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Special Issue "Materials for Drug Delivery"

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (30 November 2014)

Special Issue Editor

Guest Editor
Dr. Loo Say Chye Joachim (Website)

School of Materials Science & Engineering College of Engineering NanYang Technological University, Singapore

Special Issue Information

Dear Colleagues,

Drug delivery is an inter-disciplinary research field that encompasses expertise from the pharmaceutical, clinical, biological, chemical, and materials sciences. The focus of drug delivery is often to exploit biocompatible materials to transport and release pharmaceutical compound(s) into the body, to achieve the desired therapeutic outcome in the safest possible manner. In this Special Issue on “Materials for Drug Delivery”, the scope will be on new developments in drug delivery systems, and how these are utilized for the treatment of various diseases, such as cancer, infectious, neurological, cardiovascular, and metabolic diseases. Recent advances in controlled release, targeted delivery, new materials, and evaluation of drug delivery systems through in vitro and/or in vivo studies would be the highlight of this Issue.

Dr. Loo Say Chye Joachim
Guest Editor

Submission

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. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as 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 refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials 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 1400 CHF (Swiss Francs).

Keywords

  • controlled release
  • sustained release
  • site-specific delivery
  • targeted
  • drug delivery systems
  • biodegradable polymers
  • biocompatibility
  • nano- and micro-particles
  • pharmaceutical reformulations

Published Papers (10 papers)

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Research

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Open AccessArticle High Throughput Screening of Valganciclovir in Acidic Microenvironments of Polyester Thin Films
Materials 2015, 8(4), 1714-1728; doi:10.3390/ma8041714
Received: 1 December 2014 / Revised: 19 March 2015 / Accepted: 30 March 2015 / Published: 13 April 2015
Cited by 1 | PDF Full-text (635 KB) | HTML Full-text | XML Full-text
Abstract
Ganciclovir and valganciclor are antiviral agents used for the treatment of cytomegalovirus retinitis. The conventional method for administering ganciclovir in cytomegalovirus retinitis patients is repeated intravitreal injections. In order to obviate the possible detrimental effects of repeated intraocular injections, to improve compliance [...] Read more.
Ganciclovir and valganciclor are antiviral agents used for the treatment of cytomegalovirus retinitis. The conventional method for administering ganciclovir in cytomegalovirus retinitis patients is repeated intravitreal injections. In order to obviate the possible detrimental effects of repeated intraocular injections, to improve compliance and to eliminate systemic side-effects, we investigated the tuning of the ganciclovir pro-drug valganciclovir and the release from thin films of poly(lactic-co-glycolic acid) (PLGA), polycaprolactone (PCL), or mixtures of both, as a step towards prototyping periocular valganciclovir implants. To investigate the drug release, we established and evaluated a high throughput fluorescence-based quantification screening assay for the detection of valganciclovir. Our protocol allows quantifying as little as 20 ng of valganciclovir in 96-well polypropylene plates and a 50× faster analysis compared to traditional HPLC measurements. This improvement can hence be extrapolated to other polyester matrix thin film formulations using a high-throughput approach. The acidic microenvironment within the polyester matrix was found to protect valganciclovir from degradation with resultant increases in the half-life of the drug in the periocular implant to 100 days. Linear release profiles were obtained using the pure polyester polymers for 10 days and 60 days formulations; however, gross phase separations of PCL and acid-terminated PLGA prevented tuning within these timeframes due to the phase separation of the polymer, valganciclovir, or both. Full article
(This article belongs to the Special Issue Materials for Drug Delivery)
Open AccessArticle Tribo-electrification and Powder Adhesion Studies in the Development of Polymeric Hydrophilic Drug Matrices
Materials 2015, 8(4), 1482-1498; doi:10.3390/ma8041482
Received: 1 March 2015 / Revised: 19 March 2015 / Accepted: 23 March 2015 / Published: 30 March 2015
Cited by 1 | PDF Full-text (2104 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The generation of tribo-electric charge during pharmaceutical powder processing can cause a range of complications, including segregation of components leading to content uniformity and particle surface adhesion. This phenomenon becomes problematical when excipients are introduced to a powder mixture alongside the highly [...] Read more.
The generation of tribo-electric charge during pharmaceutical powder processing can cause a range of complications, including segregation of components leading to content uniformity and particle surface adhesion. This phenomenon becomes problematical when excipients are introduced to a powder mixture alongside the highly charging active pharmaceutical ingredient(s) (APIs). The aim of this study was to investigate the tribo-electric charging and adhesion properties of a model drug, theophylline. Moreover, binary powder mixtures of theophylline with methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC), having different polymer to drug ratios, were formed in order to study the impact of polymer concentration, particle size, substitution ratio and molecular size on the tribo-electric charging and surface adhesion properties of the drug. Furthermore, the relationship between tribo-electric charging and surface adhesion was also studied. The diversity in physicochemical properties of MC/HPMC has shown a significant impact on the tribo-electric charging and adhesion behaviour of theophylline. It was found that the magnitude of electrostatic charge and the level of surface adhesion of the API were significantly reduced with an increase in MC and HPMC concentration, substitution ratios and molecular size. In addition, the tribo-electric charge showed a linear relationship with particle surface adhesion, but the involvement of other forces cannot be neglected. Full article
(This article belongs to the Special Issue Materials for Drug Delivery)
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Open AccessArticle Eudragit S100 Coated Citrus Pectin Nanoparticles for Colon Targeting of 5-Fluorouracil
Materials 2015, 8(3), 832-849; doi:10.3390/ma8030832
Received: 13 January 2015 / Revised: 6 February 2015 / Accepted: 13 February 2015 / Published: 27 February 2015
Cited by 3 | PDF Full-text (817 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In the present study, Eudragit S100 coated Citrus Pectin Nanoparticles (E-CPNs) were prepared for the colon targeting of 5-Fluorouracil (5-FU). Citrus pectin also acts as a ligand for galectin-3 receptors that are over expressed on colorectal cancer cells. Nanoparticles (CPNs and E-CPNs) [...] Read more.
In the present study, Eudragit S100 coated Citrus Pectin Nanoparticles (E-CPNs) were prepared for the colon targeting of 5-Fluorouracil (5-FU). Citrus pectin also acts as a ligand for galectin-3 receptors that are over expressed on colorectal cancer cells. Nanoparticles (CPNs and E-CPNs) were characterized for various physical parameters such as particle size, size distribution, and shape etc. In vitro drug release studies revealed selective drug release in the colonic region in the case of E-CPNs of more than 70% after 24 h. In vitro cytoxicity assay (Sulphorhodamine B assay) was performed against HT-29 cancer cells and exhibited 1.5 fold greater cytotoxicity potential of nanoparticles compared to 5-FU solution. In vivo data clearly depicted that Eudragit S100 successfully guarded nanoparticles to reach the colonic region wherein nanoparticles were taken up and showed drug release for an extended period of time. Therefore, a multifaceted strategy is introduced here in terms of receptor mediated uptake and pH-dependent release using E-CPNs for effective chemotherapy of colorectal cancer with uncompromised safety and efficacy. Full article
(This article belongs to the Special Issue Materials for Drug Delivery)
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Open AccessArticle Exploring the Preparation of Albendazole-Loaded Chitosan-Tripolyphosphate Nanoparticles
Materials 2015, 8(2), 486-498; doi:10.3390/ma8020486
Received: 14 December 2014 / Revised: 28 January 2015 / Accepted: 30 January 2015 / Published: 5 February 2015
PDF Full-text (388 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this study was to improve the solubility of albendazole and optimize the preparation of an oral nanoparticle formulation, using β-cyclodextrin (βCD) and chitosan-tripolyphosphate (TPP) nanoparticles. The solubility of albendazole in buffers, surfactants, and various concentrations of acetic acid solution [...] Read more.
The objective of this study was to improve the solubility of albendazole and optimize the preparation of an oral nanoparticle formulation, using β-cyclodextrin (βCD) and chitosan-tripolyphosphate (TPP) nanoparticles. The solubility of albendazole in buffers, surfactants, and various concentrations of acetic acid solution was investigated. To determine drug loading, the cytotoxic effects of the albendazole concentration in human hepatocellular carcinoma cells (HepG2) were investigated. The formulations were prepared by mixing the drug solution in Tween 20 with the chitosan solution. TPP solution was added dropwise with sonication to produce a nanoparticle through ionic crosslinking. Then the particle size, polydispersity index, and zeta potential of the nanoparticles were investigated to obtain an optimal composition. The solubility of albendazole was greater in pH 2 buffer, Tween 20, and βCD depending on the concentration of acetic acid. Drug loading was determined as 100 µg/mL based on the results of cell viability. The optimized ratio of Tween 20, chitosan/hydroxypropyl βCD, and TPP was 2:5:1, which resulted in smaller particle size and proper zeta positive values of the zeta potential. The chitosan-TPP nanoparticles increased the drug solubility and had a small particle size with homogeneity in formulating albendazole as a potential anticancer agent. Full article
(This article belongs to the Special Issue Materials for Drug Delivery)
Open AccessArticle Evaluation of Lapatinib Powder-Entrapped Biodegradable Polymeric Microstructures Fabricated by X-Ray Lithography for a Targeted and Sustained Drug Delivery System
Materials 2015, 8(2), 519-534; doi:10.3390/ma8020519
Received: 1 December 2014 / Revised: 16 January 2015 / Accepted: 30 January 2015 / Published: 5 February 2015
Cited by 2 | PDF Full-text (1059 KB) | HTML Full-text | XML Full-text
Abstract
An oral medication of a molecular targeted drug, lapatinib, is taken regularly to maintain the drug concentration within the desired therapeutic levels. To alleviate the need for such cumbersome administration schedules in several drugs, advanced drug delivery systems (DDSs), which can provide [...] Read more.
An oral medication of a molecular targeted drug, lapatinib, is taken regularly to maintain the drug concentration within the desired therapeutic levels. To alleviate the need for such cumbersome administration schedules in several drugs, advanced drug delivery systems (DDSs), which can provide time-controlled and sustained drug release, have recently received significant attention. A biodegradable synthetic polymer, such as polycaprolactone (PCL), is usually used as a carrier material for DDSs. In this paper, lapatinib powder-entrapped, PCL microstructures were fabricated with a precise X-ray lithography-based method. In vitro experiments on HER2 positive-human gastric cancer derived NCI-N87 cells were performed to appraise the drug release characteristics of the fabricated DDSs. The in vitro results indicate that after the X-ray lithography process, the lapatinib powder is still working well and show time- and dose- dependent drug release efficiencies. The cell growth inhibition characteristics of one hundred 40-μm sized microstructures were similar to those of a 1 μM lapatinib solution for over 144 h. In conclusion, the developed lapatinib-entrapped PCL microstructures can be used in molecular targeted delivery and sustained release as effective cancer-targeted DDSs. Full article
(This article belongs to the Special Issue Materials for Drug Delivery)
Open AccessArticle Preparation of pH Sensitive Pluronic-Docetaxel Conjugate Micelles to Balance the Stability and Controlled Release Issues
Materials 2015, 8(2), 379-391; doi:10.3390/ma8020379
Received: 17 November 2014 / Accepted: 13 January 2015 / Published: 23 January 2015
Cited by 5 | PDF Full-text (928 KB) | HTML Full-text | XML Full-text
Abstract
A novel polymer-drug conjugate was prepared by the chemical reaction between the copolymer Pluronic P123 and the docetaxel via a pH sensitive hydrazone bond. These pluronic P123-docetaxel (DTX) conjugates (P123-DTX) could form the stable drug-loaded materials that can self-assemble into the defined [...] Read more.
A novel polymer-drug conjugate was prepared by the chemical reaction between the copolymer Pluronic P123 and the docetaxel via a pH sensitive hydrazone bond. These pluronic P123-docetaxel (DTX) conjugates (P123-DTX) could form the stable drug-loaded materials that can self-assemble into the defined nano-micelles in aqueous solution because of their obvious amphiphilic property and low critical micelle concentration. The spherical morphology and particle size of the prepared nano-micelles were characterized by transmission electron microscopy and dynamic light scattering, respectively. Moreover, after the introduction of pH sensitive hydrazone bond, P123-DTX micelle showed a pH dependent drug release behavior. At pH 5.0 (in 48 h), the cumulative release amount of DTX were ~84.9%, which is about six times higher than that at pH 7.4. The prepared novel p123-DTX conjugates may offer a great benefit for drug delivery and controlling the drug release. Full article
(This article belongs to the Special Issue Materials for Drug Delivery)
Open AccessArticle Cholesterol-Enhanced Polylactide-Based Stereocomplex Micelle for Effective Delivery of Doxorubicin
Materials 2015, 8(1), 216-230; doi:10.3390/ma8010216
Received: 13 December 2014 / Accepted: 7 January 2015 / Published: 12 January 2015
Cited by 8 | PDF Full-text (1550 KB) | HTML Full-text | XML Full-text
Abstract
Nanoscale micelles as an effective drug delivery system have attracted increasing interest in malignancy therapy. The present study reported the construction of the cholesterol-enhanced doxorubicin (DOX)-loaded poly(D-lactide)-based micelle (CDM/DOX), poly(L-lactide)-based micelle (CLM/DOX), and stereocomplex micelle (CSCM/DOX) from the equimolar enantiomeric 4-armed poly(ethylene [...] Read more.
Nanoscale micelles as an effective drug delivery system have attracted increasing interest in malignancy therapy. The present study reported the construction of the cholesterol-enhanced doxorubicin (DOX)-loaded poly(D-lactide)-based micelle (CDM/DOX), poly(L-lactide)-based micelle (CLM/DOX), and stereocomplex micelle (CSCM/DOX) from the equimolar enantiomeric 4-armed poly(ethylene glycol)–polylactide copolymers in aqueous condition. Compared with CDM/DOX and CLM/DOX, CSCM/DOX showed the smallest hydrodynamic size of 96 ± 4.8 nm and the slowest DOX release. The DOX-loaded micelles exhibited a weaker DOX fluorescence inside mouse renal carcinoma cells (i.e., RenCa cells) compared to free DOX·HCl, probably because of a slower DOX release. More importantly, all the DOX-loaded micelles, especially CSCM/DOX, exhibited the excellent antiproliferative efficacy that was equal to or even better than free DOX·HCl toward RenCa cells attributed to their successful internalization. Furthermore, all of the DOX-loaded micelles exhibited the satisfactory hemocompatibility compared to free DOX·HCl, indicating the great potential for systemic chemotherapy through intravenous injection. Full article
(This article belongs to the Special Issue Materials for Drug Delivery)
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Open AccessCommunication Sustained Release of Hydrophilic l-ascorbic acid 2-phosphate Magnesium from Electrospun Polycaprolactone Scaffold—A Study across Blend, Coaxial, and Emulsion Electrospinning Techniques
Materials 2014, 7(11), 7398-7408; doi:10.3390/ma7117398
Received: 5 September 2014 / Revised: 28 October 2014 / Accepted: 6 November 2014 / Published: 17 November 2014
Cited by 2 | PDF Full-text (782 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The purpose of this study was to achieve a sustained release of hydrophilic l-ascorbic acid 2-phosphate magnesium (ASP) from electrospun polycaprolactone (PCL) scaffolds, so as to promote the osteogenic differentiation of stem cells for bone tissue engineering (TE). ASP was loaded and [...] Read more.
The purpose of this study was to achieve a sustained release of hydrophilic l-ascorbic acid 2-phosphate magnesium (ASP) from electrospun polycaprolactone (PCL) scaffolds, so as to promote the osteogenic differentiation of stem cells for bone tissue engineering (TE). ASP was loaded and electrospun together with PCL via three electrospinning techniques, i.e., coaxial, emulsion, and blend electrospinning. For blend electrospinning, binary solvent systems of dichloromethane–methanol (DCM–MeOH) and dichloromethane–dimethylformamide (DCM–DMF) were used to achieve the desired ASP release through the effect of solvent polarity and volatility. The scaffold prepared via a blend electrospinning technique with a binary solvent system of DCM–MeOH at a 7:3 ratio demonstrated a desirable, sustained ASP release profile for as long as two weeks, with minimal burst release. However, an undesirable burst release (~100%) was observed within the first 24 h for scaffolds prepared by coaxial electrospinning. Scaffolds prepared by emulsion electrospinning displayed poorer mechanical properties. Sustained releasing blend electrospun scaffold could be a good potential candidate as an ASP-eluting scaffold for bone tissue engineering. Full article
(This article belongs to the Special Issue Materials for Drug Delivery)
Open AccessArticle A Novel Exploration of a Combination of Gambogic Acid with TiO2 Nanofibers: The Photodynamic Effect for HepG2 Cell Proliferation
Materials 2014, 7(9), 6865-6878; doi:10.3390/ma7096865
Received: 17 July 2014 / Revised: 28 August 2014 / Accepted: 28 August 2014 / Published: 24 September 2014
Cited by 3 | PDF Full-text (496 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
As a good photosensitizer, TiO2 nanomaterials show potential biomedical applications, such as drug carriers or enhancers in photodynamic therapy. In this contribution, novel nanocomposites through the blending of TiO2 nanofibers with the active compound, gambogic acid (GA), were explored, and [...] Read more.
As a good photosensitizer, TiO2 nanomaterials show potential biomedical applications, such as drug carriers or enhancers in photodynamic therapy. In this contribution, novel nanocomposites through the blending of TiO2 nanofibers with the active compound, gambogic acid (GA), were explored, and the results showed that GA could inhibit cancer cell proliferation in a time-dependent and dose-dependent manner, inducing apoptosis and cell cycle arrest at the G0/G1 phase in HepG2 cells. It is evident that after the GA-TiO2 nanocomposites were cultured with the cancer cells, the cooperation effect could effectively enhance the cytotoxicity of GA for HepG2 cells. Meanwhile, if activated by UV irradiation, under the presence of GA-TiO2 nanocomposites, this would lead to significant apoptosis and necrosis for HepG2 cells with a photodynamic therapy (PDT) effect. Associated with the controlled drug-release from these nanocomposites, TiO2 nanofibers could readily cut down the drug consumption in HepG2 cells and reduce the side-effect for the normal cells and tissue, which may be further utilized in the therapeutic alliance for cancer therapy. Full article
(This article belongs to the Special Issue Materials for Drug Delivery)
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Review

Jump to: Research

Open AccessReview Polysaccharides for the Delivery of Antitumor Drugs
Materials 2015, 8(5), 2569-2615; doi:10.3390/ma8052569
Received: 24 January 2015 / Revised: 11 April 2015 / Accepted: 24 April 2015 / Published: 13 May 2015
Cited by 6 | PDF Full-text (1555 KB) | HTML Full-text | XML Full-text
Abstract
Among the several delivery materials available so far, polysaccharides represent very attractive molecules as they can undergo a wide range of chemical modifications, are biocompatible, biodegradable, and have low immunogenic properties. Thus, polysaccharides can contribute to significantly overcome the limitation in the [...] Read more.
Among the several delivery materials available so far, polysaccharides represent very attractive molecules as they can undergo a wide range of chemical modifications, are biocompatible, biodegradable, and have low immunogenic properties. Thus, polysaccharides can contribute to significantly overcome the limitation in the use of many types of drugs, including anti-cancer drugs. The use of conventional anti-cancer drugs is hampered by their high toxicity, mostly depending on the indiscriminate targeting of both cancer and normal cells. Additionally, for nucleic acid based drugs (NABDs), an emerging class of drugs with potential anti-cancer value, the practical use is problematic. This mostly depends on their fast degradation in biological fluids and the difficulties to cross cell membranes. Thus, for both classes of drugs, the development of optimal delivery materials is crucial. Here we discuss the possibility of using different kinds of polysaccharides, such as chitosan, hyaluronic acid, dextran, and pullulan, as smart drug delivery materials. We first describe the main features of polysaccharides, then a general overview about the aspects ruling drug release mechanisms and the pharmacokinetic are reported. Finally, notable examples of polysaccharide-based delivery of conventional anti-cancer drugs and NABDs are reported. Whereas additional research is required, the promising results obtained so far, fully justify further efforts, both in terms of economic support and investigations in the field of polysaccharides as drug delivery materials. Full article
(This article belongs to the Special Issue Materials for Drug Delivery)

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