PLA and its composites are biodegradable and degrade under physiological conditions to harmless and non-toxic products that can be easily excreted through the kidneys. These attributes of PLA, its composites and its copolymers make it a strong candidate for different biological applications such as tissue engineering, drug delivery systems, and various medical implants. Recently, researchers have been focusing on the use of PLA and its copolymer poly(lactic-co -glycolic) acid, PLGA as novel drug carriers for localized delivery on account of their biocompatibility, biodegradabilityand easy processability . Atif et al. prepared pH sensitive chitosan and PVA (CS/PVA) blended hydrogels cross-linked with tetra-ethoxy orthosilicate to observe the dexamethasone loading and release profile in SGF and SIF. PVA has an effect on the degree of swelling (DS) of hydrogels as DS decreases with the increase in its percentage in the hydrogels.
Through suppressing drug release in the oral cavity, taste-masking formulations can prevent the unpleasant tastes of drugs as the polymers are insoluble at higher pH. While being more soluble at lower pH, pH-sensitive polymers can release the drugs in the stomach or intestine for drug absorption or therapeutic purposes at the released sites. The pH difference between the oral cavity (pH 5.8 – 7.4)  and the stomach (pH 1 – 3.5) is thus commonly exploited by pH-responsive polymers to control drug release as summarized in Table 2. For example, aminoalkyl methacrylate copolymer (Eudragit E) is a Food and Drug Administration (FDA)-approved cationic polymer having high solubility below pH 5. Microspheres of Eudragit E containing sumatriptan succinate  or donepezil hydrochloride  have been prepared by spray-drying technique.
Eudragit Â® L 100-55 is also available as a powder with 95 % ready to use solution in acetone and alcohols and shows solubility in 1N NaOH. Soluble in intestinal fluids above pH 5.5, used to form enteric coat films.
Multiparticulate systems are useful for treatment of patients; due to their resulting high efficiency and robustness. There are various technologies present in the market based on the various methodolgies. pH sensitive release systems should be promising in the future.
In one embodiment, the internal phase can include polymers such as methylcellulose, hydroxypropylmethylcellulose, polymethylmethacrylate, or polyvinylpyrrolidone (PVP). The internal phase can also be structured. A “structured” internal phase, as used herein, means a solid, semisolid, or a gel whose shape is relatively stable and does not usually aggregate to form a large globule. A structured internal phase therefore provides controlled drug release and stabilizes the physical state of the matrix.
Effect of hydrotalcite on the swelling and mechanical behaviors for the hybrid nanocomposite hydroge…
Macromol. Jabeen, S.; Islam, A.; Ghaffar, A.; Gull, N.; Hameed, A.; Bashir, A.; Jamil, T.; Hussain, T. Development of a novel ph sensitive silane crosslinked injectable hydrogel for controlled release of neomycin sulfate. Int.
In another study, doxorubicin was loaded into PbAEM micelles, showing pH-dependent drug release and higher antitumor efficacy relative to free doxorubicin . The pH-responsiveness of drug release and amount of drug leaked at pH 7.4 of this poly (Î²-amino ester) system are similar to those of the hydrazone PHSMpop-up TAT system.
Ensuring the precision you need – every time: Excipients for Instant & Modified Release dosage forms
- The carboxylate ions caused repulsion and swelling ratio increased .
- The controlled release pharmaceutical according to claim 16 which comprises poly (acrylic acid/L-dopa), poly (acrylic acid/ carbidopa) and a pharmaceutically acceptable vehicle.
- The chemical structures of the monomers, alginate, and the arrangement of G and M blocks are shown in Figure 9b-d, respectively.
- Moreover, cationic KALA peptide has been produced by replacing some alanine residues by lysines for gene delivery purposes .
- Shantha et al. synthesized pH-sensitive interpolymeric hydrogels of chitosan, N-vinyl pyrrolidone, and polyethylene glycol acrylate.
The synthesis of pHEMA was also previously reported by du Pont de Nemours scientists in their publication in 1936 describing it as a hard, brittle and glassy polymer . The development of hydrogels for biomedical applications gained particular attention in the 1970s especially in the field of stimuli sensitive hydrogels, the so called smart hydrogels of modern times.
Adv. Drug Deliv. Rev.
WO2013164315A1 – A delayed release drug formulation – Google Patents
Acrylamide/methacrylamide monomer has been grafted onto many natural polymers to develop different properties such as mechanical strength, pH sensitivity, muco-adhesivity, and superabsorption property in the hydrogel matrix . Mukhopadhyay et al. reported pH sensitive poly(acrylamide) grafted N -succinyl chitosan (PAA/S-CS) hydrogels as a successful carrier for the oral drug delivery of insulin. They observed 38% insulin loading efficiency and 76% encapsulation efficiency whereas 26% insulin release was found at pH 1.2 (acidic stomach pH) and 98% release at pH 7.4 (intestinal pH). They found no toxicity in the reported hydrogels and 4.43% bioavailability. These hydrogels appeared to be successful carriers for insulin capable of lowering the blood sugar level in diabetic mice .
However, the week mechanical strength of pure natural polymer hydrogels is major limitation in exploiting them in the controlled drug delivery. On the contrary, synthetic polymer hydrogels have strong mechanical strength. Moreover, synthetic polymers are easy to prepare and cheap. The properties of these polymers can be modified easily . However, synthetic polymers have very low biodegradability and biocompatibility.
From the results, it can be concluded that SP2 hydrogel showed significant drug loading and encapsulation efficiency and in vitro drug release properties which can be considered as optimum. It can also be concluded that this hydrogel is useful for oral delivery of hydrophilic drug. This hydrogel can be investigated as hydrophobic drug carrier. This hydrogel has high mechanical strength and can be explored for tissue engineering applications. Excellent interconnected porous network would allow an efficient nutrient transfer and gaseous exchange, which can enhance the cell proliferation and cell survival on these hydrogel matrices.
Aiming at overcoming the PEG dilemma, PEG was conjugated to poly(2-(dimethylamino)ethyl methacrylate) cationic polymers for pDNA condensation . The transfection efficiency of the PEG-detachable polyplex particles was 100 times higher at pH 5 than at pH 7.4. Eudragit F is another example of enteric polymers used for colon-targeted DDS  due to its solubility at pH higher than 7.0.Å tembÃrek and coworkers developed a multiple-unit dosage system based on drug/chitosan core coated with Eudragit F for colon-specific drug release. As Eudragit F and chitosan are designed to dissolve in the small intestine and the colon, respectively, drug could be protected from undesired release until it reaches the colon after oral administration. In nine healthy volunteers after oral administration of the system containing caffeine as a model drug, caffeine first appeared in the saliva at 7 h post administration.