title: Hydrazone linkages in pH responsive drug delivery systems.
abstract: Stimuli-responsive polymeric drug delivery systems using various triggers to release the drug at the sites have become a major focus area. Among various stimuli-responsive materials, pH-responsiveness has been studied extensively. The materials used for fabricating pH-responsive drug delivery systems include a specific chemical functionality in their structure that can respond to changes in the pH of the surrounding environment. Various chemical functionalities, for example, acetal, amine, ortho ester, amine and hydrazone, have been used to design materials that are capable of releasing their payload at the acidic pH conditions of the tumor or infection sites. Hydrazone linkages are significant synthons for numerous transformations and have gained importance in pharmaceutical sciences due to their various biological and clinical applications. These linkages have been employed in various drug delivery vehicles, such as linear polymers, star shaped polymers, dendrimers, micelles, liposomes and inorganic nanoparticles, for pH-responsive drug delivery. This review paper focuses on the synthesis and characterization methods of hydrazone bond containing materials and their applications in pH-responsive drug delivery systems. It provides detailed suggestions as guidelines to materials and formulation scientists for designing biocompatible pH-responsive materials with hydrazone linkages and identifying future studies.
authors.affiliation: Discipline of Pharmaceutical Sciences, School of Health Sciences, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa.
authors.forename: Sandeep J
authors.initials: SJ
authors.lastname: Sonawane
authors.affiliation: Discipline of Pharmaceutical Sciences, School of Health Sciences, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa.. Electronic address: kalhapure@ukzn.ac.za.
authors.forename: Rahul S
authors.initials: RS
authors.lastname: Kalhapure
authors.affiliation: Discipline of Pharmaceutical Sciences, School of Health Sciences, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa.. Electronic address: govenderth@ukzn.ac.za.
authors.forename: Thirumala
authors.initials: T
authors.lastname: Govender
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D002626:Chemistry, Pharmaceutical / Q000379:methods; D004337:Drug Carriers / Q000737:chemistry; D016503:Drug Delivery Systems / Q000379:methods; D006801:Humans; D006835:Hydrazones / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008823:Micelles; D053758:Nanoparticles / Q000737:chemistry; D004364:Pharmaceutical Preparations / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D004337:Drug Carriers; D006835:Hydrazones; D008823:Micelles; D004364:Pharmaceutical Preparations; D011108:Polymers
keywords: Amphiphilic; Conjugates; Dendrimers; Hydrazone linkages; Nano drug delivery; pH-Responsive