Gels: 6th Anniversary

A special issue of Gels (ISSN 2310-2861).

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 62855

Special Issue Editors


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Guest Editor
Biomimetic Materials and Tissue Engineering Laboratory, Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208, USA
Interests: bioinspired gels; gels for stem cell delivery; self-assembled micelles for growth factor immobilization; models gels to control cell microenvironment; composite materials with structure at multiple length scales; skeletal tissue engineering
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Department of Chemical Engineering, University of Massachusetts Lowell, Lowell, MA 01854, USA
Interests: biomaterials; tissue engineering; cardiovascular diseases; biomineralization; wound healing; additive manufacturing; point of care diagnostics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Hydrogels are the foundation of all biological materials. Due to their high water content and permeability to oxygen, nutrients, and proteins, hydrogels resemble the natural extracellular matrix of living tissues. Synthetic as well as natural hydrogels are used extensively in medicine as viscous gels, nano- and microgels, films, thin sheets and coatings, and matrices for targeted drug release, temporal delivery of growth factors, and cell encapsulation. Due to their biocompatibility and tunable properties, water soluble oligomers, macromers, and polymers have generated a great amount of interest in printing complex, patterned, multicellular tissue structures for biosensing and tissue regeneration. It is our honor to invite you to submit manuscripts for inclusion in the Gels: 6th Anniversary Special Issue. Related topics include hydrogels in drug, protein and gene delivery, tissue engineering and regenerative medicine, biofabrication and tissue printing, injectable and in situ gelling, patterning and microfluidics, agriculture, food, cosmetic, and environmental and eco-friendly applications.

Prof. Dr. Esmaiel Jabbari
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Gels is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Hydrogels with hierarchical and self-assembled structures
  • Environmentally sustainable, compatible, and resorbable hydrogels
  • Load-bearing and self-healing hydrogels
  • Hydrogels for cell encapsulation and biofabrication
  • Hydrogels for micro-patterning, microfluidic devices, and high-throughput screening
  • Hydrogels for injectable, in situ gelling, and minimally-invasive applications
  • Hydrogels for modulating the immune response
  • Hydrogels for spatiotemporal delivery of growth factors
  • Particulate, nano-, and microstructured hydrogels for drug delivery
  • Hydrogels for protein, RNA, and DNA delivery
  • Hydrogels in tissue engineering and regenerative medicine
  • Hydrogels in cosmetic, hygiene, and personal care products
  • Hydrogels in agriculture, food production, and eco-friendly applications

Published Papers (13 papers)

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Editorial

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2 pages, 182 KiB  
Editorial
Editorial for Gels 6th Anniversary Special Issue
by Esmaiel Jabbari and Gulden Camci-Unal
Gels 2022, 8(5), 249; https://doi.org/10.3390/gels8050249 - 19 Apr 2022
Viewed by 1262
Abstract
This Special Issue celebrates many outstanding quality papers published in Gels over the past six years since its first issue was published in 2015 [...] Full article
(This article belongs to the Special Issue Gels: 6th Anniversary)

Research

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15 pages, 3406 KiB  
Article
Decellularized Articular Cartilage Microgels as Microcarriers for Expansion of Mesenchymal Stem Cells
by Esmaiel Jabbari and Azadeh Sepahvandi
Gels 2022, 8(3), 148; https://doi.org/10.3390/gels8030148 - 27 Feb 2022
Cited by 6 | Viewed by 3492
Abstract
Conventional microcarriers used for expansion of human mesenchymal stem cells (hMSCs) require detachment and separation of the cells from the carrier prior to use in clinical applications for regeneration of articular cartilage, and the carrier can cause undesirable phenotypic changes in the expanded [...] Read more.
Conventional microcarriers used for expansion of human mesenchymal stem cells (hMSCs) require detachment and separation of the cells from the carrier prior to use in clinical applications for regeneration of articular cartilage, and the carrier can cause undesirable phenotypic changes in the expanded cells. This work describes a novel approach to expand hMSCs on biomimetic carriers based on adult or fetal decellularized bovine articular cartilage that supports tissue regeneration without the need to detach the expanded cells from the carrier. In this approach, the fetal or adult bovine articular cartilage was minced, decellularized, freeze-dried, ground, and sieved to produce articular cartilage microgels (CMGs) in a specified size range. Next, the hMSCs were expanded on CMGs in a bioreactor in basal medium to generate hMSC-loaded CMG microgels (CMG-MSCs). Then, the CMG-MSCs were suspended in sodium alginate, injected in a mold, crosslinked with calcium chloride, and incubated in chondrogenic medium as an injectable cellular construct for regeneration of articular cartilage. The expression of chondrogenic markers and compressive moduli of the injectable CMG-MSCs/alginate hydrogels incubated in chondrogenic medium were higher compared to the hMSCs directly encapsulated in alginate hydrogels. Full article
(This article belongs to the Special Issue Gels: 6th Anniversary)
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19 pages, 1395 KiB  
Article
Swelling and Drug Release in Polymers through the Theory of Poisson–Kac Stochastic Processes
by Alessandra Adrover, Claudia Venditti and Massimiliano Giona
Gels 2021, 7(1), 32; https://doi.org/10.3390/gels7010032 - 22 Mar 2021
Cited by 6 | Viewed by 2010
Abstract
Experiments on swelling and solute transport in polymeric systems clearly indicate that the classical parabolic models fail to predict typical non-Fickian features of sorption kinetics. The formulation of moving-boundary transport models for solvent penetration and drug release in swelling polymeric systems is addressed [...] Read more.
Experiments on swelling and solute transport in polymeric systems clearly indicate that the classical parabolic models fail to predict typical non-Fickian features of sorption kinetics. The formulation of moving-boundary transport models for solvent penetration and drug release in swelling polymeric systems is addressed hereby employing the theory of Poisson–Kac stochastic processes possessing finite propagation velocity. The hyperbolic continuous equations deriving from Poisson–Kac processes are extended to include the description of the temporal evolution of both the Glass–Gel and the Gel–Solvent interfaces. The influence of polymer relaxation time on sorption curves and drug release kinetics is addressed in detail. Full article
(This article belongs to the Special Issue Gels: 6th Anniversary)
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16 pages, 4034 KiB  
Article
Modelling Organic Gel Growth in Three Dimensions: Textural and Fractal Properties of Resorcinol–Formaldehyde Gels
by Elisha Martin, Martin Prostredny, Ashleigh Fletcher and Paul Mulheran
Gels 2020, 6(3), 23; https://doi.org/10.3390/gels6030023 - 5 Aug 2020
Cited by 9 | Viewed by 2755
Abstract
Tailoring the properties of porous organic materials, such as resorcinol–formaldehyde gels, for use in various applications has been a central focus for many studies in recent years. In order to achieve effective optimisation for each application, this work aims to assess the impact [...] Read more.
Tailoring the properties of porous organic materials, such as resorcinol–formaldehyde gels, for use in various applications has been a central focus for many studies in recent years. In order to achieve effective optimisation for each application, this work aims to assess the impact of the various synthesis parameters on the final textural properties of the gel. Here, the formation of porous organic gels is modelled using a three-dimensional lattice-based Monte Carlo simulation. We model growth from monomer species into the interconnected primary clusters of a gel, and account for varying catalyst concentration and solids content, two parameters proven to control gel properties in experimental work. In addition to analysing the textural properties of the simulated materials, we also explore their fractal properties through correlation dimension and Hurst exponent calculations. The correlation dimension shows that while fractal properties are not typically observed in scattering experiments, they are possible to achieve with sufficiently low solids content and catalyst concentration. Furthermore, fractal properties are also apparent from the analysis of the diffusion path of guest species through the gel’s porous network. This model, therefore, provides insight into how porous organic gels can be manufactured with their textural and fractal properties computationally tailored according to the intended application. Full article
(This article belongs to the Special Issue Gels: 6th Anniversary)
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18 pages, 2342 KiB  
Article
Effect of S-triazine Ring Substitution on the Synthesis of Organic Resorcinol-Formaldehyde Xerogels
by Martin Prostredný, Caio Ledingham, Ivan A. Principe, Abdelkarim S. M. Altoumi and Ashleigh J. Fletcher
Gels 2020, 6(3), 21; https://doi.org/10.3390/gels6030021 - 31 Jul 2020
Cited by 1 | Viewed by 2775
Abstract
Resorcinol (R) and formaldehyde (F) gel synthesis has been well-studied along with alternative reagents. We present the synthesis of formaldehyde-based xerogels using chemically similar s-triazine precursors, with comparison to traditional analogues. The substitution ranges from tri-hydroxyl to tri-amine, with an intermediate species, allowing [...] Read more.
Resorcinol (R) and formaldehyde (F) gel synthesis has been well-studied along with alternative reagents. We present the synthesis of formaldehyde-based xerogels using chemically similar s-triazine precursors, with comparison to traditional analogues. The substitution ranges from tri-hydroxyl to tri-amine, with an intermediate species, allowing changing chemistry to be investigated. Each molecule (X) offers different acid/base properties, known to influence gel formation, as well as differences in crosslinking potential. Varying X/F ratios were selected to recreate the stoichiometry used in RF systems, where one represented higher F to match the increased reaction sites of the additives. X/C ratios were selected to probe different catalyst (C) ratios, while working within the range likely to produce viable gels. Results obtained show little impact for ammeline as an additive due to its similarity to resorcinol (activation sites and pKa); while melamine and cyanuric acid show differing behavior depending on the level of addition. Low concentrations show melamine to have the most impact due to increased activation and competition for formaldehyde; while at high concentrations, cyanuric acid is shown to have the greatest impact as it creates a more acidic environment, which diminishes textural character, possibly attributable to larger clusters and/or weaker cross-linking of the system. Full article
(This article belongs to the Special Issue Gels: 6th Anniversary)
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14 pages, 3056 KiB  
Article
Characterization of Enriched Meat-Based Pâté Manufactured with Oleogels as Fat Substitutes
by Artur J. Martins, José M. Lorenzo, Daniel Franco, Mirian Pateiro, Rubén Domínguez, Paulo E. S. Munekata, Lorenzo M. Pastrana, António A. Vicente, Rosiane L. Cunha and Miguel A. Cerqueira
Gels 2020, 6(2), 17; https://doi.org/10.3390/gels6020017 - 22 May 2020
Cited by 54 | Viewed by 5771
Abstract
Nowadays, one of the strongest factors affecting consumers’ choice at the moment of purchasing food products is their nutritional features. The population is increasingly aware of the diet–health relationship and they are opting for a healthy lifestyle. Concerns with the increasing number of [...] Read more.
Nowadays, one of the strongest factors affecting consumers’ choice at the moment of purchasing food products is their nutritional features. The population is increasingly aware of the diet–health relationship and they are opting for a healthy lifestyle. Concerns with the increasing number of heart-related diseases, which are associated to the consumption of fats, are placing the functional food market in a relevant growth position. Considering that, our goal was to develop, under semi-industrial processing conditions, a healthy meat-based spreadable product (pâté) with reduced fat content through replacement of pork fat by healthier structured oil. Beeswax was used to develop an edible oleogel based on linseed oil with a high content of linolenic acid. A decrease of the hardness and adhesivity was verified for pâtés with oleogel incorporation. Linseed oil inclusion was the main factor leading to an increase of polyunsaturated fatty acids (PUFA) content in pâté samples. A decrease up to 90% in the n-6/n-3 (omega-6/omega-3) ratio can signify a better nutritional value of the obtained pâté samples, which can result in a possible upsurge in omega-3 bioavailability through digestion of these pâtés. This could be an interesting option for the consumption of n-3 polyunsaturated fatty acids, targeting, for example, the reduction of cardiovascular diseases. Full article
(This article belongs to the Special Issue Gels: 6th Anniversary)
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23 pages, 2915 KiB  
Article
Quaternization of Composite Algal/PEI Beads for Enhanced Uranium Sorption—Application to Ore Acidic Leachate
by Mohammed F. Hamza, Amal E. Mubark, Yuezou Wei, Thierry Vincent and Eric Guibal
Gels 2020, 6(2), 12; https://doi.org/10.3390/gels6020012 - 30 Mar 2020
Cited by 31 | Viewed by 3965
Abstract
The necessity to recover uranium from dilute solutions (for environmental/safety and resource management) is driving research towards developing new sorbents. This study focuses on the enhancement of U(VI) sorption properties of composite algal/Polyethylenimine beads through the quaternization of the support (by reaction with [...] Read more.
The necessity to recover uranium from dilute solutions (for environmental/safety and resource management) is driving research towards developing new sorbents. This study focuses on the enhancement of U(VI) sorption properties of composite algal/Polyethylenimine beads through the quaternization of the support (by reaction with glycidyltrimethylammonium chloride). The sorbent is fully characterized by FTIR, XPS for confirming the contribution of protonated amine and quaternary ammonium groups on U(VI) binding (with possible contribution of hydroxyl and carboxyl groups, depending on the pH). The sorption properties are investigated in batch with reference to pH effect (optimum value: pH 4), uptake kinetics (equilibrium: 40 min) and sorption isotherms (maximum sorption capacity: 0.86 mmol U g−1). Metal desorption (with 0.5 M NaCl/0.5 M HCl) is highly efficient and the sorbent can be reused for five cycles with limited decrease in performance. The sorbent is successfully applied to the selective recovery of U(VI) from acidic leachate of uranium ore, after pre-treatment (cementation of copper, precipitation of rare earth elements with oxalate, and precipitation of iron). A pure yellow cake is obtained after precipitation of the eluate. Full article
(This article belongs to the Special Issue Gels: 6th Anniversary)
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10 pages, 2447 KiB  
Article
Investigation of Gel Properties of Novel Cryo-Clay-Silica Polymer Networks
by Patrik Berg, Carsten Dieter Prowald and Dirk Kuckling
Gels 2020, 6(2), 11; https://doi.org/10.3390/gels6020011 - 30 Mar 2020
Cited by 1 | Viewed by 3162
Abstract
Several methods to increase the mechanical and swelling properties of Poly(N-isopropylacrylamide) gels are known. In this study different methods were combined to systematically alter the gel properties. The combination of nanocomposite and cryo gels as well as silica post modification was [...] Read more.
Several methods to increase the mechanical and swelling properties of Poly(N-isopropylacrylamide) gels are known. In this study different methods were combined to systematically alter the gel properties. The combination of nanocomposite and cryo gels as well as silica post modification was used to modulate the gel strength. This new cryo-clay-silica gel based on N-isopropylacrylamide was investigated in respect to degree of swelling, kinetic of thermo responsive behavior and tensile strength. Here, the properties of new cryo-clay-silica gel were compared with properties of clay-, silica-clay and cryo-clay gels. Full article
(This article belongs to the Special Issue Gels: 6th Anniversary)
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20 pages, 3478 KiB  
Article
Tailoring Properties of Mixed-Component Oleogels: Wax and Monoglyceride Interactions Towards Flaxseed Oil Structuring
by Noadia G. Barroso, Paula K. Okuro, Ana P. B. Ribeiro and Rosiane L. Cunha
Gels 2020, 6(1), 5; https://doi.org/10.3390/gels6010005 - 31 Jan 2020
Cited by 50 | Viewed by 6855
Abstract
The combination of oleogelators in oil structuring has an untapped potential, since effective pairs have usually been found by serendipity. The aim of this work was to evaluate the combination of berry (BEW) or sunflower wax (SHW) with glycerol monostearate (GMS) in flaxseed [...] Read more.
The combination of oleogelators in oil structuring has an untapped potential, since effective pairs have usually been found by serendipity. The aim of this work was to evaluate the combination of berry (BEW) or sunflower wax (SHW) with glycerol monostearate (GMS) in flaxseed oil (FXO) at 5 and 25 °C. The thermal and mechanical properties, microstructure, and stability of oleogels were investigated. Self-standing and translucent gels were obtained from BEW in FXO. However, the mixture BEW:GMS resulted in a decrease of dynamic moduli. Moreover, changes in the crystal network and a reduction of oil binding capacity were noticed. Thus, the GMS prevented the complete organization of BEW in polyunsaturated chains of FXO. Conversely, a positive interaction was found for GMS:SHW, since both alone were not able to impart the structure in FXO. Interestingly, gel was formed with improved properties, even with a small addition of GMS, although an ideal ratio of 1:1 (GMS50:50SHW) was found. Oxidative stability analysis showed that all gels resembled the behavior of liquid oil (~12.00 meqO2/kg) over 30 days storage. Therefore, semi-solid systems with nutritional and techno-functional claims were created by using waxes and fatty-acid derivative oleogelator in a rational fashion; this opened the opportunity to tailor oleogel properties. Full article
(This article belongs to the Special Issue Gels: 6th Anniversary)
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Review

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23 pages, 4019 KiB  
Review
Functional Hydrogels for Treatment of Chronic Wounds
by Ilayda Firlar, Mine Altunbek, Colleen McCarthy, Murugan Ramalingam and Gulden Camci-Unal
Gels 2022, 8(2), 127; https://doi.org/10.3390/gels8020127 - 17 Feb 2022
Cited by 73 | Viewed by 9537
Abstract
Chronic wounds severely affect 1–2% of the population in developed countries. It has been reported that nearly 6.5 million people in the United States suffer from at least one chronic wound in their lifetime. The treatment of chronic wounds is critical for maintaining [...] Read more.
Chronic wounds severely affect 1–2% of the population in developed countries. It has been reported that nearly 6.5 million people in the United States suffer from at least one chronic wound in their lifetime. The treatment of chronic wounds is critical for maintaining the physical and mental well-being of patients and improving their quality of life. There are a host of methods for the treatment of chronic wounds, including debridement, hyperbaric oxygen therapy, ultrasound, and electromagnetic therapies, negative pressure wound therapy, skin grafts, and hydrogel dressings. Among these, hydrogel dressings represent a promising and viable choice because their tunable functional properties, such as biodegradability, adhesivity, and antimicrobial, anti-inflammatory, and pre-angiogenic bioactivities, can accelerate the healing of chronic wounds. This review summarizes the types of chronic wounds, phases of the healing process, and key therapeutic approaches. Hydrogel-based dressings are reviewed for their multifunctional properties and their advantages for the treatment of chronic wounds. Examples of commercially available hydrogel dressings are also provided to demonstrate their effectiveness over other types of wound dressings for chronic wound healing. Full article
(This article belongs to the Special Issue Gels: 6th Anniversary)
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28 pages, 2885 KiB  
Review
Hydrogels for Three-Dimensional Ionizing-Radiation Dosimetry
by Maurizio Marrale and Francesco d’Errico
Gels 2021, 7(2), 74; https://doi.org/10.3390/gels7020074 - 21 Jun 2021
Cited by 30 | Viewed by 4943
Abstract
Radiation-sensitive gels are among the most recent and promising developments for radiation therapy (RT) dosimetry. RT dosimetry has the twofold goal of ensuring the quality of the treatment and the radiation protection of the patient. Benchmark dosimetry for acceptance testing and commissioning of [...] Read more.
Radiation-sensitive gels are among the most recent and promising developments for radiation therapy (RT) dosimetry. RT dosimetry has the twofold goal of ensuring the quality of the treatment and the radiation protection of the patient. Benchmark dosimetry for acceptance testing and commissioning of RT systems is still based on ionization chambers. However, even the smallest chambers cannot resolve the steep dose gradients of up to 30–50% per mm generated with the most advanced techniques. While a multitude of systems based, e.g., on luminescence, silicon diodes and radiochromic materials have been developed, they do not allow the truly continuous 3D dose measurements offered by radiation-sensitive gels. The gels are tissue equivalent, so they also serve as phantoms, and their response is largely independent of radiation quality and dose rate. Some of them are infused with ferrous sulfate and rely on the radiation-induced oxidation of ferrous ions to ferric ions (Fricke-gels). Other formulations consist of monomers dispersed in a gelatinous medium (Polyacrylamide gels) and rely on radiation-induced polymerization, which creates a stable polymer structure. In both gel types, irradiation causes changes in proton relaxation rates that are proportional to locally absorbed dose and can be imaged using magnetic resonance imaging (MRI). Changes in color and/or opacification of the gels also occur upon irradiation, allowing the use of optical tomography techniques. In this work, we review both Fricke and polyacrylamide gels with emphasis on their chemical and physical properties and on their applications for radiation dosimetry. Full article
(This article belongs to the Special Issue Gels: 6th Anniversary)
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33 pages, 4001 KiB  
Review
Thermoresponsive Nanogels Based on Different Polymeric Moieties for Biomedical Applications
by Sobhan Ghaeini-Hesaroeiye, Hossein Razmi Bagtash, Soheil Boddohi, Ebrahim Vasheghani-Farahani and Esmaiel Jabbari
Gels 2020, 6(3), 20; https://doi.org/10.3390/gels6030020 - 4 Jul 2020
Cited by 36 | Viewed by 7254
Abstract
Nanogels, or nanostructured hydrogels, are one of the most interesting materials in biomedical engineering. Nanogels are widely used in medical applications, such as in cancer therapy, targeted delivery of proteins, genes and DNAs, and scaffolds in tissue regeneration. One salient feature of nanogels [...] Read more.
Nanogels, or nanostructured hydrogels, are one of the most interesting materials in biomedical engineering. Nanogels are widely used in medical applications, such as in cancer therapy, targeted delivery of proteins, genes and DNAs, and scaffolds in tissue regeneration. One salient feature of nanogels is their tunable responsiveness to external stimuli. In this review, thermosensitive nanogels are discussed, with a focus on moieties in their chemical structure which are responsible for thermosensitivity. These thermosensitive moieties can be classified into four groups, namely, polymers bearing amide groups, ether groups, vinyl ether groups and hydrophilic polymers bearing hydrophobic groups. These novel thermoresponsive nanogels provide effective drug delivery systems and tissue regeneration constructs for treating patients in many clinical applications, such as targeted, sustained and controlled release. Full article
(This article belongs to the Special Issue Gels: 6th Anniversary)
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16 pages, 2257 KiB  
Review
Coating and Functionalization Strategies for Nanogels and Nanoparticles for Selective Drug Delivery
by Filippo Pinelli, Giuseppe Perale and Filippo Rossi
Gels 2020, 6(1), 6; https://doi.org/10.3390/gels6010006 - 4 Feb 2020
Cited by 68 | Viewed by 7635
Abstract
Drug delivery is a fascinating research field with several development opportunities. Great attention is now focused on colloidal systems, nanoparticles, and nanogels and on the possibility of modifying them in order to obtain precise targeted drug delivery systems. The aim of this review [...] Read more.
Drug delivery is a fascinating research field with several development opportunities. Great attention is now focused on colloidal systems, nanoparticles, and nanogels and on the possibility of modifying them in order to obtain precise targeted drug delivery systems. The aim of this review is to give an overview of the main available surface functionalization and coating strategies that can be adopted in order to modify the selectivity of the nanoparticles in the delivery process and obtain a final system with great targeted drug delivery ability. We also highlight the most important fields of application of these kinds of delivery systems and we propose a comparison between the advantages and disadvantages of the described functionalization strategies. Full article
(This article belongs to the Special Issue Gels: 6th Anniversary)
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