*Polymer Properties: Functionalization and Surface Modified Nanoparticles DOI: http://dx.doi.org/10.5772/intechopen.84424*

*Role of Novel Drug Delivery Vehicles in Nanobiomedicine*

graphene nanosheets, titanium-based nanoparticles, core-shell nanoparticles, hollow core-shell (hCS) nanoparticles, hollow polymer-polymer nanoparticles (HPPNPs), polymer-metal nanoparticles (PMNPs), polymer-metal blends (PBs), polymer-silica nanocomposites (PSiNCs), polymeric micelles (PMs), solid-lipid nanocapsules (SLPNCs), liposomal nanoparticles, albumin-based nanoparticles, chitosan-based nanoparticles, platinum-based nanoparticles (PtNPs), ceramic nanoparticles, carbohydrate nanoparticles, etc. are reported and corroborated in the literature [2–5]. Furthermore, a significant interest in the synthesis and characterization of polymers followed by the design and development of polymeric nanoparticles (PNPs) with surface tunable properties has become an essential due to the various applications. For example, the amino acid-based polymer is much more suitable for the preparation of nanoparticles because of its biosafety and nontoxic and biodegradable nature. Similarly, thermosensitive polymer, for example, poly-Nisopropyl acrylamide (PNIPAM), shows lower critical solution temperature (LCST) at ~32°C, and it is much more useful to prepare the nanoparticles or capsules with thermally tunable morphology and other futuristic characteristic properties [6]. However, the main advantage to polymer scientists is they can easily synthesize the polymer to engineer the nanoparticles followed by the significant functionalization and surface modifications by changing the solvents, concentration, and stirring methods or by changing the functional groups which are present in the synthesized polymer complex. Similarly, the ionic (cationic and anionic) polymers referred to as polaxomers can help to modify the surface of the particles. Polymeric nanoparticles are under a wide range of utilization in the field of biomedical, nanobiotechnology, nanobiopharma, and other pharmaceutical domains. For example, they are very much used in the field of drug delivery systems (DDSs), gene delivery systems (GDSs), protein delivery systems (PDSs), cell delivery systems (CDSs), and tissue engineering followed by plastic surgery, etc. [7, 8]. However, polymers have numerous industrial applications as well, such as cell phone manufacturing companies, soft drink and water bottle industries, electronics and electrical engineering departments, automobile industries, and many other industrial usages based on the requirements. Interestingly, polymeric nanoparticles with porosity have multidirectional usages such as drug or nanomedicine loading and its target specific release. The nanoparticles with ~200 nm (in diameter) are the ideal size for the biomedical applications. The pore size with ~100 nm in the polymer nanoparticles or capsules is much more suitable for drug delivery and cancer therapeutics. According to International Union of Pure and Applied Chemistry (IUPAC) definition, the microparticle size should be <2 nm, (in diameter) and meso-particles or mesoporous particle and capsule size *ca.* 2–50 nm, and nanoparticles (particle size 50–200 nm) have been referred for various applications [6–8]. The effective and potential working capacity of nanoparticles has been defined by their size, shape, morphology, porosity, and other thermal properties. However, the qualitative quantification of use of polymer-based nanoparticles and their potential applications completely depends on the characteristic features like surface modification, size, and shape tenability. For example, many properties like color and atomic orientation are differing

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from the sizes of bulk to nanoscale [9, 10].

The word polymer derived from Greek has been split into two meaningful words: (1) poly means many, and (2) meros or mers means units or parts. More specifically monomer is the smallest repeating unit for the development of polymer. Simply polymers are made up of monomers. The word monomer is also derived

**2. Classification of polymers**

from the Greek. Mono means one or single and mer means part/s. As reported in **Table 1**, there are varieties of polymers classified based on their biodegradability, biocompatibility, thermal stability, pH-responsive nature, environmental responsive nature, etc. Based on occurrence these are again categorized into three types: (1) natural polymers, for example, starch, chitin, cellulose, etc., (2) synthetic polymers, for example, polystyrene (PS), polyurethane (PU), polyvinyl chloride (PVC), and (3) semisynthetic polymers, for example, cellulose nitrate, guncotton, cellulose acetate, etc. Absorbable synthetic polymers include polyvinyl alcohol (PVA), polylactic acid (PLA), polycaprolactone (PCL), and polyglycolic acid (PGA), and these are homopolymers. The heteropolymers include polytrimethylene carbonate (PTMC), polyetherimide (PEI), polydioxanone (PDO), polylactide-co-glycolide (PLGA), and the combination of block copolymers like and poly-glycolide-co-trimethylene carbonate (PGTMC) which are best examples for heterogeneous polymers. Apart from these polymers, there are pH-sensitive polymers like poly-L-lysine which is positively charged at lower pH conditions [22, 23]. Liposome and poly-histidine are the systems with pH sensitivity, and this can be easily interacted with negatively charged particles or membranes to promote fusogenic properties. Furthermore, some hydrogel-based nanoparticles show unique characteristics toward various biomedical as well as industrial applications. Liposomal and hydrogel based systems has tendency towards pH-sensitivity and it is a characteristic property to tune-up their morphology for many therapeutic applications. For example, PLGA, MeO-PEG-NH2, and PAMAM-based nanoparticles show pH-dependent destabilization and thus are used for cytoplasmic experiments because of its ease of permeability through the membrane to deliver nanomedicines and nanoparticles [9, 10, 22, 23]. The NIPAM/pNIPAM (N-isopropyl acrylamide/ (poly-N-isopropyl acrylamide)) is the best example for the thermal sensitive polymer which shows lower critical solution temperature (LCST) or cloud point at ~32°C **Table 1**. Because of the thermal behavior, it is termed as magic or smart polymer and used for various medical and industrial usages. However, these polymers are mainly prepared based on two polymerizations reactions such as (1) addition polymerization and (2) condensation polymerization methods [24, 25].


#### **Table 1.**

*Show the different types of polymers with their monomer units and their chemical formula followed by the structures in* **Figure 1a–j***.*

**Figure 1.**

*Some of the polymers with their chemical structure, name, and active functional groups which are involved in functionalization and polymerization reactions.*

Hence, polymers are prepared by the abovementioned two versatile polymerization methods, and there are several modified methods and approaches that can be followed for the preparation and synthesis of polymers such as ring-opening polymerization (R-O-P), emulsion polymerization, precipitation polymerization, diffusion polymerization, macroinitiator polymerization, macroinitiator polymerization, and atom transfer radical polymerization (ATRP) methods. As per the literature, first in the 1970s, lactic acid (LA)-based nanoparticles and capsules are

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**Figure 2.**

*Polymer Properties: Functionalization and Surface Modified Nanoparticles*

used for biomedical and other pharmaceutical applications, and later it has been extended for various fields [26]. Polymers when considered for biomedical applications, it needs to refer self-assembly nature and functionality followed by the formation of spherical and sphere-shaped nanocapsules and particles particularly for drug delivery systems. Based on degradability, thermosensitivity, and pHresponsive nature, these are again categorized into various classes and reported in **Figure 2** with some examples. However, biodegradable polymers which show a tendency to degrade in biological systems such as polylactic acid (PLA), polyglycolic acid (PGA) and poly terephthalic acid (PTA), polycaprolactone (PCL), and amino acid (AA)-based polymers are potential materials to engineer nanoparticles and capsules for nanotechnology and nanobiotechnology applications. The polymers which do not degrade in the biological systems are termed as non-biodegradable polymers such as carboxymethyl, ethyl cellulose, and acetates of cellulose. The poly anhydrides like poly sebacic acid (PSA), poly adipic acid (PAA), and other environmental-responsive polymers also enlisted in the non-biodegradable polymers. Thermo-responsive (temperature-sensitive) polymers show a significant change in the size and shape of nanoparticles to tune up based on requirements [27]. The thermosensitive behavior of PNIPAM and pH-responsive nature of L-glutamic acid gamma benzyl ester (L-GluA-5-BE), L-aspartic acid beta benzyl ester (L-AspA-4-BE), polyethylene glycol (PEG), poly L-glycolic acid (PLGA), and PAMAM allow changing the morphology of nanoparticles as well surface profile of the NPs and capsules (**Figure 1**). Apart from these polymers, electrical-responsive polymers show piezoelectric effects which are a characteristic property to mold the nanoparticles based on requirements. The supramolecular interactions between the atoms and molecules lead to compression or elongation and stretching of bonds, and it can play a vital role to change the properties of final compounds. However, polyvinylidene fluoride (PVDF) polymer has been considered as one of the magic polymers which allow structural and morphological modifications through the appropriate

The chemically responsive polymers allow internal changes through the formation of anionic and cationic and amphiphilic nature through the oxidation, reduction, and redox (both oxidation and reduction) reactions and lead to surface modification based on smooth and rough surface. As per the literature, the increase in the size of the particles depends on an increase in monomer units or polymer units. Sometimes branching and hyper-branching nature also lead to the formation of larger nanoparticles and capsules. Polymers prepared with the

*DOI: http://dx.doi.org/10.5772/intechopen.84424*

synthesis and preparation methodologies [28].

*Some of the polymers categorized based on their characteristic properties.*
