**5. Advantages with polymer nanoparticle**

These polymer-based nanoparticles are developed in principle to protect the guest particles or molecules from degradation and its functional activity, for example, porous polymer nanoparticles or nanocapsules loaded with anticancer drugs or nanomedicines [47]. Because of the soft nature of polymer NPs and nanocapsules, it is very easy to modify the surface of the particles and their monodispersion based on its applications. The enhanced absorption and modification of the drug distribution throughout the surface of the particles or capsules lead to the target-specific or tissue- or cell- or organ-specific pharmacokinetics and dynamics in various biomedical and pharmaceutical usages. Polymer-based nanoparticles and capsules allow easy surface functionalization and modification to tune up them with desirous properties. Sometimes smooth surface of the polymer thin films can become rough due to the internalization and incorporation of metal and other inorganic nanoparticles such as FeONPs, ZnONPs, AlNPs, AgNPs, AuNPs, SiO2NPs, etc. The surface properties like particle smoothness and roughness or porous nature of particles in composite can give better results, but its surface and size may not fit for

the usage of biomedical applications [48]. In such cases the composite of polymer thin film embedded or doped with some other metal nanoparticles or organic and inorganic materials needs to be molded without changing its original activity or characteristic properties. However, the functional groups such as amide (–NH), amine (–NH2), acid (–COOH), aldehyde (–CHO), keto (–C=O), ester (R–COO–R), anhydride (R–CO–O–CO–R), acid halides, hydrogen halides, salts, and solvents (organic, inorganic) can also influence the surface properties for the nanoparticles or nanocapsules. Based on the requirement, it can be chosen to modify the particles surface and size, shape, etc. The concentration of the solvent also affects the pattern of the nanoparticles and nanocapsules. Sometimes additives like precursors and surfactants can also show an adverse effect on the morphology of polymer nanoparticles [49]. The activity (bioactive nature) of polymer nanoparticles and nanocapsules can disturb the body metabolism. The active functional groups with their potential resonance capabilities can also interact with body fluids and interfere to shore-up the mutations. Apart from the solvent, there are several factors which can affect the patterning of the surface of the nanoparticles such as pH, thermal stability, rubbery nature, solid (amorphous and crystalline) nature, environmental conditions, etc. The stability, biocompatibility, and route or synthesis methodology are also playing a vital role to tune up the surface properties of the polymeric nanoparticles and capsules. For example, (a) protein nanoparticles have stability issues during storage. If the storage conditions are not followed properly, they may get contaminated and become toxic [50]. But these protein-based NPs are very much compatible with their unique characteristic features such as nontoxic nature and nonantigenic nature. As per the existing literature, it is known that bulk protein in plasma can easily bind to a variety of drug molecules through its trajectory while carrying them to deliver target specifically. And these are very much flexible to ease scale-up manufacturing and other nanobiotechnological applications; (b) albuminbased nanoparticles are very much suitable for the morphological modifications and to tune the surface properties. These are biocompatible and biodegradable without any detrimental activities upon mankind usages. Sometimes these albumin-based nanoparticles are used for drug delivery and other biomedical applications. However, protein albumin contains a huge number of charged amino acid residues, and it binds water-soluble drugs through charge interactions, and it leads to surface modifications and morphological changes [51].
