Water and hydrogels

Jhon, Mu Shik; Andrade, Joseph D.

doi:10.1002/jbm.820070604

Cited by 294 publications

(160 citation statements)

References 31 publications

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“…There are three types of hydration water, each possessing different physical properties [9]. Type I (freezing or free, bulk-like water) melts at the normal melting point of pure water (0 o C).…”

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confidence: 99%

The effect of pH and ionic strength of dissolution media on in-vitro release of two model drugs of different solubilities from HPMC matrices

Asare-Addo

Conway

Larhrib

et al. 2013

Colloids and Surfaces B: Biointerfaces

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The evaluation of the effects of different media ionic strengths and pH on the release of hydrochlorothiazide, a poorly soluble drug, and diltiazem hydrochloride, a cationic and soluble drug, from a gel forming hydrophilic polymeric matrix were the objectives of this study. The drug to polymer ratio of formulated tablets was 4:1. Hydrochlorothiazide or diltiazem HCl extended release (ER) matrices containing hypromellose (hydroxypropyl methylcellulose (HPMC)) were evaluated in media with a pH range of 1.2-7.5, using an automated USP type III, Bio-Dis dissolution apparatus. The ionic strength of the media was varied over a range of 0-0.4 M to simulate the gastrointestinal fed and fasted states and various physiological pH conditions. Sodium chloride was used for ionic regulation due to its ability to salt out polymers in the midrange of the lyotropic series. The results showed that the ionic strength had a profound effect on the drug release from the diltiazem HCl K100LV matrices. The K4M, K15M and K100M tablets however withstood the effects of media ionic strength and showed a decrease in drug release to occur with an increase in ionic strength.For example, drug release after the 1 hr mark for the K100M matrices in water was 36 %.Drug release in pH 1.2 after 1 hr was 30 %. An increase of the pH 1.2 ionic strength to 0.4 M saw a reduction of drug release to 26 %. This was the general trend for the K4M and K15M matrices as well. The similarity factor f 2 was calculated using drug release in water as a reference. Despite similarity occurring for all the diltiazem HCl matrices in the pH 1.2 media (f2=64-72), increases of ionic strength at 0.2 M and 0.4 M brought about dissimilarity. The hydrochlorothiazide tablet matrices showed similarity at all the ionic strength tested for all polymers (f2= 56-81). The values of f2 however reduced with increasing ionic strengths.DSC hydration results explained the hydrochlorothiazide release from their HPMC matrices.There was an increase in bound water as ionic strengths increased. Texture analysis was employed to determine the gel strength and also to explain the drug release for the diltiazem 3 hydrochloride. This methodology can be used as a valuable tool for predicting potential ionic effects related to in vivo fed and fasted states on drug release from hydrophilic ER matrices.

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confidence: 99%

The effect of pH and ionic strength of dissolution media on in-vitro release of two model drugs of different solubilities from HPMC matrices

Asare-Addo

Conway

Larhrib

et al. 2013

Colloids and Surfaces B: Biointerfaces

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“…138 The use of organic hydrogels in industry preceded biomedical applications by a few decades as patents for titanium oxide hydrogels were filed already in the early 1900s. 139 A movement emerged to replace plastics used as 1 st generation biomaterials with hydrogels, in an effort to ensure implant longevity.…”

Section: Collagen Hydrogelsmentioning

confidence: 99%

Multifunctional Biomimetic Scaffolds Tailored for Cardiac Regeneration

Wickham¹

2015

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Linköping 2015Cover: Scanning Electron Microscopy image of a mesenchymal cell on polycaprolactone fibers.During the course of the research presented in this thesis, Abeni Wickham, was enrolled in Forum Scientium, a multidisciplinary graduate school at Linköping University. ColophonThis thesis is not only the summation of 5 years of research, but also a material manifestation of my happiness.It has not been straightforward and I have had numerous failures, disappointments and doubts. These have always been positive moments, as each difficult moment gave me the chance to choose a different path to still achieve my research goals.I have spent the past few years fighting for what I love the most; answering the questions that I ask myself every day. I have been lucky to have two supervisors, Daniel and Bo who pushed me to be better scientifically and family/friends who kept me grounded.During this work, I found who I really am; this thesis is a representation of me.ii Abstract Nature has had millions of years to perfect the structural components of the human body, but has also produced the dysfunctions that result in the cancers and diseases, which ruin that perfection. Congenital heart defects, and myocardial infarction lead to scarring that remodels heart muscle, decreasing the contractility of the heart, with profound consequences for the host. Regenerative medicine is the study of strategies to return diseased body parts to their evolutionarily optimum structure.Cells alone cannot develop into functional tissue, as they require mechanical support and chemical signals from the extracellular matrix in order to play the correct role in the body. In order to imitate the process of tissue formation optimized by nature, scaffolds are developed as the architectural support for tissue regeneration. To mimic the elasticity and strength seen in the heart muscle is one of the major scientific conundrums of our time. The development of new multifunctional materials for scaffolds is an accepted solution for repairing failing heart muscle. In this thesis I accept the notion that endogenous cardiac cells can play a major role in addressing this problem, if we can attract them to the site of defect or injury and make them proliferate. I then proceed to show how improving on a commonly used synthetic polymer was used to develop two new biomaterials.Polycaprolactone (PCL) fibers and sheets were studied for their ability to adsorb proteins based on their surface energies. We found that although the wettability of the PCL might be similar to positive controls for cell attachment, the large differences in surface energies may account for the increased serum protein adsorption and limit cell adhesion. The effect of fiber morphology was then investigated with respect to proliferation of mesenchymal stem cells and cardiac progenitor cells. PCL was also mechanically enhanced with thiophene conjugated single walled carbon nanotubes (T-CNT); where small concentrations of the T-CNT allowed for a 2.5 fold increase in the percentage of elong...

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“…Hydrogel properties (e.g. swelling) and drug release profiles are frequently related to the water content within the gel (Lee et al 1975;Jhon & Andrade 1973;Shi et al 2012). Drug loading into the hydrogel is also an important parameter that can influence by the solvents that are used (Lewis et al 2008).…”

Section: Introductionmentioning

confidence: 99%

The preparation of HEMA-MPC films for ocular drug delivery

Al-Shohani

Awwad

Khaw

et al. 2017

British Journal of Pharmacy

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There is a need to prolong drug residence time using a biocompatible formulation in the subconjunctival space after surgery to treat glaucoma. Drug releasing discs were prepared with 2-(hydroxyethyl)methacrylate (HEMA) and 2-methacryloyloxyethyl phosphorylcholine (MPC). The ratio of bound water (Wb) to free water (Wf) ratio increased from 1:0.3 to 1:6.8 with increasing MPC (0 to 50%, w/w). The optimal balance between water content, SR and mechanical strength were obtained with 10% MPC (w/w) hydrogels. Water-alcohol mixtures were examined to facilitate loading of poorly soluble drugs, and they showed greater hydrogel swelling than either water or alcohol alone. The SR was 1.2 ± 0.02 and 3.3 ± 0.1 for water and water:ethanol (1:1) respectively. HEMA-MPC (10%) discs were loaded with dexamethasone using either water:ethanol (1:1) or methanol alone. Drug release was examined in an outflow rig model that mimics the subconjunctival space in the eye. Dexamethasone loading increased from 0.3 to 1.9 mg/disc when the solvent was changed from water:ethanol (1:1) to methanol with the dexamethasone half-life (t½) increasing from 1.9 to 9.7 days respectively. These encouraging results indicate that HEMA-MPC hydrogels have the potential to sustain the residence time of a drug in the subconjunctival space of the eye.

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Water and hydrogels

Cited by 294 publications

References 31 publications

The effect of pH and ionic strength of dissolution media on in-vitro release of two model drugs of different solubilities from HPMC matrices

The effect of pH and ionic strength of dissolution media on in-vitro release of two model drugs of different solubilities from HPMC matrices

Multifunctional Biomimetic Scaffolds Tailored for Cardiac Regeneration

The preparation of HEMA-MPC films for ocular drug delivery

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