**5. Bioengineered materials: Ideal and recent advances for drug delivery systems**

#### **5.1. Nano-engines of drug delivery systems**

**4.5. Targeting strategies for kidney diseases**

276 Application of Nanotechnology in Drug Delivery

to achieve the goal of targeting drugs to the various renal diseases.

**4.6. Common strategies for smart polymeric particulate targeted delivery**

The ideal proposed model for site-targeting delivery is fabricated from a biocompatible, nonimmunogenic and biodegradable polymer and acts as the central of support to three main characteristics of attachments such as site-specific targeting moiety, solubilizer and drug moiety, which should have drug delivery capacity, capable of transport and active molecule should bonded to the polymer via spacer, and the linkage is cleaved by particular enzyme(s) at the final targeted site respectively. In order to develop a new polymeric vehicle for a particular drug, the polymer distribution in the systemic circulation has to be analyzed since it's right away affects on activity of drugs. For controlling the systemic distribution of drugs, we need to consider minimum two strategies which are active or passive targeting. Previously, the drug is delivered to target site using some specific antibodies, which are specific to target cell-surface [251-254]. This method gives efficient targeting to tumor site; however, the antibodies can produce immunogenic activity. But, the passive targeting with bio-polymers vehicles cannot produce immunogenicity or toxicity, this might enhance the active molecule efficacy, such as increased half-life by increased size of the nano-particulate complex, increased permeability at the targeted area and polymer vehicle interacts to the body organs. Those elements must be increase the absorption of the drug molecule; which minimize the dosage and low unwanted effects [255, 256]. Moreover, in the advanced fabrication of molecular imprinting technology can provide efficient smart polymeric systems with the ability to recognize specific bio active molecules. This advanced fabrication technology has tremendous possibility to meet the requirements for satisfactory dosage forms developments. Depends upon the particular application the fabricated systems can decide the delivery, efficiency,

Macromolecule is a very large molecule, which can accumulate in the kidneys. Generally, the molecular weight of the macromolecular vehicle is bigger than that of the prodrugs, so this kind of system can achieve the goal. Pro-drugs have the ability to select the target in the kidney because it can release the active drug by the action of renal enzymes. The various strategies of kidney-targeted drug delivery systems has to be considered such as biodynamical strategy of renal artery perfusion, macromolecular carriers which includes enzymes, immune proteins and peptide hormones, pro-drugs which includes folate, sugars, and amino acids, and other strategies including various nano-particulate systems. The molecular weight and charge [245, 246] of polymers is the main factor, it can influence their distribution in various organs including kidney. In general, increasing the molecular weight of polymers leads to decreases urinary clearance. Some of the polymers have been eliminated rapidly from the systemic circulation but it does not excrete from the kidney, and its accumulated in the renal systems. So it clearly proposed that the selection of effective and active multi-functionalized polymeric nanoparticles can uptake by the particular kidney cell types. So the selection of polymers is one of the prime strategies for consideration to achieve the efficient kidney targeting. These new possibilities to develop kidney targeting conjugates and other nano-particulate drug delivery systems. Including various polymers based nanoparticles give excellence strategies

Engineered materials have been utilized for developing smart drug delivery systems. Design and multi-functionalities fabricate of efficient smart drug delivery systems are vitally neces‐ sary for medicine and healthcare development. In the material science field provides biode‐ gradable, biocompatible, environment-responsive, and highly effective novel polymeric system for targeted delivery. Nanotechnology provides bottom-up and top-down nanofabri‐ cation with size controlled and multi-functionality of particulate for targeted delivery. New materials invention and advanced technology have been synergistically achieved in drug delivery so far. The essential goals of medical pharmacology provide the right medicine, right dosage, and right route at the right time to the right patient, so more research need to optimize the therapeutic efficacy of the drug. This is the essential principles is behind the smart drug delivery. A smart, controlled delivery system needs synergistic consideration of several factors; these have been summarized in Figure. 7. It is difficult to get all consideration factors in a smart controlled delivery system due to other influencing factors. Also high quality, reliability, efficiency and reproducibility are the most significant issue while designing such a smart system. Also the smart systems have to induce the drug release and stop the release by their own manner. It would be highly benefited, if the system recognizes the disease affected part, estimated the disease affected ratio, and then acted to release the exact quantity of active drugs. This kind of drug delivery system can fulfil the medicine and healthcare requirements.

**Figure 7.** Requirements of several factors for simultaneous consideration to design a polymeric nanoparticle for the smart drug delivery system
