All patients will receive full mouth scaling and root planing with hand instruments and ultrasonic scalers at baseline. Thereafter, in the test quadrant, 1 ml of 0.8% hyaluronic acid gel will be administered subgingivally in all selected test sites at baseline and 1 week later. The following clinical parameters will be recorded at baseline, after 6 weeks and 12 weeks post treatment. Oral hygiene instructions will be given to all patients. The clinical measurements and treatment will be performed by a single examiner.For every patient and control subject, GCF samples will be collected at baseline, 6 weeks and 12 weeks post treatment. The samples will be pooled from two periodontal sites with clinical attachment level of 3 mm or more (in the two different quadrants). The sampling area will be isolated with cotton rolls and carefully will be cleaned supragingivally with sterile cotton pellets. A sterile absorbent paper point will be inserted into the gingival crevice or pocket until resistance will be felt. The paper point will be held in place for 30 s and then will be transferred to a vial containing 100 μL of distilled water and vigorously will be mixed. The paper points will be removed, and the samples will be centrifuged and will be washed twice with distilled water. The resultant pellets will be resuspended in 0.4 mL of distilled water. The samples will be coded and stored at −70 °C until use for ELISA test for identification of Human beta Defensin-2.