (CNC) in PVA lenses. The nanoparticles were shown to disintegrate in a physiological 0.2 mM concentration of lysozyme resulting from the hydrolysis of the chitosan chains by lysozyme. An extended release over a 28-hour period was demonstrated once the nanoparticles had been integrated into the composite lenses, with nanoparticle-CNC PVA lenses showing even greater potential for extended release. The platform shows great promise in developing enzyme-triggered ocular drug delivery systems.
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