Konda Reddy Kunduru

Polysaccharide-Based Conjugates for Biomedical Applications

Polysaccharides contain different functional groups (such as hydroxyl, amino, carboxylic acid, aldehydes) that make them ideal for conjugation. They are biodegradable, biocompatible, and hydrophilic. Polysaccharide conjugates have been used in drug, gene, and macromolecule delivery, tissue engineering, and other biomedical applications. Polysaccharide conjugates have also been used primarily for solubilization and controlled release of hydrophobic moieties. The advent of nanotechnology, gene therapy, and tissue engineering influenced the way these conjugates are now used. Modern day conjugates are modulated to be thermoresponsive, pH-responsive, photoresponsive, or target-specific (receptor mediated targeting). This Review briefly introduces different polysaccharides followed by different synthetic strategies used for conjugation; finally, recent applications were compiled.

Castor Oil-Based Biodegradable Polyesters

This Review compiles the synthesis, physical properties, and biomedical applications for the polyesters based on castor oil and ricinoleic acid. Castor oil has been known for its medicinal value since ancient times. It contains ∼90% ricinoleic acid, which enables direct chemical transformation into polyesters without interference of other fatty acids. The presence of ricinoleic acid (hydroxyl containing fatty acid) enables synthesis of various polyester/anhydrides. In addition, castor oil contains a cis-double bond that can be hydrogenated, oxidized, halogenated, and polymerized. Castor oil is obtained pure in large quantities from natural sources; it is safe and biocompatible.

Poly(lactic acid) Based Hydrogels.

Polylactide (PLA) and its copolymers are hydrophobic polyesters used for biomedical applications. Hydrogel medicinal implants have been used as drug delivery vehicles and scaffolds for tissue engineering, tissue augmentation and more. Since lactides are non-functional, they are copolymerized with hydrophilic monomers or conjugated to a hydrophilic moiety to form hydrogels. Copolymers of lactic and glycolic acids with poly(ethylene glycol) (PEG) provide thermo-responsive hydrogels. Physical crosslinking mechanisms of PEG-PLA or PLA-polysaccharides include: lactic acid segment hydrophobic interactions, stereocomplexation of D and L-lactic acid segments, ionic interactions, and chemical bond formation by radical or photo crosslinking. These hydrogels may also be tailored as stimulus responsive (pH, photo, or redox). PLA and its copolymers have also been polymerized to include urethane bonds to fabricate shape memory hydrogels. This review focuses on the synthesis, characterization, and applications of PLA containing hydrogels.

Injectable formulations of poly(lactic acid) and its copolymers in clinical use.

Poly(lactic acid) and its copolymers have revolutionized the field of drug delivery due to their excellent biocompatibility and tunable physico-chemical properties. These copolymers have served the healthcare sector by contributing many products to combat various diseases and for biomedical applications. This article provides a comprehensive overview of clinically used products of poly(lactic acid) and its copolymers. Multi-dimension information covering product approval, formulation aspects and clinical status is described to provide a panoramic overview of each product. Moreover, leading patented technologies and various clinical trials on these products for different applications are included. This review focuses on marketed injectable formulations of PLA and its copolymers.

2 – Nanotechnology for water purification: applications of nanotechnology methods in wastewater treatment

Providing clean and affordable drinking water is one of the modern-times challenges. The world’s growing population causes water scarcity, and pollutants contaminate whatever water sources are left. Nanotechnology has provided innovative solutions for water purification. This chapter reviews nanotechnology-enabled water-treatment processes, showing how they transform our water supply and wastewater treatment. The following topics are discussed: different nanomaterials, properties, mechanisms, advantages compared to existing methods, limitations, research needs for commercialization, and toxicities of nanomaterials.

Poly(α-hydroxy acid)s and poly(α-hydroxy acid-co-α-amino acid)s derived from amino acid.

Polyesters derived from the α-hydroxy acids, lactic acid, and glycolic acid, are the most common biodegradable polymers in clinical use. These polymers have been tailored for a range of applications that require a physical material possessing. The physical and mechanical properties of these polymers fit the specific application and also safely biodegrade. These polymers are hydrophobic and do not possess functional side groups. This does not allow hydrophilic or hydrophobic manipulation, conjugation of active agents along the polymer chain, etc. These manipulations have partly been achieved by block copolymerization with, for example, poly(ethylene glycol), to obtain an amphiphilic copolymer. The objective of this review is to survey PLA functional copolymers in which functional α-hydroxy acids derived from amino acids are introduced along the polymer chain, allowing endless manipulation of PLA. Biodegradable functional polyesters are one of the most versatile biomaterials available to biomedical scientists. Amino acids with their variable side chains are ideal candidates for synthesizing such structural as well as stereochemically diverse polymers. They render control over functionalization, conjugation, crosslinking, stimulus responsiveness, and tunable mechanical/thermal properties. Functionalized amino acid derived polyesters are widely used, mainly due to advancement in ring opening polymerization (primarily O-carboxyanhydride mediated). The reaction proceeds under milder conditions and yields high molecular weight polymers. We reviewed on advances in the synthetic methodologies for poly-α-hydroxy esters derived from amino acids with appropriate recent examples.

Controlled iodine release from polyurethane sponges for water decontamination.

Iodinated polyurethane (IPU) sponges were prepared by immersing sponges in aqueous/organic solutions of iodine or exposing sponges to iodine vapors. Iodine was readily adsorbed into the polymers up to 100% (w/w). The adsorption of iodine on the surface was characterized by XPS and SEM analyses. The iodine loaded IPU sponges were coated with ethylene vinyl acetate (EVA), in order to release iodine in a controlled rate for water decontamination combined with active carbon cartridge, which adsorbs the iodine residues after the microbial inactivation. The EVA coated IPU were incorporated in a water purifier and tested for iodine release to water and for microbial inactivation efficiency according to WQA certification program against P231/EPA for 250l, using 25l a day with flow rate of 6-8min/1l. The antimicrobial activity was also studied against Escherichia coli and MS2 phage. Bacterial results exceeded the minimal requirement for bacterial removal of 6log reduction throughout the entire lifespan. At any testing point, no bacteria was detected in the outlet achieving more than 7.1 to more than 8log reduction as calculated upon the inlet concentration. Virus surrogate, MS2, reduction results varied from 4.11log reduction under tap water, and 5.11log reduction under basic water (pH9) to 1.32 for acidic water (pH5). Controlled and stable iodine release was observed with the EVA coated IPU sponges and was effective in deactivating the bacteria and virus present in the contaminated water and thus, these iodinated PU systems could be used in water purification to provide safe drinking water. These sponges may find applications as disinfectants in medicine.

Molecular Weight Determination of Polyethylene Terephthalate

Abstract Polyethylene terephthalate (PET) is one of the most widely used polyesters today – it is used in packaging, fabric, engineering, electronics, and biomedical industries. Different methods for PET molecular weight determination are reviewed in this chapter. Molecular weight is the most important characteristic for determining the mechanical properties and ability to fabricate these materials for different applications. Experiences and several recent findings from the authors’ laboratory are also included for forensic PET fiber comparison and PET molecular weight analysis. Finally, a few recent applications utilizing PET are reviewed, focusing on biomedical research such as the next generation of PET fibers, high-tenacity polyester fibers (HT PET), and PET clay nanocomposites.